would this work?

[BradC]

Originally Posted by nexsuperne

I take it that I have to pressurise the low and high side seperately? Or do I put the propane in at 70psi on the low side, and the compressor does the rest?

You would do well to read the Manifesto. AC_Hacker goes into a great deal of gory detail about how these things work, and how you might modify them. It's a very long read from end to end, but I assure you by the end you will have all the information and confidence you need to rip into it and make a masterpiece.

[nexsuperne]

I have got as far as page 10 on the manifesto....so I'll keep reading!

Thanks

[AC_Hacker]

Originally Posted by nexsuperne

I have got as far as page 10 on the manifesto....so I'll keep reading!

Thanks

Please pay special attention to all cautions and comments regarding R-290.

Among other things:

• Work outside
• Wear a face shield
• Wear gloves & other protective clothing (preferably non-synthetic)
• Do not work alone

BradC, if you have other safety comments, now is a good point to add them...

-AC_Hacker

[nexsuperne]

All safety points duly noted. I only want to build an ashp, not make a mistake and create a propane bomb.

I have been looking at another post for a dual compressor ashp. What size refrigerant to waterplate hx should I use for a single compressor 1 ton acu?

[BradC]

Originally Posted by AC_Hacker

Among other things:

• Work outside
• Wear a face shield
• Wear gloves & other protective clothing (preferably non-synthetic)
• Do not work alone

If I had to offer extra advice, I'd re-iterate point 2 about 4 times. Go down to the local safety shop and buy 2 pairs of safety glasses. Buy a tinted pair for in the sun work, and a clear pair for other times. Put them on and keep them on.

I work outside, but it's surprising how still air does not disperse Propane. I have a little box fan with a squirrel cage motor (most of them have this). It generates no sparks, and it helps disperse the gas quickly if I vent some (which I do quite a bit).

Propane that has been through a filter/drier loses 99% of its smell. It loses none of it's asphyxiation and skin irritation ability. It's not toxic to touch, just don't go bathing in the stuff, or breathing lots of it.

Really, if you treat it as any other flammable chemical (Alcohol, Petrol ...) and use a good whack of common sense (sadly lacking in todays litigious society) it's pretty hard to get hurt.

[AC_Hacker]

Originally Posted by nexsuperne

All safety points duly noted. I only want to build an ashp, not make a mistake and create a propane bomb.

I have been looking at another post for a dual compressor ashp. What size refrigerant to waterplate hx should I use for a single compressor 1 ton acu?

This should help.

-AC_Hacker

[nexsuperne]

I have a full face mask that I use for welding, and I have a fair bit of experience with propane, as I make woodburners from old gas bottles.

[nexsuperne]

The 1 ton ac unit I have is filled with r407c. Can I put r290 in it? I am trying to extract as much heat as possible from this setup. I am looking at a 30 plate refrigerant to water exchanger to replace the condenser hx. Is it possible to use compression fittings to change the pipework, as I am not able to braze?

[AC_Hacker]

Originally Posted by nexsuperne

The 1 ton ac unit I have is filled with r407c. Can I put r290 in it?

The first thing you need to research is lubricant compatibility.

I haven't worked with R407c, so I'm not sure. I can tell you from my experience with R-22 & R-290 that they both use mineral oil lubricant, so there is no compatibility issue there. So this is an issue you need to research.

Another thing is refrigerant characteristics.

Again, I don't know about R-407c, but from my experience with R-22 & R-290, they are repeatedly cited as being very similar. I also know that a lot of sxuccessful amateur work has been done with this change-over.If you look at a graph of the pressure - temperature chart for each refrigerant it is quite evident that they are both very similar.

The refrigerant characteristics will affect things like the metering device. The characteristics of R-22 and R-290 are so similar that the same cap tube can be used from one to the other and a useful, working unit can be fashioned in this way. Better performance can be had by custom sizing the cap tube to perfectly match the new refrigerant... possibly a hassle. If you use a TXV valve, which has an adjustable screw, the adjustment is very simple.

As you research these issues, you might consider that finding an R-22 unit that has the same size compressor that you want, may be a desirable option.

Originally Posted by nexsuperne

I am trying to extract as much heat as possible from this setup. I am looking at a 30 plate refrigerant to water exchanger to replace the condenser hx. Is it possible to use compression fittings to change the pipework, as I am not able to braze?

Regarding the HX, the most important aspect is the surface area of the HX that has refrigerant on one side and water on the other side. So the HX you are looking at has 30 plates... How big is each plate? if you multiply the area of each plate times the number of plates (actually the number of plates minus one), you will have total surface area.

On the forum entry, I listed several manufacturers that make plate-type heat exchangers. So you should try to find a plate exchanger that will work in a refrigerant-to-water application. They have sizing formulas or tables or charts that will indicate this. They probably refer to this as sizing tables or sizing chart, etc.

Regarding compression fittings, yes they can be used. The standard for the refrigeration industry is the flair fitting. These work pretty well. BradC uses them in his work.

I did make the mistake of using a pipe threaded HX with a brass flair fitting adapter. It turned out that the brass flair fitting adapter did not have tapered threads like the pipe thread, and even though I used tons of teflon tape, it still leaked... it leaked slowly, but it leaked.

Nothing beats brazed connection. They are strong and leak-proof (if they are done correctly) and vibration proof.

Brazing equipment is not so expensive and brazing technique is not so hard to learn.

Silver / Phosphor-Bronze brazing rod is expensive, but you don't need very much.

AC_Hacker

[nexsuperne]

The thing about the plate hx is that I have a differential temperature controller on the water circulator. If the temperature of the hx is 4C higher than the bottom of the thermal store, then the pump switches on. If I try to pull more heat than is available, then the pump will shut down.

Once I have tested this unit to see what maximum heat output is, then I will program the compressor to only switch on when it is of benefit to the heat input on the store.

I have modified the freeze and start up protection, so that it delays compressor start, and also stops the compressor when the evaporator is 2C, to allow for defrost. The original controller needed manual intervention to turn the power on, click onto 'cooling' mode. There was also the issue of the airtemp being below 16C, which stopped the compressor running. I got around that by putting a 2kohm resistor in the airtemp sensors place.

The R22 is listed on the BOC website in the same class as r407c, and they list 'care50' which is a propane/ethane mix. They also list 'care45' which is propene? (Not a spelling mistake). To avoid hacking the acu at the moment, I am going to insulate the condenser with 25mm solid pir insulation and the put an air to water exchanger inside the same box, as there is an air blower in this box. I know there will be slight losses,but the current condenser hx bends around a corner, so my original idea of bending the hx down into an insulated water tank wont be possible.