The Homemade Heat Pump Manifesto - Page 114

Vlad · 02-23-12, 11:28 PM

Add my 2 Window A/C's with Cap tubes, and a 7KW reverse cycle ducted heat pump that originally had a fixed piston orifice and now has an EEV.

Quote:

Originally Posted by BradC

The properties of R290 are so compatible with those of R22 that it's almost always a direct swap. Certainly charging critically charged systems can be a bit fussy, and yes superheat is important, but it's by no means impossible for the DIY hacker.

The problem with R290 is nobody(I mean big guys) want to promote it because it puts "environmental" BS in danger. Also it is so cheap, then they can't justify 10-20$ per lb price.

For DIY it is almost perfect solution, but with limitations. Like for indoor use legal charge in Canada must be less then 350 gram. In the US a have no idea.

Vlad · 02-23-12, 11:46 PM

What I found about R290 is bits and pieces here and there. There is no even an accepted name for this refrigerant. They are R22a, R290, Propane, all kinds of "greens..." and "enviro..." etc. Also there is a bunch of blends of propane and butane.

The technical details are also differ from site to site. If we could share our own experience and known info this would help to summarize list of properties.

What I found (again some info can be controversial) is

1 R22a = R290 = pure refrigerant grade propane, which is dry and scent is added for safety reason.

2 R22 PT chart almost = propane PT chart. We can simply use R22 Pt chart for simplicity and usually they are more detailed.

Sorry I wanted to say R22a PT chart looks like R290 chart. But R290 chart is more complete.

3 R22 Cap tube when used with propane must be 16-20 % longer. Because propane is easy to push through the cap tube (it is like water VS alcohol)

4 Superheat MUST be in 20F zone because propane is tend to condense and compressor is getting liquid in suction line. This can dramatically shorten life of compressor.

5 I found that many recommend liquid line-suction line HX because it helps maintaining superheat and increases COP (substantially compare to R22)

6 Legal charge for indoor use in Canada 350 gram.

7 If you want to use BBQ propane, it must be dry. If you use liquid line filter/dryer it will remove moisture but WILL also REMOVE the smell from propane.

8 There is controversial information about COP. Some people say it is much more efficient compare to R22 some say COP differ but not significant.

Lets put together as much info as possible about R290 and see what we can do.

Also I wanted to add about charging system. Do not charge any refrigerant as a vapor because you will add non condesable gases like nitrogen into your system. Always charge liquid into suction line while compressor is running. Just be careful and meter refrigerant with your gauges.

Vlad · 02-24-12, 04:35 AM

Quote:

Originally Posted by Geo NR Gee

His system flowed this way: compressor, condenser, sightglass, receiver, pressure switch, filter dryer, txv, evaporator, txv bulb, sight glass, pressure regulator, pressure gauge, back to compressor.

My understanding of a normal system with a cap tube would be this way: compressor, condenser, receiver, filter, sight glass, txv, evaporator, back to compressor.

You missed the point cap tube is critically charged system, you do not need receiver. Cap tube is not able to control extra refrigerant available in receiver. You will flood compressor with extra refrigerant.

As you can see in the video he put sight glass in suction line (I don't know why never seen before). He is asking himself why he can see droplets of refrigerant there. Yes it must be only gas there. It is how compressor is flooded.

One of the reasons his compressor is flooded might be the location of txv bulb. The bulb is located above txv, charge from bulb can migrate to txv element. Also I can see bulb is located on top of the tube (must be a bit on sight) tube looks oxidized and must be cleaned to have good thermal contact. Bulb must be strapped with copper strap and not tape or plastic straps(I can' see this detail).
The other major problem is evaporator coil header. As you can see top part goes directly into suction header.

Quote:

Originally Posted by Geo NR Gee

Why would he use the pressure valve? I have yet to learn why he would do the evaporator like he did.

He doesn't need this valve for ac application if system is designed right.

