LET THIS SIGNAL THE END OF THE FRIDGE PUMP QUESTIONS!

Quote: Originally posted by Chainhit222

what is that white band around your head

Quote: Originally posted by Chainhit222

hang a air freshener off of it

I also spilled the oil all over the grass when I drained one to measure the oil volume in there, and then walked away for a minute leaving it balanced on it's side.

There was a blast furnace near our house, back in the olden days. Rather than use expensive hardcore (which is always expensive), the builders bought all the clinker from the furnace.

That means the lawn is now laced with an under layer of fairly caustic crap. When I clean the glassware, I'll often purposefully spill the washes of sulphuric over the lawn. It loves it. And me taking the occasional wazz on there in the dead of night.

Thanks for all the nice replies. It did indeed take forever to make something that long on a 256mb computer, so I'd be happy if just one person got some use out it.

I think more of us should post videos. This is one of, well probably the best at home chemistry forum on the web. Yet youtoop is populated by unhelpful, kind of boring videos about acetone peroxide and pipe bombs. I think team science madness could do a little better than that (len and his sodium, the lead acid chambers, etc). It could also make the massive project threads a lot more productive. It's hard to have an unnecessary flame war when you can see the other person.

All of you will have cameras that record, and can click upload. I expect a lot of us have glassware and odd things the standard younoober will want to see or knowledge of SOMETHING others can learn from. None of us know everything, but I suspect some of your are downplaying your own ability versus the standard youtube viewer.

I troll Jeri Ellsworth's videos a lot, she does them for electronics and are a good example of what I mean.

First person to make a video with their face and voice in it gets an instant subscription from John.

Demethylation, I may do that since it's very pretty seeing all the purple and orange everywhere, it's an odd reaction (as it can seems to be able to do a very passable impression of tar and illustrates how there is a spectrum within the hard / soft definitions of lewis acids) and it'd give me a chance to whip out some fancy looking glass.

It's cost me a few thousand pounds in equipment and reagents to figure out the demethylation, and a few years, amongst other things. £1k per view?

[Edited on 8-9-2010 by peach]

Great video Peach
I need to get a metric nomograph, it would save me so much time using an internet calculator. I've gone and got one out of an old fridge now so I can join in the fun It's not pulling the best the vacuum (I could only get warm water to boil, no gauge yet) but as you said in the video, it could just be the refrigerant boiling off still. I'll have to make some videos on AlCl3 production, once I make a new youtube account with a user name I didn't pick when I was 13.

I have to start getting some money together to pay for the things you see in the videos (being jobless and having £10+k's worth of student debt), so you can have a customized, hand written, all units and laminated nomograph for a £2 + p&p gift thru palpaid.

"But John... you have all those pumps! Why do you need MOAR money!?", I'm refitting them to sell them, not collecting them.

I checked that pump again just now, and the pressure had gone up a bit, indicating there's still refrigerant in it. I've flicked it back on, blocked the intake and will leave it overnight to go.

You should expect some level of nuncing around from the pumps when they first come out, they will take time to sit still.

You don't have to be doing something super novel to make a worthwhile video, you could just post up a reply to that one featuring you pulling one out and doing the same thing to show it in a different way. It may also raise questions I didn't cover.

[Edited on 8-9-2010 by peach]

A pump that requires additional back pressure? Yikes.

Thanks for the update on these, and a video (with a bit of detail) would be great (once it's uploaded, click 'video reply' on mine and then link to yours, so it's all in one place), since I didn't have one to hand to take to bits and talk about in those videos. If I find one, or anyone would like to post me one, I'll do a video about those too.

I'd also like to look at and take apart the pumps from superfreezers. Donations welcome.

I've seen videos of 95kW (yikes) scroll compressors, wonder whats in there?

When I have it all pretty looking I'll do a video response; it won't contain anything of the disassembly, but I'll try to cover what I know. It is a old R22 new-old-stock AC pump, so it seems to be a pretty good way of getting new pumps without refrigerant if you can source them.

HOLY MOLY, you've gone purple!

Excellent! To see another person helping on this.

I have a few annoying observations to make, which I don't really want to knowing how hard it is to make these videos but thought they'd be helpful in some way.

• I am now getting near rotary pressures (or possibly better) from pistons. But yep, they're 100% not going to do that without modification. ~15-10mBar is the lowest I've seen them go with two in series, unmodified.
  
• Piston fridge pumps also have a starter winding, it's hidden inside the can. If you pull the electrics off, you'll see the three terminals. The black cylinder stuck to the side is a starting relay. The thing I forgot to put back on whilst busying myself with my nipple and the pliers. You can see the relay hanging off those flying leads (the black and white bits of plastic) near the vice. Some of them also have a 5uF cap on there as well.

I also forgot to point out how the motor will burn it's self out if left in the 'hum' state.

Those filters are SO damn expensive from BOC. They're just a bit of material in a plastic can.

I also missed out what the oil in the pistons was. The oil bit is helpful.

73C YIKES in a few minutes! That's friction for you. Mine was at 51C after 3h+ none stop, with high vacuum grease on the piston. I can see why there are so many questions about cooling these pumps from the US / Canada guys. 150C, I could fry my breakfast on that after an all night distillation.

Subscribbled and ratified.

Thanks again for the video and trying to help!

[Edited on 14-9-2010 by peach]

Very nice! Kudos to Peach for special comedic effects, and to aonomus for organization and conciseness.

I must say that Peach has tied axehandle in turning his living quarters into an industrial development laboratory.

@Magpie

Darn right! I'm not letting go on those things until they a.) can't do any better, b.) explode.

The way they are from the factory is just to make things simple for the home user who's never going to want to see it, let alone do anything to it. The R600a means they're essentially designed to pump from a butane cylinder, fairly flammable stuff. The severe lack of rubber based seals or vanes should make them fairly corrosion / solvent resistant also. And they're built to a standard inside where I seriously suspect they can do a lot better than they will straight out of the skip, with not much effort. I have honestly seen Edwards etc brand names that look worse inside, for thousands.

@aonomus
Could you bend a bit of sheet metal into a heatsink, or submerge the pump?

If you remove the can, you may (like I found with pistons) be able to run it on it's own for better cooling? I don't know, those AC things never turn up at the tip round here. It's too cold most of the time to need one, but I love having cool fresh air around. I have all the windows open and heating off right now, and it's 5am in September.

