Relay problem with hot water tank?

Active member

Our hot water tank is on a separate zone in our radiant floor heating system. Most of the time the system works fine, but whenever we use "too much" hot water (fill the bathtub and run the dishwasher) the boiler does not come on to heat the water tank. If we take the relay for the household hot water out of the "zone box" and then put the relay back in place, the boiler immediately fires up to heat the hot water tank. No one has been able to figure out why popping the relay out and then back in resolves this issue or why this issue occurs in the first place. We replaced the relay with a new one but that did not resolve the issue. The other zones that heat the rooms are not affected.

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central heating Maidenhead|boiler installation Reading