The domestic hot water tank is a Bradford White 70 gall heat exchanger. It is connected to 3 solar thermal panels, and also has an electrical connection, which has been turned off, since it is never reqd. The DSH supply connects to the tank at the top, while the return is attached at the bottom.

also has an electrical connection, which has been turned off, since it is never reqd

So, I presume that you aren't getting much solar input right now (even with three panels). Your water heater resistance element is turned off, but you have plenty of hot water which means all of it is coming from the desuperheater. How many people using that hot water in your household? When they installed the hot water system what did they tell you about how much hot water you'd get during the heating season? I don't understand why the engineer told you that the hot water was robbing the house of heat. Obviously, that isn't supposed to happen


You said the electrical usage was high, but what is it?

Um, does your buffer tank connect to the top two ports on the heat pump or the middle two ports?

Posted By senr on 16 Feb 2011 08:19 AM
The CM unit was bought in Jan 2010, and installed in March 2010. Yes, the heating is via radiant pipes. First floor is slab on grade. There is 3" insulation, 6" concrete slab, then a 2" topping slab in which the radiant is buried. Tile is the floor finish. Smaller second floor is conventional wood frame construction, with a topping slab with radiant pipes and tile finish.

The compressor does run non stop, and that can't be good.

Temperatures are in the foll range :

Ground Source water/gylcol in = 49.50
Ground Source Out = 47.50
CM Load water in = 102.30
CM Load water out = 106.30
Buffer Tank supply = 100 - 106 (2 zones)
HWG in = 100
HWG out = 155

Thanks

Your temperatures differences are unusually low for both the load and the source side. Unless you have an unusual amount of waterflow, your refrigerant circuit is not taking enough heat out of the water. That also explains the relatively high temps of the loop. This will result that the load does not get satisfied and will cause the compressor to run much longer, resulting in a relatively high DSH output, Your DSH pump seems to be shut off and you have thermal siphoning there, resulting in very low flow and a very hot LWT for the DSH. A tech should quickly be able to measure the flow to confirm the lack of adequate heat extraction. Everything points towards your refrigerant circuit. Compressor, refrigerant amount usually on top of the list.

Thanks for the info. What should the differential be in your experience? Is the supply temperature from the buffer tank too low also? Is the size of buffer tank - 40 gall to small?

You need a tech. size of buffer doesn't matter in this discussion.
j

Posted By senr on 18 Feb 2011 08:52 AM
Thanks for the info. What should the differential be in your experience? Is the supply temperature from the buffer tank too low also? Is the size of buffer tank - 40 gall to small?

I don't know what the setpoint is for your buffer tank (hydronic), it might be set to shut off at 106 degrees. But if your pump runs continuously, that points to the likelihood that it does not reach the setpoint due to a lack of output. The temp differential is a straight function of the amount of heat extracted and the flow. If the flow is within specs (it is kind of hard to have so much flow that your temp diff is cut in half), your heat extraction is off (compressor, refrigerant etc). With normal flow and in 2nd stage, I would expect a temp differential between 4-5 F.

The Buffer tank is set High point at 120 with a temp differential of 14 degrees, that is 106 degrees. I will try to have flow meters installed.
Thank you very much for all your assistance.

Posted By senr on 18 Feb 2011 12:49 PM
The Buffer tank is set High point at 120 with a temp differential of 14 degrees, that is 106 degrees. I will try to have flow meters installed.
Thank you very much for all your assistance.

Don't bother with the flow meters, if your setpoint is 120 and you do not reach it, you heat extraction is off.You should also bring down you setpoint differential to 6 degrees.

The buffer tank panel does show that 120 is reached.

Senr, it should be easy to confirm that your hot water tank connects to the TOP two water ports and the heating system buffer tank connects to the MIDDLE two water ports on the heat pump.

Senr, it should be easy to confirm that your hot water tank connects to the TOP two water ports and the heating system buffer tank connects to the MIDDLE two water ports on the heat pump.

Yes, that is correct

Posted By senr on 18 Feb 2011 02:45 PM
The buffer tank panel does show that 120 is reached.

Bring your differential down to 6-8 degrees. That should help.

Also the closed loop source pressure is about 26 psi. Thats seems to be too low. Shouldn't it be in the 50 - 75 psi range as per the manual. I am trying to install pressure guages at source water in and out and load water in and out to further troble shoot this issue.

System can work at 26 PSI.
RE pressure gauges you would generally only have one as we are looking for a relatively small delta P and gauge disparities could muddy the water.
J

Took some more readings, as per CM Refrigeration Trouble shooting form:
Suction Temp = 36.8 degrees
Suction Pressure = 94
Saturation Temp = 28
SuperHeat = 8.8
Discharge Temp = 201
Discharge Pressure= 490
Saturation Temp = 132
Subcooling = 90.8
Liquid Line temp = 41.2
Source water in temp = 53.1
Source water out temp = 51.7
Source water in Pressure = 23
Source water out pressure = 16
Load water in Temp = 100.6
Load water out temp = 107.6

Waiting for pressure guages to be installed in Load line.

Does this seem correct, or is the unit faulty?

Thanks for feedback!!

Hopefully an expert will chime in here... :-)

But
23-16 = > pressure drop of 7.... which is off the charts for this unit... This means your water flow is too high.
But given a 7 psi drop, you are moving around 20? GPM. (6.2 drop => 15 GPM)

So you get 20 * (53.1-51.7) * 485 = 13580.... this seems way low to me. (even if the HWG is running)

You need to be sure your "Source water in/out temp" and "Source water in/out Pressure" are accurate.

6.2 drop indicate about 16 gpm flow, which means given your low delta T on the source side, your refrigerant circuit is not taken the heat out of your water. Given that your numbers are correct, it is operating at 25-30% of the capacity specs.

CM Tech help agrees that unit is not performing properly. However they are only sending a new CXM board with a DIB panel. They also say they will also send a new TXV!!

Will this help. I just don't know why they just don't have the courtsey to replace this obvious lemon! This si the first season that it has been in use.

Any ideas if the new TXV will help matters. Thanks everyone...

Posted By senr on 25 Feb 2011 10:56 AM
CM Tech help agrees that unit is not performing properly. However they are only sending a new CXM board with a DIB panel. They also say they will also send a new TXV!!

Will this help. I just don't know why they just don't have the courtsey to replace this obvious lemon! This si the first season that it has been in use.

Any ideas if the new TXV will help matters. Thanks everyone...

I think they focus too much on the techs bias or fixation that it is the DSH.

im in maryland with a 2 1/2 ton climatemaster tranquility 27 split system with a closed loop wells. i have had the system for 1 1/2 years. after the first year my compressor completely failed and my installer replaced it. the desuperheat seems to have lost all of its output. the gas pressures are nomianal and the circulator pump is verfied to be pumping well but when in stage one the temp rise is between 1-2 degrees. the rise is soo low you cant feel the difference touching both elbows at the wtr heater connections at the compressor unit. during most of the 1st year in heat or cooling mode the diffence was noticable. my installer is mystified and im frustrated. the sensor close to the compressor is bypassed. my question is does the desuperheater heat exchangers ever go bad?? or what else could it be? i think this compressor base unit is a lemon. i want them to swap it out. please help rob