He does need hard start kit for compressor. When you have cap tube system equalizes in off cycle. With txv you need extra torque to start compressor, because it is under pressure on discharge side.

Quote:

Originally Posted by Geo NR Gee

My concern with your earlier statement about the difference in Cap tubes in a R22 vs. R22a system. I have a small R22 system that was evacuated and charged with R22a. It has not preformed as well as the original R22. The charge was measured according to the R22a equivalency charts supplied by the manufacturer. In fact, when it wasn't working correctly the first time, I gave it more refrigerant. Then to be sure I, removed it and started over with the advised amount.

I am still learning. Would the Superheat of 20f still apply in a factory sealed system when using R22a? In otherwords, if we didn't know the factory specs (as any DIY would experience on hacking a system) would monitoring Superheat vs Subcooling be best?

Yes you need superheat @ 20F otherwise your compressor will be flooded by liquid refrigerant.

Subcooling is completely different thing. It allows your system to run more efficient and it helps your MD to function properly. If you have 10F or more subcooling it means your MD is getting only liquid refrigerant and NOT GAS/LIQUID MIX. Without subcooling refrigerant will be in gas/liquid mix state.

If you have factory designed system and you need to charge it. First thing is you check factory charge amount.

If we changed components in your system, which is our case you need to find right amount of refrigerant.

It is very tricky for cap tube because it is critically charged. It is easier for txv system because txv will take care (with limitations) of providing right superheat.

BradC · 02-24-12, 05:22 AM

Quote:

Originally Posted by Vlad

What I found about R290 is bits and pieces here and there. There is no even an accepted name for this refrigerant. They are R22a, R290, Propane, all kinds of "greens..." and "enviro..." etc. Also there is a bunch of blends of propane and butane.

A refrigerant as listed by ASHRAE has a defined number. R290 is pure propane. Full stop. End of story.
R22a is not an ASHRAE sanctioned mnemonic by any stretch and what you get in the bottle is anybody's guess. Same with Envirosafe and all the rest of the substitute blends.

As for charging as a vapor, you only stand to add non-condensibles if you have them in your bottle in the first place.

The stench is removed by the filter drier, however it is also removed as it seems to dissolve in mineral oil, so it stays in the compressor sump.

R290 PT curve approximates R22, but the pressures are quite a bit lower.
This PT has R22 in Blue and R290 in Orange. Pressure in PSI, Temp in C

Have a look at the R290 for heatpumps thread, it's got some pretty comprehensive information in it.

Vlad · 02-24-12, 05:24 AM

Sorry about posting "discouraging" details. But refrigeration systems are complicated and require more attention then most people think. If you just want to play with ac you do not need details. But if you want to build it right be ready for homework.

Vlad · 02-24-12, 05:38 AM

Quote:

Originally Posted by BradC

A refrigerant as listed by ASHRAE has a defined number. R290 is pure propane. Full stop. End of story.

I do agree when it comes to R290 it is refrigerant and it is pure dry propane. But people as DIY want to use BBQ "propane" which is mix of something...

Quote:

Originally Posted by BradC

R22a is not an ASHRAE sanctioned mnemonic by any stretch and what you get in the bottle is anybody's guess. Same with Envirosafe and all the rest of the substitute blends.

R22a PT chart looks like R290 . We can guess it is just propane.

Quote:

Originally Posted by BradC

As for charging as a vapor, you only stand to add non-condensibles if you have them in your bottle in the first place.

When you charge system with BBQ propane you get what you have there propane, butane, some other gasses I guess including non-condensibles like air.
Charging as liquid is industry standard, especially with blends.