I know that you could theoretically run a lab rotary without the oil box on it, you'd just need to catch the oil in the exhaust and let the pump suck it back in through a bit of tube or something like that (there's a port on the bottom of the pump heads). Again, the box is there to make it look neater and make it easier for the normal users. But it may be worth the slight extra effort required in ripping it off to get it running cooler during 3-6h distillations.

With the solvents thing, it's worth sticking some carbon in the way if only to trap the traces. But, as I say in the nomnomnomograph video, if the thing you're working on isn't particularly sensitive to heat, you can always raise the pressure a little to catch the solvent in the condenser. No need to buy the trap, or the nitrogen. Or even use such a low pressure in the first place.

Remember, the Buchi V700 pump has a pressure of ~10mBar, dead on the piston fridge pump pressure range; 35-20mBar normal, 15-10mBar for two in series or one with vacuum pump oil squirted in.

The Buchi V700 is $2,160!

When doing filtrations that I know are going to clog up (and so boil the solvent), I'll stick the flask in the freezer for a while when I know I'm getting close to needing it. Then wrap it in a microfibre cloth or two.

As soon as the solvent tries to boil on the way through, it's going to evaporatively cool it's self and stop (due to the insulation).

[Edited on 14-9-2010 by peach]

Connecting the tube straight to the air inlet is a great idea peach I might have to try that and then reseal the can so the oil can still flow around, I wouldn't have to worry about sucking solvents and water through it then.
I have a fridge pump question though...
I got one from uni today, they were throwing out some fridges and freezers from the biochem building, I couldn't help myself. I got it home and opened it up to wire the plug on and realized the capacitor isn't there I doubt I'd be able to get it either without tearing the whole thing apart. There was the power cord which led into the little box on the side of it and a white cord that ran out into the fridge somewhere. The white cord had 4 wires, one earth, one white, brown and blue. the brown and white both connect to the relay I think it is in different spots and the blue attaches to the motor protector along with a wire from mains.
Here's photos, they'd explain it better than me. I was wanting to put the cap from my old compressor onto this one but don't know which two wires to use.



Hopefully I can get this running, I was wandering around the building and saw a few -80C freezers, if this was one of those then I'd have a pretty hefty pump


[Edited on 17-9-2010 by spong]

You definitely want to ignore what the liquid does at first, it'll almost always start to boil, or at least de-gas, as soon as the vacuum is applied, then stop. Temperature measurements at that stage are fairly useless.

I tried checking mine with eugenol, because it normally boils at somewhere around 250C and I knew the oil was relatively pure, meaning it'll distort the measurements less at low pressures. The glass had also just been given a very good clean and the thermometer is a pricey mercury one from Germany made to a BS standard.

Your 17-20mmHg translates to 22.5-26.5mBar, about what I was getting with the fridge pump out of it's casing.

I suspect, even with a cold basement, that water may be skewing the pressure the rotary can achieve. You may need to give it another go with some reasonably pure, high BP oil and ice around the receiver. Also, try measuring the amount of material going in and coming back out at the start and end of the distillation (with a pipette or scale that will give some level of accuracy given the volume / mass used), to tell you if any has buggered off during the process.

I've tried distilling things like cyclohexane (ATM BP ~80C I think) under fridge pump vacuum. Even with my coil condenser cooled with ice, a remarkable amount has 'disappeared' when it comes to checking the results.

{edit}I have a PDF in the works where I've plotted various methods of weighing against the recently calibrated 0.1mg balance I have access to. I've tried those nasty looking £8.99 0.01g weed dealer scales from China, the digital ones for the kitchen, splitting piles of table salt by eye, using rulers over pens as balance beams and using randomly selected coins out of my pocket as reference masses. The nasty looking £8.99 are keeping a less than 1% error up to about 50g, despite me spilling agar and all kinds of crap over them, overloading them and never calibrating them. The kitchen ones have a huge amount of error in that region, but that then drops to about 1% over 100g. Stacks of coins can also produce a reference mass with vanishingly low errors as the error goes positive and negative over the years by an equal amount, so stacks of them cancel each elements error. Amusingly, I can see the mint tweaking the presses as the mass of the coins changes over the years. There is a very stable, periodic sine wave pattern.{/edit}

@sponge bob square panties

Try starting it without the cap, a lot of them work fine without it. If that fails, I'll double check mine (or check it anyway if I remember next time I'm beside it). I currently have so much to do it's becoming tricky to keep up with it all.

Print, colour in.... "I know I've gone outside the lines, but that's okay, because I like bein' myself"


[Edited on 18-9-2010 by peach]

Quote: Originally posted by psychokinetic

Peach, would a fridge pump be able to get to such a vacuum that spongebob squarepants would expand to fill a 20L jug?

Quote: Originally posted by aonomus

I think that while my pump vacuum is high, its useless for low boiling stuff unless I can cool my condenser down way below RT using some sort of refrigeration system (that is pretty hardcore).

I've been watching the rest of your youtube videos and love them. A lot of them are virtually identical to what I'm interested in or thinking of, the magnets in fingers, syringe pumps, arduino's, axel f.

Shame we don't live a bit closer.

In terms of the pressure problems, you can simply bleed a bit of atmosphere into the system at the intake of the pump to raise the pressure.

I'm working on some things you may be interested in. I stuck a pressure and vacuum gauge on a 60ml BD Plastipak and measured a peak of 100psi+ when squeezing it with my hands, before the tiny length of vacuum hose I was using to connect them with started to balloon out. The pressure sits still for a long while, but is slowly dropping on the one I'm leaving clamped (it looks like it's leaking round the seal). I'll report back on where it finally stays put and may try solvents (which would encourage the seal to swell and block the pressure in better).

Sticking the vacuum gauge on there, it can drop the pressure by 9/10th's of an ATM with one pull of the plunger. I don't have a one way valve handy to try lots of pulls.

I'm wondering about pumping solvent, noble gases, reactive gases, circulating jackets, running higher pressure reactions, arranging three in a rotary setup and driving them with a geared microwave turntable motor, using them for flash chromatography and so on. All of which I'm sure you could apply your Arduino talents to or produce something useful with. E.g. use a length of black iron pipe & some caps to hold the syringe and force the plunger down with a stepper. I'm still having major problems getting into microcontrollers. I've tried, multiple times, and am now reading John's book on the MSP430, since I have one. I am worried about picking up an Arduino in case it teaches me to program in a manner too reliant on the compiler and someone else's work; which may scupper my plans down line.

