Central Heating Fault At My Mums

cruickgl

Hello, I hope someone can help. I am having the annual problems at my mums house with her central heating !! Put simply, she has got hot water but the boiler will not fire for the heating. Now the details. She has a Glowworm Flexicom 15hx boiler, a hot water tank, Grundfos Selectric Pump, Drayton MA1 mid-position valve with a Lifestyle LP522 Programmer and the wiring centre, all in the same cupboard.
I turned on the heating yesterday and, in order to check it was all working, turned the room stat full round to 30c to make sure the boiler fired. Went upstairs and nothing....turned the cylinder stat up and the valve went to mid position and boiler fired. Radiators also started to warm up. Turned cylinder stat off and valve went to CH and nothing. Went round the rads and bled them all (had air in a bedroom one) but still the boiler not firing. Got a meter and opened the wiring centre up and got my mum to turn the room stat up and down (its an old dial one) and got 240v bursts when it should be on and not 240v when it was right down, so am confident the room stat is working fine.


Now, due to lasts years !!!!!!ing around I had to buy a new motorised valve (just the top motor bit) so that bit is only a year old. So, I took the motorised valve off and the spigot only turns 45 degrees...and I needed to use some bullnose pliers with a bit of effort to manipulate the valve.....is this normal or should it be more free than that?? I am wondering if the actual valve is crudded up and needs replacing, and even though the motorised valve is right over on the CH side when the heating should come on its not and therefore no signal is sent to the boiler to fire.....does this sound right ?? or could I have a programmer fault or even a boiler problem (though if it fires when the DHW needs heating I don't think that's it??
Basically what testing can I do, and how?? as if it is not the valve I don't want to drain the system to change it out if I can prove the valve is working ok.
Does this sound clear as mud?? I hope not, but if someone can talk me through it I would be grateful....my mum has had various problems over the last few years and I'm fed up with calling a heating engineer in if its something not gas related that I might be able to sort myself and save her £200. Cheers in advance.

espresso

Remove the actuator from the valve.

With the programmer set to heating ON, turn the room stat up high and see if the motorised valve operates and fires up the boiler.

You may be able to free up the tight valve spigot by repeatedly turning it back and forth but they do only move about 45 degrees full travel.

Cyberman60

Yes, it sounds as if it is the valve. I replaced my three-way valve last year myself as it had seized and I was only getting heating and no hot water. If you test by switching between options of heating only, hot water only or both heating and hot water you should hear a whirring noise as the valve operates.

cruickgl

Hi, only just read your replies. Have been at work all day. I will pop round my mums tonight and have a go.....if the boiler doesn't fire with the actuator off then can I assume the motorised actuator is faulty?? If so, is it likely to be the synchronous motor that you can buy from screwfix for about £15 (item 28670) or would it be the whole thing??? And if its the whole unit and its only about a year old...could it be worthwhile changing the whole valve unit in case a stiff spigot has caused the motorised valve to fail ??

espresso

cruickgl wrote: »

Hi, only just read your replies. Have been at work all day. I will pop round my mums tonight and have a go.....if the boiler doesn't fire with the actuator off then can I assume the motorised actuator is faulty??

It depends just how tight the valve spigot is to turn. Taking it off the valve, the boiler should fire when it operates - depends if it does or not?

could it be worthwhile changing the whole valve unit in case a stiff spigot has caused the motorised valve to fail ??

The motor is unlikely to have burnt out if it is only a year old. They are designed to stall when they reach the end of their travel with power applied.

...............

cruickgl

Hello, just to let you know I have fixed the problem. I took the actuator off and ran the heating and the boiler did not fire. I did some checks in the wiring centre and followed the wiring through and discovered the orange wire from the actuator came away in my hand when I tugged it. I have re-terminated it and the system is running fine. The orange wire ultimately ends up signalling the boiler to activate....or in my case not. Thanks to all who helped start me off on my fault finding trip.

Ruski

I was going to say check the microswitch in the actuator head is making contact when opened - same diagnosis, just the other end of the cable


Always give your terminals a tug when you think you've finished!


Russ