Washington Hp Home DIY Geothermal

I forgot to mention the CW/CCW rotation switch may be hidden under black dot of tape about 5/16" in diameter. Just peel it off to access.

 

My cxm board does not have the "A" terminal on the P1 strip like in your drawing. I do have the "A" terminal on the P2 terminal strip. Except the "C" terminal seems to have continuity with "A" which causes the load pump to run continuous, even with no power to the heat pump. The relay I'm using is a Honeywell RA89A.

 

I think this is what I was looking for, I hope it's that easy.

 

You must have the DXM2 control board with "A" terminal on P2. No matter, it is functionally equivelant. It is powered when the compressor is running.

The HW RA89A is a powered relay with its own 24v transformer. It requires a dry contact closure (nonpowered) to operate. You can NOT use a powered 24v signal from the HP transformer in a circuit from the relay transformer. Power from different transformers must be isolated.

At this point you have the option of gutting the transformer out of the RA89A or installing an isolation relay (such as a RIBU1C) between the HP and the RA89A.

 

It was that easy, auto changeover is now fully functional. Thank you

 

After 2 full winters I am pleased to report that this system has performed even better than expected. The slab and radiant walls heat the home very comfortably and the heat pump runs infrequently with long, healthy run times.

The first winter the house wasn't fully 100% enclosed and I was heating up the slab for the first time during a very cold bit of weather. The loops got down below 30*F, well into the 20's I think, and had no problem keeping the house warm.

The second winter heating the home I think 42* was the lowest temp I saw on the loops, so much better performance. I found a 'sweet spot' of 70*F on the T stat (down from 73) and 12* delta T on the buffer tank (up from 10). I would like to get data logging and know exactly how its doing, but for what I hear the heat pump do and see in the power bills, things are working great. For the heating side...

The problem I am having now is with getting the cooling side of the system going. The auto changeover and everything works perfectly but the heat pump keeps going into lockout mode. I thought there is a minimum loop temp of 50*F for running in cooling mode. The temp gauge on the manifold right now is reading 58*F, however the heat pump keeps locking out and I'm assuming it is something to do with loop temperature? We do not have a lot of demand for cooling where I live, but a little a/c makes hot days so much more comfortable.

 

Good to hear all your hard work is paying off in heating.

What is the fault code while cooling? That will point us in the right direction. Also what is your cooling set point?

 

Thanks! The fault is flash code 2. I had the cooling set at 50*F with a 10* delta. I realized that may have been trying to go too cool so raised it to 55*F and still woke up to a lockout this morning?

 

Flash code 2 is a High Pressure fault. This usually would indicate while Cooling low or no source flow. But wait a minute, a look at the Climatemaster TBW wiring diagram shows FS1 (source flow switch) and FS2 (load flow switch) all wired in series with the High Pressure Switch. Any one can be locking out the unit. A High Pressure fault is immediate with no retries. Try to confirm flow source and load by making sure pumps are running and valves are actuated before the compressor starts.

How long does the unit run before it locks out? Is that consistent or intermittent? And does it make it through more than one cycle?

 

Yes the load and source pumps are both running when the compressor starts. And with the heat pump wired as stage 2 on the HBX per your advice, there is a good amount of time for the 3 way valves to fully actuate before the compressor starts.

It will run until fault then it cycles the source pump for a couple minutes and the compressor retries. It will do this 3 times before full lockout, at which point I can remove the demand and it will reset.

The run times before fault or lockout have been intermittent. I have noticed longer run times when the load temp is warmer, but its been so intermittent that its difficult to see a pattern.

 

I checked pressures at the P/T ports with compressor running. Load side pressures are the issue. I also ran in heating mode and had the same high pressures, once I observed the problem I did not let it run until lockout. The flash code 2 led was already blinking. 40psi in and 38psi out on the load side, the same or similar in heating or cooling mode.

Source side had 14psi in and 8psi out. Delta T is within spec on load & source, heating & cooling.

 

Also from my notes here, when I commissioned the system 2 years ago the load pressures were 16psi in and 13psi out.

One year ago I had the same lockout issues with cooling so I just opted not to use it since the delivery system was incomplete.

Heating has always worked fine so I have not a reason to check pressures until now.

 

Its usually the simplest thing. Sometimes so simple that you feel dumb once you realize.

Routine maintenance is important! I cleaned out the wye strainers and suddenly everything seems to be well.

Ill give it some time to be sure but at the moment its cooling without faulting and pressures are back in the teens where they should be.

 

I spoke too soon. It ran for a while, brought the buffer tank down to 55*F with the fan coil running for part of that time. Faulted and retried 3 times and eventually locked out, flash code 2. Load side pressure before lockout was 20 psi in and 17 psi out.

