Saturday, August 13, 2022

Interrupted Energy Savings With My Rheem Hybrid Heat Pump Water Heater

Rheem Professional Prestige
Pro Terra Hybrid Electric Water Heater
PROPH65 T2 RH375-50
S/N Q 272 026 175
Publicizing defect of year-2020 Control Board Part Number AP21386 Rev 00 and, perhaps, associated thermistors. Offering hope of the durability of replacement Control Board Part Number AP22260 and replacement thermistors Part Number SP20845.

Electricity usage in my rental home has spiked since April, 2022. A problem was evident to me in charting the April billing. Quite amazingly a problem was suggested in early-June by my electricity provider, Pacific Power!. Electricity usage had been down 40% for fourteen months since HPWH installation in February, 2021.

For three months, all of the savings were cancelled, running on resistance heaters with periodic automatic attempts to revert to Heat Pump Mode. Now-repaired and seeming to run reliably 100% in Heat Pump Mode, I hope the charting of electricity usage will again inspire others to replace their ordinary electric or gas water heaters,

Here is the chart at 12/2/2022:

And here is monthly tracking by Pacific power, leading them to again notify excessive usage.

With the notice of excessive usage, Pacific Power offered this conservation advisory:

All that is potentially helpful is a table at page 4 of 15:

I am overdue to find savings in a HVAC heat pump, and that is not a factor in excessive usage now, except that we must not resume usage of a window air conditioner next Summer. Renters have never used electric space heaters.

Counseled by Rheem, we viewed the condenser plates, finding normal dry conditions; no icing. The HPWH smoothly running in Heat Pump mode chilling the garage, is then dismissed of involvement in unusual draw of electricity except that, maybe someone is taking really-long showers.

We tripped the circuit breaker feeding a proper cable underground to a Shed on 12/4/2022 for whatever reason, as the least bothersome next step. Daily usage did not change. We are wanting again the energy-conserving usage for same months a year ago, for the month of November 2021: 431 KWH, 13 KWH per day, $51 billed, instead of that for
November 2022:  954 KWH, 28 KWH per day, $99 billed.

Something is still very much amiss.

Rating my interaction with Pacific Power, I suggested that they should care to know what is happening. I had asked: Could I log demand on each circuit breaker? Answer: No. 

I am not keeping up an Excel chart of July 2022 over smaller time scale, that better illustrates history associated with the Heat Pump Water Heater:

Now return to the naive beginning of this post:

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,

See little resemblance to a GEN 5 THERMISTOR REPLACEMENT diagram among materials emailed by Rheem. The work area is on the far side opposite the Control Board. The tank cylindrical wall is very much in the way. Cylindrical foam insulating jackets held by many zip ties must be removed and are found bonded to thermistors by gooey thick adhesive wrap.

A Rheem YouTube video will be shared days later but will be of little help:

Rheem hybrid thermistor access

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.

Each thermistor kit has three new clips to choose from. Learn that the clip removal or attachment is thus with a twist.

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 right 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.

What does the warning mean? is vague here. Is risk only with ingesting or chewing the gum? I won't touch it.

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, 

Use & Care Manual

Rheem AP21681 Rev 02

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:

 Rheem AP21681 Rev 02

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.