I also put the gauge on a fridge compressor and read 600 - 800psi, mainly towards 800. The nomograph result I got for redistilling some 250C oil under vacuum, run in reverse, would suggest something like 550psi. Either way, it's worryingly high and I won't stand in the same room as it at this early stage of things (that's saying something considering what else I get up to, minus gloves, masks or goggles).

Quote: Originally posted by Magpie

I'm confused as to how you measured your vacuum. If using water I would start out with the water as cold as possible, letting it warm to room temperature slowly under your pump's vacuum. When the water starts to boil I would shut down the pump and measure the water temperature. Then go to a vapor pressure table or graph (vapor pressure vs temperature) and look up the vapor pressure corresponding to the temperature you measured. This vapor pressure is the pressure of your vacuum chamber. I don't see any need for a nomograph. If this is what you did, then I just didn't understand.

Quote: Originally posted by psychokinetic

Peach, would a fridge pump be able to get to such a vacuum that spongebob squarepants would expand to fill a 20L jug? Would he survive? Would he go back to his normal shape, or be forever known as Spongebob Flaccidpants?

Quote: Originally posted by spong

Yeah hopefully it would work without it, which pins should I wire the mains power onto? There's three, one of them would be the starting coil wouldn't it? I might have a rummage around that dumpster again on Monday and see if I can pull the cap out, there was some glassware in it too but most of it was broken. I tried testing my pump out with the water boiling method, 34C, 50mbar... Not too good.

I might have missed something, but how did you test it if it's not wired to anything? Unless you mean a different pump?

Those pins shouldn't be wired direct to the mains. The pump will almost certainly sit there going "Hummmmm" if you do, then it'll burn out and need to go in the bin.

You need to push that starting relay back on there.

Quote: Originally posted by watson.fawkes

I believe that Mr. Squarepants is an open-cell foam, and therefore no.

Quote: Originally posted by starch

peach thank you for this amazing thread you have really cleared a lot of questions up for me thank you very much indeed take care

No, it's seriously fine, continue telling me how nice I am. Presents, kisses and monetary donations are especially welcome.

The overheating thing, anomonus has demonstrated, is a big divide between the US and Europe.

In the US, a lot of guys seem to be using those rotary things from AC units. And his was absolutely roasting in no time.

The piston kind, the little humming black boxes in the backs of kitchen fridges / freezers, they don't seem to have any major heat issues. I've never used a fan on one, and run them for half a day solid, or more. They do get fresh cup of tea hot, but a fan from a computer fan will sort that if you're worried about it.

I have now gone fridge pump cracky, and have been coming up with all kinds of ideas I want to try with them (decent vacuum, 500psi+ positive pressures and they're free, there's lot of things they could potentially do). So there may be more unusual things on the way. I would have put some more up by now, but an item I need has mysteriously gone missing (that kind of missing where you put it down, turn around, turn back and it's gone for two weeks).

I was hoping there'd be some easy way to drop the temperatures even more, but the laboratory super freezers (I've now discovered) are genuinely quite complicated. They use one pump to cool the other. But that's not still out of the question, since I haven't read into it enough (e.g. stick one freezer inside another).

I've also been looking at how syringes perform, the big, wash your horse's nasty cut out, disposable kind. They can be used to generate reactive gases for tests or producing small batches of things. And they don't pop until at least over 100psi.

I think they're polypropylene, which is fine around cyclohexane. One of the key solvents for chromatography. Combined with a suitable polar solvent, they could make a very cheap flash chromatography setup. The current industry innovation in flash is mid pressure, ~150psi. Some domain as the syringes can manage.

Feel free to ask away. The reason I started this thread was to finally clump all the fridge questions in one place, get them answered and move on. Because every forum I've ever visited about science is stuck in neutral with the fridge pump questions.

[Edited on 26-9-2010 by peach]

Quote: Originally posted by peach

(that kind of missing where you put it down, turn around, turn back and it's gone for two weeks).

Quote: Originally posted by hissingnoise

Oh, right - the kind with two outcomes - 1) wife or SO finds missing item after search lasting 3 microseconds and 2) wife busy (cooking or shopping or whatever), so distressed hobbyist freaks out using foul language in loud voice thereby pissing off said wife or SO; peace only being restored in wee, small hours. Know them well. . .

If I was going to be pessimistic, I might suggest things like that 'go missing' when they're tidying up.

I think I've mentioned this before, but I've never had any fire problems despite leaving solvent soaked cloths all over the place, it in the sink and on me, whilst I sit around smoking or using a blow torch.

A 'fee-male' cat entered the scene not long ago and, for the first time in around a decade plus, within literally 30s, whooompf.... the surface is on fire, the drain is on fire.... she's shitting her pants.

Reason, attempting to light a candle and then place it next to the used cloths.

When I was in my teens, I was trying to clean bia-tch-umen tar off the bathroom floor at one point, which had been used to stick the tiles down in the days of old. I was sat, with the door closed, with the entire floor drenched in petrol and the can next to me. I turned around at one point to discover, yes... ANOTHER CANDLE had been light nearby. My face was going numb by that point (after hours of the addictive petrol smell), yet even I was still coherent enough to realize that might be a poor choice of time to light a candle, in the middle of the day.

Not long after, that incident, I came home to discover my mum had set the curtains on fire (and they were still on fire). Cause.... candle.

Girls + letting THEM light the candles.... bad, bad, combination. That's probably why their hearts melt when they discover a pro has done it for them.

Star Trek votes pro for domestic violence (upskirt cam);




Anyway, I'm STILL looking for this thing.

I always thought, if God does exist, I'm probably getting stuck in limbo for a few centuries when I die. Where I'll eek out my time coming back as a ghost, moving pens, pencils and other stationary items when they're needed.

"It looks like you're writing a letter, so I'm taking this pen"



[Edited on 26-9-2010 by peach]

How about oil from the output? Were you saying in one of the videos that you weren't seeing any?

I just powered up one of the pumps that I've scavenged (it's a piston type fridge pump; looks like what you're using). I'm seeing something from the out tube. You can feel a faint something on your fingers in the output stream, and a piece of tissue shows something after a few seconds. Unless that might be residual traces of refrigerant coming out the oil? It's only been run out of the fridge for an hour or so. I do have the tube aloft, above the pump.

I anticipated getting some kind of a filter on that if the pump is otherwise usable.

Got a kick out your elastic band ball. I cadge elastics directly from our postie regularly. He's a bit more 'enviromentally conscious'; many of them just drop them on the pavement.



ok, cool, got the snap up; my nice elastic bands, oh, and a pump. I've not been running it like this, I jerry rigged the cooling hose after all the alarmist overheating info that I'd read (or misunderstood)

as shown, the kitchen/lab tool migration has been eliminated by merging the two locations

I'm in western Canada, not far from where Fraser empties into the Strait of Georgia.

