ideal classic boiler overheating

[steve28um]

hi.. i have an ideal classic LX & FF50 boiler and the overheat reset stat is regularly cutting out every couple of days. I changed the boiler thermostat to low setting but did not stop the o/heat stat cutting out. I initially assumed it was a faulty boiler stat. as would expect that to operate before the o/heat stat. but there are days when the boiler runs normally with no issue, but I guess it could be an intermittent stat issue. I have also had one specific radiator which gets an airlock...Have bled it regularly but does not seem to cure the issue..... Have also had a couple of occasions with pipes banging in the airing cupboard which i am guessing is the 'kettling' scenario. Not sure if its a straight forward boiler stat problem...or if the air getting into the system is a cause.... Any help for a newbie would be appreciated...

 

[Agile]

Pump over run???

Tony

 

[gas4you]

Check there is water in the f & e tank in the loft first.

Then if you bleed upstairs rads do you get plenty of water out?

If not could be cold feed blocked.

Could be intermittement fault on pump/pump wiring. I would have thought banging would be lack of flow or lack of water.

Never seen a pump over run on a classic Tony

 

[steve28um]

hi..Thks for the feedback...appreciate it....check'd the F&E tank and there is water present. When i bled the one rad that gave me an issue it did seem to have a constant trickle of water and all other rads upstairs are fully heating up with no issue. I checked the pump in the airing cupboard and its a wilo gold 50. I did check it after the boiler thermostat correctly shut down the boiler and it was not running. Not sure if that means its because it has no o/run or it has one but is not working.....

 

[lopez11]

Almost certainly the gas pressure is to high, get an RGI to check them

 

[steve28um]

There was an engineer who did come out and he did comment the boiler ctls all looked ok but he did mention that the pressure was a bit higher than expected but nothing major. He did reduce it but still getting the o/heat reset kicking out every couple of days.... With the little knowledge i have, i couldn't understand why the boiler t/stat didn't keep the temp. down before the o/heat reset kicked in but from what i read it seems that only controls the temp of the hot water and not the actual temp. of the boiler..

 

[gas4you]

Boiler stat should control the temp of water in the boiler. End of.

 

[lopez11]

And it should and it did.

But what he asked was WHY.

I sugested gas pressure because it,s cast iron hx,er and they produce heat to the water even after they turn of, and if the pump doesnt remove it, guess what happens next.

 

[Agile]

If the boiler is a little scaled up and there is no pump over run then the latent heat in the c.i. heat exchanger will be higher and can cause tripping of the o/h stat.

You need to check to see exactly when it trips???

Is it when the boiler shuts down?

Easy test is to have the boiler firing with the system hot and then cut the mains!

Its rare but sometimes a gas valve will stick on at the end of firing! Cutting the mains should immediately shut off the flame EVERY time!

Tony

 

[lopez11]

Turn boiler on and set thermostat lower if boiler turns of with pipes warm turn up stat. Now the clever bit, if the boiler gets hotter and then turns off. Guess what!!!!! Thats right. There,s nothing wrong with the stat.

Then follow previouse, advise, and call an engineer to turn the gas pressure down.

 

[steve28um]

Ran ok for a few days but finally was around when it failed.... It seems that the o/heat reset operates when the boiler was running.. before the t/stat had switched the boiler off. Noticed also that when the thermostat turns off it usually switches the pump off instantly, but when the o/heat reset switched in, I could hear the pump still running....so that wasn't switched off instantly when the o/heat reset kicked in...

Stephen