damian139 Registered User
#1

Built a single storey extension to rear of house three years ago, and subsequently had a stove professionally fitted. 90%of the twin wall steel flue is outside the house. No problems lighting stove with current temperatures but when it gets artic i'll have to heat the inside of the flue by opening the elbow outside, otherwise smoke will blow back into the house. The cowl is H type, and flue run is in accordance with standards. Question is- any way to retro insulate external flue? Not keen on coughing up a grand for new flue if it can be avoided

zuluman Banned
#2

I understand that upon first reading it does not seem that you have a problem with draught but I am wondering as a relatively quick and inexpensive experiment if replacing the H cowl with a normal 'chinese hat' would help the situation?

Stove Fan Registered User
#3

Scrunched up very loose newspaper warms the flue up quickly with very little smoke. Or a tealight candle in 10 minutes before lighting.

Is your flue straight or has bends in it? Is your stove rear flued or top? If rear flued it should have no horizontal runs more than 6 inch. Does the stove work perfectly with no smoke coming out when lit? Having a H cowl sounds like a downdraft may of been an issue. Was it an issue?

If rear flued does the flue run through the wall at a 45 degree angle and join to a y branch/support base of the twin wall and then run vertically.

Or,

If top flued a piece of pipe above stove 45 degree bend and then twin wall pipe through the wall to join the y branch/support base and then twin wall flue above.

These 2 ways are how it should be. The main thing is no long horizontal runs.

Twin wall insulated flues can get cold. I dont know of any other way of improving the flues insulating properties.

Stove Fan

damian139 Registered User
#4

Ta for the replies!
Flue is out the rear, the only horizontal run is thru the wall, run is then vertical from the elbow. 2 small angled flue to get around the gutter, then vertical again to the H cowel.
I've tried lighting scrunched up paper with no success, but might give the tealight a go thanks, the 'Chinese hat' cowl is also a possibility
Thanks again

Stove Fan Registered User
#5

damian139 said:
Ta for the replies!
Flue is out the rear, the only horizontal run is thru the wall, run is then vertical from the elbow. 2 small angled flue to get around the gutter, then vertical again to the H cowel.
I've tried lighting scrunched up paper with no success, but might give the tealight a go thanks, the 'Chinese hat' cowl is also a possibility
Thanks again


Hi, There should be no horizontal run more than 6 inches 150mm to comply with regulations. I am sure the regulations here are the same as the UK? Having a horizontal flue through the wall does not allow an easier passage of smoke and fumes. Please sweep this flue regularly!! The horizontal run will accumulate soot and without regular sweeping will block the flue.

Get a carbon monoxide detector installed.

I am extremely surprised a professional company would install a flue with long horizontal runs.

Stove Fan

damian139 Registered User
#6

Stovefan- I'm really appreciative of ur help- I think the horizontal run is as good as it gets, I've cleaned the flue for the winter, and will look after the horizontal run as suggested,I already have the room vented, with a detector. You're gonna like this though- ive bought a Stanley cara for our main, brick fireplace, house built 1996 , is a flue liner money well spent?
Thanks
Damian

Stove Fan Registered User
#7

damian139 said:
Stovefan- I'm really appreciative of ur help- I think the horizontal run is as good as it gets, I've cleaned the flue for the winter, and will look after the horizontal run as suggested,I already have the room vented, with a detector. You're gonna like this though- ive bought a Stanley cara for our main, brick fireplace, house built 1996 , is a flue liner money well spent?
Thanks
Damian



Hi When it was installed with a rear flue it should of had a 45 degree bend fitted on the stoves rear exit and then joined to a 45 degree Y branch pipe on the main insulated flue and then up. This Y branch is also the base support for the vertical chimney above. Basically so that the flue does not collect soot.

See here and notes underneath. http://www.miflues.ie/applications.aspx?app=1

And this is how your chimney installation should look like.

http://www.stovesonline.co.uk/external-insulated-flue-system.html

A flue liner is definately the proper job. Your flue will be lined with a clay sectional liner but more suited to an open fire. With an open fire there is more heat and air going up the chimney and so it keeps the flue drier and warmer.
With a stove there is less heat and air going up the chimney and so the chimney remains cooler and as the flue is cooler is more inclined to get condensation on the inside.

