Partially Blocked Flue? Please Comment On Pic...

[MR]

I'm appealing for some help from anyone who has had experience with flue's going from a fire (in living room) up through into attic, and then eventually through the roof. I have just had a fire fitted and the 'smoke test' worked fine but after the install the flue is not 'pulling' or sucking up enough and so the install is not complete. My fitter has tried fitting a flue extension kit with unfortunately the same results. The fitter concede I must have a blocked flue and recommended an electric fire or an electric power-flue directly behind the fire in living room (which is noisy incidentally).

I wasn't taking his opinion lightly and took my digital camera into the attic and took a shot down the flue and the picture I got is posted here:

my query is that I do not know what to expect when looking down the flue but it does appear that I have approx a third of what seems to be hollow breeze block half way down the flue. Is this what I should expect to see or is this perhaps causing my problem? Is this the way my flue was supposed to be installed when the house was built or is it just a shoddy job?

The angle I have taken it at seems as if the block is hollow and my initial thoughts are to hire some rods and try and break this off... however your comments are very much valued before taking this a step further.

[BigWallop]

See my reply in: free.uk.diy.home

[BigWallop]

To cross post your questions between groups, just place the address of both in the TO section of the mailing. It saves you having to post it twice or three times to the different groups. :-))

[The Natural Philosopher]

There is a simple formula that says for a fire to draw properly and not smoke, it needs an aperture not more than 7 and preferably 5 or less times the flue cross sectional area.

Not really gleaning anything useful from your photo sadly, I can't tell if this is the case in your case.

Smokey fires are cured by raising the grate, or dropping a smokehood down to reduce the aperture

[jerrybuilt]

I can't *get* free.* newsgroups.

A cross-psot is better than a multi-post for several reasons!

be [e-mail]! Shop all amazing products and get our special offers!

[tarquinlinbin]

It appears that you have a pre-cast concrete block flue or similar.

First things first,check the makers instructions for the fire and see if it is suitable for a pre cast flue?

YES ?

did you have a fire fitted to it and did it work ok before??

This is a common problem with this flue type and rodding out any cement "snots" is a common fix. Access is a problem though. I have done flue inspections using a remote camera in this sort of situation before.

A fan powered flue assistance device is probably a no in this situation.

joe

[Kalico]

one but not sure why you are able to take a pic 'down' the flue from inside the attic. Does it have a soot box in there?

The most common cause for lack of draw is the wrong type of flue terminal on top of the pot. What does yours look like?

Also, can you give me an idea of age of property?

Thanks Rob

[MR]

Many thanks for all the posts and suggestions so far. I've been back in the loft and taken some more pics that can be found here:

Pic 1 = This is the Flue 'hole' in the loft with the metal tubing that was used with the flue extension kit.

Pic 2 = Now this is with metal tubing removed with a heavy blob of what seems to be cement/putty on the end (this incidentally was loose and I have not used ANY force at all to remove the tubing for the photo).

Pic 3 = This shows the flue in relation to the pitched roof.

Pic 4 = This is the fire we have had chosen and had installed.

Now I'm wondering from the posts whether the loose tubing in Pic 2 could be posing a problem as this is not secured fully (flush/air-tight) to the hole in the loft. Should this be in any way loose or am I correct in thinking it should be flush/fully sealed to the exit hole?

Again your thoughts and comments are appreciated.

PS - The fire that was there previously seemed to work OK, but we have only recently bought the house and the fire was one of the first things we changed. The house is 30years old. And the flue did leave through a roof tile at the utmost point of the roof, but then when the flue extension was tried it was taken out around 1/2 way up the roof where a tile was cut etc.

[Gavin Gillespie]

thinking it

I have a similar block type flue, and when I was discussing my heating with a heating engineer, he asked me if the flue was connected to a flexible pipe, or a dual skin solid pipe, mine is the latter, but he said that if it had been a flexible pipe, he would have advised me not to use it until it was replaced with a solid one. I did not ask why, as it was not relevant in my case, but it seemed important to him.

[Dave Liquorice]

That round hole leads up to a chimney/external vent I take it and you can feel an up draft at that round opening? The other end of the pipe then goes to the rectangular hole in your earlier photograph.

All these joints need to be gas tight otherwise the flue gases will seep out. Flue gases aren't the best things for ones health...

