Water Source Heat Pump

[A-Tech]

Today I diagnosed a water source HP with a bad TEV. I am now having doubts about being correct and would appreciate any help you guys can give. Water temp is 80F and the dx coil is clean. Blower is working normal. When the compressor starts the suction pressure immediately drops to 25psig and the head shoots up to 300psig tripping the safety. I back flushed the water coil and it was free flowing with little debris. I checked to make sure the reversing valve would slide and it does. It seems to me if the restriction was at the TEV this should simulate a pumpdown situation and that would mean a lower high side. It would seem to me that to get the lower suction and higher head the restriction would have to be before the water cooled coil (a/c position). Thank you for any help you can give. Kenny:confused:

[klrogers]

Normally yes a closed TEV would not cause the head pressure to rise that high, however do you know the history of the unit? Perhaps the tech before saw low suction and added refrigerant, now you have a condenser coil bundle full of liquid refrigerant and your head pressure will be much higher.

[d_griff]

run it in heat mode to check it out that way.

[matt8085]

I had a similar situation to the one you're describing. Turned out the inlet and outlet condensor water were piped backwards. Fixed the piping problem and the thing ran like a top.

[Roscoe]

Did you pull the inlet screen.?

[psychometric]

Does it run long enough to see if you are frosting anywhere? What brand is the unit, and rough age of it?

[51fitter]

I had a water cooled condenser where the water reg got stuck closed not allowing any flow causing a high head. As long as you are sure there are no clogged cleanouts and you have strong flow through the condenser (if that is what you have) I would go after the TEV. An overcharge would push the low side up also most of the time. However with a heatpump, someone could have charged it in the winter to get more heat out of it. Now come summertime it's tripping on you. :eek:

[A-Tech]

The unit is a Mammoth. The screen is at the water pump, no screen at the H/P. The unit trips out in about a minute so no sign of frosting. I did back flush the water coil and it was clean. The piping is marked and appears to be correct. I have not followed the line all the way back to confirm. The unit has been in operation for about three years so I don't suspect the water lines are incorrect. How likely is it that the feeder tube inside the TEV is clogged? Are the bypass valves built into H/P TEV's? I have verified the operation of the reversing valve but how common is it for these passages to become stopped up? Thanks to everyone!!

[Airmechanical]

I had a similar situation to the one you're describing. Turned out the inlet and outlet condensor water were piped backwards. Fixed the piping problem and the thing ran like a top.

if that was the case here, the suction pressure would be more than 3 times what the op said it was!

there is a restriction in the refrigeration circuit!



.

[madhat]

I'd go with it piped backwards and someone bumped the charge up on the unit. Also is it an open loop, had a WS HP building in Silver Spring, open loop all the condensors were full of concrete, from the construction nearby. They don't use water reg valve for heatpumps unless a dual water reg is used,(a very rare animal) or a winter bypass is installed.

[Airmechanical]

I'd go with it piped backwards and someone bumped the charge up on the unit




what!



.

[heatingman]

Check the TD from discharge at the comp to Discharge at the condensor inlet. Check liquid line temp difference from condensor outlet to evap inlet( cooling mode) Do the same with the suction line outlet of evap to inlet of comp. Temperature loss will indicate restriction. a degree or 2 is ok but if your in the 5 degee loss range there is a restriction. likely cuprits are the slide valve, and any filters, or added on service ports. If there are no restrictions, then the txv is not opening. Try removing the bulb and warming it up(hot water), this should cause it to open evn if bulb has lost some charge.

[The Doctor]

A-tech, once I had one with pressures like you're describing with a broken cap tube on the txv. like 40, and more like 400, on an old climatemistress, I mean master. :) That was right on New Hampshire Avenue,
Mad hat , where are ya?

[A-Tech]

I took the unit down today and upon closer inspection discovered the powerhead cap tube had rubbed against itself until it lost it's charge. Replaced the powerhead and all is well. Thank you to everyone who responded to my questions.

[Shophound]

I took the unit down today and upon closer inspection discovered the powerhead cap tube had rubbed against itself until it lost it's charge. Replaced the powerhead and all is well. Thank you to everyone who responded to my questions.

Pat yourself on the back; your initial diagnosis was dead on...I never doubted it. :cool: