New renters were unaware the unit was running in Electric mode,The garage was not being nicely refrigerated in Summer heat. Quiet in the garage was not alarming.
Half-way through a three month incident I was at last painfully aware, and driven to find a repair. I was the installer. The unit was sold to me by General Pacific, Inc. a large supplier of parts for industrial electrical equipment to Bonneville Power Administration and also a low-cost supplier of heat pumps and more to area weatherization contractors. I buy and install many Panasonic bath fans, with pricing 30% below that at Home Depot. The Rheem HPWH was a one-off for myself.
Who to I call? I talked with a competent plumber at Portland's "Water Heater King" store where I am a good customer, and learned there are large problems with the Control Board, being resolved by Rheem at no cost. Just call the Rheem heat pump service people in Montgomery Alabama, at 800-995-0982 weekday daytime hours. Get parts and do the repair myself. The parts offered are the Control Board, Part Number AP22260, and three identical Thermistor Kits, Part Number SP20845.
Thermistors? They are supposed to be ultra rugged. How could they fail? I would try just replacing the Control Board. Still, get a look at the thermistors. Detach power leads and detach the tank lid with its ten screws,
A Rheem YouTube video will be shared days later but will be of little help:
Go ahead now to replace the Control Board. It is all of the black expensive-looking control interface and display, up-front as I oriented the tank. Pry off a cover. Remove two screws. Extend many leadwires to view connections at the backside.
View the backside of the replacement board. I will hold the boards side-by side and move connectors one at a time.
Wires as found with a minimum of crossings.. Swapped leads may not be as neat.
Back together and seeming to be solidly in Heat Pump mode. Next morning though, I will be called by a Rheem technician, advising for the first time that the thermistors must be replaced. Some unique identifier associated by a past alarm, causes thermistor rejection ever-after, regardless of control board replacement. Something like that. All advice is verbal. Each new conversation is with a different Rheem call center person, trained with a different set of knowledge.
First swap the thermistor easiest to reach, "Suction," on yellow leads.
Higher up on the same pipe, swap a thermistor from blue leads, Discharge.
Gray leads, Evaporator.
Repair completed. I had worked atop a piece of 3/4" plywood resting on the tank cylinder wall and the heat exchanger, doing no harm. The work areas are inconveniently close to the cylinder wall and the heat exchanger. It was never intended that a home owner would do this. I could not replace the six cable ties I cut. In the factory, this tidy assembly might have been completed before the tank cylinder was applied. The odd object at hight hand is my banged-up work light propped at the tank wall edge.
I am offended by large pieces of gummy material, two pieces four inches square, not the same as butyl strips about one inch square applied in the factory to better couple a thermistor to adjacent tube surface temperature. The huge squares are not scored for separation to useful size.
At two places on each thermistor kit box, there is warning in effect to not touch the dangerous gum. I will treat the nasty squares as needing professional disposal. Not in my trash. I will mail them to Rheem, with complaint, as a pdf printing of this blog post.
If thermistors are a repair item, the factory wrap of tubes and thermistor should be a thick fabric with velcro strips. No foam tubing and zip ties. Surely there are incidents of disastrously cutting a leadwire somewhere, reaching blindly with sharp snips.
Avoid any need of cancer-causing gum.
Study the principal guide for consumers here,
Rheem randomly sent this PDF as an email attachment, following one phone conversation. Now a Google search brings nine results, none the guide. Therefore, I store a copy in Google My Drive:
The troubleshooting and repair parts listings did not imagine the control board failures now occurring. Nothing I have done here is mentioned.
It is odious that one offered solution here while under warranty, is free replacement of the entire HPWH. There's a lot of bad carbon in that. Repairs must be offered at no cost for at least twenty years, the least lifetime I think is reasonable for a water heater. The consumer trust thus guarded is essential to needed adoption of a HPWH, in every home, well-subsidized again in the Inflation Reduction Act of 2022,
I await honest statements from Rheem about what is happening. Why the thermistor swaps? Is there a better solution in circuit board recognition of sensors surely still good, avoiding replacements.