Boiler cutting off before thermostat temp is obtained

[garrymum]

Hi
Conventional CH system, waster cylinder and CH header tank in the loft. Boiler is a Potterton Suprima. Should the boiler remain on until the temperature set by thermostat is obtained? Even if I set thermostat to 30 deg the boiler cuts out (not locking out), just stops then re-starts some time later.

Is this normal practice? If the boiler was over heating, would the light on the boiler turn red or flash?

 

[crockett]

Airlock in the boiler for some reason? Have you had any work done recently? other than that, an over sensitive boiler stat ?

 

[electronicsuk]

How much later is 'some time later'? If the return water temperature to the boiler is satisfied then the boiler will stop, regardless of whether or not there is call for heat from the room stat. Of course, the return temp will drop quickly again if there's any significant heat loss in the system, which there certainly will be if all your radiator valves are open.

 

[garrymum]

Airlock in the boiler for some reason? Have you had any work done recently? other than that, an over sensitive boiler stat ?

I did do a full drain / flush and refill on Monday. Also added a new dose of Sentinel X100. All rads are getting hot and the boiler is not making any strange noises (well it does sould like a steam train sometimes but it has been like that months. Not since I drained the system.)

 

[garrymum]

How much later is 'some time later'? If the return water temperature to the boiler is satisfied then the boiler will stop, regardless of whether or not there is call for heat from the room stat. Of course, the return temp will drop quickly again if there's any significant heat loss in the system, which there certainly will be if all your radiator valves are open.

Will time when it next happens. I put the thermostat on 30 so I could start balancing the system. Already taken first round of temps and makde some adjustments. Was going to take 2nd round of temps when I heard the boiler shut off. I did check both the flow and return pipes coming from the top of the boiler and there was not a huge difference in temps.

 

[garrymum]

How much later is 'some time later'?

Room stat on 30, boiler has just knocked off for 2.5 minutes. The status light on the boiler was flashing green / clear. Then for the last 10 seconds the light flashed green / amber and the boiler fired up.

 

[D_Hailsham]

I see you had balancing problems nearly two years ago.

Read How to balance a CH system

 

[garrymum]

I see you had balancing problems nearly two years ago.

Read How to balance a CH system

I am currently trying to balancing the system. Is the boiler shutting off then due to an un-balanced system?

Currently the drop on all my radiators varies between 0 and 10. This is the second round of readings, first temps were between 0 and 14.

 

[D_Hailsham]

I am currently trying to balancing the system. Is the boiler shutting off then due to an un-balanced system?

Unusual. The boiler's own thermostat will turn it off when it reaches the temperature set. What temperature is the boiler set to?

Currently the drop on all my radiators varies between 0 and 10. This is the second round of readings, first temps were between 0 and 14.

I gave you the link to the Balancing Instructions as you should not be getting such a wide temperature variation., even after the first round.

Is the bypass correctly set?