Hot Water too Hot with Vaillant Ecotec Boiler and Vented System Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[jhc62]

I have a Vaillant ecotec boiler with a hot water tank and vented central heating system with a Y 3 port honeywell motorised valve
I have a Salamander pump driving a disabled shower enclosure.
If I set the tank thermostat to 60'C and the hot water setting on the Vaillant to 60 and the radiator setting on the Vaillant to 60 the shower works fine.
The salamander cuts out if the hot water > 60'C

If I set the Vaillant radiator temperature to 65-70 on a cold day, the radiators are warmer but the hot water also gets too hot and the salamander shower pump pulses and you are advised to switch off or you'll damage it.
My question is why does the radiator setting heat up the hot water as well ?
I've checked the tank thermostat so is it a 3 port valve fault or a wiring fault ?

[jhc62]

Replacing the hot water tank thermostat seems to have fixed the problem. I had checked the thermostat with a multimeter on several occasions while it was running and gave the right result, obviously it was sticking intermittently and causing the hot water to overheat.