Boiler won't come on unless triggerd by cylinder thermostat

[keshdevon]

Hi.
I am having problems with my central heating. My boiler seems to work fine (a 30 year old Thorn Olympic) and I have plenty of hot water.
Problem is with the radiators - they only seem to heat up when the boiler is actually running, then gradually cool again. The pump continues to run quietly in the airing cupboard throughout.
I have replaced the room thermostat and still no joy. I can never get the room up to the room thermostat temperature.

It means the only way I can get the heating to come back on is to wait for the hot water to cool down, or run the hot tap for a while!

Does anyone have any suggestions what I should try? Is the diverter valve stuck?


I am planning to get the boiler etc replaced in summer anyway so I don't really want to be spending out money on it now. Its had this problem for a while now, but Im getting chilly with all this snow around!

I hope someone can help, Thanks.

 

[clf-gas]

Two or three port valve

 

[seco services]

Problem is with the radiators - they only seem to heat up when the boiler is actually running

thats what the boilers for. or the boiler would be pointless having it.

 

[keshdevon]

Its a 3 port valve.

So why won't the boiler keep running and the radiators stay on.

 

[seco services]

programmer on heating only
wall stat up
is pump running ?
is boiler running.

 

[clf-gas]

Its a 3 port valve.

So why won't the boiler keep running and the radiators stay on.

Becuase the valve isnt moving and the boiler is only firing for call from cylinder stat, watch the little arm on the valve, is it moving.

Can you test for 240v on the white wire.

 

[seco services]

Its a 3 port valve.

So why won't the boiler keep running and the radiators stay on.

Becuase the valve isnt moving and the boiler is only firing for call from cylinder stat, watch the little arm on the valve, is it moving.

Can you test for 240v on the white wire.

it must be moving or you wouldn't get heating when hw calling.
its more likely stuck in mid position and not moving when hw satisfied.

 

[superdupergasman]

end switch on the 3 port valve is faulty, or the valve is jammed in mid position not allowing the end switch to be made.

remove the head of the valve and check the little spindle on the body is moving freely.

If it is replace the valve head.

Good luck.

 

[clf-gas]

it must be moving or you wouldn't get heating when hw calling.
its more likely stuck in mid position and not moving when hw satisfied.

Thats what I was meaning

 

[seco services]

it must be moving or you wouldn't get heating when hw calling.
its more likely stuck in mid position and not moving when hw satisfied.

Thats what I was meaning

so if its jammed in mid position power on the white won't matter
as its jammed any way.

 

[keshdevon]

Hi

clf-gas
The programmer only has options for water and heating together, or hot water only.
Wall stat is turned to max - it can only be about 15C in the room now
Pump is running
And boiler will run, when triggered by cylinder stat.

seco services
I dont have the means to test for power on the valve cable right now. I cant see any little arm on it to look for movement.

Picture below shows what is in the airing cupboard.

That is the three port valve on the left, isn't it.

Superdupergasman
Which bit of the valve opens up?

 

[keshdevon]

Ok, so ive been looking round this forum more. Now Im not sure that is a 3 port valve, but is instead some type of motorised valve.

The black box on the side of the blue valve/diverter has the numbers 1 to 5 on it and a white knob that chooses the setting. Should I be looking at this?

 

[seco services]

its not a mot valve.
have to admit not sure on what it is.

has it anymore writing on it ?

 

[clf-gas]

it must be moving or you wouldn't get heating when hw calling.
its more likely stuck in mid position and not moving when hw satisfied.

Thats what I was meaning

so if its jammed in mid position power on the white won't matter
as its jammed any way.

Correct

I was asking as isnt this call for heat from roomstat

 

[keshdevon]

It says
SMC Commodore Controller and not much more