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

[Dan Robinson]

It should be noted that the angle of the fans induction has no bearing on pressure being positive or negative in modern boilers.

Some burners burn horizontally and downwards.

 

[ChrisR]

Sure - should I draw it upside down too?

 

[Dan Robinson]

Can just imagine people looking at an Icos/Isar setup and thinking they have an exception to the rule.

Interestingly (maybe) the Intergas burners are side firing burners.

Not that that has 'owt to do with case pressures

I need a drink.

 

[MJN]

Superb - thanks Chris. Makes perfect sense.

Mathew

 

[gaswizzard]

(As an ACS gas assessor, I must have drawn this a thousand times!)

POC entering air intake is not the issue with regard to these positive pressure case boilers , flue integrity tests reveal POC in air intake to be negative.

These type boilers supply primary/secondary air to burners under positive pressure , any breach of casing integrity will result in flame lift-off which in turn can cause flame chilling (high CO) (anyone who's removed/cracked the case on these type boilers will note how the flame lifts off burner head in the search for O2) , the positive pressure case boilers require an air tight seal due to the fact POC in flue gas is either diverted up through Hex and into exhaust or simply exit through breached case/seal.

Tested many of these positive pressure case boilers and yet to see POC in air intake (20.9% O2 is the norm for these)

 

[ChrisR]

Presumably you're still smarting from having your posts deleted from another thread, but now you're digging yourself a hole again.

a) You've been measuring the wrong thing, and
b) I can't wait to hear how pocs get from the burner out through the case seal, against the flow of all that air coming the other way

 

[gaswizzard]

Presumably you're still smarting from having your posts deleted from another thread, but now you're digging yourself a hole again.

, regardless , facts are facts , would you like to carry on?

Why would I be 'smarting'? and why would I have any grievance with you?

 

[gaswizzard]

a) You've been measuring the wrong thing

Really? , what should we be 'measuring' with regard to POC entrained into air intake?

 

[gaswizzard]

I can't wait to hear how pocs get from the burner out through the case seal, against the flow of all that air coming the other way

Considering the fan has no sealing gasket some POC will be 'circulated' through intake side of fan and back into combustion chamber , the combustion cover front plate is also not sealed along with large square hole where pilot viewing window resides.(potty profile)

"digging a hole" , what do you mean? , all i've done is state another opinion to which you've taken offence.

 

[ChrisR]

The flue is what needs to be sealed , which it is.
it wouldn't matter if "air" recirculated round the fan - it's all the same stuff. It wouldn't get contaminated there.
Air goes IN through the inspection hole to the cc, not out...

Why would I be 'smarting'?

Because you've had your sniping unhelpful posts on another thread deleted, now you've made one so full of errors I assume you aren't thinking straight.
Suggest you look it up.

 

[gaswizzard]

The flue is what needs to be sealed , which it is.
it wouldn't matter if "air" recirculated round the fan - it's all the same stuff. It wouldn't get contaminated there.

If casing seal was breached the effects of flame impingement (CO) would circulate back through fan INTAKE resulting in POC leak through 'leaky' case seal , much like the 'snowball effect'.

Because you've had your sniping unhelpful posts on another thread deleted, now you've made one so full of errors I assume you aren't thinking straight.
Suggest you look it up.

Full of errors? please.

I know exactly what post you are referring too (two boilers) , what I can't understand is why you feel I have an issue with you? , I don't feel all my posts are unhelpful or rude , maybe you should read them some time.

We all have off days so don't tar me like you would a Troll just for making one mistake on one thread. (presumably)

I'm done.

 

[ChrisR]

If casing seal was breached the effects of flame impingement (CO) would circulate back through fan INTAKE resulting in POC leak through 'leaky' case seal , much like the 'snowball effect'.

Of course it can snowball, but but that happens via the outside of the boiler, because the pocs ARE sealed from the fan intake, inside it. You're looking for seals in the wrong place. After the flames, there are seals to the inside of the case, so it's not reliant on the case seal.

It also happens via the holes you get when prima/profile flues corrode through near the end, but that's a fault.
You don't get flame impingement as soon as the case seal leaks. Positive case pressure boilers like Netaheats were designed with an allowance for case leakage - through grommet holes etc. Try your FGA round those.
As I daresay you now, a profile won't run with the case off because of the aps, but if there's just a small rust hole the FGA readings are normal.

Starting back in CORGI days they said look for case seal leaks with an FGA, before smoke plumes came along.
I used to put a smoke bomb in the inlet - Netaheats always leak smoke and stink.

The point about the small red arrow though is that it happens even when there's NO fault in the boiler. It's almost impossible to separate the inlet and exhaust, though they tried harder on the Netaheat after they'd killed a dozen or so. So you can't avoid some of the pocs coming back in the flue. That's the same on a -ve case boiler, but it doesn't come out via any leak so no matter.

If you want to measure it you can't use Oxygen, you have to use CO2 or CO, though there may be very little CO because they're set up with a lot of Excess Air.
Think for a minute what your 20.9% O2 in the inlet would go to if you had say 150ppm CO, (ignoring the CO2 for a minute) it would go to 20.885%. Would you guarantee to see that difference?

If you have enough air leaking out then sure, you're depriving the burner, but the problems start way before that happens.

So, your first post with its "facts" was way off - and I though "Oh no it's him" after the other thread....
Truce?

 

[gaswizzard]

Truce?

My little pinky is extended.