Takyka's home made heatpump discussion - Page 2

takyka · 10-29-14, 09:29 AM

Hi,

As weather turned to be colder recently, I started my ASHP to heat my house. In the background, there is the NG boiler as automatic backup, but until now, it was not in use.:-)
I had some concern regarding ice build up on evaporator coils as I don't have built in reversing valve or any other defrosting device. But it seems, It's not an issue until -1-2°C (25-28°F) even if the weather is humid and foggy. There is no any ice settling above +2C (35F) and just slowly building up at the above mentioned freezing temperatures. Whatever Ice is created during operation, can melt on it's own during resting period. (At these temperatures usually the HP runs for 30-40 minutes and resting for 20-30mins.) When compressor stops and EEV closes, there is a slow temperature increase on the evaporator, which takes it a litlebit above freezing. Enough energy released to melt the formed ice layer. Lucky me. :-)
I beleive, the key for the modest iceing is the oversized evaporator with enoug airflow and the use of EEV due the tight control of superheat.

The COP is not the best possible yet, 3.1-3.2 at freezing and ~4 at 7°C (45F), but I'm planning to have modifications to rise it significantly. (In Hungary, COP has to be abowe 3 for any savings over NG).

T.

theoldwizard1 · 10-29-14, 10:01 AM

I just found this thread and because I am so new to heat pumps I have questions about the mechanical end of things.

What are the specification of the compressor and where did your purchase it ?
What are the specification of the heat exchangers and where did your purchase them ?
Why R407C ? (I am guessing it is easier/cheaper to obtain where you are.)
What type of refrigerant pressures and temperatures are you seeing while the unit is running ?

I have heard that R410 is "more efficient" than most common refrigerants up until a certain temperature. True or False ?

takyka · 10-30-14, 03:58 AM

Hi,

My compressor is a Matsu****a 4ps164 it's a 2,7kW output unit salvaged from a mini-split AC. The evaporator is from the same AC. As it was a dual unit with two separate compressors and refigerant lines, I paralelled the two coil. Originaly I planned to make W2WHP. For such system R407C is superior to anything else available, as it is a zeotropic blend. As a trigger, a BPHX failure turned me to make an ASHP. That time the system was 90% ready, I sticked what I have done (it was done for R407C) and just push the laying arround outdoor unit to the end of the evaporator lines.
In my opinion, Zeotropic blends are not the best for ASHP but with some tricks the results can be very close to azeotropic systems.
At arround freezing temperatures, I have ~3.2Bars on evaporator side and ~12Bars at condenser. I have a failure in evaporator return line causing excessive pressure drop, so evaporator pressure is not ideal. I'm planning to replace piping soon...

I would not say R410 is superior to anything in general. I would say, it is more economical for manufacturers than any other refrigerant commonly available nowdays. Due the higher specific weight, specific heat and heat transfer, manufacturers can make smaller machines from less material. They can reduce compressor displacement, reduce piping diameter, and HX sizes. More $ for less...

The reason it's not better than other refrigerant (from our, DIY prespective) is because we can't benefit from better heat transfer property of R410. The botleneck in heat transfer is not on refrigerant-HX transition but on the other side. The better heat transfer of R410 does not have much effect as the heat transfer is much more worse at air(water) side.

T.

mejunkhound · 10-30-14, 09:20 AM

Is propane (R290) legal in Hungary?

takyka · 10-30-14, 09:59 AM

It is banned for heating or AC applications in EU. It is allowed for cooling purposes indoors, with limitations.

Stupid thing, it is allowed to use even the 11kg propane-butan gas tank for heating or cooking purposes indoors by burning the gas. But not allowed to use it in a hermetic HP.

T.

NiHaoMike · 10-30-14, 01:42 PM

R410a is better at lower temperatures, worse at higher temperatures compared to R22, with the crossover point around 80-90F condensing. Against R290 or blends that are mostly R290, it only has an advantage at very low temperatures.

Then there's R32 which is superior to R410a across the board. Ironically, R32 is half of R410a (other half is R125). The R125 adds a lot to the GWP while reducing efficiency. I suspect they really put it in to get an excuse to phase it out once the patents expire.

jeff5may · 10-30-14, 04:49 PM

I truly believe that r410a was invented by the industry as a "new gimmick" refrigerant because the patents on the other, once expensive refrigerants had expired. The way things are now, nothing else will really work well in systems designed for it. The pressures are too high to use anything else and get the same heat flow.

