Does the temperature of my hot water tank have any affect on my hot water boiler system?

Asked by Mindy
Littleton, CO

Do I need to have my hot water tank set on the hottest setting for maximum efficiency for my boiler system?


Andy Mazal

Answered by Andy Mazal

Boulder, CO

Vertical Elements, LLC

February 18, 2014

Mindy: You were not specific as to whether your boiler system also heats your domestic hot water, which is often known as a "side-arm" tank. I assume that it does, however, since a separate gas-fired water heater would have no effect on your boiler. Assuming I'm correct in my assumptions, then no, the setting on the hot water tank will not affect the efficiency of your boiler. In fact, the hotter it is set, the more the boiler will run and the more energy it will use. The hot water tank is essentially a "zone" to your boiler. You probably have a couple of zones in your house (upstairs / downstairs, etc.), each controlled by a separate thermostat. Well, your hot water tank is just another zone -- when it calls for heat, the boiler fires and circulates hot water through pipes inside the tank, transferring the heat from these pipes to the water in the tank. So, you should set the water heater thermostat to the lowest possible setting you can, without running out of hot water. Use a cooking thermometer to test the temperature at a faucet; it should be around 120 - 125 degrees. Much hotter than that and you're just wasting energy (and at risk of scalding.) Andy Mazal BPI Building Analyst

Tagged In: hot water Tank, hot water boiler

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