Ok, I give up, WTF is wrong with this Ravencrap 82E boiler

[PEDANTICVINDICTIVEMAN]

Useless piece of ****e, CH works fine, diverter was leaking so changed that anyway, fitted new CH sensor and DHW sensor, Litres a min flow rate correct, gas rate correct, gets decent temp rise but then cuts off without modulating down, if you turn the DHW stat down and up it modulates to suit, so gas valve working ok, connect a "loose" CH sensor to the red wires and it works fine, reconnect to "fitted" sensor and it works a while then cuts off with no modulation and water runs cool then boiler cuts in and out in and out so on on on on.
There is no plated xchanger on these boilers.

 

[scatmanjohn]

Sounds like the heat exchanger not passing the heat over (sludge/scale)

CH sensor also acts as an high limit stat so will cut off if the primary water is getting too hot in HW mode.

 

[gas_man_gaz]

had the aps dropping out wen hot before, but sounds like the heat int transferring

 

[PEDANTICVINDICTIVEMAN]

I came to the conclusion it was gonna be muck in the HE, but the water in the system wasn't dirty, anyway put a litre of X400 in it and said call me in 2 weeks.

"Eventually" FFS, got through to their tech dept, the guy said what I suspected, HE problem.

 

[oilhead]

Surely problem is with secondary water, not primary water. X400 will make no difference.

 

[onlyfitidealboilers]

scaled main heat exchanger. on dhw circuit

 

[PEDANTICVINDICTIVEMAN]

If X400 don't fix it I will have to replace the HE

 

[Agile]

I expect he had a dripping hot tap!

I would not fit a new HE as I would renovate the scaled one.

Tony

 

[PEDANTICVINDICTIVEMAN]

Rented property, I suggested replacing it last year as the flue was too near bedroom window and POC getting in, against my recommendation of junking the pile of crap, the flue was extended at great expense to a metre away.
A different plumber replaced the PCB before I came on the scene, so with the amount of money spent already may as well repair the damn thing.
Faffing around with the the existing HE isn't on, as I ain't prepared to spend the time, a straight HE replacement will have to do, also means a guaranteed fix.
There is already a Liff scale reducer thing on the cold incoming.