The industry has admitted that it will be phased out eventually, so it is a steppingstone for the future. More likely than not, a new, patented refrigerant will replace it about the time the patent runs out. Also, a replacement refrigerant will probably not be compatible with R410a systems, requiring thousands of users to need a whole new system.

I prefer to "opt out" of the whole deal. There are plenty of existing refrigerants that work just fine. I would much rather pay a tech to come out and tinker with my "obsolete" system than pay much more for a whole new one. Meanwhile, I will have a heyday with the abundance of cheap R22 systems on the second-hand market.

theoldwizard1 · 10-31-14, 11:14 AM

Quote:

Originally Posted by NiHaoMike

R410a is better at lower temperatures, worse at higher temperatures compared to R22, with the crossover point around 80-90F condensing. Against R290 or blends that are mostly R290, it only has an advantage at very low temperatures.

Then there's R32 which is superior to R410a across the board. Ironically, R32 is half of R410a (other half is R125). The R125 adds a lot to the GWP while reducing efficiency. I suspect they really put it in to get an excuse to phase it out once the patents expire.

Quote:

Originally Posted by jeff5may

I truly believe that r410a was invented by the industry as a "new gimmick" refrigerant because the patents on the other, once expensive refrigerants had expired. The way things are now, nothing else will really work well in systems designed for it. The pressures are too high to use anything else and get the same heat flow.

Jeff - So you can't run R32 in a R410A system ? There are a lot of "new" R410A compressors salvaged out of damaged A/C units on eBay at reasonable prices.

Do either of you gentleman have any cost or performance data on R32 vs R410A ?

NiHaoMike · 10-31-14, 11:28 AM

R32 will work in a R410a system, although the expansion valve may need adjustment and you have to watch the discharge temperatures. Main problem is that it's not readily available by itself.

jeff5may · 11-24-14, 02:11 PM

Sorry, just got back to this thread today. Read this:
R32 - A Step Towards More Environmentally Friendly AC - Systems and Heat Pumps | Refrigerants and Energy Efficiency | Danfoss

And another:
http://www.airah.org.au/imis15_prod/...C_Nov13_01.pdf

10-29-14, 09:29 AM	#11
takyka Helper EcoRenovator Join Date: Jul 2014 Location: Hungary Posts: 34 Thanks: 0 Thanked 16 Times in 10 Posts	my ASHP status report Hi, As weather turned to be colder recently, I started my ASHP to heat my house. In the background, there is the NG boiler as automatic backup, but until now, it was not in use.:-) I had some concern regarding ice build up on evaporator coils as I don't have built in reversing valve or any other defrosting device. But it seems, It's not an issue until -1-2°C (25-28°F) even if the weather is humid and foggy. There is no any ice settling above +2C (35F) and just slowly building up at the above mentioned freezing temperatures. Whatever Ice is created during operation, can melt on it's own during resting period. (At these temperatures usually the HP runs for 30-40 minutes and resting for 20-30mins.) When compressor stops and EEV closes, there is a slow temperature increase on the evaporator, which takes it a litlebit above freezing. Enough energy released to melt the formed ice layer. Lucky me. :-) I beleive, the key for the modest iceing is the oversized evaporator with enoug airflow and the use of EEV due the tight control of superheat. The COP is not the best possible yet, 3.1-3.2 at freezing and ~4 at 7°C (45F), but I'm planning to have modifications to rise it significantly. (In Hungary, COP has to be abowe 3 for any savings over NG). T.

10-29-14, 10:01 AM	#12
theoldwizard1 Apprentice EcoRenovator Join Date: Oct 2014 Location: SE MI Posts: 105 Thanks: 3 Thanked 12 Times in 9 Posts	I just found this thread and because I am so new to heat pumps I have questions about the mechanical end of things. What are the specification of the compressor and where did your purchase it ? What are the specification of the heat exchangers and where did your purchase them ? Why R407C ? (I am guessing it is easier/cheaper to obtain where you are.) What type of refrigerant pressures and temperatures are you seeing while the unit is running ? I have heard that R410 is "more efficient" than most common refrigerants up until a certain temperature. True or False ?

