Heat Pump Help

[gregs]

Need some help with a heat pump. It is a Rudd Ultra series RPQL-024JEZ. It is at my in-laws house and they have 2 of the same units, one upstairs and one downstairs. The upstairs stopped working the other day and they called. Basically the indoor air handler works (fan blows) but the outdoor unit does nothing. I have worked on these before and somewhat familiar with them. Went down there tonight to check it out. Found the situation as they described. They have had issues with it doing this in the past but there ac guy wasn’t able to fix it. But he had figured out if you power off both units at the breaker and leave it sit for 5 minutes then turn one on first then the other it would reset and clear the problem. But alas that no longer solved the problem.

I verified that it has power to the outdoor unit at the control board. It does absolutely nothing. On the control board is a digital display that shows error codes. When the unit is working correctly it displays a 0 when it’s waiting to come on. If you turn the power off to the outside unit while the indoor unit is still on, you get an error code of L I think. But now it only displays a - on the display. Also it has a test button that allows you to override and start the compressor and fan for 5 seconds. I have used this button in the past to test the fan motor. But now that button does nothing. It also has another button that if you press it and the test button at the same time it displays past error codes. It does nothing when you press these. It leads me to believe that the control board is bad.

Looking for anyone that can confirm the displayed “code” is not really a code. I have attached pictures of it and the code list with nothing that looks like -.

 

[gregs]

Doing some quick research I found what I believe is the correct replacement board and it’s fairly reasonable ($150ish). Not sure if there is anything else I should replace. It does have another defrost board but I don’t think it would be a problem. I have replaced the fan motor, relay and capacitor last year. All the wiring looks good and I verified everything is still plugged in and connections are clean and tight.

https://www.supplyhouse.com/Rheem-47-102090-82-Control-Board-Kit?srsltid=AfmBOopNe4unrJlb7wzi2M9wXjSb2c88q5DbaXH-G-lqkHQvpzS9wtSg

 

[gregs]

It has this small relay mounted near the defrost board and it looks like that’s where the wires are going. I don’t think this would cause the problem but not sure.

 

[danski0224]

On the control board is a digital display that shows error codes. When the unit is working correctly it displays a 0 when it’s waiting to come on. If you turn the power off to the outside unit while the indoor unit is still on, you get an error code of L I think. But now it only displays a - on the display. Also it has a test button that allows you to override and start the compressor and fan for 5 seconds. I have used this button in the past to test the fan motor. But now that button does nothing. It also has another button that if you press it and the test button at the same time it displays past error codes. It does nothing when you press these. It leads me to believe that the control board is bad.

Looking for anyone that can confirm the displayed “code” is not really a code. I have attached pictures of it and the code list with nothing that looks like -.

Generally speaking, if the self test function on a component does not work, then the component is bad.

If the shown results do not match anything in the manufacturer described results, then it is bad.

You can try disconnecting other field wiring other than main power in to see if the behavior is the same.

I would recommend a surge protector if you install another board.

 

[gregs]

Generally speaking, if the self test function on a component does not work, then the component is bad.

If the shown results do not match anything in the manufacturer described results, then it is bad.

You can try disconnecting other field wiring other than main power in to see if the behavior is the same.

I would recommend a surge protector if you install another board.

Thats kinda what I think as well regarding the test function not doing anything and the weird display. Downloaded the manual for it this morning and went thru it and the wiring diagram to see if something jumped out as being a possible issue. The unit is an hour and half away, so I was limited to what testing I could do last night. But so far everything indicates the control board is bad. There is also a single red LED that is supposed to light when the thermostat calls for operation and its not doing anything as well. It should come on when you press the test button to overide and make the compressor and fan kick on, but it doesnt. The fact that the display just shows a single segment that looks like a dash(never changes) and there are no codes that match that, seems to indicate there is a problem. The only thing I didnt verify last night was the 24v from the thermostat, but I did figure out that without the thermostat and air handler being on (circuit breaker) then nothing happens on the control board (no - on the display). So I think thats all ok as well as the fact that it does operate the fan in the air handler when you try to turn it on.

