CH takes a while (or not at all) to come on?

Hi there,
I've posted before regarding my noisy motorised valve: //www.diynot.com/forums/viewtopic.php?t=154371
(which I've not done anything about yet) so this may be related.

Anyway, my boiler is an Ideal Classic FF350.

I've had some trouble with the CH before but it seemed to right itself on it's own: //www.diynot.com/forums/viewtopic.php?t=79636

The problem I have now is that the central heating takes a long time to fire up (if at all) when the system is cold. eg. When I get up in the morning and the heating has been off all night and the the house is cold, normally I would turn the thermostat up and the heating would come on and stay on until the thermostat temp was reached. Now, however, nothing happens when I turn the thermostat up (even to max 30C). It has sometimes come on if I keep turning the thermostat up and down but more often than not nothing happens. The heating will eventually come on anything from 10 minutes to 30 minutes later and work as normal. The other thing I have noticed is that the temp seems off. I tested this with a thermometer and the temperature is +5C out on the thermostat.

Any ideas as to what to check (bearing in mind I know nothing of plumbing!)?

Thanks for any help, it's much appreciated.

I would be looking at the ch zone valve, or the 3 port valve depending on what you have.

One assumes that everything is ok for the HW? If so this eliminates the boiler.

gas4you said:

I would be looking at the ch zone valve, or the 3 port valve depending on what you have.

One assumes that everything is ok for the HW? If so this eliminates the boiler.

Click to expand...

Yes the HW is fine.

If you have a 3 port mid position valve, it would not surprise me if the second microswitch is faulty. Dirty/burnt contacts can stop the power going out of the orange wire to fire the boiler.
When both HW and CH are selected and both are in demand, the valve will go to mid position and you'll get both HW and CH. (NOTE It's the cylinder stat that lights the boiler).
As soon as HW is satisfied cylinder stat cuts out and valve moves to CH only position. The boiler will have stopped momentarily but starts again from the power coming out of the orange wire. But if the microswitch is faulty then it wont happen.
It's possible the valve is not going across to the CH only position, but this can be checked by taking the actuator head off the spindle and testing it without any interferance from the spindle which might be stiffish.

Thanks for that info Mandate. Any chance of a step by stepo guide on how to do that as I'm a novice? I can take a photo of the valve unit if it would help identify it?

If you're a novice and have little understanding of the working of the motorised valves, I think you will struggle trying to pinpoint the true cause of the problem.
If you only get heating along with HW, the problem is valve related.
Could be wiring (grey wire not live)
Could be stiff spindle. Could be motor. could be any of the two microswitches.
You may have to replace 'motor', 'actuator head' or the whole 'valve'.
If you're not in a position to replace whatever is necessary, you could use a qualified heating engineer.
There's plenty on this forum regarding motorised valves if you wish to know more.