boiler overheating and kettling

[markl77]

Hi all. I have an old boiler in my house. it was already installed when i bought the house 4 years ago but can see it ain't modern. It's an Ideal Classic NF70. It is not a combi boiler and we have a tank in the airing cupboard.

It's been working fine until recently when it's suddenly started playing up! I think i have narrowed down the problem to be with the boiler itself. When the heating is on it appears to be working fine but if it's just a call for hot water to heat the tank I have the problems. The boiler doesn't cut off when it reaches temp and just keeps heating until it boils in the system. I have the potentiometer dial (boiler temp setting) set to 3 normally (goes up to 6) and I have tried turning it down to 1 (when the return water pipe is almost too hot to touch) and the boiler just stays lit. If I work the dial forwards and backwards a few times (6 to 1 and back again etc) it then seems to work for a very short time with the boiler staying off until the return water pipe has cooled sufficiently and then comes on and goes off as it should. but the next time the water is on its not working again.

I am guessing that I don't see the problem when the heating is on as it's a large house with lots of rad's and i presume that this is cooling the return sufficiently to prevent the kettling.

I have checked all of the various other components in the system (pump, valves and controls) and all seem to be working fine.

What part do you think may need replacing? Potentiometer, thermostat sensor, pcb or anything else I may not be aware of?

thanks in advance

Mark

 

[KenGMac]

markl77, good evening.

As I understand things to do with Gas Central Heating Boilers, You as an individual are not permitted to "tamper" with a Central Heating Boiler. OK you own the device but???

Any work on, or servicing, replacement of parts, must be undertaken by a "competent person" who is a "Gas Safe" Engineer [was called CORGI Registered Engineer]

Why? simply because to "tamper" with a Central heating Boiler is simply dicing with death, get is wrong and in your case Carbon monoxide poisoning / possible death?? OR?? gas explosion, severely damaged home, possible no home? big bang ?

As an aside any Gas Central heating Boiler should, stress "SHOULD" be serviced by a gas Safe Engineer annually, this to ensure the safe working of the Boiler, a service can also cut down on Fuel bills by optomising the boilers working.

Bottom line, do not attempt to tamper with the Boiler leave it to the professionals [PLEASE???]

Ken

 

[algas]

Just check you don't have a partial blockage or air lock on the pipework to the cylinder, sometimes there will be a manual air release at the highest point.

 

[markl77]

Hi Ken

I appreciate your comments but thought I'd be fine swapping the faulty part as I'm not going anywhere near the gas feed or associated combustion parts. Perhaps just diagnosing the part requiring replacement and then getting a "gas safe" registered plumber to make the change will be the best course of action.

Hi Algas

I have bled the system and there was a little air but still having the problem. The circuit from the boiler to the tank is very short with a mag clean installed and as the system is returning HOT water on the return to the boiler I wouldn't have thought it would be a blockage.

 

[ianmcd]

you need a component change and unfortunately you can not do this yourself, the component is not expensive and requires opening the combustion chamber, hence we are not allowed by site rules to tell you what the component is

 

[Agile]

Far better to let the boiler engineer diagnose what the problem really is.

Otherwise you could get it wrong, tell him what to change and still find you have the fault!

Tony

 

[Agile]

Hi Ken

I appreciate your comments but thought I'd be fine swapping the faulty part as I'm not going anywhere near the gas feed or associated combustion parts.

Any work on a boiler associated with controlling the combustion and the associated safety devices is classed as gas work.

Furthermore, after any work is done on a gas appliance certain tests need to be done to ensure that it is working safely.

Tony