No heating - any clues?

[Suzanna]

Hello, wonder if anyone can help me? I recently had problems with my boiler (had to keep resetting it and the blue light flashed constantly) and an engineer fitted a new PCB board. This solved the blue flashing light problem but we still have problems with the boiler. We have hot water whenever we need it but the heating sometimes refuses to come on (40 - 50% of the time). We try resetting the boiler; turning the thermostat up and down; turning the electric off and back on - most things we can think of. The blue light no longer flashes and the hot water is constant - just this weird situation with the heating. The red light in the airing cupboard flashes as if it's trying to receive the thermostat signal but nothing happens. I hope I'm making sense here. The boiler is a Greenstar Ri. I have tried to contact the heating engineer who fitted the PCB board, only last week, but he is not getting back to me.
Thanks

 

[picasso]

Do you have a wireless stat ? if so have you tried changing the batterys.?

 

[CombustionGuy]

more information on the room stat and box in airing cupboard would help (make and model of controls

 

[Suzanna]

Thank you! We very recently replaced the batteries in the thermostat.
The programmer is a ST6400C Honeywell
The thermostat is a Drayton Digitat SCR

Any ideas?

Thank you once again.

 

[picasso]

Is there a green light on the reciever ? the red light is a signal being recieved from the stat but its the green light that turns the heating on.

 

[ServiceNumpty]

The problem will be the faulty Drayton SCR, the relay within the unit doesn't 'engage' although the light will come on.

 

[picasso]

I reckon your right just the op didn't mention a green light.

 

[Suzanna]

Thanks for this. The receiver does have a green light. I have stood by the receiver to check this (on many occasions) and the red light flashes, then the green light will come on. Occasionally, the boiler will then fire up but often it does not despite the green light being present.
About half an hour ago I managed to fire up the boiler by turning the electric off in the airing cupboard and pressing the 'over ride' button. This does work very occasionally but often has no effect. It seems to have a mind of its own and will work sometimes and sometimes won't.

 

[Suzanna]

Thinking about it ... the green light is often intermittent. I notice now (when the boiler is on) the green light is constantly on.

 

[ServiceNumpty]

You can normally hear a click when the Drayton SCR operates, if the green light comes on without the audible click then my moneys on the SCR

 

[Suzanna]

You can normally hear a click when the Drayton SCR operates, if the green light comes on without the audible click then my moneys on the SCR

Thanks for this. I'll test this theory out tomorrow and will listen for the 'click'. I don't want to turn the heating off now to check because it's a bit chilly in the house and I doubt I'll be able to get it to work again!
I'll let you know if I hear anything and thanks very much for taking the time to assist me

 

[Suzanna]

I tried to start the heating today on many occasions and have only just succeeded by, once again, turning the electric off in the airing cupboard and switching on again - although this often has no effect at all.
Before I got it going, the green light was on the SCR and the red light occasionally flashed but still nothing happened. When I managed to boot the boiler (by turning electric off and on), the green light went out and the red light began flashing. The green light then came on and I heard a faint 'click' and the boiler fired up. Does this mean that it is not a faulty SCR? If so, any other ideas as to what it could be? It's frustrating and baffling!
Thank you!

 

[ianmcd]

link out your external controls and this will confirm whether it is a stat fault or a boiler fault, does sound like an SCR fault

 

[Suzanna]

link out your external controls and this will confirm whether it is a stat fault or a boiler fault, does sound like an SCR fault

Thanks for this but what does 'link out' mean? Is it easy to do? Sorry to sound so dim but I do not know anything about central heating.

 

[gigz]

Isolate boiler electrics, follow cable into the boiler. You will have a L N E, then another two wires (possibly grey and black). Take these two out and put a short piece of wire between these two terminals. Then use the boiler controls. If this works then you know its the external controls at fault.