Dxgshpwh (ground source heat pump water heater) - Page 7

MEMPHIS91 · 06-02-15, 03:07 PM

Randen, Yes I am very pleased so far.

Thats a good idea, i'll pulling the loops in tighter and higher.

AC, I added about 1 teaspoon of refrigeration mineral oil. And yes I was giving it a while to settle out. Probably only 15 minutes or so though.

Jeff, Can you explain that alittle better. "at least 10F" You mean the suction line before the muffle should be at least 10F?

I'm bout to fire her back up and see what happens.

MEMPHIS91 · 06-02-15, 05:14 PM

Update. 50 gallon tank. Its been running for 2 hours, has jumped from 72 to 78F water and used .5 Kwh. More details on that later.

CRAZY! It spiked at 194F!!
But i think I found out why, just because my compressor was at 235F I decided to put a small fan on the compressor, and instantly my temperature on the high side drop to 150F at 10 psi. I think I need better cooling on the compressor. Maybe more wraps of copper tubing? The ones I have wrapped now are not very tight, only part of it is touching.

randen · 06-02-15, 08:44 PM

Hmm

Compressor is running hot. And 2 hrs and only 6 Deg. F gain Something is not right. Did you happen to check your DX and tank HX tubes to be clear of kinks.

I can't see the gage very well but is the low side only 12 psi. I believe you need to in-crease your charge. I found anything less than 18 psi didn't move any heat.

Let the compressor cool and add some charge and try again.

Randen

MEMPHIS91 · 06-02-15, 09:05 PM

Quote:

Originally Posted by randen

Hmm

Compressor is running hot. And 2 hrs and only 6 Deg. F gain Something is not right. Did you happen to check your DX and tank HX tubes to be clear of kinks.

I can't see the gage very well but is the low side only 12 psi. I believe you need to in-crease your charge. I found anything less than 18 psi didn't move any heat.

Let the compressor cool and add some charge and try again.

Randen

When I get back to around 18 psi the cap tube sounds like something is squirting into it and it is back is surge. My psi drops and raises 2-3 psi with the sound as well. I for sure probably put to much oil. I unhooked my high side gauge and my hand was instantly covered in oil. But my water number look much better.
So best way to get the oil out?

jeff5may · 06-02-15, 09:56 PM

The things you are describing sure not out of the ordinary for an r290 system. For one, the mineral oil and propane dissolve in each other like carbonated soft drink. The oil will follow a leak. The cap tuBe doesn't care if it passes liquid, gas or oil. The compressor cares. It wants a little oil and lots of gas, no liquid refrigerant.

The thing that concerns me is your gauge readings. With 60 degrees or better ground temp, you should be having no frost leading to or from your borehole. If there is frost going from the cap tube into the hole, either you are low on charge or the cap tube is plugged up. If there is frost coming from the hole into the compressor suction side, the obstruction is in the borehole close to the exit.

Since you have low suction pressure and high discharge temperature, I suspect your charge is low. The compressor is trying to move gas, but the high compression ratio and low flow rate is making it work hard without much cooling. The 20 psi gas in the suction side has a boiling point below freezing, thus the frost. Going through the borehole, it is coming out with 40 degrees of superheat.

All this talk of superheat begs some explanations. Superheat is simply the difference in temperature between the saturated suction temperature ( read the r22 scale on your gage) and the actual refrigerant temperature. When the propane passes through the cap tube as a liquid, it has a boiling point that is high due to the discharge pressure.

As it leaves the cap tube, it encounters a sudden and drastic pressure drop. As a result, the boiling point drops suddenly and the liquid evaporates and boils. When the refrigerant changes phases, it assumes the saturated suction temperature until it all boils off.

MEMPHIS91 · 06-02-15, 10:06 PM

That picture shows 12psi low and 145 psi high.

The numbers I am getting now that randen said to add some is 25 psi low and 165 psi high. With MUCH better heat transfer. I drained the system and turn the compressor of its side with the service port valve removed, oil PORED out. So I think that will help some.

The compressor is not getting liquid. The suction line wraps around the pump 3 times. I bet it picks up 25+F. Pretty sure that is how I am those higher than normal 170-185F high side temps. And that is being measured at the tank itself.

Gonna pull a long deep vacuum and let it hold over night.
Thanks for all your replies!

randen · 06-02-15, 10:18 PM

Memphis91

A teaspoon of oil is not enough to be concerned about. And yes if you remove your gage you do get a mist of oil all good.

I believe your system is starving for refrigerant. It is possible that some funny stuff is occurring with some droplets of oil messing about in your cap tube. But once your system gets all the tubing coated and you have a healthy charge dissolving the oil I believe what you are seeing with the surging will subside.