I'll take your suggestion with the cup, see what happens.

As far as the pump, I'd be surprised if it's not the piston type. Everything that I've seen so far, without doing pump surgery, indicates: piston. It's dead quiet. Like you say, you could miss that it's even running.

Not so much concerned about losing oil as breathing it, or air-brushing the room with it

You're a psychic ! I did work crating and/or palleting boilers and furnaces for a (brief) time. At that time I don't think that saran wrap type products had made their appearance in the shipping department. In an unguarded moment the air powered wood stapler came to rest on my boot and drove a 2 inch staple through one of my toes, straddling the bone. Ahhhh, happy memories!

Silicon seals will work fine at distillation pressures, don't stress. I've checked it, they do. So will epoxy glue. You just need to be sure it's not on a connection that'll be routinely knocked around and bent.

As I show in one of the videos, I can put my hand over the intake on the rotary pump (below 1mbar) and it's fine (I've seen a guy doing it with a 40CFM rotary with a roots blower on top of that). You can't judge the vacuum that way as an absolute vacuum is only ever -atmospheric, not -200bar. You'd have a far, far worse time trying to inhale off a freshly filled cylinder of nitrogen. About 200x worse.

Neither is a $15 auto guage going to get even close to accurate on rotary pressures. I have a fairly expensive mechanical gauge that you see in some of those videos, it still can't deal with it.

This is where vacuums start getting expensive. Sub 100mbar and down below 1mbar, you need expensive gauges. Look for mechanicals that start at 100mbar (1/10th atmospheric) if you're going the mechanical route, not 1000mbar (atmospheric). 1/10th atm is where volatiles start boiling around room temperature, and where high BP oils boil at water bath temperatures (you should be using a foil TP, not baths).

Also in those videos, you see the fridge pumps and aspirators are right down near the outer space line compared atmospheric pressure. It's a massive leap for the gauge to make, trying to read accurately in the last 1% of it's range.

Physics labs will usually have quite a few different, very expensive, gauges on a chamber, involving things like Iridium (a platinum group metal). And they'll break if switched on at the wrong time.

Auto gauges are designed to deal with atmosphere to the turbo pressures. And a turbo in a car is no where near the turbo in a physics lab.

This is why I go on a big anti-rotary campaign a lot of the time. Under those pressures, the solvents boil too low to capture, the pumps costs a lot, maintaining them costs a lot and the gauges are expensive. And using them for a solvent boil off is the wrong idea in the first place if you don't have liquid nitrogen in the condenser. Even dry ice isn't cold enough for solvents under rotary pressures. Then there are yet more problems. Liquid oxygen collecting in the condenser. Storing the cryogens, pumping them, the hazmat delivery on the cyrogens, the training needed to handle them. The cost rockets up into the thousands (new dual stage edwards $2k? controller $1k? trap $200+?, cryogenics $xlotsmorex, special vacuum taps $more). For what? Lots of TRULY unnecessary, counter productive zeros? Solvent in the pump? Even curly arrow has fallen into the trap, and other chem bloggers, of thinking a rotovap should go on the latest rotary pump. No. Even Buchi says no, and then charge you $1-2.5k for their pump, which works at fridge pump / cold aspirator pressures.

Talking about pressures, here's my thought for the day. Even in space, the maximum pressure differential is only 1 atm, 14psi. At the bottom of the Mariana trench in the sea, the pressure is about 16,000 psi with humans inside. That's not messing around!

Jelli-fishies in the Mariana trench (it's 6-7 miles down! and pitch black, at 16kpsi).


[Edited on 29-9-2010 by peach]

Quote: Originally posted by peach

Provided they're all in one thread from now on, that's cool also. It was having the splattered all over the forum and being repeated that wasn't helping.

Quote: Originally posted by peach

It was having the splattered all over the forum and being repeated that wasn't helping.

Quote: Originally posted by peach

being repeated that wasn't helping.

Quote: Originally posted by peach

being repeated

Quote: Originally posted by peach

repeated.

A long spring, or anything like that will do as well. In the UK PVC tubing is stiff enough it'll work, because it's quite a bit tougher when it's cold.

You can use anything to control the vacuum so long as it creates a controllable hole.

The quirky results thing, sometimes if I leave some of them on for hours, the pressure starts bouncing up and down a bit, which bumps the flask and the temperatures. I haven't tried it yet, but I suspect putting two in series will get rid of that.

The precise pressure isn't super important a lot of the time. If you're distilling something and you know it has a big percentage of some splittable component in it, you'll see it appear on the thermometer at some temperature. So long as the temperature sits still, it's doing what you want it to, distilling it without much oxygen around and at a significantly lower temperature.

Knowing the precise pressure is only important when you're trying to identify something using the boiling point as a piece of evidence. If you already know what it is and that there's lots there, that's not a problem.

Filtering things, the pressure is easily low enough. If it won't filter on a fridge pump, it probably won't do much better on a lab pump.

One of the main problems with filtering things as the paper or sinter starts to clog is that the pressure in the flask and around the filter drops really low. The solvent then boils and cools it's self to a near solid. So the filter element literally freezes up and zero will go through. That could actually happen worse with a lab pump, as the lower pressure isn't going to help pull things through much, but it will boil the solvents way below zero.

I've had some filtrations where it'll literally all day or days to get them through. The solution isn't high vacuum;

Wrap a super dry, fluffy towel around the vacuum flask, preferably all precooled. When the solvent tries to boil, it will rapidly stop as it can't pick up anymore heat to do so.

Stick a second hand, ultra cheap, adjustable hot air gun near the filter element and stem and gently warm them up.

That can get those same filtrations done in minutes.

If that fails, fire up the stirring. The very CAREFUL stirring.

The filter cake.

That is the last resort. If it's a paper filter, there's a good chance you'll rip the paper and dump your thus far hard won cake into the flask. Much swearing will follow. If it's a glass sinter, you'll damage the sinter and make cleaning it a whore of a job. Lots more swearing and possible alcohol problems as you deal with buying another funnel.

The solvent solidification thing is a bit unexpected and it took me a minute to work out what was going on when I first saw it happen. But it can stop a filtration dead, so there won't be a single drop coming through.

It starts happening when you're dealing with very fine, packable cakes and volatile solvents. Precipitates with a particle size around 10um or below are a good bet it's on the way.

