Room thermostat not always starting boiler

[rwb196884]

Hi,

Our house has two central heating zones: the living room which has a programmable thermostat, and the rest of the house that has a simple dial (Honeywell) in the hall (it will be 10 years old).

We have the heating on continuous and use the thermostats to turn it on and off.

I have noticed that after turning up the dial in the hall the heating does not always start. (Sometimes there is a long delay before the boiler starts.)
However, turning up the heat in the living room will cause the boiler to start promptly and all radiators to get warm, but then turning the living room down again will turn off the whole system.

What are the possible causes of this problem?

Thanks,
rwb.

 

[Harvest Fields]

That the thermostat in the hall is not actually connected to anything and that you only have one zone that is connected to the stat in the lounge

 

[SavageW]

If two zones could be the zone Valve connected to the hallway stat is not fully motoring over to make the switch live to the boiler.So you turn up the living room stat an the zone valve this controls motors over fully an fires the boiler,but the zone valve the hallway thermostat controls has only partially opened (burnt out motor or valve body slightly seized) meaning all the rads will heat,which could explain why then you turn the living room stat down all the rads stop heating because the other zone valve is not giving demand to the boiler

 

[firemant]

If you select Living Room only (other stat right down), does it heat alone or does it bring on the rest of the house?. If this is the case, then a jammed (partially) open Motorised valve.(I would say new valve required)
If the ROTH stat (with LR off) eventually, or sometimes, brings on the ROTH, then an intermittent fault with the MV (sort of as per SavageW). This could just be the motor on its way out, and typically presents erratic behaviour along the lines of your issue. I would suspect a motor would suffice

Does a satisfied stat independently turn off its own zone?

 

[rwb196884]

You were correct SavageW. The valve failed completely on 24th December, followed on 27th by the other.

Specifically, the lever in the valve was not pushing the microswitch properly and therefore not sending the signal to the boiler to start up.