Priming flue very difficult in winter


  #1  
Old 07-12-15, 08:08 PM
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Priming flue very difficult in winter

The fireplace we have is an outside brick chimney and then s modern cylindrical flue has been inserted inside for a new fireplace. In winter -30 Celsius outside, the smoke congress straight back in the house. Priming the flue with newspaper doesn't seem to help... probably due to temperature, the 30-40ft flue, and maybe air surrounding the metal insert but inside the brick is cold.
Any ideas how to solve this?
Eventually it warms bit not before too much smoke has been generated. Warming with candles didn't work either.
 
  #2  
Old 07-13-15, 04:43 AM
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When was the last time the flue was cleaned?
 
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Old 07-13-15, 05:11 AM
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Hi gwerty,
The science involved in getting a chimney to draft properly has been lost in decades of home remedies, ie open a window. All of your statements sound exactly correct, outside chimney, cold air in and around it, two story house, and a battle to get it started. And I will guess the actual fireplace is located in the lower portion of the house. With those extremely cold temperatures your are fighting strong natural pressures. Avoid the "open a window" approach as whenever that window is closed the combustion gasses may be directed back into your home as the chimney cools.

Where does your new fireplace draw its combustion air, is it a sealed unit?

Since you can't rebuild your house to move that chimney inside, your best approach might be a power vent on top.

Bud
 
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Old 07-13-15, 06:28 AM
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When was the last time the flue was cleaned?
Was cleaned last autumn but we had the problem in the winter only a few months after.

Hi gwerty,
The science involved in getting a chimney to draft properly has been lost in decades of home remedies, ie open a window. All of your statements sound exactly correct, outside chimney, cold air in and around it, two story house, and a battle to get it started. And I will guess the actual fireplace is located in the lower portion of the house. With those extremely cold temperatures your are fighting strong natural pressures. Avoid the "open a window" approach as whenever that window is closed the combustion gasses may be directed back into your home as the chimney cools.

Where does your new fireplace draw its combustion air, is it a sealed unit?

Since you can't rebuild your house to move that chimney inside, your best approach might be a power vent on top.

Bud
It draws air from inside the house and it's a slow combustion burner. So, effectively, you close the front door of it and open/close a little lever which allows air to be drawn in down over the window (keeping it clean) and into the fire and then up the vent.

A power vent is run by electricity?
 
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Old 07-14-15, 11:16 AM
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How about a damper outside. This will keep the chimney warmer than outside so it should draw as soon as a fire is lit.

Lyemance 13 in. x 13 in. Energy-Saving Damper
 
  #6  
Old 07-15-15, 06:57 AM
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Will a damper be effective in -30 Celsius or colder in the winter?
I would say at least half of the brick chimney is outside the house so might not be effectively warmed by the house heating when the fire is off.
The old fireplace has some venting at the bottom which also allows a strong cold draft into the house, I need to block these up with mortar.
So, the damper would have to cover not only the metal flue insert but also the brick surrounding (ie the old chimney).
The current metal flue sticks out of the top of the old brick chimney.
 

Last edited by qwertyjjj; 07-15-15 at 07:27 AM.
  #7  
Old 07-15-15, 08:11 AM
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When you do some searching you will see you are not alone. A brief look and I saw several references to fans used to prime the chimney. Turn them on for a minute or two before you light the fire and then shut them off. I can't speak for any particular produce so recommend you search as your setup may differ. here is one of the links i looked at.
Chimney Flue Vent Fans - Wood Stove Draft Inducer Fans | Rockford Chimney Supply

Bud
 
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Old 07-15-15, 11:40 AM
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It seems to attach near the base so is presumably just a fan that pushes air up to reverse the flow?
Secondly, because this is an insert in the existing chimney - how can I stop cold air coming down the brick part of the chimney when the fire is not on? It creates a big cold draft in the house. I presume the open brick chimney would have to be blocked but the metal flue insert be left open?
 
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Old 07-15-15, 11:50 AM
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I would think the metal flue would be passing through a metal cap that would be sealing the top of the bricks.

A traditional fireplace is sometimes equipped with a cleanout below the fire box. If yours had one, what was done when the insert was installed?

Bud
 
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Old 07-19-15, 06:31 AM
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There was no cleanout, it was just a brick bottom, like an open fireplace.
 
 

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