The relay I questioned is for the defrost control. I dont think it would come into play as all that doesnt work until it gets around 5 degrees according to the manual. The control board seems to be a somewhat popular part that gets ordered so I guess I am going to order one of those. I feel like at a $150 its fairly reasonably priced as I was thinking it would be 2 or 3 times more than that, even if you could get it.

 

[gregs]

After looking thru the manual some more at the diagnostic codes I think I did find one that matches. It looks like a _ instead of a - that I thought it was. It lists the code as "ICC Board Mis-operation" and "Check ICC board compressor relay". The ICC is the control board and I believe the compressor relay is one of the ones on the board. I am going to order a new board and think that will fix the issue hopefully. I will then take the old board and see if I can test the relays and possibly repair it for a spare for the other unit.

 

[gregs]

Good news & not as good news. Got the new control board and went down after work to replace it. Also ordered a new compressor start cap and defrost relay because they where inexpensive and originals. Got everything swapped without incident. Tested the old cap just because and it was still good. Also tested the compressor windings for good measure. Threw the squirrel in and fired it up on cooling mode. Everything started and worked correctly. The display shows the correct readout and everything sounds normal. Checked the hot and cold pipes with my built in thermometer and they felt normal. Adjusted the set point a couple of degrees lower and let it run. After 10 minutes or so, it reached the set point and shut down like normal. Went out and double checked the readout and it was at 0 / standby like it should be. Hot damn its good to go, so I sat down to eat something for dinner (9pm). After about 10-15 minutes I had the brilliant idea that I should test the heat side. Ambient temperature was around 65 degress inside and out. Switched the thermostat from cool to heat and went outside to check the unit. It started and was running but the compressor was making a very slight rattling noise (I think it was the compressor but later thought maybe it was the reversing valve?). Anyhow after running a couple of minutes the outside unit shut down and gave code 21 (low pressure control trip). Double checked all my wiring and nothing was wrong there. By then it was getting late and I still had the 1.5hr drive back home.

So now I need to figure the heat side out. It has a defrost control board that the reversing valve is connected to. I need to test voltage in heat mode to see if its powering the reversing valve. But then I have to determine which mode the reversing valve gets powered (heat or cool). The other option could be a reversing valve that is stuck (which I have had on another unit years ago). Or could it be low on freon? But it seemed to work ok on cooling mode. This would be a lot easier if it was closer.... The things I get myself into.

 

[danski0224]

Low pressure is likely low refrigerant.

You would see this with gauges and superheat and subcooling. In cooling mode.

Probably have to pull out the charge and weigh it against nameplate data and lineset length.

 

[gregs]

Low pressure is likely low refrigerant.

You would see this with gauges and superheat and subcooling. In cooling mode.

Probably have to pull out the charge and weigh it against nameplate data and lineset length.

Very well could be. Strange that it works ok in cooling mode. Was thinking with a ambient temperature of 65 the load would be fairly even for either heat or cooling?

 

[danski0224]

Too cold to check AC.

As I understand it, proper cooling charge means proper heating charge.

 

[gregs]

If it ends up thats the problem then they would need to use there local repair company. I guess i need to narrow it down some more.

 

[gregs]

Looks like the reversing valve is electrically engaged in the cooling mode. So I need to verify its not powered in the heat mode. The other thought would be the piston inside the valve sticking and not sliding back to the heat position. Probably slim chance for either of these but I feel like I should check and put a set of gauges on it to see whats going on.

The one thing that was strange is the fact that there was a faint rattling noise in heat mode but not cool mode. I guess the heat load was higher than the cool load?

 

[PWC Repair]

Check the pressures with gauges. The older Rheem/Ruud units are well known for failing pressure switches. If yours has the type sweated into the lines, just add a flare tee and a screw on pressure switch to avoid opening the system. On a sticky reversing valve I've had a lot of contractors through the years have really good luck with the Supco 88 oil additive........it's like Slick 50 for your HVAC system LOL!.