10-30-14, 03:58 AM	#13
takyka Helper EcoRenovator Join Date: Jul 2014 Location: Hungary Posts: 34 Thanks: 0 Thanked 16 Times in 10 Posts	Hi, My compressor is a Matsu***a 4ps164 it's a 2,7kW output unit salvaged from a mini-split AC. The evaporator is from the same AC. As it was a dual unit with two separate compressors and refigerant lines, I paralelled the two coil. Originaly I planned to make W2WHP. For such system R407C is superior to anything else available, as it is a zeotropic blend. As a trigger, a BPHX failure turned me to make an ASHP. That time the system was 90% ready, I sticked what I have done (it was done for R407C) and just push the laying arround outdoor unit to the end of the evaporator lines. In my opinion, Zeotropic blends are not the best for ASHP but with some tricks the results can be very close to azeotropic systems. At arround freezing temperatures, I have ~3.2Bars on evaporator side and ~12Bars at condenser. I have a failure in evaporator return line causing excessive pressure drop, so evaporator pressure is not ideal. I'm planning to replace piping soon... I would not say R410 is superior to anything in general. I would say, it is more economical for manufacturers than any other refrigerant commonly available nowdays. Due the higher specific weight, specific heat and heat transfer, manufacturers can make smaller machines from less material. They can reduce compressor displacement, reduce piping diameter, and HX sizes. More $ for less... The reason it's not better than other refrigerant (from our, DIY prespective) is because we can't benefit from better heat transfer property of R410. The botleneck in heat transfer is not on refrigerant-HX transition but on the other side. The better heat transfer of R410 does not have much effect as the heat transfer is much more worse at air(water) side. T. Last edited by takyka; 10-30-14 at 04:00 AM..*

10-30-14, 01:42 PM	#16
NiHaoMike Supreme EcoRenovator Join Date: Oct 2008 Location: Austin, TX Posts: 1,154 Thanks: 14 Thanked 257 Times in 241 Posts	R410a is better at lower temperatures, worse at higher temperatures compared to R22, with the crossover point around 80-90F condensing. Against R290 or blends that are mostly R290, it only has an advantage at very low temperatures. Then there's R32 which is superior to R410a across the board. Ironically, R32 is half of R410a (other half is R125). The R125 adds a lot to the GWP while reducing efficiency. I suspect they really put it in to get an excuse to phase it out once the patents expire. __________________ To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her...

10-30-14, 04:49 PM	#17
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	I truly believe that r410a was invented by the industry as a "new gimmick" refrigerant because the patents on the other, once expensive refrigerants had expired. The way things are now, nothing else will really work well in systems designed for it. The pressures are too high to use anything else and get the same heat flow. The industry has admitted that it will be phased out eventually, so it is a steppingstone for the future. More likely than not, a new, patented refrigerant will replace it about the time the patent runs out. Also, a replacement refrigerant will probably not be compatible with R410a systems, requiring thousands of users to need a whole new system. I prefer to "opt out" of the whole deal. There are plenty of existing refrigerants that work just fine. I would much rather pay a tech to come out and tinker with my "obsolete" system than pay much more for a whole new one. Meanwhile, I will have a heyday with the abundance of cheap R22 systems on the second-hand market. Last edited by jeff5may; 10-30-14 at 05:06 PM..

10-30-14, 09:20 AM	#14
mejunkhound Apprentice EcoRenovator Join Date: Apr 2011 Location: PNW Posts: 197 Thanks: 0 Thanked 47 Times in 31 Posts	Is propane (R290) legal in Hungary?

10-30-14, 09:59 AM	#15
takyka Helper EcoRenovator Join Date: Jul 2014 Location: Hungary Posts: 34 Thanks: 0 Thanked 16 Times in 10 Posts	It is banned for heating or AC applications in EU. It is allowed for cooling purposes indoors, with limitations. Stupid thing, it is allowed to use even the 11kg propane-butan gas tank for heating or cooking purposes indoors by burning the gas. But not allowed to use it in a hermetic HP. T.

10-31-14, 11:28 AM	#19
NiHaoMike Supreme EcoRenovator Join Date: Oct 2008 Location: Austin, TX Posts: 1,154 Thanks: 14 Thanked 257 Times in 241 Posts	R32 will work in a R410a system, although the expansion valve may need adjustment and you have to watch the discharge temperatures. Main problem is that it's not readily available by itself. __________________ To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her...

11-24-14, 02:11 PM	#20
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	Sorry, just got back to this thread today. Read this: R32 - A Step Towards More Environmentally Friendly AC - Systems and Heat Pumps \| Refrigerants and Energy Efficiency \| Danfoss And another: http://www.airah.org.au/imis15_prod/...C_Nov13_01.pdf Last edited by jeff5may; 11-24-14 at 06:20 PM..