Heating does not come on!

[alfie]

Hi,

Today my Heating did not come one [Happy Xmas :-( ]

If I click the room thermostat up to ensure the heating should kick in and switch the programmer on for heating - nothing happens. The boiler does not fire up. The pilot light does stay on, I had to change the thermocouple about 2 months ago.

If I turn the hot water on then the boiler fires up OK and goes off when the Water is up to temperature.

I had a look in the Airng cupboard at the wiring board and with a Multimeter I could see that the Voltage changed ( between 0 and 240VAC) from the Room Thermostat and from the Programmer when they were switched ON and OFF.

Any idea what is supposed to strike up the boiler for Heating ?

The motorised Valve doesn't move either.

What should I check next ?

The boiler is a Myson 50B

Help

Alfie

[Mike Dodd]

I'm in danger of speaking of things that I know next to nothing about, so treat with a pinch of salt...

But, the motorised valve should be switched by the CH demand, so the fault appears to be related more to do with the wiring on the thermostat / programmer than the boiler or valve. Is it possible (do you feel confident) to bypass the CH demand from the programmer (i.e. short it to Live, or whichever phase it switches) to check that the programmer hasn't gone open circuit.

(in the manner of the Haynes manuals, everywhere, sensible advice left to the end...) - you have checked that the programmer is set to enable the CH?, and that it wasn't switched off (leaving just HW on) for the summer?

[Fentoozler]

9/10 this is the syncron motor inside the motorised valve head. Is it a Honeywell or Drayton? Change the motor (for Honeywell, they recommend you get a Honeywell motor as it they are more robust as their valves can remain open (i.e. powered) to CH if that was the last demand, even if demand has now ceased, therefore more wear on the motor). If it is a Danfoss HSA3 or HSA3D then its unadvisable to replace the motor, you should change the whole head. Plumb Center sell motors I think, as do Screwfix for that matter. If that doesn't cure it, you've probably got a faulty head unit - again it will depend whether this is a dry or wet exchange - a general guide is that Honeywell heads will have a raised dimple on top if they are exchangeable, no dimple then you must exchange the whole valve & head. Drayton will have a button on the side which you can depress and the head will come off, no button then you have to swap the whole thing.

Of course, you may simply have a faulty room stat or programmer. If you have an ACL/Lifestyle programmer, these are prone to strange errors and malfunctions. Honeywell room stat - join yellow (2) and red (1) together to loop out the room stat. Remember, this is 240v so isolate beforehand.

Angus

PS: On many motorised valves, you can manually override the head onto CH mode by pulling a lever over and hooking it open - this should activate the micro-switch and turn on your heating if timer and stat is set to demand. This doesn't always work though.

[Fentoozler]

**** yellow = (3), my mistake

[Mike Dodd]

Aha?, the CH demand goes THROUGH the motorised pump? (i.e. demand is carried through to the boiler only when the valve is open for CH?) - if so then I'd agree with your description, since this is a single point of failure (which I'd discounted, not realising that the valve controls the demand to the boiler)

(ok, just googled on a 3-port, yes, demand is through the valve - all now makes sense!)

Suspect valve itself is jammed if no CH demand for a while - maybe remove the actuator and loosen the valve by hand (with a pair of pliars) before refitting the actuator?

[alfie]

Thanks, it is a Ddrayton Valve, I will replace the Synchron motor and see what happens.

[alfie]

Thanks, I have had the valve to bits and checked connections and to check the voltage. Even with the Motor is not in situe but still wired up the motor does not turn - I hope it is the Motor.

[Steve S]

I happened to be in the dreaded B&Q this evening, and spotted that they are selling synchronous motors for motorised valves. If you are in desperate need....

Steve S

[alfie]

Thanks alot, I will get myself down there tomorrow.

[Andrew Gabriel]

Wickes also keep one type of them.

[alfie]

Good news, I fixed my Heating. I tested the Synchron Motor by putting a plug on it and pluging it into mains socket and it ran fine. I checked the voltage on the wiring board and all the signls form the programmer, room stat, cylinder stat looked good. So I took out the little circuit board and worked out the circuit layout and discovered that one of the micro switched was not working - swapped it out and hey presto - all working.

Thanks all for your help - it only cost me pennies (plus about 3 hours of my time to fix).

Alfie

[Steve S]

"alfie" wrote >

Well done, Alfie. Isn't it satisfying when you 'beat the system' by repairing down to component level?Thanks for the posting the outcome.

Steve S