There looks plenty of room in the box flue I'd be tempted to take that single skin flexable liner right down to a register plate above the fire or even to the flue outlet of the fire (if it has one) with just the single joint into the round hole. In fact I'd probably investigate getting the liner right up to the pot as well.

[Gavin Gillespie]

investigate

In my system, the flue is similar to a breeze block, with the centre piece missing, and would be nowhere near wide enough to take the flexible pipe.

I have just had another look at the original picture, and I do not think the concrete is a blockage, merely an infill, at the side of the block built flue.

[Andrew Gabriel]

They were created by someone who didn't like newsadmins in response to being disciplined for abuse of usenet or failing to get groups created by recognised means or some such IIRC. Consequently, much of the usenet transit systems don't carry them and article propagation is very poor compared with all the other top level groups.

I run a news transit system, and I don't take any of the free.* groups. A couple of years ago, I looked into them and noticed that they seem to run as disconnected islands; we'll get groups of articles from one peer and completely different ones from another peer in the same free.* newsgroup. Volume was low and they were pretty much all just copies of existing newsgroups. Really, they should be left to die.

[tarquinlinbin]

chimney pot as such on the roof?

As i have said,it looks like you have a pre-cast concrete block flue system. It might be terminated with a ridge terminal or a standard 5" GC1 type terminal. The flexible liner is a joke,it should be twin walled flue pipe rising as vertically as poss to the terminal with pipe properly supported,clamped and joints taped to seal.

Check the manufacturers instructions for the fire,does it say it is suitable for fitting to a pre cast concrete block flue.

Flue blocks and associated accesories should comply with BS 1289. The cross sectional area should not be less than 16500mm 2 with a minimal internal dimension of 90mm. Before 1986 these dimensions where csa

13000mm 2 and 63mm

[Andrew]

Agreed - see

- they make the flue block system. You should never use single wall flexible pipe to connect flue termination block to the ridge terminal, that is what twinwall (Selkirk) is for. Flexible tube is only for lining existing brick chimneys.

Also, it is not allowed to have angles less than 45 degrees from the vertical - and yours looks like it is horizontal, apart from having what looks like a horridly bodged connection.

The smoke test failure is probably caused by the horizontal part of the flue. What was there before ?.

[Andrew]

Something is bothering me about photo 1. It looks to me as if the inside of the termination flue block slopes up and away from the front lip. This suggests to me that the block is upside down !!. Can you actually see *down* into the flue blocks below the termination one ?. I.e. looking down towards the fire ?.

[Ed Sirett]

I have just come onto this thread. Oh Sh*t. We have a really bad installation here: 1 Flexible liner used where rigid flue pipe should be used. 2 Terminal block on flue block system looks completely wrong - should be 45 degrees not vertical. 3 Flexible liner detached from flue block. (Though that may have been done for the camera.)

Looks like at _minimum_ a doouble wall metal flue system needs to be put in, also the top block block need removing and replacing with the correct item.

[MR]

Thanks for the updates guys. To answer some questions posed...

1) The picture pointing down the flue was taken by carefully sliding in my digital camera into the hole you see in the attic (PIC 2 here: ) This hole is a 90 degree angle so it goes in say 10-12inches or so then goes straight down. (like an upside down L ). 2) I have had several people comment onthe flexible metal tubing coming from the hole and after reading up this SHOULD be a rigid flue pipe. 3) Liner was detatched from block - this was very loose as previously mentioned and basically came out without any force! The blob of compound was not secure at all.

I'm working with them to come out armed with the info and BS Standards/regs quoted in this thread. I'll update you on what comes of the visit... your further comments are still appreciated.

Thanks once again...

[Kalico]

My guess is that the fire that was fitted before was not of the 'living flame' type. at least with flames that are open to the room, Possibly it was a radiant fire or the flames were behind glass? Let me know.

Either way, it would be helpful to see what flue terminal you have fitted up top as I suspect it is incorrect for the fire you are using. The Corgi fitter who did the fire should have been able to advise you on this.

You are correct that ALL the joints must be gas tight. The idea is to get as near as possible to a continuous and constant diameter flue running all the way to the terminal, which of course, should be the correct type. In my experience, about 80% of all older homes with gas fires have the wrong type of terminal fitted. Even none at all would be better, but invites those pesky pigeons to fall down after becoming intoxicated on the flue gases whilst sitting on the pot for warmth.

Hope this helps a bit.

Rob