It's also more prone to happen with sinter / frit funnels, because the cake will clog the entire surface the vacuum is trying to suck through, and effectively produce a stopper in the top of the flask. Solvent boils off in the sinter, the rest coming through solidifies. The problem snowballs too, well, iceballs. It starts, clogs a bit, makes it's self worse, cools more, clogs more, cools more and so on until it's solid.

Pretty much anything that forms visible grains or crystals, or only has a tiny amount of fine muck in it, will be fine though.

[Edited on 6-10-2010 by peach]

With the inclusion of a drip tray, you could use the surplus to deep fry. I bet deep friend, freeze dried product is mighty greasy. All the better for my Atkins diet.

thanks for the replies

that rotovap thing sounds cool

what part of the fridge do I salvage that from?

night

edit ooops, I was negligent when it came to reading through the beginning of this thread (I skipped right to the videos). Your compressor is a different type than mine. Mine is labeled R12 and if I'm understanding correctly uses a different oil. So these considerations don't apply. Please correct me if I'm wrong in this. Again, thanks and good night ~food edit

[Edited on 6-10-2010 by food]

Precisely.

And using an air aspirator is dead on, as the BP of most volatiles approachs 20C as the pressure get's to around 50mBar. Which is a warm water aspirator, fridge or diaphragm pump.

I just did a search for the RV10 videos on google and the first link I clicked, World News, had my videos on there. This is my 15 minutes of fame then, complete with a 6 year old girl's headband on.

That IKA is not as expensive as I was expecting it to be with all those motors and displays on there, but at $4k it's still a fair chunk of cash that would need you to be doing some intensive boil offs for it to be worth it.

I'm glad your guys at work have figured out that theirs will actually mong out if connected to a rotary or high vacuum line. As the majority of web based things I've read have been the opposite. Going straight onto some monster pump and then wondering why it keeps bumping like a jiggly girls ass on MTV, or why the pump oil is constantly filling with solvent.

I'd buy one for at home use if I could get hold of a rotovap cheap, but I'd spend money on more normal glass first (more beakers, stirring rods, weighing boats, blah blah blah). A rotovap is, of coarse, useless if you have nothing needing it's services. And a lot of the glass that produces things that then go into the rotovap will also evaporate solvents very quickly.

It's all down to evaporation speed alone. So the savings in evaporation time have to balance out the massive capital cost for it to be worthwhile. I can empty a 500ml flask in not a lot of time just with a stir bar and hotplate. In a uni lab were you have 30 guys all trying to run things through, the extra minute or two is important. At home, hmmmmmmm, questionable at $4k.

I saw a funny TV show from the US, a cookery one. Expecting to see hand whisks and folding spoons, to my surprise, he had a brand new Buchi sat on the worktop.

That's not an ice cream machine.

I know they do food science at school, but that's taking things a bit far.

compressor oil

Quote: Originally posted by food

The older is labelled R12, which was the older 'bad' refrigerant. The newer is labelled R134a, the new refrigerant. The older model will use mineral oil, the newer one will most likely use a synthetic oil.

I got my new fridge pump working I ended up cutting off the extra blue wire and wiring the white and brown together. It gets down to 40mbar using water to calculate it, I then put this one and my old one from the shop fridge in series, they quickly boiled water at room temp and at 13C, giving 15mbar using an online calculator. I knew they could do better than that with more time so I tried clove oil, it boiled at 64C, assuming a boiling point of 255C the calculator gave a pressure of 4mbar
Provided eugenol/clove oils heat of vaporization was somewhere around 43KJ/mol (does anyone have this data by any chance?) and the clove oil has a boiling point somewhere between 248-260 then that's a pretty good vacuum
Thanks for the help/ideas Peach, it didn't need a capacitor after all that

Silicone Compressor Oil?

Recently scavenged a compressor pump from an R134a shorty fridge that runs nearly silently so i'm guessing its piston based. The factory lubricant is most likely an ester oil of some sort to be compatible with R134a and would not do too well in wet filtering or distillation applications. I have relatively cheap access to silicone oil , and am wondering if any of you have had experience with replacing factory lube with this silicone oil in fridge pumps. A quick google search suggests silicone oil is preferred for vacuum applications due to low out gassing. Any incompatibilities if there is still a bit of the factory lube left in and mixed with the new silicone oil? Any suggestions as to removing the factory oil from the sealed can? Thanks

@Peach many thanks for all the info and splendid videos!



[Edited on 19-11-2010 by trichosaurus]

[Edited on 19-11-2010 by trichosaurus]

food here .. with some feedback. I'd been wondering about the oil making it out of the .. output end. I picked up a basic filter from a place supplying parts for air tools etc. It was CAN $10. Very basic. When I searched I discovered a wide range of filters for various devices that could be presed into service scrubbing the compressor outlet. ie. This site may be of interest to other members, http://www.mcmaster.com .

Budget and convenience moved me to pick up this item.



I haven't used the pump much, but it seems to be doing 'something'. There's a valve, lower right in snap, to drain off captured oil. That's about it. I mounted it on the copper outlet tube with a section of plastic hose for gasket.

The pump is very quiet. I forgot to power it down and it was on for around 40 mins or so just inhaling away. After that, depressing the valve on the filter gave a little gush of oil. So, yes, it is doing something.

In anticipation of longer runs I've upgraded the cooling system. From latex bondage spirals (earlier snap) to a cooling unit scarfed from a computer. It's like an auto radiator with a pair of fans; needs cold water and 12VDC. Also seems to work and to do 'something'. Sucks down the temperature on the pump housing.




I'm expecting good things from this.

I think you guys are wasting your time using these pumps unless you are looking for a distillation setup or a roughing pump. 40 mb = 30,000 microns if I did the math right. For a decent laser you need to get down to say 60 microns or lower. The link below is only a hundred bucks, 126 with shipping, and gets down to 37.5 microns. Assuming you blow half this trying to get a vacuum system built out of a refrigerator you are not gaining much. Double that amount and you have a brand new pump which will do very well. Myself I look at the pumps you are using as roughing pumps at best. I used to use one for this reason just to save on my expensive pumps, never turning them on until the roughing pump has gone as far as it can. Later I found a surplus rotary in need of a rebuild so it only gets to 150 or so microns as my roughing pump, replacing my old refrigeration compressor pump. Just seems to me the pump below is a better use of your time.

http://cgi.ebay.com/3CFM-REFRIGERATION-AIR-CONDITIONING-VACU...

