How should a boiler flue be tested

[gas112]

A folded seal would probably never show on a combustion test as it would still be sealed regards products entering the air duct .
Its as the condense runs back down on the incline then collects at the fold and eventually finds it way out as a drip

 

[Lower]

The installer does seem a reasonable chap and I'm sure will either do the appropriate test or would do whatever test I ask.

Can someone explain how an a combustion test would show a leak in the flue? Surely a combustion check will just check that the boiler is working correctly and not creating CO? I assumed there would be some kind of sniff text around each joint.

 

[Steelmasons]

Hmmm seems to be more 'dick measuring' going on here than offering help or advice to the OP

Crack on then.

 

[ianmcd]

Simply carrying out a flue gas analysis in this situation will tell you nothing ,unless a serious return of Products, in which case other faults would have shown long before testing was required, an analysis of the air intake MAY have shown if the joint seal had failed but I have seen flue O rings fouled without any cross contamination of products but condensate can still drip, OP your engineer has called it correct so far so let him do his job

 

[jeff the gasman]

Trust him. If he kills you you can sue him!

 

[Piers1989]

some very interesting people on this forum...

"mines bigger than yours" comes to mind...

 

[Richardthe3rd]

Hmmm seems to be more 'dick measuring' going on here than offering help or advice to the OP

For what it's worth...just simply explain to the engineer your concerns. I'm sure he's perfectly capable of carrying out a flue gas analysis test for you. Peace of mind is priceless

Oi!! Leave me out of it!!

Not many gas engineers in 2014 that are worth their salt wouldn't stick their probe up some old dear's flue after working on her boiler.

I may not whip it out if I was working on the hydraulics, but for anything else, then yes, it only takes a few minutes to get it out the van, purge it going up the garden path & then ram my probe in.

A FGA is wonderful piece of gear, I even use my 425 to do tightness testing.

Full flue integrity testing required after today ladies, so I hope your equipment is in order??.........

 

[Richardthe3rd]

Simply carrying out a flue gas analysis in this situation will tell you nothing ,unless a serious return of Products, in which case other faults would have shown long before testing was required, an analysis of the air intake MAY have shown if the joint seal had failed but I have seen flue O rings fouled without any cross contamination of products but condensate can still drip, OP your engineer has called it correct so far so let him do his job

Some good points there Ian.

 

[Dean744PiN5]

but for anything else, then yes, it only takes a few minutes to get it out ,purge it going up the garden path & then ram my probe in.

and what about your flue analyser....oo' er misses

 

[Lower]

Simply carrying out a flue gas analysis in this situation will tell you nothing ,unless a serious return of Products, in which case other faults would have shown long before testing was required, an analysis of the air intake MAY have shown if the joint seal had failed but I have seen flue O rings fouled without any cross contamination of products but condensate can still drip, OP your engineer has called it correct so far so let him do his job

So the flue gas test is to see if any flue gases have leaked into the air intake? I presume a co/co2 leak into the intake would then be measurable in what ends up coming out of the flue.

The fold in the seal was very small. I can see that water would leak past but i would expect that the actual gap left by the fold would be tiny.

So there is no definitive test for the integrity of the flue seals? The reason for all the questions is the boiler is in my son's playroom and directly underneath his bedroom.

 

[Richardthe3rd]

Simply carrying out a flue gas analysis in this situation will tell you nothing ,unless a serious return of Products, in which case other faults would have shown long before testing was required, an analysis of the air intake MAY have shown if the joint seal had failed but I have seen flue O rings fouled without any cross contamination of products but condensate can still drip, OP your engineer has called it correct so far so let him do his job

So the flue gas test is to see if any flue gases have leaked into the air intake? I presume a co/co2 leak into the intake would then be measurable in what ends up coming out of the flue.

The fold in the seal was very small. I can see that water would leak past but i would expect that the actual gap left by the fold would be tiny.

So there is no definitive test for the integrity of the flue seals? The reason for all the questions is the boiler is in my son's playroom and directly underneath his bedroom.

I can understand your concerns mate. Could your RGI Plumber replace the flue system for a nominal amount? It may ease your mind a little with a new flue system?

 

[Steelmasons]

Damaged exhaust seal will show O2 in air intake to be less than 20.9 wih CO in excess of 1ppm , no ifs no buts..... period.

Condense leaking into/@ air intake joint would be cross contamination.

 

[Richardthe3rd]

Damaged exhaust seal will show O2 in air intake to be less than 20.9 wih CO in excess of 1ppm , no ifs no buts..... period.

Condense leaking into/@ air intake joint would be cross contamination.

100% agree mate. These details of course are no earthy use to the OP, he has employed the services of a RGI, for whom the respoonsibilty of the boiler flue integrity is in his hands.

The OP can instruct him to replace the whole flue system, if he so desires.

 

[Lower]

Installer called this morning. He says he can't get the seal on its own so has to buy a whole flue kit which he's going to supply me at cost (£60ish) as he thinks its unreasonable that the manufacturer won't supply the seal alone.

Had a good chat with him about the leak and why it happened. He says he did come back and resolve a folded seal issue about a year after he put the boiler in but just reseated the flue in the seal and the leak went. He said that it wasn't common practice to check the flue with a exhaust gas analyser at the time.

After a bit of discussion, he's suggested that as he's had to buy a whole flue he'll fit a new elbow with seal to the top of the boiler but leave the existing straight section in place to avoid any damage to the decoration etc. He will then check exhaust gases and intake air for any sign of leakage.

I'm happy with that.

Thanks for all the input to this thread. I'm not a RGI and have no intention of doing any work myself, but i am an engineer so like to know how things work and be comfortable with the work being done.

 

[Lower]

Further to the post above the RGI did indeed come back and replace the elbow. He tested for leaks and found none.

6 month on there is a slight rusty water leak again from the flue in roughly the same place.

Could this be water getting into the flue from outside and running back in?