Fridge compressors?

[rtbcomp]

^^ sod all. Yes.

 

[eil]

How much air will a fridge compressor produce? Would you be better with an old belt drive compressor plodding away?

Depends on the size of the fridge though

 

[rtbcomp]

The bigger ones deliver (sod all) x 2

 

[the snooper]

years ago I had a more industrial type refrigeration compressor similar to this one and it moved very little air and was heavy

 

[Rig Pig]

They don't sound very promising!

 

[barracuda816]

^depends on use and if you would be ok with a large receiver

 

[rtbcomp]

A big receiver will only deliver air until it's empty and then take ages & ages to refill.

I had a few hundred litres and half a dozen compressors filling it using Economy 7, kept my office nice and warm. Was looking for a way to heat my water tank, but never got round to it.

 

[normspanners]

I did start to build a high pressure compressor and the last stage was going to be a large freezer compressor fed by a engine driven compressor the idea was to fill a 47 kilo propane to close to max pressure and that would run an air powered central heating pump, I designed and made from a brake chamber, the system was for a canal boat, it was totally silent, and would run all night on one charge of air.

 

[rtbcomp]

^^ that sounds interesting.

I fiddled around with the idea of using my compressors as a source of heat rather than compressed air. To generate the heat you still need to pressurise the air, so I'd use the stored potential energy to generate electricity. Sort of a combined heat & energy storage system. I ran mine at 150 psi and reckoned I got 2Kw of heat for about 1Kw of electricity.

There is a commercial system that stores energy by liquifying air, they reckon it was about 75% efficient, but I don't think they recovered the heat or coldness produced during the process.

 

[normspanners]

The pump I made would be close to 100% efficient i would say because it was the pressure that moved the water, on the other side of a diaphragm and a spring that reset it. so no air was wasted.
The principle was that it the engine would be run every day to charge batteries etc and help heat the water therefore the engine compressor would be running anyway, the engine pump would feed direct to the tank until 12bar ish, the fridge compressor inlet would be then fed by the engine pump to attain the extra pressure needed because fridge compressors can easily achieve 18 bar or more, to store the extra energy required rather than have space wasted by more tanks.
there would be no wasted power and the energy stored, does not diminish over time as batteries do etc.
The guy wanted air on board for his 'workshop', but then during the day the fridge compressor would run the air/water pump just off the amount it produced and that would run off the small output genny.

 

[oddbob]

I've recently finished putting this together (after it sitting in bits for over a year!).

The compressor was from a fridge freezer and restarts under pressure without a problem ...mind you, the cutout's only set to 100psi. I thought it best to add a fan, but, to be honest, it doesn't really need it as it only takes about 12mins to fill from empty and I rarely use more than a tank full at a time. The 25ltr tank was from a dead direct drive compressor.

I only really use it for airbrushes, but it will run a small gravity fed touch up gun for a reasonable length of time before the pump can't keep up.

The key thing in building one is to be sure you fit some kind of oil level indicator on the compressor, 'cause they do like to spit their oil into the tank!

 

[normspanners]

Nice setup but what might be better is the outlet from the compressor to go vert up in 22mm for as high as possible that will give the oil time to separate and drop back into the comp body so that when oil is spat out it can recycle.

 

[oddbob]

Nice setup but what might be better is the outlet from the compressor to go vert up in 22mm for as high as possible that will give the oil time to separate and drop back into the comp body so that when oil is spat out it can recycle.

Now why didn't I think of that ...I'll give it a try.

 

[oddbob]

I did consider putting a separater on the outlet, but didn't get around to it.

 

[normspanners]

Ha I ask of myself sometimes, the opposite -----WHY DID I THINK OF THAT !!

 

[monkeymark]

I've recently finished putting this together (after it sitting in bits for over a year!).

The compressor was from a fridge freezer and restarts under pressure without a problem ...mind you, the cutout's only set to 100psi. I thought it best to add a fan, but, to be honest, it doesn't really need it as it only takes about 12mins to fill from empty and I rarely use more than a tank full at a time. The 25ltr tank was from a dead direct drive compressor.

I only really use it for airbrushes, but it will run a small gravity fed touch up gun for a reasonable length of time before the pump can't keep up.

The key thing in building one is to be sure you fit some kind of oil level indicator on the compressor, 'cause they do like to spit their oil into the tank!

That's very good. With regards to the oil level, how did you go about that? The bambi one I have on loan has a sight glass in the side about 1/5 from the bottom. Not sure how easy a compressor would be to open to check clearance before drilling.

 

[rtbcomp]

.

That's very good. With regards to the oil level, how did you go about that? The bambi one I have on loan has a sight glass in the side about 1/5 from the bottom. Not sure how easy a compressor would be to open to check clearance before drilling.

Have look at that link I posted earlier, you have to grind away the lip between the top and the body of the unit. Getting it oiltight afterwards is a nightmare!

I considered removing all my pumps from their cases and installing them in a common sump.

 

[oddbob]

That's very good. With regards to the oil level, how did you go about that? The bambi one I have on loan has a sight glass in the side about 1/5 from the bottom. Not sure how easy a compressor would be to open to check clearance before drilling.

It's quite common (if you look at Youtube) for people to cut the top off at the seam with a grinder/slitting disk to get at the inside, but I didn't fancy that ...thought there was too much risk of badly contaminating everything, plus you've then got the hassle of fixing the top back on in a watertight way (the compressor sprays the oil around the inside whilst running). What I ended up doing was drilling a hole with a small diamond core drill (the type you'd use for glass), so as not to create any swarf and avoid breaking through in a savage way, also drilling upwards, without draining the oil first, so that when I broke through the oil gushed out taking any crap with it. I then gingerly tapped the hole (M8 if I remember correctly) from underneath again and flushed it, without moving it, by pouring white spirit into the air intake pipe (which just goes into the casing). I then screwed and soldered in a cobbled together brass fitting to take a length of clear hose.

edit... looks like I've repeated some of what rtbcomp has said there!

 

[rtbcomp]

By grinding the lip you avoid getting stuff inside. I tried sealing the joint with silicone gasket and using a large Jubilee clip to hold it in place, but it still leaked.

 

[oddbob]

By grinding the lip you avoid getting stuff inside. I tried sealing the joint with silicone gasket and using a large Jubilee clip to hold it in place, but it still leaked.

Bambis use a sort of profiled jubilee clip don't they? ...wonder if they sell them as spares?