pre cast flue smoke test

[shaundolman]

Hi I have a 4 year old house with a pre cast flue fitted for a gas fire.
The house as always had a electric fire fitted and recently had a plumber out to fit a gas fire as the flue and gas pipe are already there.
The first thing the plumber did was a smoke test and most of the smoke came back into the room so there was a problem that he couldn't fix.
I then got intouch with the house builder who said it wasn't under warranty.
I decided to remove the flue inside the loft and found a lot of spiders webbing etc of which i cleared out and also the rect of the flue etc looks brand new.
I then did a smoke test myself before calling the plumber out to fit the fire and smoke still came out of the fire and not all going up the chimney.
I did have the patio door open to the lounge when testing as didn't think this would make any difference. My neighbour has the exact same flue and gas fire which is ok so don,t think its that.
Can anyone verify on how to do a smoke test and would it have made a difference having the doors open to the outside.
Many thanks Shaun.

 

[PlumbGas]

You want to put some heat into the flue first with a blow torch or something similar for about 5 mins, then carry out the test again with all doors and windows shut, also any extractr fans in the room on, use a smoke match first, before any of this is carried out a visual inspection should be carried out, a competant RGI should be able to carry out these tests for you and i suggest that if your previous gas man didn't do these things than he is not competant.

 

[expertgasman]

Also block most of the opening with card or wood, before inserting the smoke pellet. Test before a pellet with a smoke match or rolled up newspaper. If the flue doesn't pull this, it wont pull a bomb.

Also check for webs in the pre cast flue as well.

We dont give gas advice in this section, but I think it is fair for you to try this before engaging an RGI

 

[shaundolman]

Hi and thanks for the quick replies.
I will get the gas man back in to do the test properly but just wanted to hopefully rectify the problem before calling him back again.
He did warm the flue up before putting in the smoke pellet and then sealed the front with the gas fire he was going to fit and smoke came out of the front.
I then went into my loft and removed the flue at the top to find loads of cobwebs as the fire has never been used. After cleaning it all out then did another smoke test which smoke came out of the front worse but was this down to me having the patio doors open.
Would having the patio doors open to the outside make a big difference to the smoke drawing up the chinmney.
Thanks Shaun.

 

[gas112]

YES all dors and windows must be closed during a smoke bomb test

 

[expertgasman]

YES all dors and windows must be closed during a smoke bomb test

Why?

Open doors and windows will assit the flue, and there is no problem in conducting the flue test with doors open.

a SPILLAGE test MUST be conducted with all doors nd windows closed, as you must test it in the worst case scenario. Followed by a further test with a kitchen extractor fully on, if fitted, with connecting doors open

So OP, the failed test was not down to the door being open, but more likely a restriction in the PC flue

 

[jackpike]

if its a 4 year old house, it will be still be in warrantee, most builders are overseen by nhb and the precast flue is part of the building and would appear from your description that has never been put in correctly, of blocked with motar when firstly built, I've seen this many times,
I would try poking some 15mm speedfit pipe up the flu to see if you can locate where the blockage is, it won't be in the metal flue part, a spiders web over a 5 inch flue will just disintigrate ,

 

[shaundolman]

YES all dors and windows must be closed during a smoke bomb test

Why?

Open doors and windows will assit the flue, and there is no problem in conducting the flue test with doors open.

a SPILLAGE test MUST be conducted with all doors nd windows closed, as you must test it in the worst case scenario. Followed by a further test with a kitchen extractor fully on, if fitted, with connecting doors open

So OP, the failed test was not down to the door being open, but more likely a restriction in the PC flue[/quote


Have just had the corgi registered. Gas fitter back who has done a smoke bomb test with all windows and doors shut and no smoke at all came back down as it all went up the flue. Must have been down to the cobwebs etc at the top of the flue that I cleared out. The fitter as now past the flue and stated that all windows and doors must be closed for the flue to draw properly .

 

[shaundolman]

Have just had the corgi registered. Gas fitter back who has done a smoke bomb test with all windows and doors shut and no smoke at all came back down as it all went up the flue. Must have been down to the cobwebs etc at the top of the flue that I cleared out. The fitter as now past the flue and stated that all windows and doors must be closed for the flue to draw properly .

 

[gas112]

The main reason for the smoke bomb is to check the integrity of the flue also to check that it pulls so you carry it out in the same manner as you would an initial spillage test.
Reason being if the flue did not pull you would not then fit the fire as it would then fail a spillage test.

Expertgasman surprised at you this is basic core stuff try bombing a fire during ACAS and saying you would not close windows and doors.

 

[expertgasman]

[quote="gas112";p="2145204"]The main reason for the smoke bomb is to check the integrity of the flue
Absolutely


also to check that it pulls so you carry it out in the same manner as you would an initial spillage test.
Reason being if the flue did not pull you would not then fit the fire as it would then fail a spillage test.

Expertgasman surprised at you this is basic core stuff try bombing a fire during ACAS and saying you would not close windows and doors.[/quote]

TBH, you may have a point, and it certainly is not wrong to do it with all doors etc. closed. But TBF, I don't make a point of closing everything till the ST, which I conduct scrupulously. To a large extent, experience helps to interpret smoke test performance.

The fitter as now past the flue and stated that all windows and doors must be closed for the flue to draw properly .

OP: either you misunderstood your RGI, or he is wrong. If there is a difference, open doors will ASSIST flue pull, not cause it to fail. A possible exception is where the room is open plan and an upstairs window is open

 

[gas112]

Its more than a point i have its the correct way to do it .

 

[expertgasman]

Perhaps kirk would like to clarify the requirements.

As far as I am concerned the bomb is to test integrity. During the test, you are in and out of the house, so by definition, you can not keep doors closed. If you close the door with anything other than a mild push, there WILL be smoke blown back in the room, and the loft hatch is open.

However, I am always willing to concede that I may have an incorrect assumption, promulgated over the last 35 years.