I have a question for someone. What kind of glue sticks to plexiglass and seals down to say one micron. My vacuum station gets down to near 60 microns, and my big pump takes it down to just under a micron. I posted pics of the station elsewhere. I took it out of storage, meaning to build my own CO2 laser for years but never getting around to it until recently. Anyway I was down to 11 microns and heard a crack, the Plexiglas is half inch thick but I fear it is gone now. Imagine a 14 inch square surface with inlet in center. Glued to the Plexiglas surface is a neoprene disc which the bell jar sits on. My fear was after seeing the crack that while the bell could hold a micron, the Plexiglas could suddenly implode upwards into the bell jar. So I set out to rebuild the entire top deciding to tear it apart and add a metal plate under a new sheet of 1 inch Plexiglas to eliminate the possibility of implosion. The worst that could happen now is the metal starts to pull up cracking the Plexiglas surface, yes wrecking the top forcing another rebuild but eliminating the implosion risk.

When I first built the station 60 microns was the best I could do, by design I had already added a port to connect a better pump but until recently 60 microns was my limit. I know the Plexiglas - epoxy - neoprene works as I have pumped the bell jar to 60 microns, shut the valve and seen it hold there all day, implying the epoxy was sealing to the Plexiglas well.

I used epoxy to glue the disc to the Plexiglas surface. What appears to be happening now is around 11 microns the disc starts to swell upward and leaking begins. As far as I can tell the epoxy does not 'wet' the Plexiglas. Maybe 'wet' is a poor term, by this I mean the air seems to be leaking between the hard epoxy and the Plexiglas surface. The epoxy is rock solid and firmly stuck to the Plexiglas, yet this is the only route I can find for air to leak in. I would have thought the interface between epoxy and Plexiglas would be thin to a very microscopic degree yet it appears air is actually finding it's way under the epoxy. So my question is, considering out gassing and other important parameters, what type of glue does anyone think would be good to glue the disc to the Plexiglas surface?

If you study the link below you will see the piston pump is the poorest vacuum of any on the chart.

http://www.highvacpumps.com/engineering/pressure.html


As I hate reading these pages to see useless dead links I will swipe their image and leave it here, just in case the link ever goes dead.



[Edited on 12-19-2010 by IrC]

Quote: Originally posted by aonomus

I would argue the point that these setups are 'useless'. These are good for a roughing pump and/or distillation/convenience vacuum filtration pump there is nothing as cheap and sacrificial. Not everyone has access to cheap pumps from Harbor Freight either. I'd agree that a $75-100 rotary from Harbor Freight is essentially sacrificial, but if you can't get your hands on one.... For physics experiments however, I agree that these are mostly useless. Regarding your cracked plexiglass: A thought comes to mind. Pull a *light* vacuum and drip DCM into the crack, allowing the vacuum to suck it in. Let it work its way in and then leave it to dry, the solvent weld will be better than nothing. I think that if anything, the distortion in the plexiglass disc is causing your leaks. Perhaps if your plexiglass is clear underneeth (ie: no steel backing plate), you could drip water into any possible spots where leaks could be occuring and let the liquid show you where leaks occur visually.

Quote: Originally posted by Contrabasso

Looking at a fridge pump as a PRESSURE pump, has anyone any real world experience. I have a task that needs 100psi in very little quantity. Quieter would be better so not an ordinary paint spray compressor please

I recently bought a fridge compressor from eBay (I know I could have got one for free, but this was £2.40 brand new). I plan to use it from time to time for filtrations and perhaps reduced pressure distillations, if it has the oomph.

I've done some research online, watched a number of of the videos in this thread and read through some posts, all of which has been very helpful. However, I'm having trouble with something 100x more basic than most of what has been discussed - how do I actually wire it up?

http://chisko.com/prodotto-146273/COMPRESSORE-perfor-R600a-G... - the most detailed information on the pump I can find (basically what it says is that it's a 1/10HP pump for use with R600a refrigerant)

Here's a picture of the pump:


Don't know why, but I find it extremely aesthetically pleasing. Probably the smooth black egg-like shape

Here's a picture of the electrical connections:



So my questions are:
Can I just wire it up to a 230v mains outlet? (The label on the side suggests that I can, but I want to double check)
If yes, where do I attach each wire?
If no, what other bits and bobs do I need to get it going?


A couple of other things:
The 'service' outlet - should I just ignore it?
Do I need a manometer?
How vital is an air bleed?

Thanks for the help,

Mossy.

[Edited on 5-2-2011 by Mossydie]

Quote: Originally posted by Mossydie

Help is really appreciated - I'm way out of my depth here.

USE A LOCAL CIRCUIT BREAKER!

{edit}I have also just noticed a mistake I am making in this post. That is not a starting relay, it's the overload switch

Awww..... it still has the caps on from the factory, the innocence!

£2.30 isn't bad at all. If you can get one that cheap, may as well save yourself the hassle of possibly get bitched at by the bin guys and ending up with a dead one.

I'll post some photos of the ones I have so you can compare yours with mine, it's always nice (to me) to know what's happening INSIDE a black box or WHY something works. In fact, I like it so much, I'll often break things in working it out, or otherwise retard my life (e.g. revising) in wanting to understand it rather than just memorise it.

The compressors tend to have lots of connections on them because all the wiring in the fridge, for the light, door switch, temperature control and so on is done from the side of the compressor; lots of the connections are simply repeats of other ones, another point to connect the mains powered bulb to for example. The guys wiring the fridges up at the factory have all the wiring terminated in push on spade connections, so they can jam them onto the connections as yet another fridge goes past.

I suspect the layout for this one is as follows;

Brown is live, the fused wire from the plug.

Blue is the neutral. Those visible strips of metal in the circles are all two pieces, but each piece is one strip, so all the connections on that strip will be for live or neutral respectively.

That alone should be enough to get the pump going, if you wire a fused plug to those two. The compressors are low wattage, so use a low value fuse like a 3 amp. That way, the fuse will burn out before the compressor if it ever gets stuck for some reason. It also means you won't roast yourself so badly if you get stuck to it, in a bad way.

This isn't necessary, but for the sake of understanding what's likely going on, I'll add it anyway - others might find it useful working out different layouts

The bit circled in green and yellow, I think may be the earthing points. Obviously, the can of the compressor is one big metal lump. There are also circuits inside the fridge that are at mains voltage when it's working normally, and damp, and metal tubing people can poke knives into when defrosting. You can check if this bit is the earthing block, as it will feature some form of direct metal to metal connection with the case of the compressor.

