I’m looking for some help/guidance. We have a geothermal system with 2 ClimateMaster Tranquility units - a 2 ½ ton unit for the first floor and for the 2nd /3rd floors a 3 ton split unit with the ClimateMaster compressor in the basement. The system was installed in 2011 and has been working well until about 6 weeks ago when we started getting an “E4 - Low Water Temp” error on the first floor thermostat. Since then we have had our geothermal contractor out three times to evaluate the system and have been told that they can’t find anything wrong. We still do not have a resolution for the error. If we shut the unit off and restart it generally comes back online and seems to run properly for a few days up to a couple of weeks, although the error message seems to be happening more frequently lately. The 2nd/3rd floor unit seems to be working well and without any error messages. Any suggestions as to next steps to find and fix the error would be much appreciated. Thank you.

So what is the actual entering (EWT) and leaving water temperatures (LWT)? Surely your contractor would have measured these parameters during troubleshooting. Is the loop water temperature actually low or is there a problem with a sensor? We can't provide any meaningful suggestions without having more details.

What kind of thermostat do you have? Is it the communicating thermostat that provides EWT and LWT?

If your loop water temperature is actually low, how low is it?

Do both units share the same water loop or do they have their own individual loop? Are the loop(s) vertical (in wells) or horizontal (in trenches)?

Has there been anything that might have disturbed the ground near the loops that possible might have collapsed or kinked a pipe?

Has any water been added to the loops? If so, this might indicate a loop is air locked.

Thank you arkie6. I do not have the EWT and LWT but per the contractor, all those parameters looked good. The thermostat is the original Climatemaster thermostat and the same type as used with the 2nd/3rd unit which is functioning properly. The 2 units share the same open loop (well) which, per the contractor, also seems to be functioning well.

I can't help without data. Just because your contractor says they "looked good" doesn't carry much weight. Do you have a way to measure the water temperature? Most units have what are called PT or Pete's ports for Pressure-Temperature ports on the brass elbow where the loop water lines enter and leave the unit. They will typically have a small brass cap that you remove to expose a rubber insert with a small slit in it. You can insert a small diameter HVAC or meat thermometer into these ports and take a temperature measurement when the unit is running to get EWT and LWT.

Is the well pump and dump or does the water coming from the heat pumps get pumped back into the well?

Which unit runs more, the 2.5 ton unit or the 3 ton unit? Which sees more use in heating mode? Which sees more use in cooling mode?

Since you are on open loop well water, do you know about the water quality? Does it have low, medium, or high dissolved mineral content? If you don't know, fill a quart saucepan with the well water and boil it dry on the stove and see what is left. This same thing happens in your heat exchanger in cooling mode, just slower.

Have you ever had the water-to-refrigerant heat exchanger cleaned? You could have mineral buildup on the water side of the heat exchanger that is blocking flow and causing the water temperature to drop more than usual in heating mode.

Thank you again arkie6. Sorry I don’t have the data that would help figure this out. The first floor (2.5 ton unit) runs more. The well pump dumps back into well. I haven’t boiled the water yet as you suggested but I suspect the mineral content is high. No, I never had the water-to-refrigerant heat exchanger cleaned but will ask when they come back to service the unit on Monday. (They are returning to place a “data monitor” from ClimateMaster on the unit.)

When they come back, have them take temperatures on the entering water (EWT) and the leaving water (LWT) after the unit has been running in heating mode for some time and report what temperatures they are getting. The best time would be in the morning after a cold night with lots of run time in heating mode. If you know when they are going to be there, and if necessary to keep the unit running, gradually (1 deg F increments) raise your thermostat setpoint to keep the unit running in heat mode. Or open some windows. You want the unit running for an extended time period before taking these measurements. Also have them take and report the water pressure at the supply and return PT ports. The difference in pressure across these ports can also provide an indication if the heat exchanger is partially blocked with mineral content. If that is the case, you can have the the heat exchanger acid soaked to dissolve the minerals and flush them out.

Where are you located? You never did state if the 2.5 ton unit sees any run time in cooling mode. Heat exchanger mineral buildup primarily occurs in cooling mode where the heat exchanger is hot and dumping heat into the water supply.

We're in Southern New England. Yes, both units run in cooling mode during the summer. I'll ask them about the other data points you suggested. Keeping the problem unit running has been difficult over the past 48 hours as the E4 - Low Water Temp error in coming on frequently. Where the unit had run for several days between error codes, now it's only running a few hours before the code come back on (after shut -off and waiting a few hours to restart.) Thanks again.

You have to wait a few hours before you can restart it? Or you wait a few hours just because?

If you have to wait a few hours then it sounds like the well water is freezing in the heat exchanger. It could be form low flow from build up as stated about. As you know when water freezes it expands with great force and could crack the heat exchanger. I wouldn't run the unit till you know the exiting water temp.

No, I don't have to wait a few hours to start it. The contractor suggested I turn it off and wait a few minutes to restart. This has happened so frequently lately that I have just kept it off for a few hours. It does not seem to make much of a difference whether I shut down for 5 minutes or a few hours, the unit comes back on and then runs for a few minutes, a few hours, or a few days before the error code comes back on.

So you are pumping out of your well and dumping the water down the same well? Or are you dumping it down another well? Or are you dumping it outside?

I am in the finishing stages of a house. We have our geo set to pump out of our well and then dump it external to the house. I have since found that is almost 30% cheaper to just heat the house with NG hot water tank heater using our heated floors. So I am no longer wasting water in the winter. But in summer the plan is to use the water from the well for geo cooling and then water the grass with the excess water. Trying to learn from others. May dump the water back down the same well in summer till it gets to hot and then water grass with warm water.

Keep us up to date, and good luck.

Duplicate........sorry

Duplicate......sorry

Supervising technician came out yesterday, took a look at the 2.5 ton (1st floor) and 3 ton (2nd/3rd floor) units and then the well pump. Noticed that the pressure from the well pump was fluctuating (from ~ 10 to 55 psi) and diagnosed this as the root cause of the problem. He shut the well pump off and is waiting on the someone to look at the well pump next. In the meantime, we're on back up heat.

Well pump has a controller (ECM) to maintain pressure or just uses a standard pressure switch to turn it off and on?
Thoughts:
If ECM - could be controller?
If Standard pressure switch - well could be going dry?

There is constant pressure controller in line with a "pro-pump". Fingers crossed it's just the controller. In the meantime, the thermostats show "aux heat" and the air handlers are blowing hard to keep up. Should I switch to "emergency heat"? (Reluctant to given how much electricity this will take.) Thanks for the help.

Why was fluctuating well pump pressure only affecting the downstairs 2.5 ton unit and not the upstairs 3 ton unit?

Aux Heat = electric heat strips
Emergency Heat = electric heat strips

Likely there is no difference between Aux Heat and Emergency Heat. If there is any difference between Aux Heat and Emergency Heat, it would just be the quantity of heat strips engaged. Electricity cost wise it would not make much difference either way.

If you have a gas stove turn on some burners. Though would recommend a Carbon Monoxide detector if ran for a long time.

Thanks for input. Can't explain why only the downstairs 2.5 unit is affected by fluctuating well pump. Asked the same question to the technician who blamed it on a valve to the upstairs unit stuck in open position.

Will use Aux / Emergency heat sparingly until this is resolved. No gas so no option there.