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Issues with Sanden CO2 Heat Pump Water Heater
I had a Sanden CO2 Heat Pump Water Heater system with a 43 gal tank installed just under 6 months ago to replace an aging 80 gal electric tank.
While I am impressed with the energy savings, there are two issues that have plagued the system since install. I can't say Sanden technical support has been helpful or very responsive to my concerns which has been disappointing.
The system is used for DHW only. I have a Taco recirculation pump. The system was installed by a professional in the area, and far as I can tell it was done correctly.
The issues are as follows:
1) Wide fluctuations in hot water temperature. If you request hot water at the wrong time (basically right before the system thinks it should start making more hot water again) you may end up with a barely warm enough shower. I like decently warm showers, as does my wife, so maybe this isn't an issue for most people. But this was never an issue with our old electric tank. I know the system is set to turn on at 113F, but I have found at times that some showers are only getting water in the 105-106F range for the duration of the entire shower. If the heat pump was recently on then the water is piping hot and there are no concerns about temperature. This is an issue no mater the temperature set point (150F,160F,165F etc).
2) System pressurizes all of the water lines in the house. Anytime the heat pump is running, it pressurizes the lines in the house. If you open a faucet or flush a toilet you notice a distinct increase in pressure that subsides after about 5 seconds. This hasn't caused a problem....yet. I can hear my toilets release a bit of water here and there when the system is on. This is more annoying than anything else. The setup does not include an expansion tank like my old resistance hot water heater. This was not an issue on the old resistance hot water heater setup. Seems very unrefined, especially at this price point.
To trouble shoot these issues I turned off the Taco recirc pump for several days. The issues continued.