Ideal classic Boiler overheat

[diamondgas]

Hi bigrinks .... soz about the few replies been walking in the Lake District across the weekend 🙂

Regards the circulation issue please do not rule out the primaries but from the info you've given they are less likely! If the boiler is cutting out then the heat build up is enough to trip the overheat usually around 90C+ ... That points to circulation if you know the flow is getting that high at some time. The conclusion would be; heat not being removed quickly enough or a dodgy o-heat!

Regards the fault being in the return, you just do not know? If it's effecting ALL radiators then it's either the heating primary flow or return. Either one will cause grief 🙂

Here's a question I haven't asked as yet; Does the boiler cut out on hot water only at all? Coz if it's cutting out on both hot water and heating circuits then it'll deffo point toward the boiler/pump/or primary circulation pipework! 🙂

 

[e/bourneplumber]

what happens if you turn off all the upstairs rads and have heating on only? does the downstairs circuit heat up properly?

 

[bigrinks]

Hi bigrinks .... soz about the few replies been walking in the Lake District across the weekend 🙂

Regards the circulation issue please do not rule out the primaries but from the info you've given they are less likely! If the boiler is cutting out then the heat build up is enough to trip the overheat usually around 90C+ ... That points to circulation if you know the flow is getting that high at some time. The conclusion would be; heat not being removed quickly enough or a dodgy o-heat!

Regards the fault being in the return, you just do not know? If it's effecting ALL radiators then it's either the heating primary flow or return. Either one will cause grief 🙂

Here's a question I haven't asked as yet; Does the boiler cut out on hot water only at all? Coz if it's cutting out on both hot water and heating circuits then it'll deffo point toward the boiler/pump/or primary circulation pipework! 🙂

I think your on to something here!...

Right normal operation water and heating on. boiler set to position 3 (43DC water out), system will heat rads from cold until hot then start this 2m cutting in / out cycle.

With heating off and only water on the boiler didnt start (presumably cause its at temp). turning up the boiler temp control to full resultign in boiler starting, running for 2 mins then starting this 2 min cycle.

both balancing valves are part open/shut.

So i guess we are now saying its the pump, primary circuit or boiler temp gauge. Can the later be easily sourced/replaced?

 

[bigrinks]

what happens if you turn off all the upstairs rads and have heating on only? does the downstairs circuit heat up properly?

Heats up but never hot. Boiler starts the 2mins trip cycle. Given the choice it seems to prefer to heat upstairs. Think the issue is now definatley the boiler tripping which prevents the heat being pumped around.

 

[e/bourneplumber]

did you say you replaced the downstairs heating circuit in 22mm? could it be that the pipe work is crushed or blocked? if not i would have to go with above suggestions and thinks failing pump, partially blocked heat exchanger, maybe faulty auto bypass.

 

[bigrinks]

did you say you replaced the downstairs heating circuit in 22mm? could it be that the pipe work is crushed or blocked? if not i would have to go with above suggestions and thinks failing pump, partially blocked heat exchanger, maybe faulty auto bypass.

Patial replacment with 22mm as nearly all downstairs was running of 15mm with 4 rads taking a feed from a single 15mm in one instance. 100% guaranteed that new piping not crushed or bent. I used plastic pipe which is fitted nearly perfectly straight, capped ends whilst threading. Nearly full 22mm from cupboard to rads in livingroom now (except short 15mm tails).

How do i check heat exchanger and autobypass? - Doubt that any sludge build up as system relatively new and clean when drained down. Really doubt its sludge etc.

 

[e/bourneplumber]

when you first put on heating or hot water, ie when system is cold, feel the pipe work after the auto bypass, it should stay cold, it should only open when there is a pressure against it, like when a valve has closed and then the bypass should open to let the heat from the boiler cycle to cool down a bit. they are usually adjustable.

if you've got no blockage in the downstairs circuit, and no crushed pipes, and when you shut everything other than the d/s circuit the rads only get warm rather than hot, and the pipe work is all in 22mm other than the feeds to the tails of the radiators, then i would change the pump maybe to a 15.60, 6m head. heat exchanger is not something you can do yourself, and if it comes to taking out yours, i would think about getting a price for a new boiler. imo. does the boiler make a kettling noise as it heats up, like when you first put kettle on from cold, this would indicate scale in the heat exchanger, and you could have it descaled or add a descaler into the system yourself via a radiator.

also just a thought, you seem to know the layout of the pipe work pretty well, do you know where the return pipe from the down stairs circuit tees into. it could be that it is teed in the wrong place and instead of going straight back to the boiler it is going elsewhere. you may need to get some one in to have a proper look.

but i would start with the pump.

 

[bigrinks]

Thanks. not sure were the autobypass would be located!!!

I'm now thinking the limited heat in downstairs rad is because the boiler wont stay on long enough to do the business! Obviously previous thoughts was blocked or restricted system causing this.

Boiler does make a faint bubbling noise before switching off. Mind also that hf and hr at boiler dont exceed 47dc on current setting 3.

hf and hr in downstair system run in parallel around the house. If hr tees into something it shouldn't it would need to be in first floor. It must go back to tank before boiler else rads would heat when only hot water on?

 

[diamondgas]

So i guess we are now saying its the pump, primary circuit or boiler temp gauge. Can the later be easily sourced/replaced?

It certainly sounds like it is 🙂

What sort of flow temp are you getting with the boiler stat on full and/or when the "2min cycling" comences? How hot is your hot water getting by-the-way? You should be heating your cylinder to 60C!

 

[e/bourneplumber]

apologies, ive just looked at the pics and you dont have an auto bypass only a gate valve!
the scale noise is usually heard when cold as it hisses and pops when it expands with the heat, from the pics the pipe work looks ok, obviously cant see whats going on under the floor, i would start with changing the pump.
you may have to get some one in to give you better advice as they would be able to get their hands on. if you know what i mean!

 

[TipTop]

as above...sounds v low f+r temperatures...possible bypass stealing heat or bp on blr not correct??inlet pressures? meter governor?got to prove boiler operating correctly before going for system issues🙂