I’ve aquired an older RHEEM 3.6kw hot water heatpump

The heatpump unit, starts, works, runs for a while then stops - relying on the element

I want to diagnose the sensor readings and understand the run parameters to ensure it is working correctly

The PCB is stamped 052119 and exposes a socket but I am yet to find any specs on the pin out or API

Welcome any help thx.

 

If you have the model number and manufacturing date, Rheem support might provide specific diagnostics and troubleshooting documentation.

 

Have found something strange.

The 2x Hot Water sensors (Upper and Lower) are connected to a 10 pin vertically aligned header at the bottom centre of the control board.

The 2nd row of pins maps to the Lower sensor which gives a sane reading

The Upper sensor however is spread across the 4th (left) and 5th (right) pins. When checked using the different rows, we can see it reads sanely and its resistance lowers correctly when put into hot water.

The plug that these sensors is on is a typical DIN mount breakout which assumes alignment of the pins.

There were also a few cables going into this connector that had been cut off short? But otherwise you can see all the inputs to the right so everything has a home.

Of course without a schematic am not sure where the UPPER sensor should be plugged into. But it certainly looks wrong!

 

https://www.energy.gov/energysaver/heat-pump-water-heaters

 

What ambient temperature, is your heat pump dealing with

 

What ambient temperature, is your heat pump dealing with

Around 20° C

But the problem is a bit more serious, we replaced the capacitor for the compressor, and it seems to be spinning ok, but it is not the refrigerant

So that might be a problem with either the Gas or with a blockage in the system

Seems like the controller is working okay

 

With old compressors like that, the bearings get warn, and would not start only to blow the breaker and shutdown. Recognizing the motor/compressor was 20+ years old, after checking for shorts, the tech put in a larger starting capacitor and it ran. He mentioned, that we really needed a new compressor, but the larger starting capacitor would make it work for the time being.