I have put two red arrows points to those spare push on terminals. I think those are likely connected to the strips beside them, but the connection is hidden under the plastic. If you have a multimeter, or can borrow one, try setting it to Ohms and touching one probe against the terminal and the other against the strip beside it. For example, use one probe on arrow 1, and the other on the bit circled in brown. If it reads a low value (probably zero), it's all the same piece of metal. But there are TWO separate pieces in total, one for the live and the other for neutral - with a 230Vac difference between them. If you put your finger between the bit circled in blue and the bit in brown, you'll get a nasty shock.

The bit in orange is pointing to the starting relay. This is basically THE ONLY electronics needed to power the pump up. The relay is inside that little black circle with the adjusting screw on it. Inside, it's two bits of sprung metal. The pump needs a push to get it running. There is an extra winding on the motor coil inside. When power is first applied, that coil runs to get the pump going. Then the relay switches it off. It happens so extremely quickly, the start coil only needs to give the little piston a flick - like starting a prop plane engine. Don't mess around with the adjusting screw or try to take the black circle apart, it'll probably die in the process, and finding replacements is tricky enough you may as well dump the compressor and get a new one. The relays are basically all the same thing for every compressor, and even feature similar pins, but they're moulded into different shapes and won't physically fit into the different mouldings on other brands.

You can actually pull this whole white assembly off, and the black circle, without breaking the compressor. Just underneath that black circle, there are three pins sticking out the side of the casing - they look like tac nails. They're the ends of the wires on the motor inside, and they're welded or brazed to the can from the inside, to make the seal gas tight. The starting relay, and this white bit full of other connections, just pushes onto those. There are three pins because two of them are for the motor and the third is for the extra starting winding, which the relay flicks on and then off when the compressor is plugged in.

The purple bit looks like a bridge connection for something to do with the relay. If it's one strip of metal with no connections on it, ignore it.

The ENTIRE area in teal is a serious shock hazard, as there are exposed mains connections and most of the compressor is metallic. You need to put the cover back on, insulate some other way or be extremely careful when moving it. Given how much exposed metal there is, and what you'll be using it for, it is best to insulate it, as you can easily spill or splash things on it. Also make sure the connections are either pushed on so hard they take a lot of effort to get back off, or solder them on. I have had some of these where the connections where loose enough they'd fall off. The main risk there isn't sparks and explosions, it's you thinking the power has gone off and poking around with it, only for it to zap you.

When I first took one out of a fridge myself, alone and in my early teens, I didn't bother a circuit breaker or putting the cover back on. The pump went silent, as normal, once it'd pulled a vacuum in something. I had left it going for hours and forgotten it was on, then picked it up. It wasn't until I had a firm gasp of it with both hands, that one of my fingers touched the exposed mains connection, and I took a serious hit of joo-joo juice through the chest (as my other hand was on the can). I wouldn't want someone else to repeat that.

GIMP, unlike photoshop, is free.



Here's an example of a pump minus the extra connections. The only thing left is the starting relay (contactor), the live and the neutral. There should really be an earth on there too. Note that the relay is exactly the same thing, and in the same place as yours, but a different shape. This is also the pump that the factory fittings fall off if I so much as turn the casing; they need crimping on better than that.





The actual pump it's self, which sits on springs inside the casing. The motor is fairly big, and VERY quiet, so you could score a decent motor from one of these for another project if you like. I believe it is a brushless induction motor. Brushless means that there are no points for sparks to come from. This is important as a lot of refrigerants are highly flammable gases, like pentane. Brushes also wear down, so not having them significantly increases the motor's need for maintenance to essentially zero. It will almost certainly run without the starting relay if it's not connected to the piston (which is where all the friction is). The motor's spindle has only one bearing surface, at the top, and I suspect it's simply a well bored, possibly honed, bit in the cast iron, not an actual ball bearing race. Despite this, the spindle spins with almost no force once the piston is removed. The spindle is hollow, and dips down into the oil sitting beneath the motor in the casing. As it spins, oil is pulled up through it's centre and bleeds out through the top to oil the bearing surface, cam and piston; kind of how it does in a car if that makes it easier to understand.

The clunking you hear when shaking a fridge pump is this bit wobbling around inside.



This is the top of the motor. The entire pump is made up of very few cast iron, or possibly steel, components. In fact, there is very little inside there bar iron / steel and the enammeled magnet wire. At the top of the spindle is a little eccentric cam. This drives the equally tiny piston back and forth; it's about the size of a Rolo (for the UK guys ). The square block over the piston, with the cam on it, is where the oil comes up to lubricate it all. The oil doesn't spray out like a hose jet, it bleeds through.

The two dome shaped things towards the front are the points at which the compressed gas exits the piston chamber, via a length of thin copper tube brazed into the cap. I have been messing around with this one, that white PTFE tape is not usually there. Instead, the caps are sealed with little rings of what looks like resin soaked paper. I expect they are put on wet, and dry once tightened to seal the compressor up.

I am unsure why there are two domes. There has been two in every compressor I've opened, yet one of them is never actually connected to any tubing.

I can only assume there is a reason for it being there, because having the production line people screwing an extra cap on wastes time. And time is money. It may be used in different models, and this is a standard casting.



The gas returning from a fridge usually re-enters the pump head through a plastic scoop / nozzle on the front of the pump head. I've been gluing bits of copper tubing into the hole to try something with this one. The scoop is normally a piece of white plastic and looks like snorkel of some description; I suspect they're all made from polyethylene. It's worth noting that, when you use these as vacuum pumps, you will be connecting the vacuum hose to the connection where the gas usually comes back in. This is NEVER actually connected directly to the pump head it's self. The returning gas is usually used to help cool the motor, so it swirls around inside the casing before going back up the snorkel. This is not particularly important. You could argueably make the compressor even less prone to corrosion and explosions by making the connection directly, but I have run so many solvens through these I can't remember them all, and they're designed to have highly flammable things in them; things which are used as solvents in labs. It also doesn't matter so much if you plan to connect two in series, to increase the vacuum. It DOES matter if you plan to try putting two in series to create a high pressure compressor, as you will be pressurising the second compressors can to the outlet pressure of the first, which is over 500psi. BAD things may happen on doing that. With one compressor alone, it is a lot less dangerous as, if the compressor head pops, the flying bits will be caught by the metal casing, and the casing will be open to atmospheric pressure, so it can discharge pressure buildup. Also worth thinking about is that gas being compressed will be travelling over oil, which can ignite or explode in the presence of compressed oxygen.