You could join the flue pipe from the stove to the clay liner with a flue pipe to clay adapter but most times you can't fit the adaptor onto the end of the clay liner as the clay liners are generally set on brick corbelling and so the edges needed of the clay liner to create a seal are covered on the edges by the brick supporting the clay liner.

If you can't get a good seal and direct any condensation back into the flue pipe you could get tar and condensation drip out around the flue and create a big smelly mess.

This is why a continuous liner from stove to the top of the chimney is a good idea. Fitting a liner keeps the flue warm and makes sweeping easier.

Stove Fan

damian139 Registered User
#8

Stovefan
Many thanks for your invaluable advice. In spite of the extra expense, I'm gonna invest in the flue liner, no point seeking advice then ignoring it!
Damian

Stove Fan Registered User
#9

damian139 said:
Stovefan
Many thanks for your invaluable advice. In spite of the extra expense, I'm gonna invest in the flue liner, no point seeking advice then ignoring it!
Damian


Excellent You won't regret it. The stove and flue will perform better on a lined flue rather than clay and make sweeping much easier.

Stove Fan

zuluman Banned
#10

Hi,

I have a question about the possible use of a flue liner for an oil fired boiler.

The local priest here is having a problem with condensation in a chimney connected to an oil fired boiler in a church.

I have not seen the boiler or chimney etc.

The story so far is that the old boiler burst and was replaced by a new one. I was told that the new boiler is more efficient and has baffles in it.

Seemingly, the flue gases are cooler from the new boiler and this is causing condensation. I assume that while the gases are hot, they are not hot enough to 'burn' off any condensation caused.

I am wondering would a flue liner with vermiculite cure the problem. How does one calculate the correct diameter of flue liner? Will a flue liner cause back pressure in the oil fired boiler or at the boiler - flue interface?

Thanks

Stove Fan Registered User
#11

zuluman said:
Hi,

I have a question about the possible use of a flue liner for an oil fired boiler.

The local priest here is having a problem with condensation in a chimney connected to an oil fired boiler in a church.

I have not seen the boiler or chimney etc.

The story so far is that the old boiler burst and was replaced by a new one. I was told that the new boiler is more efficient and has baffles in it.

Seemingly, the flue gases are cooler from the new boiler and this is causing condensation. I assume that while the gases are hot, they are not hot enough to 'burn' off any condensation caused.

I am wondering would a flue liner with vermiculite cure the problem. How does one calculate the correct diameter of flue liner? Will a flue liner cause back pressure in the oil fired boiler or at the boiler - flue interface?

Thanks


Yes it wants a flexible flue liner installed suitable for oil. It should cure the problem. Im very surprised that the plumber didnt fit a balanced flued new boiler. This flue goes through the wall and has two concentric ducts. One for the air supply into the burner and one to vent fumes.
The new boiler that has been installed is open flued and requires fixed ventilation to the room with the boiler.

The installation instructions should state flue size required.

Stove Fan

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zuluman Banned
#12

Stove Fan said:
Yes it wants a flexible flue liner installed suitable for oil. It should cure the problem. Im very surprised that the plumber didnt fit a balanced flued new boiler. This flue goes through the wall and has two concentric ducts. One for the air supply into the burner and one to vent fumes.
The new boiler that has been installed is open flued and requires fixed ventilation to the room with the boiler.

The installation instructions should state flue size required.

Stove Fan


Hmmm. This is a large boiler in a church - never saw such a large sized boiler with a balanced flue.

Is there a 'fitting' that one can use to centre the flue liner in the existing liner at the bottom to stop the vermiculite falling out? It is a bit difficult to explain without a picture but there is a balancer at the bottom of the chimney ( you know the flaps with the little weight at the back)- so the flue liner can't go all the way from top to the boiler outlet in one continuous go as then there would be no balancer. So thats why the question about the fitting to let the flue liner come as far as the balancer i.e no liner from balancer to boiler outlet (only a few feet normally)

Stove Fan Registered User
#13

Hi Sorry I can't visualise this. Is this a thing thats funnel shaped? Any chance of a picture? If not a flue installer would know.

Stove Fan

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