Dxgshpwh (ground source heat pump water heater) - Page 9

MEMPHIS91 · 06-04-15, 06:52 PM

Yes, I have come to really like this compressor. I will run test with it without the coil and see what I get.
I have always been fascinated with a TXV is why I jumped at the idea. But I also want to come up with a cheap and easy system for others to be able to copy. So a cap tube system would be best.

jeff5may · 06-04-15, 08:23 PM

I never said you should change anything. The system you have rigged has been proven to work and has not kicked any breakers or popped any lines over a couple hours of runtime. Many have tried and failed to accomplish what you have done in a short time frame.

What you have now is 90% perfect. No matter which way you go from here, you're still earning an A. Getting to the 95 or 99% level, however, will take a considerable amount more will and mental ieffort. During this endless quest, you will be forced to learn things you never knew before. It may or may not end up saving you much energy, but the value lies in dispelling the magic inside of the refrigerant circuit. When you decide to call it quits on this project, you will have another skill you can conjure in this realm of HVAC magic and expensive comfort control. All of the various phase change systems are governed by the same rules and laws of nature.

I do believe this system can hold its own as is. It will work for a long time and save you much electric power versus the replaced element. All you need to do is run the system to the top of its range. Set the thermostat maybe 10 or 15 degrees hotter than its normal setting and let her rip. Keep am eye on your discharge p and t, andet some charge out if either one gets too high. Torture test the rig until you trust it, then turn the thermostat to normal. Reset the kill-a-watt meter and figure out how much energy you are saving.

I definitely would not use that txv on this compressor, though. It is WAAY too big! A half ton txv is about the size of your thumb. That one might be good for the 4 tin unit.

MEMPHIS91 · 06-04-15, 08:34 PM

Yes your very very right, I still am working at understanding that HVAC magic. To be honest I've been bit by this bug. I love tuning things and understanding more. 2 weeks ago I had never brazed/sweated a copper joint, I had never swagged before (still not that great at it), really I had done NOTHING with HVAC work. The info here and a passion for adventure has already provided me with great enjoyment. As I continue I also aim to find was to NOT do it. That way when someone thinks of a idea, they can see its been tried and failed.

TXV to big? I was wondering if it was. It was free so I'll give it back to him. And look for a much smaller one.

Again thank you for all who have been providing great advice.

*System is charging back up now*

MEMPHIS91 · 06-04-15, 10:50 PM

I took out the coil, and shortened the cap tube down to 29.5"
Some data to ponder on.
Borehole temp: 65.5F
Water temp in tank: 105.2F
Discharge line temp at entrance of tank:176.2F
Line temp at exit of tank: 108F
Discharge temp at compressor: 179.5F @ 201psi
Suction line temp at compressor: 65.5 @ 27psi
Amps:2.8

I am very happy with this charge. I plan to run cold water back into the tank tomorrow and do a redo of COP.

BradC · 06-04-15, 11:36 PM

Ok, I'm late to this party primarily because you guys are awake and at it while I'm asleep.

Don't use the TXV. Now here's why. The sole purpose of a TXV is to maximise the use of the evaporators surface area. The intention is the TXV will keep the evaporator filled to the point where you get a defined superheat at the evaporator exit. The purpose of this is to keep the evap filled with boiling liquid. The result is that the evaporation temperature varies wildly with the heat load on the evaporator. They are great for fridges, or A/C units with variable speed fans because they throttle the refrigerant mass flow in response to the heat load on the Evap.

The primary result of this is as the mass flow changes, the evaporation temperature changes. Less mass flow into the evap, but the compressor is trying to suck a constant volume results in a lower evaporator pressure and therefore it gets colder.

Your evap heat load is going to vary very little, and you will probably find that unless you are way overcharged the TXV will be wide open trying to force enough refrigerant through the evaporator to get down to a usable superheat value. You have a restrictive evaporator, so you'll also need an externally equalised TXV, making the plumbing marginally more complex.

So you don't want a TXV here.

Now, because your evap heat load is pretty much not going to change significantly, with a cap tube you can use your charge to fairly accurately dial in your wanted temperatures and pressures.

Now, lets look at your last set of numbers.
Suction temp of 65.5, pressure 27psi so your evaporation temperature is ~4F and you have a superheat of 61F. You could probably afford to put more gas in. It's a trade off. Lower superheat but higher SST will see increased compressor cooling from return vapor, but increased compressor heat from working harder.

Discharge temp, 179F, Pressure 201psi, so your condensing temperature is ~110F and you have 69 degrees superheat on your hot gas.
The fact your water temp is 105.2 and you are condensing at 110 means you have a nicely built and efficient condenser coil. Well done.

It also means that you can get your water up to about 143F before you start bumping into discharge temperature issues. 143F is ~61C and therefore you are above the minimum temperature required to ensure you kill any legionella bacteria.