Oh I just seen your post. Yes 25-35 psi is still healthy and when I had started my HPWH this is the pressures I started with. I believe you were just circulating hot gas from the friction in the compressor scroll and not moving any refrigerant to take advantage of the vapor compression cycle.

You are on the right track. These are the things that a true DIYer must push through to revel in true success.

randen · 06-02-15, 10:27 PM

Memphis91

I only now understand your previous post. When you put more charge 18 psi you seen a better water number or water temp in the tank is rising more quickly. Try starting with 30-35 psi and reduce slowly as you test for temp. rise in your tank. This may take a few days as you let it run and check the temp. vs temp rise. Install the Kwh meter and tune your system.

Randen

jeff5may · 06-02-15, 11:13 PM

As per the manifesto in post 462, the pt chart for propane is here (or there, thanks ac_hacker):

http://www.glacierbay.com/ptchartpropane.asp

For your evaporator to operate above freezing, the suction pressure would need to exceed 54 psig. Every 15 psi is an atmosphere or bar of pressure, so at 55 psig(auge), you would have almost 4 bars of suction pressure, and almost 70 psi from absolute vacuum. Compared to 15 psi of gauge pressure, this equates to 7/3 as much suction gas available for the compressor to circulate, as well as 40 psi less difference across the compressor ports. The result: a few more compressor watts, a lot more mass flow, a lot lot more heat transfer. Less run time for the same heat into the water.

Glad to see it working. Just a little bit of tuning to do, then you should be good to go.

BradC · 06-03-15, 02:20 AM

Compressors are either cooled by fan or cooled by suction gas.
Cooled by fan is obvious. You need a constant airflow over the shell. Cooled by suction gas requires a minimum mass flow and a minimum suction return temperature.

Your in-ground evaporator is going to be _very_ effective at superheating the returning vapor, and unless you are properly charged you will get inadequate compressor cooling from that. In fact, I'd hazard a guess that at your mass flow you won't get sufficient cooling unless you are spitting back liquid into the compressor shell (which you don't want to do). So the fan is the go.

jeff5may is spot on with his assessment of charge and mass flow. You need more gas. You will as a consequence draw more power, but you'll greatly increase your overall mass flow and COP. If you can get it to where your suction line to the compressor is "sweating" (ie it is cold enough to get atmospheric moisture to condense on it) then you will probably not need fan cooling either.

Get the spec sheet for your compressor, and look at the specs for evaporating temperature vs power draw. That is about where you want to be aiming.

06-02-15, 05:14 PM	#62
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	Update. 50 gallon tank. Its been running for 2 hours, has jumped from 72 to 78F water and used .5 Kwh. More details on that later. CRAZY! It spiked at 194F!! But i think I found out why, just because my compressor was at 235F I decided to put a small fan on the compressor, and instantly my temperature on the high side drop to 150F at 10 psi. I think I need better cooling on the compressor. Maybe more wraps of copper tubing? The ones I have wrapped now are not very tight, only part of it is touching. Attached Thumbnails

06-02-15, 09:56 PM	#65
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	The things you are describing sure not out of the ordinary for an r290 system. For one, the mineral oil and propane dissolve in each other like carbonated soft drink. The oil will follow a leak. The cap tuBe doesn't care if it passes liquid, gas or oil. The compressor cares. It wants a little oil and lots of gas, no liquid refrigerant. The thing that concerns me is your gauge readings. With 60 degrees or better ground temp, you should be having no frost leading to or from your borehole. If there is frost going from the cap tube into the hole, either you are low on charge or the cap tube is plugged up. If there is frost coming from the hole into the compressor suction side, the obstruction is in the borehole close to the exit. Since you have low suction pressure and high discharge temperature, I suspect your charge is low. The compressor is trying to move gas, but the high compression ratio and low flow rate is making it work hard without much cooling. The 20 psi gas in the suction side has a boiling point below freezing, thus the frost. Going through the borehole, it is coming out with 40 degrees of superheat. All this talk of superheat begs some explanations. Superheat is simply the difference in temperature between the saturated suction temperature ( read the r22 scale on your gage) and the actual refrigerant temperature. When the propane passes through the cap tube as a liquid, it has a boiling point that is high due to the discharge pressure. As it leaves the cap tube, it encounters a sudden and drastic pressure drop. As a result, the boiling point drops suddenly and the liquid evaporates and boils. When the refrigerant changes phases, it assumes the saturated suction temperature until it all boils off. Last edited by jeff5may; 06-03-15 at 10:43 AM..

