Old Glow worm Back Boiler

[GPlumb]

Here is one for you. My old Mum has an old back boiler circa 1973 ish the fire front is a glow worm 246n.

Recently i have been doing a bit of work in her house (i am a plumber) including putting TRVs on for her and fitting a new modern programmer and moving and replacing the room stat to the front room all in the aid to save on fuel prices and increase comfort.

Its a C Plan type system 2 flows, 2 returns, no MV's, primatic cylinder (gravity DHW) and the room stat just turns the pump on.

However the boiler is old and it constantly kettles, on hot water only is it much worse. The boiler has one control which i assume increase flow temp but i am not sure how the temp is sensed. Basically it fires up runs for 2 mins then starts to kettle for another 2 mins then shuts off for about 5 mins and repeats.

The system is sludge free as i cleaned it all over the summer. System is bled, aav on the primary flow etc.

Is there much i can do to try fix it? Or is there anything a corgi guy would check or look at? Most of the corgi guys i work with know very little about it as they are all sub 30 and working for companies that only fix boilers in their warranty period.

Short of ripping it all out and getting a combi in (which i will do next year) is there anything i can do to silence it?

 

[spacethegas]

i recommend descaling the boiler heat exchanger thoroughly. neutralising & flushing it very thoroughly before reconnecting. ideally it would be best to replace the primatic cylinder with an indirect so as a noise silencer & inhibitor can be added. but this would involve a system control upgrade to comply with regs. mind you this would reduce the boiler stat cycling so often.

then get a corgi out to make sure the burner pressure is set appropriately.

 

[GPlumb]

Thanks for the Response, unfortunately i can put a indirect in as we don't have access to the loft space and it would involve running a F&E through the property above (maisonette).

Is it possible that thermistor or another temp sensing device is knackered?

The cylinder has no thermostat btw.

 

[spacethegas]

it is only fitted with a b/stat. so when operating the gravity h/w it cycles so often. if you were to convert it to fully pumped it would stop it cycling so often.

i know gledhill used to (probably still) make an indirect cylinder with integral c/w storage & f/e tank.