gas fire leak test

[andy smith]

Its that time of year when the cannon gas fire (inset flame type) gets more used ... having read about smoke test on this group and in manual... I thought I give mine a test using some of those smoke matches from screwfix...

Smoke match seemed to give great clouds of smoke for 10 sec followed by smaller smoke stream for about 10 sec (like that from a cigarette).... is this how they are supposed to burn?

tested with all doors closed and fire on full blast for 10 mins... with smoke match positioned as per manual (20mm down and

20mm inside canopy).... only about half smoke went up chimney in first 10 secs... whereas all of it get drawn up flue in next 10 secs (when match was generating less smoke)...

repeated with doors open (more ventilation) ... same result.... repeated after having chimney swept ... same result ...

Have I got a problem... manual is a bit unhelpful as it say check that "most of smoke" goes up chimney...

one other thing, chimney flue is about 177mm square... gas fire has a "spigot restrictor" in place (plate covering about half of exit from gas fire to flue) ... manual say it should be removed if flue is 125mm... no other explanation but do you think it should be removed in my case (what's its purpose)? I've seen installation manuals for other makes of similar fires say to leave restrictor in place if fire installed in class 1 flue of "good" class 2?

PS gas fire originally fitted by "corgi approved" plumber for what its worth...

Andy

[BigWallop]

This is how I was taught to carry out a spillage test.

Close all doors and windows to the room containing the appliance. Let the fire run on HIGH for five minutes. Take a smoke match, light it, and using a smoke match tube, hold it at the top edge of the fire opening, 25mm down and 25mm in. Starting 50mm in from either side, run the smoke match across the opening. All the smoke should be drawn away up the flue. Any smoke returning into the room indicates that spillage is occurring. If the initial spillage test fails, run the fire for a further 10 minutes and repeat the test. When the test has been completed satisfactorily and no spillage occurs, then repeat the test with any extractor fans in the premises running on the highest setting, and any communicating doors open. Finally, repeat with all doors open.

If spillage is still indicated after undertaking all of the above, there may be a fault in the flue, or insufficient ventilation is present. If the problem cannot be easily rectified, then expert advice should be sought.

[andy smith]

Thanks - I notice you use a smoke match tube... (online supplier?) ...I just stuck a match on the end of a stick (fire was too hot to hold in hand)... would a proper tube regulate how the smoke was produced (my matches claim burn time of 20sec but most smoke produced in first 10sec)....

Any thought on "spigot restrictor"?

I'll try again and if in doubt I'll get in Corgi...

Andy

[RichardS]

You might well find it cheaper to go to an accredited Chimney Sweep if the problem lies with the flue (which it sounds as if it does).

cheers Richard

-- Richard Sampson

email me at richard at olifant d-ot co do-t uk

[Ed Sirett]

Smoke matches are like normal matches they flare up to get going. It's the second phase where they make a steady stream of smoke that is the useful one.

I find that a length of 8mm pipe makes an excellent holder to save my hand getting roasted when doing spillage tests.

The restrictor is removed for smaller flues than the one you have. Clearly the fire and flue is working OK with the restrictor in place and might well be less efficient if the restrictor were removed.

I know that a 225mm square flue is known as a Class I flue. ISTR that maybe a Class II flue is possibly a prefabricated block system flue (?). It sounds like you have an under sized chimney which is working well enough with the restrictor in place.

Manuals usually specify that most smoke goes is drawn into the appliance or that all smoke is.

[Ed Sirett]

Well it would be helpful to learn from the experienced fitter...

The screwfix matches are not very good, I have had several that failed to light and several that went out in use. I will buy from elsewhere when my existing stock are finished.