Upper and lower thermostat settings

Old 11-12-18, 07:13 PM
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Upper and lower thermostat settings

Good evening,
the wife is trying to save some money and changed the settings on our electric hot water heater. She didn't realize she only turned down the bottom one. So the top was set to about 160 and the bottom was 120. Shortly after this we ran a tub full of hot water and the wh commenced blasting hot water and steam through the pressure relief valve. What happened? We reset the thermostats back to the same level, but should I investigate something else?
Appreciate the help!
Old 11-12-18, 07:24 PM
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The combination of the high set temperature and probably high water pressure caused the relief valve to open. If it has reset and there is no dripping you should be ok. 160° is too hot for safe hot water usage. 140° should be the maximum and 120° is the recommended norm. You could increase to 125° for slightly hotter water.
Old 11-13-18, 04:43 AM
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Set both thermostats to the same temperature. You are not saving anything by turning down only one thermostat.
Old 11-15-18, 05:45 AM
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Have you run a whole tubful of hot water in the past with no more usage of any water for the next two hours and with no tripping of the relief valve?

Were either of the thermostats always set to around 160 degrees in the past?

If you do not have an expansion tank, the normal expansion of the entire tankful of new water heated to 160 may well have been enough to trip the relief valve.

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