We have a one-year-old Bradford-White 65 gallon Defender dual in/out unit which serves both domestic hot water and radiant floor heat in one room.
Leaving for a week, we turned down the radiant heat thermostat and there was no domestic hot water use. Upon return, we found water in the carpet. It's an older home with no floor drain. A careful examination of all other joints and systems led us to the conclusion the water heater pressure relief valve had dumped. (Yes, I know it should be vented into a drain or outside, but the heater is in the middle of the house in the mechanical core. I'm working on options now.)
The heater thermostat was set only 1/3 of the range between "Hot" and "Very Hot". In fifty years here, we've never had a water heater blow off. The previous B-W sat in the same place with the same load for twenty years with no problems. I'd thought as long as the thermostat was functioning as designed, the temperature and pressure would never exceed the 210-degree, 140-pound pressure relief valve design setting.
First, what happened? Is it likely we've got a weaker-than-spec pressure relief valve? Faulty thermostat?
Second, what, other than turning down the heater thermostat when we leave and proper venting of the pressure relief, what else should be done to prevent this happening again?
Third, the water heater ain't movin', so the vent has to be made to work from where it is; what are the limitations on venting up two feet and eight feet horizontally over to the outside wall?
jack vines
Leaving for a week, we turned down the radiant heat thermostat and there was no domestic hot water use. Upon return, we found water in the carpet. It's an older home with no floor drain. A careful examination of all other joints and systems led us to the conclusion the water heater pressure relief valve had dumped. (Yes, I know it should be vented into a drain or outside, but the heater is in the middle of the house in the mechanical core. I'm working on options now.)
The heater thermostat was set only 1/3 of the range between "Hot" and "Very Hot". In fifty years here, we've never had a water heater blow off. The previous B-W sat in the same place with the same load for twenty years with no problems. I'd thought as long as the thermostat was functioning as designed, the temperature and pressure would never exceed the 210-degree, 140-pound pressure relief valve design setting.
First, what happened? Is it likely we've got a weaker-than-spec pressure relief valve? Faulty thermostat?
Second, what, other than turning down the heater thermostat when we leave and proper venting of the pressure relief, what else should be done to prevent this happening again?
Third, the water heater ain't movin', so the vent has to be made to work from where it is; what are the limitations on venting up two feet and eight feet horizontally over to the outside wall?
jack vines
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