Quote:

Originally Posted by BradC

R290 PT curve approximates R22, but the pressures are quite a bit lower.
This PT has R22 in Blue and R290 in Orange. Pressure in PSI, Temp in C

Sorry I wanted to say R22a PT chart looks very close to R290 PT chart. I can assume that R22a is pure propane (hope refrigerant grade and dry)
We can use R290 chart when it comes to R22a because R290 chart is more complete.

randen · 02-24-12, 06:18 AM

Vlad

I would agree. Most of us would rather play on the side of efficiency. My first attempt at the GSHP I was very pleased with the out-come. The little 2 Ton unit is operating seemingly well. (saving a pile of cash that was destin to the fuel oil mongers) Being ground source the evaporator temps and pressures are rock steady. The condensor side as well dosen't change more than 4 Deg C. When I had tweeked the charged the unit had been operating for hours so the temps had evened out. I had used my amp probe and temp probe on the high side tube before the HX to get the temp of the liquid/gas. I was looking for the highest temp and the best current for the optimum charge. The refrigerant is propane the pressures are 45 LS 210 HS and 86 Deg. C

The 2 Ton unit is a little small for the shop and I've just finished a 3.5 Ton version to swap it out and again with cap tube. I'm understanding the theory behind the TXV changing the amount of restriction based on the temp of the evaporator. Do you think I would gain more efficiency with the TXV if the temps and pressures are so steady. Even on start -ups the temps don,t change much after about 10 min. I'm at a point where I can still cut out the cap tube and replace it with a TXV.

I realize we may tend to be a little barbaric in our methods as we learn hands on. But we do appreciate direction from people in the know. Thanks Vlad

Randen

BradC · 02-24-12, 10:13 AM

Quote:

Originally Posted by Vlad

I do agree when it comes to R290 it is refrigerant and it is pure dry propane. But people as DIY want to use BBQ "propane" which is mix of something...

See, in Australia we are lucky. LPG automotive fuel is an unquantifiable blend, but BBQ Propane is over 95% Propane.

In any case, properly measuring the P/T of what is in your bottle will tell you a _lot_ about the purity of what is in there.

I'm investigating the fractional distillation of a Propane/Butane mix. The thing that is bolloxing me at the moment is the US has a habit of adding Methanol to propane. I'm trying to come up with a useful way of separating that, but that means I actually have to pollute Propane with Methanol to try it, as our Propane is dry enough not to warrant that level of pollution.

I take our BBQ propane and circulate it through a filter/drier a couple of times and I have as close to R290 as you can mostly get. No wonder they call Australia "the lucky country".

AC_Hacker · 02-24-12, 10:55 AM

Quote:

Originally Posted by Vlad

I am not sure were to post about drilling. If somebody who knows this forum could give me some directions. I have good info and willing to share. Drilling is a whole another topic. If it does not exist may be we should start one.

Thanks guys for bringing up the geothermal well drilling issue.

Please note that a new thread called "DIY Well Drilling" has been initiated to be a repository for this important discussion.

Quote:

This thread focuses on DIY geothermal well drilling.

The largest cost associated with installation of a Ground source Heat Pump system is earth work.

Professionally made geothermal trenches are expensive, professionally dug geothermal wells are even more expensive.

It is to bring the costs of geothermal wells within the reach of more people that this new thread is initiated.

-AC_Hacker

Vlad · 02-24-12, 01:11 PM

AC thanks for starting drilling thread. Manifesto became a monster thread . It is very hard to find something here. I will upload all info and pics about my drilling experience there.

It would be good to have some kind of summary of the project (may be separate page or thread ) not a discussion but timeline. We have many projects started here and they all mixed up together. It is almost impossible follow your project or somebody else project.
People keep asking the same questions you keep re-posting....

It is just an idea.