Congratulations, you've won!

It might be interesting to play with the charge while plotting suction and discharge superheats. You might find some extra points of efficiency in there. Then again, it's getting complex and time consuming for probably not a lot of gain.

You guys doing heat pump water, please do take note. Legionnaires disease is no joke. You need to be hitting 140F regularly. This stuff breeds in warm water and it's not to be trifled with.

NiHaoMike · 06-04-15, 11:52 PM

The bacteria issue is not relevant on city water because of the chlorine added specifically to prevent it. It is a concern on well water or if you have a whole house filter that removes the chlorine.

MEMPHIS91 · 06-05-15, 08:00 AM

I ran the compressor this morning at higher charge.
Borehole temp: 65.7F
Water temp in tank: 104.0F
Discharge line temp at entrance of tank:177F
Line temp at exit of tank: 110F
Discharge temp at compressor: 179.0F @ 210psi
Suction line temp at compressor: 65 @ 31psi
Amps:2.9
----------------------------------------
Borehole temp: 65.5F
Water temp in tank: 105.2F
Discharge line temp at entrance of tank:177.2F
Line temp at exit of tank: 110.2F
Discharge temp at compressor: 179.5F @ 220psi
Suction line temp at compressor: 62.5.5 @ 35psi
Amps:3

It doesn't look like I'm gaining much. I let the compressor run for 30 minutes each time. And then cool off 30 minutes in between test.

jeff5may · 06-05-15, 09:02 AM

How big is the tank? Water takes a lot of heat to warm up. This is ok. A phase change system works more effectively when the run times are long. The less starts and shutdowns you have, the less energy is wasted.

We still don't know how the rig acts when the tank is at running temp or above. This is where it will spend most of its time, as well as where efficiency will be the worst.

MEMPHIS91 · 06-05-15, 09:12 AM

Its a 50 gallon tank.

randen · 06-05-15, 06:01 PM

Memphis91

Your experiencing what I had seen with my build. More charge did not mean more heat just more current draw (more energy). I just lowered the charge slowly incrementally and watched the Kill-o-watt. I would let it run for the day so the heat loss would offer me a good idea of the performance.

Keep up the good work, your so close now.

Randen

06-04-15, 11:52 PM	#86
NiHaoMike Supreme EcoRenovator Join Date: Oct 2008 Location: Austin, TX Posts: 1,154 Thanks: 14 Thanked 257 Times in 241 Posts	The bacteria issue is not relevant on city water because of the chlorine added specifically to prevent it. It is a concern on well water or if you have a whole house filter that removes the chlorine. __________________ 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...

06-04-15, 06:52 PM	#81
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	Yes, I have come to really like this compressor. I will run test with it without the coil and see what I get. I have always been fascinated with a TXV is why I jumped at the idea. But I also want to come up with a cheap and easy system for others to be able to copy. So a cap tube system would be best.

06-04-15, 08:23 PM	#82
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,431 Thanks: 431 Thanked 619 Times in 517 Posts	I never said you should change anything. The system you have rigged has been proven to work and has not kicked any breakers or popped any lines over a couple hours of runtime. Many have tried and failed to accomplish what you have done in a short time frame. What you have now is 90% perfect. No matter which way you go from here, you're still earning an A. Getting to the 95 or 99% level, however, will take a considerable amount more will and mental ieffort. During this endless quest, you will be forced to learn things you never knew before. It may or may not end up saving you much energy, but the value lies in dispelling the magic inside of the refrigerant circuit. When you decide to call it quits on this project, you will have another skill you can conjure in this realm of HVAC magic and expensive comfort control. All of the various phase change systems are governed by the same rules and laws of nature. I do believe this system can hold its own as is. It will work for a long time and save you much electric power versus the replaced element. All you need to do is run the system to the top of its range. Set the thermostat maybe 10 or 15 degrees hotter than its normal setting and let her rip. Keep am eye on your discharge p and t, andet some charge out if either one gets too high. Torture test the rig until you trust it, then turn the thermostat to normal. Reset the kill-a-watt meter and figure out how much energy you are saving. I definitely would not use that txv on this compressor, though. It is WAAY too big! A half ton txv is about the size of your thumb. That one might be good for the 4 tin unit.

06-04-15, 08:34 PM	#83
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	Yes your very very right, I still am working at understanding that HVAC magic. To be honest I've been bit by this bug. I love tuning things and understanding more. 2 weeks ago I had never brazed/sweated a copper joint, I had never swagged before (still not that great at it), really I had done NOTHING with HVAC work. The info here and a passion for adventure has already provided me with great enjoyment. As I continue I also aim to find was to NOT do it. That way when someone thinks of a idea, they can see its been tried and failed. TXV to big? I was wondering if it was. It was free so I'll give it back to him. And look for a much smaller one. Again thank you for all who have been providing great advice. System is charging back up now

06-04-15, 10:50 PM	#84
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	I took out the coil, and shortened the cap tube down to 29.5" Some data to ponder on. Borehole temp: 65.5F Water temp in tank: 105.2F Discharge line temp at entrance of tank:176.2F Line temp at exit of tank: 108F Discharge temp at compressor: 179.5F @ 201psi Suction line temp at compressor: 65.5 @ 27psi Amps:2.8 I am very happy with this charge. I plan to run cold water back into the tank tomorrow and do a redo of COP.

