I have a climatemaster tranquility 22 with vFlow and the communicating thermostat. The unit is 2.5 tons. I have had the unit for about a year and I installed the unit myself. I have not had any problems with the unit until now. Over the past two weeks I have had the unit trip about 6 times for a high pressure fault. When it trips the unit will stop working. Once we click through the fault screens on the thermostat the unit will resume working and will sometimes work for days without faulting again, sometime will fault again within a couple minutes. I've been watching the system status on the thermostat and have noticed that sometimes when the unit is running the dt is extremely high. Usually the dt is around 10 degrees, now it is about 40 degrees. There have been times that I have checked the system status in the past two weeks and the dt is around 10 degrees, but more often it is around 40 degrees. The communicating thermostat also reports that pump speed (whether the dt is 10 degrees or 40 degrees) is around 15%-20%. I also noticed several times when I would shut the electric off to the unit after the high pressure fault I could hear a sound that sounded like a release of pressure. Based on the information in the manual and what I'm observing, it seems like there might be a flow issue. I'm thinking either something is clogging in the system, the pump is failing, a valve has failed, or the electronic flow control has failed. Any suggestions on how to eliminate items or where I should start first?

1) Where you live: Delaware
2) Heat loss/gain calculations for your home: don't have them handy, but they showed a 2 ton unit for cooling and 2.5 ton for heating.
3) Brand, size (model), age and type of heat pump: Climatemaster Tranquility TZ 22 Digital, about 1 year old.
4) Type of loop field (open/closed/vertical/horizontal) size and design parameters: closed, horizontal, 3 3/4" loops at 700' per loop, manifolded in the basement. Loops include methanol antifreeze.
5) Average cost/Kwh of electricity and consumption: can't say specifically, can try to dig it up if it would be helpful.
6) Entering and leaving air temperatures (EAT, LAT) measured immediately upstream and downstream of the heatpump: EAT is 73 degrees, LAT is 55 degrees.
7) Entering and leaving water temperatures (EWT, LWT) measured at the geo system: Different LWT's have been observed. EWT is usually about 72 degrees, LWT is either about 84 degrees or 130 degrees.
8) Percent of load to be covered by geo and balance point: Balance point is 25 degrees.
9) Installer's assessment of your systems operation. It's been fantastic up until this point.
10) Projected operating costs, actual operating cost and previous heating and cooling costs

What is the pressure in your loop?

Based on what you have posted, I would suspect either the DXM2 control board is not outputing the proper signal to the variable speed pump, or the pump isn't responding appropriately to the control signal.

Watch the following video on Waterside Analysis Procedures on vFlow Units and follow the procedure shown to see if the pump is responding appropriately to manual demand control signals.

https://www.youtube.com/watch?v=OfjHznrx0T0

The following troubleshooting guide is also useful:

http://www.climatemaster.com/geothe...-pumps.pdf

Climatemaster literature for the TZ 22 series heat pumps including the troubleshooting guide can also be found here:

http://www.climatemaster.com/geothe...rature/tz/

The loops are at 40psi. I originally pressurized them to 80 psi; during the first heating season they slowly dropped down to 40. I've read that this is not uncommon and the pressure has been steady at 40 ever since so I saw no reason to increase the pressure.

I watched the youtube video and ran the same diagnostics on mine - I found that I can vary the pump speed and the flow responds accordingly. Flows up to 10 gpm were measured, so I don't think there is a blockage or failure of the pump itself. When I set the pump speed manually the system operates correctly, with a dt of about 9 degrees.

I'll need to dig through the troubleshooting document a little more, but its looking more and more like an issue with the control board. Would a control board malfunction like this occur when the unit is in normal operation mode but not in manual operation mode?

Note that I don't own one of these units and have never worked on one, but I am looking to purchase one (TE 030 Series). I am an electrical engineer with >25 years experience and much of this is troubleshooting electrical control systems.

Here a few things I would check based on the guidance in the troubleshooting manual:

1) Verify that the A0-2 jumper on DXM2 board is in PWM position. See triangle A-V on page 36 of the troubleshooting manual.

2) At the communicating thermostat, verify unit is configured for "Variable Speed Pump Single". The screen should show "Loop Option = Single". Also verify set for Delta T control with default heating / cooling setpoints of 7F / 10F. See section 3.4 on page 64 & 65 of the troubleshooting manual.

3) Verify you have nominal 240 VAC at the pump. See triangle A-O on page 31 of the troubleshooting manual - observe Notes.

With the unit running in cooling mode,

1) Check DC Voltage at DXM2 Board (output control signal to pump), A02-to-Ground should be .5-10 VDC (the manual isn't clear on this, but I would assume that it would be near the lower end of that range with a low delta T and near the high end of range with a high delta T - I would monitor this voltage over a period of time as the unit runs and make periodic note of the delta T and this voltage). See triangle A-J on page 29 of the troubleshooting manual.

2) Check DC Voltage at DXM2 Board (feedback signal from pump), T1-to-Ground should be 0-2 VDC with pump on. See triangle A-B on page 12 of the troubleshooting manual.