 

[gregs]

Check the pressures with gauges. The older Rheem/Ruud units are well known for failing pressure switches. If yours has the type sweated into the lines, just add a flare tee and a screw on pressure switch to avoid opening the system. On a sticky reversing valve I've had a lot of contractors through the years have really good luck with the Supco 88 oil additive........it's like Slick 50 for your HVAC system LOL!.

I haven’t been back to see how it’s working in warmer weather. Been pretty mild, so not running heat or air. I will definitely check the pressure switch. Where would you add the tee? At the point that you attach the gauges?

 

[bonneyman]

Check the pressures with gauges. The older Rheem/Ruud units are well known for failing pressure switches. If yours has the type sweated into the lines, just add a flare tee and a screw on pressure switch to avoid opening the system. On a sticky reversing valve I've had a lot of contractors through the years have really good luck with the Supco 88 oil additive........it's like Slick 50 for your HVAC system LOL!.

Though I love Supco 88, you can only use it with mineral oil systems. The OP's nameplate says his unit is a R410a system - with synthetic oil no doubt. Mineral oil (and additives) don't mix with synthetic oils. Could cause more problems.

Also on a 15 year old unit, the RV could be worn and mechanically stuck in cooling mode or partially shifted. No quick fix for that. JMHO

 

[gregs]

I had the coil in a reversing valve fail in the heat pump at work a couple of years ago. I was having a hard time locating a replacement in a reasonable amount of time. Thought to myself its just a electro-magnet. So I grabbed a rare earth magnet I had and slapped it on. I could put my hand on the valve and feel the piston "thunk" when I put it on the end of the valve. This was all done with the unit off obviously. That magnet stayed on there for a while even after I got a replacement coil. Was thinking I could try that on theres to see if I could feel the same "thunk" or possibly move it back and forth in case its stuck.

 

[PWC Repair]

Though I love Supco 88, you can only use it with mineral oil systems. The OP's nameplate says his unit is a R410a system - with synthetic oil no doubt. Mineral oil (and additives) don't mix with synthetic oils. Could cause more problems.

Also on a 15 year old unit, the RV could be worn and mechanically stuck in cooling mode or partially shifted. No quick fix for that. JMHO

Nope, Supco 88 is compatible with ALL refrigeration oils.

 

[bonneyman]

Nope, Supco 88 is compatible with ALL refrigeration oils.

I wouldn't risk it in my customers units. If the current system oil is PAG there's miscibility issues.

This chart from Chevron seems pretty thorough. Good read. Talks about converting a system from one oil to another - not just topping off and mixing.
Obviously discussing car A/C not residential. Then again car compressors are externally driven. Home A/C compressors are electrically driven which adds a whole new layer of uncertainty. Plus, we're talking about an oil additive, not just oil. No one can tell upfront what the by-products will be. Risky.

https://latinamerica.chevronlubricants.com/content/dam/external/industrial/en_us/sales-material/brochures/TBCOMP_03_01_13.pdf

 

[PWC Repair]

I wouldn't risk it in my customers units. If the current system oil is PAG there's miscibility issues.

This chart from Chevron seems pretty thorough. Good read. Talks about converting a system from one oil to another - not just topping off and mixing.
Obviously discussing car A/C not residential. Then again car compressors are externally driven. Home A/C compressors are electrically driven which adds a whole new layer of uncertainty. Plus, we're talking about an oil additive, not just oil. No one can tell upfront what the by-products will be. Risky.

https://latinamerica.chevronlubricants.com/content/dam/external/industrial/en_us/sales-material/brochures/TBCOMP_03_01_13.pdf

Where's the risk? I suppose if something were to go bad Supco would be responsible. It's right in the literature...."Compatible with ALL refrigeration oils". I really don't think they'd advertise it that way if bad things could happen. The bean counters wouldn't allow it.

 

[bonneyman]

You're right - a problem would be Supco's fault. But you'd have a heck of a time proving it. And their pockets are alot deeper than yours or mine.

It's just we go thru some many steps to prevent entry of contaminants to a refrigeration system with driers, filters, triple evacuation, nitrogen flushing that to then add something that might cause some unknown chemical interaction is risky. The literature I linked has a really good explanation of what I was thing.