Geothermal Geologix Comfort Aire HTV070 Code 2 HP Lockout

Barrym97

I bought a used geothermal unit to replace my leaky R-22 unit.
Just plug in power and hook up water. Right?

I am losing my mind. I need help.

EDIT 6/24: HP switch jumpered (I'm carefully watching gauges). Unit still cuts out after about 2 minutes. Now I get a code4 - water coil is frozen. NOTHING in the unit is frozen. Its 82 degrees in the cabinet. The thermistor seems to have right resistance for ambient temperature.

HTV070
https://www.manualslib.com/manual/838561/Heat-Controller-Geothermal.html

It is so cold and wonderful for about 2 to 2.5 minutes then CLICK... blink blink blink
It ran for 30 to 40 minutes one time.

CXM board gives a code 2. HP Lockout


https://files.climatemaster.com/97b0003n12-climatemaster-cxm-controls-heat-pump-application-manual.pdf

According to manual, it could be HP switch. Switch has continuity when unit is not powered. I hear it click right before lockout.

The problem could be water flow.

I have a 7psi delta (16 and 9 psi) at the unit.
Before compressor comes on the brass water fittings are room temperature (81 deg)
When compressor comes on, the brass fittings become:
Water in is 66.6 deg
Water out is 76.5 deg

Return air today is 86.4 deg
Supply air is 66.6 deg

This seems to be in line with "Performance Data" from manual.

This also seems to indicate that refrigeration is working and water is flowing

Another suggested cause is an over charged system.

I do not want to open the refrigerant system to test pressures - I don't want to accidentally compromise anything - let air into the system, let out r410, etc.. .

If there is ANY other reason that I could be getting HP lockout.

HELP! I have been working on this for a week - purging and re-purging my loops - testing pumps, etc. Its 95 degrees here!

The earliest appointment I could get with a geothermal guy is July 7th!!

What is wrong with my system?

Thank you for any insight

109A_5

To me High Side pressure / temperature is too much refrigerant or you are not dissipating the heat properly from the condenser coil. Is the condenser core plugged up ? If you can't dissipate the waste heat it will never work correctly.

Barrym97

Thank you. water is flowing freely through the coaxial heat exchange... about a 9 to 10 degree differential in/out - and it stays in that range while the compressor is running

EBEBRATT-Ed

You have to put gauges on it and check the refrigerant pressure when it shuts off. Could be overcharged but I doubt it. Could be a scaled-up condenser or a bad HP switch.

Can you increase the water flow and see if that helps??

Water flow is usually about 3 gpm/ton of cooling on the condenser when the unit is cooling.

109A_5

Looking at the Troubleshooting Chart

And your are confident that these are not the problem.

Reduced or no water flow in cooling
Water Temperature out of range in cooling
Overcharged with refrigerant

and the superheat seems reasonable.

This is all that is left,
Bad HP Switch

HVACNUT

At 2 to 2.5 GPM water flow, a 12° TD would be better, but that would only increase your head pressure. 
It's a package unit so it should be a factory charge, but there's only one way to find out. Weigh it out.
This issue needs gauges, and if you're not certified, then a competent geo tech can check it out. Flow through the coax, reversing valve, over charged, TXV's, etc. Do you have or can you get a service history?

pecmsg

Barrym97 said:

Thank you. water is flowing freely through the coaxial heat exchange... about a 9 to 10 degree differential in/out - and it stays in that range while the compressor is running

If the water is flowing then that delta should be much higher.

Barrym97

I've spent days purging and watching for every last tiny bubble.
I got new cartridges for my Grundfos 26-99 pumps.
Water is flowing strong.

I finally admitted to myself that it may be something on the refrigerant side.
I hooked up the high pressure gauge on my manifold. Lockout at 180psi.

HP switch (Wilspec HS100-11-0014) is taking the unit out at 180psi.... maybe...

I can't find the specs for that exact pressure switch, but replacement high pressure switches for r410a systems are rated to open at 625 and close at 425psi, I see another spec at 630/480.