Whilst the casings are thick steel, welded shut, their thickness may vary from model to model. Some pumps also feature dents in the casing for fitting a drip pan to the top, where condensation from inside the fridge collects and then evaporates back into the atmosphere over the warmth of the running pump. These varying thicknesses, none uniform shape and dents mean that the pressure holding capacity of each pump may be vastly different, adding another danger to running them in series for high pressure use.

I have not seen any signs of corrosion in these pumps, yet, that come ANYWHERE close to the levels I've seen inside used laboratory pumps. I suspect the lab pumps are suffering not just from moisture, but more likely the reactive gases being pulled through them. Either way, provided the corrosion is only on the outside of the pump head (which it universally is in my experience) it's not much of a problem. The outsides of the pump head can rust because the oil film drips back off them when the pump is switched off, whereas the chambers stay oiled. The outside is also more open to the atmosphere. And I suspect even people like Edwards are using the lowest grades of cast iron they can manage.

The 'magic' of the compressor happens just behind the plate that is bolted on at the front. There are thin strips of sprung metal that act as valves. When the piston moves forward, one closes and the other opens. When it moves back, vice versa. Without them, the compressor would do very little.

Again, the plate at the front appears to be bonded to the rest of the pump using some form of phenolic paper, which has been applied wet with glue. As it needs scraping off when the bolts are undone.

You can reseal the parts with vacuum grease if you take one to bits, as the paper seal will be ruined when it's forced open. There are actually very few points for the compressor to leak through.

One point someone has raised is that the valves are a likely candidate for what limits the compression ratio of the pump, that they don't seal perfectly. Indeed, there is no rubber seal in there, it's an oil film. I have tried replacing the oil with high vacuum grease, and it seemed to help.

So I am VERY interested to know what the pump might achieve if one added an extra, better quality, one way valve to the line on the outside. Perhaps this could give us our 1mBar pressure without having to open them up.

I will add it to the TO DO list. Just below, find a valve and afford a valve.



Here are the pins the motor makes it's connection to the outside world through. There is also an earth connection fixed directly to the casing at the same point on this one.



Here's another example. Remember that all three of those pins connect to the motor windings, none of the PINS are an earth.



This is the front of the pump with the plate and valves removed. You can see the remains of the washer I was talking about.



The smaller copper tube is the higher pressure outlet, and it is connected directly to the pump via one of those domes on the top, and brazed into place.

There is a wider bore copper tube there and there will always be two of these that don't connect to anything on the inside. This is so the factory can fill the pump with oil more easily. By having two wide tubes sticking into the side, there is no back pressure when they pump the oil in.

They then crimp and brazed one of them shut, as it's no longer needed - you will see it sticking out the side of pumps in the backs of fridges.

You can connect your vacuum line to either of these, as they both enter the pump in the same manner, through the casing and then nothing more. However, one of them will be connected to the rest of the fridge, and you'll need to cut through that to get the pump out, so you may as well use that one and leave the crimped one alone.

You can tell which line is which, our of the two connected, without opening the pump and before it is taken out, as the high pressure one will usually have an expansion bulb on it (which looks like a little CO2 vessel used in nitrous oxide and CO2 drinks fizzers).

Once it's out, you can tell just by switching the thing on and blocking one of them with your finger.

You can operate the pump with both the wider lines open to the atmosphere. You can drill endless holes in the casing if you like. But it WON'T produce a vacuum until all but one of them is blocked up again.

You can go even further, as I did above, and cut the casing open, provided you make a direct connect for the vacuum line to the pump head, as the casing is not longer providing the seal.

There are reasons for which you may want to cut the crimped tube open again. For example, to drain out the oil. There is no immediate need to do this, they work fine as they are.



This is the other side of the pins. They are brazed or welded to the casing, as all the connections are. The motor's leads connect here, and the relay sits on the other side.

There is another of those wider opening tubes, the line IS NOT connected to anything inside the pump and it is where the gas returns; the gas simply flows into the casing and up the snorkel on the pump head.

The amount of oil in there is roughly what you see in the photo, it's a about 150 to 250mls from memory, a puddle at the bottom.

Why drain the oil? If you, like I have, dump a lot of solvent through the pump, it may reduce the maximum vacuum it can achieve for a while, as the solvent will spend a long time evaporating off again. You can sort that by simply blocking the vacuum intake and leaving the pump running.

A more interesting possibility is, I have tried swapping the original oil for genuine vacuum pump oil, and seen the pressure decrease. It is likely the manufacturers are using higher vapour pressure oil because it's runnier, produces less resistance and flows into the gaps better, and because they don't need anything better.

As with the extra external valve, swapping the oil for genuine pump oil may be an easy modification that could drive these pumps down to the seriously handy level.

And again, I will attempt to investigate this with a more precise gauge. I have already tried it once. The only concern I have is that the pump does seem to run warmer, and sticking a computer fan over the top may become a good idea with thicker oils.

I have also tried cutting the cans open and coating the entire pump head in thick grease. It does work to reduce the pressure, but it is FAR too much effort and the grease needs continually putting back, by hand. So I rule that out as a useful, easy idea.



This is one of the dome caps, with the high pressure line still brazed on. You will sometimes find an expansion bulb / mist filter INSIDE the pump and connected to this line. I have shaken a few expansion bulbs and heard the rattling of what sounds like fine grains, which is why I suspect they are also functioning as mist filters in the newer models. And it may be an idea to leave the external expansion bulbs on the pump when you cut it out, for a spare exhaust filter in the deal.



You MUST use a breaker with this kind of thing. I know they usually seem to do sod all, but here you have large lumps of exposed metal, exposed mains connections, possibly loose connections, conductive salts and solutions around and you are likely not 100% sure of the wiring. The chances for a shock are very high.

Forgetting the shock problem, the breaker will also act to compensate for some of your mistakes. If you manage to wire the pump incorrectly, either this breaker or the mains breaker will flip when it detects a residual current or over current fault; which happens faaaaaar faster than a fuse can manage. You should only really consider fuses as a last line fire defence, as opposed to something that'll rapidly stop faults or shocks.

The response time of circuit breakers, and the mains ring they are feeding, is actually part of the Part P building code. The breaker has to be able to trip within a set time for a specific circuit or application, which corresponds to a specific quantity of energy being delivered to the person shorting it on the other end. They get picky enough about this that qualified electricians have to check the ring impedance (not simply it's resistance) to sign it off as safe.







[Edited on 6-2-2011 by peach]