Hello, My name is Robert. We are having a problem with a Carrier "Tranquility 27" system involving 3 units on the water loop. Every summer (hottest months) the heat pumps go out on high head PSI.installed three years ago and every summer this happens. Has anyone had intermitant problems like this before? • GPU-1 Model No. -TTH026AGS40ELPS Serial No. - L13781181 • GPU-2 Model No. -TSHO18BGS40ELWS Serial No. - L13781140 • GPU-3 Model No. -TTH026AGS40ELPS Serial No. - L13781180 Service info. • Water flow to the units has been confirmed. (It might be too much). • Water temperature to the loop has at 90 degrees. GPU1 – Water Temp In – 85 Water Temp out – 95 Temp diff = 10 degrees. • GPU 1 – Source water pressure In – 40 Source water pressure out – 33 Press drop = 7 Report 9-16-11 PM that GPU 1 – shut off - flash code 2. (High pressure lock out code2) according to page 61, Safety Feature – CXM/DXM Control.

Since you apparently reside in hell I don't think I can be of much help.    I say that because 85 degree entering water seems awful warm.  Is this a ground loop, pond loop or pump and dump setup?  I assume your entering temperatures are lower in the winter and that's why you aren't having problems then.  Now that summer is essentially over it will be hard to test any theories, but my first suggestion based on comments from people who actually know what they are talking about here, would be to try and increase your blower speed over the summers.

It could be that your loop needs a pressure battery/buffer tank. Your loop could be making ever so slight changes in its size causing loss or gain in pressure. It also could be that your loop is to small hence the 85 degree entering water temps. I don't know much about those units but my WaterFurnace books is showing not recommended operation above 90 degree water temps. Your pump may be running to fast/to slow for the temperatures your hitting.

How big is your ground loop and how much piping, what are you located, what is your soil conditions/pond conditions like(if pond open or closed loop).
P.S. I also saw your post on the "other" HVAC board, you will probably get better answers here for this sort of thing even though the other board is a bit larger.

The loop can not reject all of the heat from your house to the ground, which is why the temp gets to 95° in the summer. Several possible reasons. We need to know the loop type to give more info.

Hell, Florida...I guess they are similar. With undisturbed ground temps in 70s, closed loops here will run 85 / 95 or worse. Systems should be able to take that and higher.

It is possible unit is overcharged, has a scaled heat exchanger, a bum TXV, a board problem or a restriction somewhere. A qualified tech able to fog a mirror should be able to ascertain which of those (or some other that fails to spring immediately to my mind)

Posted By khonderd on 03 Nov 2011 07:40 AM
... 85 degree entering water seems awful warm.
...

In a warm season climate, where cooling is the dominant conditioning mode, 85°F EWT is more the typical than the exception.

Here's an example for a Dallas area location where undisturbed earth temp is 68°, and for a 30 day period average temp across a 24 hour period is 93° (plenty of well over 100° days):



Here you can see EWT (black line) for the past 13 months.  EWT 'rides' at 85° for a good month during the hottest part of the Summer.  The coldest the EWT gets is about 60° because it's such a warm season climate.  The dashed red line is avg outside temperature for a rolling 30 day period.

Best regards,

Bill