The switch has got to be the problem... Right?

So.... I jumpered the HP switch while keeping my eye on the pressure gauge...

It is pretty steady at 180 to 200psi

Then the CXM board takes the compressor out again... this time a code 4. LT1 low water coil temperature limit. This should never be code in the summer or while in cooling mode. The thermistor is just floating in the cabinent with the LT2 thermister... should be reading ambient temperature. About 82. I check thermister resistance - about 9000 ohms... about right for 82 degrees

I cut the wire... splice the ends together... infinite temperature ... get another lockout
I put a 330 ohm resister (first one I found laying around) in the circuit...that's about 260 degrees in thermister world.. definitely not too cold!!

I get another LT1 lockout

What in hot blazes is wrong?

Can LT1 be bypassed (just for testing .. of course)...

Very frustrating...

I wonder if my CXM board is bad. That seems like a nonsensical error code

HVACNUT

Didn't know this was closed loop. What type of HX? What's the in and out temps on the source side? 

Barrym97

It is a zero pressure "closed" loop - it is not pressurized.. there is a flow center in the loop

While compressor is running:
67 in 78 out today
15psi in 10 psi out

109A_5

Barrym97 said:

The thermistor is just floating in the cabinent with the LT2 thermister... should be reading ambient temperature. About 82. I check thermister resistance - about 9000 ohms... about right for 82 degrees

Substituting a fixed resistor for a thermistor may not be as good idea as it initially seems to be. If the Micro wants to see a change in temperature (over time) in the system at the place in the system where the thermistor should be located at, and does not see that change it may interpret that as a bad sensor and shuts the unit down.

The resistance at 82 degrees seems reasonable I would put the thermistor where it is suppose to be, not just floating around in the cabinet.

From the manual:

Water Coil Low Temperature Cut-Out Limit (LT1) - The
control will recognize an LT1 fault, during a compressor
run cycle if:

a) the thermistor temperature is below the selected low
temperature protection limit setting, and,
b) the thermistor temperature is rising (getting warmer)
at a rate LESS than 2°F per 30 second time period.
The LT1 input is bypassed for the initial 120 seconds
of a compressor run cycle.
LT1 Lockout Code = 4

Barrym97

a clue... why are there rust spots on my CXM board?

109A_5

That damage is water intrusion, environmental leaks or condensation. At this point you don't know if the contamination has caused any permanent damage. It may be successfully cleaned up using 91% isopropyl alcohol and / or plastic safe contact cleaner (found at HD) and an acid brush or an old tooth brush. Brush under the edges and / or flush out under the contaminated devices. After cleaning thoroughly dry off the board (compressed air or hair drier) before powering it up. If you use a hair dryer do it way away from the alcohol and / or contact cleaner cloud.

Or just replace the board if you are more comfortable with that solution.

Barrym97

Thank you all for walking with me on this install.  

I have completely bypassed  the CXM board while I watch all pressures and temps.   

House temp has dropped 10 degrees.  In about an hour.   

Unit works perfectly as long as **I** can sit in basement and be the controller board monitor.and thermostat interface. 

20ish degree drop in return vs supply

I guess that means I need a new control  board. So I just ordered one online.

 

Barrym97

New CXM board installed, everything works perfectly!
... I think...

2 more questions...

1. This unit was sold advertised as a DXM2 system. I don't think that is true.
I do not see any connections for a communicating thermostat. Am I missing something?

2. Is this unit wired for two stage operation? I mean, should I have 2 stage operation if I connect thermostat Y1 and Y2 to the board (blue terminal strip) Y1 and Y2?

Nothing is connected to Y2 (top far left) on the main circuit board. Is this ok? Should this be wired to the CXM board like G, Y1, O, W, C, etc? How can you tell when stage 2 is kicking in?

My high pressure goes from 100psi to 180 when the compressor comes on.

HVACNUT

If you have a 2 stage heat/cool thermostat, then hook up Y2 and program the thermostat. 
That's not a DXM2 board.