Boiler casing put back on - check that it is properly sealed

[Roton600]

Just a quick question on an old Thorn EMI Olympic boiler.

Just had some work done on the boiler today, now my normal service guy always check round the casing with some gizmo a "sniffer" to check for leaks to make sure the casing is sealed. Had to use someone else today (long story) but they did not do do this check.

Just wondering what should be done to check the casing is on properly and is sealed?

 

[biscuit77]

The boiler is positive pressure it should be tested around the seal with a match to check for leaks, if the match blows out then the case or seal needs adjusting. Get him back to test it.these boilers are death-traps if not serviced correctly. Do younhave a carbon monoxide detector?,if not get one and you should really think about replacin it.

 

[Gasguru]

The Thorn Olympic was manufacturered as a positive pressure boiler and therfore the casing seal should be tested, ideally with a smoke pen. A "sniffer" whatever that might be is probably not the recommended method of testing the seal.

However, a kit was available to convert the boiler to negative pressure resulting in a much safer design.

So unless you know whether the boiler had this enhancement you can't know which enigineer applied the correct test procedures. If it's still a positive pressure setup then a CO alarm (correctly installed) is a good idea.

 

[45yearsagasman]

The Olympic was also a natural room sealed boiler, so I wonder which one is in question here?

 

[Boilerman2]

I was about to say that 45!!

 

[Roton600]

Thanks to everyone

The boiler is the 20/35B the technical bulliten for the modification seems to be for the 20/35F.

What was the modification?

I do have a carbon monoxide detector alarm, i will get the guy back tomorrow to check.

 

[45yearsagasman]

The model you have does not have a fan, and the only check to be made should have been the case seals with a match.

 

[Roton600]

If you look through the inspection window at the pilot flame, the end of the thermocouple is glowing is this normal never noticed it before. a new gas valve and thermocouple has been fitted today

 

[Dan Robinson]

Its fine. Relax.

 

[Roton600]

Thanks for all the replies

 

[MJN]

Reading between the lines here, are positive pressure boilers the exception to the norm?

Reason I ask is that I'm pretty sure that my Ideal Icos is positive pressure by virtue of it blowing a gas/air mixture into the combustion chamber (hence positive pressure). Conversely, the WB 23CDi in my last house effectively sucked the combustion products out thus negative.

Until I saw this Icos I had assumed that the WB design would've been ubiquitous given the seemingly apparent inherent safety benefits.

Edit: Thinking about it, is it the case on the Icos (and others) that whilst the fan may well be blowing into the combustion chamber it is drawing its air from the flue via the outer casing hence there is still a reduced risk of combustion products leaking into the room because such products would be recirculated back into the chamber and not into the room?

Mathew

 

[Dan Robinson]

don't worry, its fine. Relax.

 

[ChrisR]

Ideal Icos is positive pressure by virtue of it blowing a gas/air mixture into the combustion chamber

No - the case pressure is negative, because the air/gas path is closed to all but the flue, after the fan.
If the case seals leak, air from the room goes IN to the case.

On a positive case pressure boiler the case is on the outlet side of the fan. (you might think it's only air being pumped into the case and therefore out through any leak, but a percentage of flue gasses can't help being sucked in by the fan, with the air.)

It's the little red arrow at the end of the flue which three quarters of gas installers forget. The green "8" is meant to be the fan...
(As an ACS gas assessor, I must have drawn this a thousand times!)

 

[MJN]

Ideal Icos is positive pressure by virtue of it blowing a gas/air mixture into the combustion chamber

No - the case pressure is negative, because the air/gas path is closed to all but the flue, after the fan.
If the case seals leak, air from the room goes IN to the case.

I think I know what you mean... Any chance you could draw it?! Seriously, the drawing you did for the positive pressure design made complete sense...

Mathew

 

[ChrisR]

On the left, a non condensing boiler. A crack in the case could lead to air disturbing the flame, but that's about it. Note that the fan is running HOT cos it's in the flue.

RIght, a condensing/modern boiler with a gas valve which presents gas at (Zero pressure relative to) atmospheric pressure.
The fan sucks the air and gas through together, into the burner.
Faster fan = bigger flame.
The pinky purple part is closed, so the case is still negative pressure relative to atmosphere.