06-04-15, 11:36 PM	#85
BradC Apprentice EcoRenovator Join Date: Dec 2010 Location: Western Australia Posts: 148 Thanks: 1 Thanked 48 Times in 34 Posts	Ok, I'm late to this party primarily because you guys are awake and at it while I'm asleep. Don't use the TXV. Now here's why. The sole purpose of a TXV is to maximise the use of the evaporators surface area. The intention is the TXV will keep the evaporator filled to the point where you get a defined superheat at the evaporator exit. The purpose of this is to keep the evap filled with boiling liquid. The result is that the evaporation temperature varies wildly with the heat load on the evaporator. They are great for fridges, or A/C units with variable speed fans because they throttle the refrigerant mass flow in response to the heat load on the Evap. The primary result of this is as the mass flow changes, the evaporation temperature changes. Less mass flow into the evap, but the compressor is trying to suck a constant volume results in a lower evaporator pressure and therefore it gets colder. Your evap heat load is going to vary very little, and you will probably find that unless you are way overcharged the TXV will be wide open trying to force enough refrigerant through the evaporator to get down to a usable superheat value. You have a restrictive evaporator, so you'll also need an externally equalised TXV, making the plumbing marginally more complex. So you don't want a TXV here. Now, because your evap heat load is pretty much not going to change significantly, with a cap tube you can use your charge to fairly accurately dial in your wanted temperatures and pressures. Now, lets look at your last set of numbers. Suction temp of 65.5, pressure 27psi so your evaporation temperature is ~4F and you have a superheat of 61F. You could probably afford to put more gas in. It's a trade off. Lower superheat but higher SST will see increased compressor cooling from return vapor, but increased compressor heat from working harder. Discharge temp, 179F, Pressure 201psi, so your condensing temperature is ~110F and you have 69 degrees superheat on your hot gas. The fact your water temp is 105.2 and you are condensing at 110 means you have a nicely built and efficient condenser coil. Well done. It also means that you can get your water up to about 143F before you start bumping into discharge temperature issues. 143F is ~61C and therefore you are above the minimum temperature required to ensure you kill any legionella bacteria. Congratulations, you've won! It might be interesting to play with the charge while plotting suction and discharge superheats. You might find some extra points of efficiency in there. Then again, it's getting complex and time consuming for probably not a lot of gain. You guys doing heat pump water, please do take note. Legionnaires disease is no joke. You need to be hitting 140F regularly. This stuff breeds in warm water and it's not to be trifled with.

06-05-15, 08:00 AM	#87
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	I ran the compressor this morning at higher charge. Borehole temp: 65.7F Water temp in tank: 104.0F Discharge line temp at entrance of tank:177F Line temp at exit of tank: 110F Discharge temp at compressor: 179.0F @ 210psi Suction line temp at compressor: 65 @ 31psi Amps:2.9 ---------------------------------------- Borehole temp: 65.5F Water temp in tank: 105.2F Discharge line temp at entrance of tank:177.2F Line temp at exit of tank: 110.2F Discharge temp at compressor: 179.5F @ 220psi Suction line temp at compressor: 62.5.5 @ 35psi Amps:3 It doesn't look like I'm gaining much. I let the compressor run for 30 minutes each time. And then cool off 30 minutes in between test.

06-05-15, 09:02 AM	#88
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,431 Thanks: 431 Thanked 619 Times in 517 Posts	How big is the tank? Water takes a lot of heat to warm up. This is ok. A phase change system works more effectively when the run times are long. The less starts and shutdowns you have, the less energy is wasted. We still don't know how the rig acts when the tank is at running temp or above. This is where it will spend most of its time, as well as where efficiency will be the worst.

06-05-15, 09:12 AM	#89
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	Its a 50 gallon tank.

06-05-15, 06:01 PM	#90
randen Uber EcoRenovator Join Date: Apr 2011 Location: Strathroy Ontario Canada Posts: 658 Thanks: 9 Thanked 192 Times in 130 Posts	Memphis91 Your experiencing what I had seen with my build. More charge did not mean more heat just more current draw (more energy). I just lowered the charge slowly incrementally and watched the Kill-o-watt. I would let it run for the day so the heat loss would offer me a good idea of the performance. Keep up the good work, your so close now. Randen