 

Good move on cleaning strainers and recording pressure drops. Both look good.


So let's review what we know.
1) DXM Control board reports High Pressure fault in Heating and Cooling.
2) TBW has Source Flow Switch and Load Flow Switch wired in series with High Pressure Switch. Any one will trigger an High Pressure Fault at the DXM control board.
3) Source and Load flow appear correct while running.
4) Source and Load temperatures appear correct while running.

Something in the High Pressure safety circuit is dropping out during operation. Intermittent faults will be tough to diagnose unless you happen to catch the culprit red handed. It could be an actual Fault with source or load flow intermittent failure or be a flaky bad switch or loose connection in the safety circuit.

In Cooling with low 50-60 EWT on load and source side with flow verified will not cause a High Pressure switch to open. Normal highside pressures under those conditions would be in the lower 200's psi. The switch opens at 600PSI. I seriously doubt you have an actual High Pressure condition unless the source flow is dropping out. Conversely, if source flow dropped out in heating you would get Flash Code 4 -LT1 freeze protection fault not a High Pressure Fault. I believe this rules out any source flow issues.

Also in Cooling with low 50's EWT on the loadside if flow dropped out I would expect a Flash Code 5 -LT2 freeze protection fault. A brazed plate HX must be aggressively protected from freezing. That's why ClimateMaster has added the flow switches into the safety circuit. ClimateMaster also recommends while cooling loadside LWT be no lower than 40F with no antifreeze in the loadside. LT2 freeze protection of 30F refrigerant temperature can allow pure water to freeze in the hx in a no or low flow condition. Check your loadside LWT while cooling especially as the tank approaches setpoint. A too large differential can drive cooling loadside EWT to well below 50F and in turn drive loadside LWT below 40F. This will help determine whether any possible freezing is causing low flow and then opening the FS2 loadside flow switch. Conversely, if load flow dropped out in heating I would expect an actual High Pressure refrigerant fault.

So, first trace and check for loose connections on loadside pump connections and High Pressure safety circuit. Then check Cooling loadside LWT. If that all checks out we will need to check for bad flaky switches or least likely a bad flaky control board.

 

Also, as a reminder any temperature readings should be taken with the HWG disabled. Place dip switch 12 ON at the HWG control board to disable.

 

Thank you very much Geoxne for the troubleshooting help. I have been watching the load side temps and I think I was just trying to achieve to low of temperatures, faults were seeming to happen at or below 55* . With a tank setting of 60* and delta T of 10* it didn't fault all day. Now Im trying a tank setting of 58* and a delta T of 4* and timing the run cycles to see how it does. With this new setting as the tank approached the set point the load side LWT was 48*. Could it be that tank settings of 55* and lower are the cause of the issue?

Also once I checked the HWG I realized dip switch 12 was already in the ON position. Which is odd, I had assumed it was enabled because the pipes to the buffer tank get hot when the compressor is running.

 

Do you mean differential (controller temperature range to run past setpoint) instead of Delta T (temperature difference across HX)?

A large differential can push operating temperatures to the edge of operating envelope. I understand you want to encourage longer run times but you may also be driving down operating temperatures. Also keep in mind, water is most dense at 39F. Flow rates with any given pump will drop at lower temperatures.

Yet, to me all the temperatures look right. If you are having success adjusting setpoint and differential, keep it up. It will help shed some light on what is happening. Take your time, one step at a time and see what happens.

 

Can we review how you measure temperature.

How are you piped, meaning do you use the "direct to load" piping, meaning bypassing the buffer tank with a "T" and sending some of the water directly to the load?

How did you "set" you delta T to 10F?

Delta P of 3 on the load side indicated only a about 10 gpm, load side freezing is suspicious.

Do you see the red light blinking before lockout?

 

I have been measuring temperature with permanently installed gauges in the piping. The load side thermometers are about 6"-8" from the front of the heat pump. The source side thermometers are in the manifolds, about 3'-4' from the heat pump. The buffer tanks each have a temp sensor in the middle of the tank and temp is displayed on the HBX eco550.

Yes, both the hot and cold sides use load direct piping.

With the HBX eco550 I can set a desired target temperature and temperature differential for the buffer tank. With the tank set at 55* and delta=10, its trying to bring the buffer tank (temp sensor) to 50*.

Per Table 8 above (if I'm reading it right) load side pressure drop with the 036 unit at 50* should be 2.6psi at 9gpm.

The light on the front of the unit, no. It will light up when it faults, then go off during retry. Then after 2 retries it will lockout and the red light is illuminated until reset. The red light inside, its had flash code 2 in memory so its blinking frequently except after I had the power off once.