I just built a new home and have a natural gas well on the property. I installed a tankless water heater that runns for natural gas. The problem I have is that when the gas well is not providing gas we have no hot water. I would like to install a back-up electric hot water heater and need to know how to connect it into the system. Should I have shut off values and turn them on when I need it and fire up the elelctric heater or is there a way to keep them both on at the same time.

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Originally Posted by js242

i just built a new home and have a natural gas well on the property. i installed a tankless water heater that runns for natural gas. The problem i have is that when the gas well is not providing gas we have no hot water. i would like to install a back-up electric hot water heater and need to know how to connect it into the system. Should i have shut off values and turn them on when i need it and fire up the elelctric heater or is there a way to keep them both on at the same time.

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Interesting question. It bwould not be cost efficient to have both heater run atv the same time.
I wouls hook the heaters up ins series, ( hot from the gas to cold in the electric) with a bypass valve, (see image) on the backup heater.
The gas heater to be downstream from your back up heater.
Install a switch near the electric heater so you can turn it on or off. When the gas fails turn on the power and shutthe bypass valve and open up the two valves on the electric water heater and you're in business.
If you wanted to keep them both on at the same time you could keep the bypass closed and use the gas heater as a primary heater and the electric as a storage tank. That way if the gas failed the electric heater would pick up the load without you having to doanything.
Sound like a Plan? Cheers, Tom