02-23-12, 11:46 PM	#1132
Vlad Apprentice EcoRenovator Join Date: Aug 2010 Location: Windsor ON Canada Posts: 229 Thanks: 4 Thanked 30 Times in 22 Posts	R22a R290 Propane refrigerants. What I found about R290 is bits and pieces here and there. There is no even an accepted name for this refrigerant. They are R22a, R290, Propane, all kinds of "greens..." and "enviro..." etc. Also there is a bunch of blends of propane and butane. The technical details are also differ from site to site. If we could share our own experience and known info this would help to summarize list of properties. What I found (again some info can be controversial) is 1 R22a = R290 = pure refrigerant grade propane, which is dry and scent is added for safety reason. 2 R22 PT chart almost = propane PT chart. We can simply use R22 Pt chart for simplicity and usually they are more detailed. Sorry I wanted to say R22a PT chart looks like R290 chart. But R290 chart is more complete. 3 R22 Cap tube when used with propane must be 16-20 % longer. Because propane is easy to push through the cap tube (it is like water VS alcohol) 4 Superheat MUST be in 20F zone because propane is tend to condense and compressor is getting liquid in suction line. This can dramatically shorten life of compressor. 5 I found that many recommend liquid line-suction line HX because it helps maintaining superheat and increases COP (substantially compare to R22) 6 Legal charge for indoor use in Canada 350 gram. 7 If you want to use BBQ propane, it must be dry. If you use liquid line filter/dryer it will remove moisture but WILL also REMOVE the smell from propane. 8 There is controversial information about COP. Some people say it is much more efficient compare to R22 some say COP differ but not significant. Lets put together as much info as possible about R290 and see what we can do. Also I wanted to add about charging system. Do not charge any refrigerant as a vapor because you will add non condesable gases like nitrogen into your system. Always charge liquid into suction line while compressor is running. Just be careful and meter refrigerant with your gauges. Last edited by Vlad; 02-24-12 at 05:56 AM..

02-24-12, 05:24 AM	#1135
Vlad Apprentice EcoRenovator Join Date: Aug 2010 Location: Windsor ON Canada Posts: 229 Thanks: 4 Thanked 30 Times in 22 Posts	Sorry about posting "discouraging" details. But refrigeration systems are complicated and require more attention then most people think. If you just want to play with ac you do not need details. But if you want to build it right be ready for homework.

02-24-12, 06:18 AM	#1137
randen Uber EcoRenovator Join Date: Apr 2011 Location: Strathroy Ontario Canada Posts: 657 Thanks: 9 Thanked 191 Times in 129 Posts	Vlad I would agree. Most of us would rather play on the side of efficiency. My first attempt at the GSHP I was very pleased with the out-come. The little 2 Ton unit is operating seemingly well. (saving a pile of cash that was destin to the fuel oil mongers) Being ground source the evaporator temps and pressures are rock steady. The condensor side as well dosen't change more than 4 Deg C. When I had tweeked the charged the unit had been operating for hours so the temps had evened out. I had used my amp probe and temp probe on the high side tube before the HX to get the temp of the liquid/gas. I was looking for the highest temp and the best current for the optimum charge. The refrigerant is propane the pressures are 45 LS 210 HS and 86 Deg. C The 2 Ton unit is a little small for the shop and I've just finished a 3.5 Ton version to swap it out and again with cap tube. I'm understanding the theory behind the TXV changing the amount of restriction based on the temp of the evaporator. Do you think I would gain more efficiency with the TXV if the temps and pressures are so steady. Even on start -ups the temps don,t change much after about 10 min. I'm at a point where I can still cut out the cap tube and replace it with a TXV. I realize we may tend to be a little barbaric in our methods as we learn hands on. But we do appreciate direction from people in the know. Thanks Vlad Randen

02-24-12, 01:11 PM	#1140
Vlad Apprentice EcoRenovator Join Date: Aug 2010 Location: Windsor ON Canada Posts: 229 Thanks: 4 Thanked 30 Times in 22 Posts	AC thanks for starting drilling thread. Manifesto became a monster thread . It is very hard to find something here. I will upload all info and pics about my drilling experience there. It would be good to have some kind of summary of the project (may be separate page or thread ) not a discussion but timeline. We have many projects started here and they all mixed up together. It is almost impossible follow your project or somebody else project. People keep asking the same questions you keep re-posting.... It is just an idea.