75ZT Community

Not yet Dave. Haven't had time to be honest.

Well, the engineer from help-link came out today (I forgot we have insurance cover earlier). Decided that the fault wasn't in the mechanicals but was an electrical fault as the boiler switched on OK when selecting H/W but not when selecting C/H.

We await the advent of the electrician with bated breath

room thermostat or three port valve

Does the valve have sensor switches?

I imagine it is opened to heating slightly as we get one or two warm rads when the water heating is on. Apparently, the pump runs for one second or so when the heating is switched on then stops.

They have what is called a syncron motor.

http://www.ebay.co.uk/itm/SYNCRON-MOTOR ... _500wt_676

When the thermostat calls for heat this give power to the motor. the motor drives across, opens a paddle in the waterway and at the same time makes contact with a micrswitch, this microswitch then gives power to the pump and boiler. Pump and boiler come on and water is sent via the port opened in the valve to the rads, little bit more to it than that but in essence that's it

Thanks Dave. Pretty much certain it is the valve assembly then.

The microswitches inside can fail. Slightly worse if they fail on as one of mine did. Couldn't understand why the boiler was running when we went to bed one night. Boiler hot but rads and HW off. Boiler would fire for a few seconds but with no heat being delivered anywhere, switch of again quite quickly. Sometimes the motors can be a problem too and not have enough power to hold the valve operated.

I replaced the zone valves as I was draining the system to do some other work, but you can usually get replacement heads with motor and switch, or if it's just the motor, they can be obtained for some valves.

Tehy're coming out tomorrow to replace the valve. That's not bad service for a Saturday I suppose.

All fixed. Good service from the company as well as no charge

It was the valve itself not moving sufficiently to switch the heating circuit.

I hope you impressed him with your understanding of how the system works

takestock wrote:I hope you impressed him with your understanding of how the system works

He spent more time quizzing me regarding the aerodynamics of the Nimrod and U2 Dave.