We had a customer call with a question about an AO Smith FPTU-50-130 electric / heat pump water heater.

The question is: What happens if the heat pump part fails, will there still be hot water?

The installation manual does not answer this directly, and the optional "MODE" setting of electric water heating is only active for 48 hours. After this time, the water heater goes back to using the heat pump. (Hybrid mode)

I found a "Customer review" on AO Smith's web site:

" I had previously installed an ao smith 80 gallon heat pump/hybrid hot water tank. I got an alarm and error code that told me to call support. After talking with support and doing the tests that they suggested, it was determined that the heat pump had failed. Fortunately, the electric mode still worked which gave me time to get a replacement HW tank. The support people gave me a return authorization number so that I will be reimbursed for the cost of the new water heater. "

It looks like the unit will enter into an "Electric only" mode if there a problem with the heat pump section. (Like a low-pressure switch opening).

Fault codes:

ECC fault code

Diagnosis: The compressor runs, but will eventually go into fault of ECC, requiring a reset after a day or two.

Trouble shooting:

Look for an 8-degree drop across the evaporator (Exposed refrigerant coil).

There is a good chance there is a refrigerant leak, look for oil residue in the drain pan, leak test with an electronic detector. 

Call for factory Tech support/ warranty replacement authorization. Call our Technical Assistance Hotline at 1-877-817-6750 for further assistance.