06-02-15, 11:13 PM	#69
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	As per the manifesto in post 462, the pt chart for propane is here (or there, thanks ac_hacker): http://www.glacierbay.com/ptchartpropane.asp For your evaporator to operate above freezing, the suction pressure would need to exceed 54 psig. Every 15 psi is an atmosphere or bar of pressure, so at 55 psig(auge), you would have almost 4 bars of suction pressure, and almost 70 psi from absolute vacuum. Compared to 15 psi of gauge pressure, this equates to 7/3 as much suction gas available for the compressor to circulate, as well as 40 psi less difference across the compressor ports. The result: a few more compressor watts, a lot more mass flow, a lot lot more heat transfer. Less run time for the same heat into the water. Glad to see it working. Just a little bit of tuning to do, then you should be good to go. Last edited by jeff5may; 06-08-16 at 11:45 PM.. Reason: spelling

06-02-15, 03:07 PM	#61
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	Randen, Yes I am very pleased so far. Thats a good idea, i'll pulling the loops in tighter and higher. AC, I added about 1 teaspoon of refrigeration mineral oil. And yes I was giving it a while to settle out. Probably only 15 minutes or so though. Jeff, Can you explain that alittle better. "at least 10F" You mean the suction line before the muffle should be at least 10F? I'm bout to fire her back up and see what happens.

06-02-15, 08:44 PM	#63
randen Uber EcoRenovator Join Date: Apr 2011 Location: Strathroy Ontario Canada Posts: 657 Thanks: 9 Thanked 191 Times in 129 Posts	Hmm Compressor is running hot. And 2 hrs and only 6 Deg. F gain Something is not right. Did you happen to check your DX and tank HX tubes to be clear of kinks. I can't see the gage very well but is the low side only 12 psi. I believe you need to in-crease your charge. I found anything less than 18 psi didn't move any heat. Let the compressor cool and add some charge and try again. Randen

06-02-15, 10:06 PM	#66
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	That picture shows 12psi low and 145 psi high. The numbers I am getting now that randen said to add some is 25 psi low and 165 psi high. With MUCH better heat transfer. I drained the system and turn the compressor of its side with the service port valve removed, oil PORED out. So I think that will help some. The compressor is not getting liquid. The suction line wraps around the pump 3 times. I bet it picks up 25+F. Pretty sure that is how I am those higher than normal 170-185F high side temps. And that is being measured at the tank itself. Gonna pull a long deep vacuum and let it hold over night. Thanks for all your replies!

06-02-15, 10:18 PM	#67
randen Uber EcoRenovator Join Date: Apr 2011 Location: Strathroy Ontario Canada Posts: 657 Thanks: 9 Thanked 191 Times in 129 Posts	Memphis91 A teaspoon of oil is not enough to be concerned about. And yes if you remove your gage you do get a mist of oil all good. I believe your system is starving for refrigerant. It is possible that some funny stuff is occurring with some droplets of oil messing about in your cap tube. But once your system gets all the tubing coated and you have a healthy charge dissolving the oil I believe what you are seeing with the surging will subside. Oh I just seen your post. Yes 25-35 psi is still healthy and when I had started my HPWH this is the pressures I started with. I believe you were just circulating hot gas from the friction in the compressor scroll and not moving any refrigerant to take advantage of the vapor compression cycle. You are on the right track. These are the things that a true DIYer must push through to revel in true success.

06-02-15, 10:27 PM	#68
randen Uber EcoRenovator Join Date: Apr 2011 Location: Strathroy Ontario Canada Posts: 657 Thanks: 9 Thanked 191 Times in 129 Posts	Memphis91 I only now understand your previous post. When you put more charge 18 psi you seen a better water number or water temp in the tank is rising more quickly. Try starting with 30-35 psi and reduce slowly as you test for temp. rise in your tank. This may take a few days as you let it run and check the temp. vs temp rise. Install the Kwh meter and tune your system. Randen

06-03-15, 02:20 AM	#70
BradC Apprentice EcoRenovator Join Date: Dec 2010 Location: Western Australia Posts: 148 Thanks: 1 Thanked 48 Times in 34 Posts	Compressors are either cooled by fan or cooled by suction gas. Cooled by fan is obvious. You need a constant airflow over the shell. Cooled by suction gas requires a minimum mass flow and a minimum suction return temperature. Your in-ground evaporator is going to be _very_ effective at superheating the returning vapor, and unless you are properly charged you will get inadequate compressor cooling from that. In fact, I'd hazard a guess that at your mass flow you won't get sufficient cooling unless you are spitting back liquid into the compressor shell (which you don't want to do). So the fan is the go. jeff5may is spot on with his assessment of charge and mass flow. You need more gas. You will as a consequence draw more power, but you'll greatly increase your overall mass flow and COP. If you can get it to where your suction line to the compressor is "sweating" (ie it is cold enough to get atmospheric moisture to condense on it) then you will probably not need fan cooling either. Get the spec sheet for your compressor, and look at the specs for evaporating temperature vs power draw. That is about where you want to be aiming.