Boiler flue

[rosinante]

Good morning Illuminati,
Having an issue with pressure loss on my Grant oil combi boiler I decided to isolate the heating system by allowing the boiler to cool overnight then closing the output valves to the radiator circuit and repressurising the system , put 2 bar in and the pressure fell before my eyes, while the covers were off I noted the air hose for combustion was disconnected from the flue, J reconnected and then returned valves and pressure to normal and started the boiler, the burner fired right up and then cyclically faded and relit, so I believe air starvation , disconnecting hose restored normal combustion , so two issues, flue and pressure loss , the pressure vessel was replaced in April of this year and a boiler service conducted.
Can the flue be cleaned out on the intake side? It is vertical and about 5 metres maximum length, pokes out of the roof of our bungalow, fairly accessible , advice on this most welcome, it looks very similar to that sold in Screw fix, cream coloured outer with clipped joints. Then there is the issue with pressure loss , can't get a boiler tech anytime soon , all to busy , should add we are both to old to be getting on a roof , guidance welcome
Thanks in advance
Chris

 

[dobbslc]

Sounds dodgy. Has someone previously disconnected that pipe to get the boiler to work due to a blocked flu?
Having been a hairs breath away from dying from carbon monoxide poisoning when I was a teenager I'd leave it turned off until you can find out what's wrong with it. Have you checked the valve on the pressure vessel for water when you press it down? If water sprays out its failed.

 

[rosinante]

Will try that but it was replaced in April , the exhaust part of the flue is OK its the outer air inlet that is problematic

 

[rosinante]

Checked pressure vessel , no water so diaphragm seems good, reading up on glue and braving the rain the roof termination and fitting all look good , in the loft there's white powdery stuff on floor and outside of flue, short of a major job can't see how flue can be disassembled and cleaned on inlet side, exhaust seems fine as boiler runs happily no fumes can be smelt , it's an oil boiler,

 

[voipio]

If the water pressure falls straight after repressurisation, then there's got to be quite a leak somewhere. Possibly worth considering it might be the boiler itself, if you can't find any other leak.

 

[waddycall]

It’s probably a failed seal in one of the flue joints letting it pull its own flue gasses down the air inlet and snuffing the flame out. No one should be leaving the inlet of a balanced flue disconnected. Turn it off and get someone else to look at it. If the service engineer you used is oftec registered you should probably report them. Make sure you have a CO alarm and check it works.

 

[waddycall]

Have you checked to see if the pressure relief valve is discharging?

 

[chrismac]

My issues for leaks were on the same boiler, pressure relief, drain port on water storage vessel drain located under the burner and automatic air vent all at different times, I cant remember now but does the heat exchanger come into this loop as I remember chasing a leak and thought this was the only option left, but managed to find it else where.

 

[rosinante]

Have you checked to see if the pressure relief valve is discharging?

Yes went out the pipe curved back to building was dry , had cobwebs in , now the fact that the burner air intake is disconnected from balanced flue , when connected the burner runs cyclically , so starved of air , there is a damper adjustment on burner , what gets me is how long has this been an issue as it was serviced in April ,
Auto vents look dry , will have a look , heat exchanger is right at front and no evidence of leakage, hopefully will be able to get a chat to a oil boiler plumber next week , , thanks for your reply

 

[rosinante]

Checked drain as above all dry, air damper on no 4, ,
Chris

 

[rosinante]

It’s probably a failed seal in one of the flue joints letting it pull its own flue gasses down the air inlet and snuffing the flame out. No one should be leaving the inlet of a balanced flue disconnected. Turn it off and get someone else to look at it. If the service engineer you used is oftec registered you should probably report them. Make sure you have a CO alarm and check it works.

There's the problem , no one available or returning messages left, we don't know how long it's been like it , as said new pressure vessel fitted and new nozzle on burner plus service April this year , we bought the place in June , ,

 

[rosinante]

Would I be able to smell the burnt oil fumes around the open air inlet port ?

 

[gaz1]

so two issues, flue and pressure loss , the pressure vessel was replaced in April of this year and a boiler service conducted.

There's the problem , no one available or returning messages left, we don't know how long it's been like it , as said new pressure vessel fitted and new nozzle on burner plus service April this year , we bought the place in June , ,

you will need to check your details on the sale of the property as you might need to claim upon it

the property has been sold with a defective boiler which has been stated it was serviced and passed when in reality its unfit for use

 

[gaz1]

Good morning Illuminati,
Having an issue with pressure loss on my Grant oil combi boiler I decided to isolate the heating system by allowing the boiler to cool overnight then closing the output valves to the radiator circuit and repressurising the system , put 2 bar in and the pressure fell before my eyes, while the covers were off I noted the air hose for combustion was disconnected from the flue, J reconnected and then returned valves and pressure to normal and started the boiler, the burner fired right up and then cyclically faded and relit, so I believe air starvation , disconnecting hose restored normal combustion , so two issues, flue and pressure loss , the pressure vessel was replaced in April of this year and a boiler service conducted.
Can the flue be cleaned out on the intake side? It is vertical and about 5 metres maximum length, pokes out of the roof of our bungalow, fairly accessible , advice on this most welcome, it looks very similar to that sold in Screw fix, cream coloured outer with clipped joints. Then there is the issue with pressure loss , can't get a boiler tech anytime soon , all to busy , should add we are both to old to be getting on a roof , guidance welcome
Thanks in advance
Chris

treat both the flue and service ports as what they are 2 seperate systems so yeah check the flue

rod the flue if access is available

as goes for pressure vessel check for leaks and replace that vessel if no leak is found

you could be over pressurising your system and when it fires up its flowing out the prv valve check to make sure valves are on to the rest of the system

oil burners have an issue of cycling firing up on them when the burner has issues

reillo they have been posted on the forum on how to repair maintain them

 

[rosinante]

treat both the flue and service ports as what they are 2 seperate systems so yeah check the flue

rod the flue if access is available

as goes for pressure vessel check for leaks and replace that vessel if no leak is found

you could be over pressurising your system and when it fires up its flowing out the prv valve check to make sure valves are on to the rest of the system

oil burners have an issue of cycling firing up on them when the burner has issues

reillo they have been posted on the forum on how to repair maintain them

The boiler runs fine when drawing air from the room , don't want to start pulling anything apart ,read that the damper is adjustable to set up during commissioning, I imagine a flue gas analysis would be required to set this up properly, the valves to the water and heating system are open and both work when system pressure is OK, looking at flue it would need dismantling to clean ,

 

[Kayos]

It has already been said multiple times but get someone in and leave well alone

Based on what I have read there is an issue than needs someone with experience and the right kit to sort it

Yes, you don't technically need to be qualified/competent/registered to work on it, but good luck with that if it all goes sideways

 

[gaz1]

while the covers were off I noted the air hose for combustion was disconnected from the flue, J reconnected and then returned valves and pressure to normal and started the boiler, the burner fired right up and then cyclically faded and relit, so I believe air starvation , disconnecting hose restored normal combustion , so two issues,

what you speak of is a pressure switch fault not starvation as your fan will blow enough air down into the system

thats blown air up the exhaust system if not enough flow that boiler will shut down

for reillo a cycling firing is something different but when you disconect that tube your boiler fires as normal so its not a cycling firing of the boiler

reillo oil boiler cyclically faded and relit, - Google Search