Poor initial draw on retrofitted cast iron insert

[Lower]

In my house i have a cast iron insert fireplace that has been fitted in place of the original 1920's fireplace. The work was done before we bought the house.

The chimney has been recently swept but is very, very tall. The roof is already steeply pitched and the chimney protrudes through the edge of the roof and then rises above the ridgeline.

When the fire is intially lit the draw is very poor and smoke comes out of the fireplace into the room. Once the fire starts to take hold and the heat starts to rise up the chimney the chimney then draws very well.

The smoke coming out of the fireplace on iniital lighting is a problem though as its discolouring the paint above it.

I had the chance to stick my head up the fireplace today and there is the remains of the old throat a couple of inches above the insert. There is a damper/flap that comes off the top of the insert that kind of shields the old throat, but will the old throat he affecting the draw?

What sort of throat, if any, should there be above this sort of fireplace?

Thanks in advance.

 

[Nige F]

A deep throat

 

[bobby spray]

I doubt that the throat is to blame. I have an original 1890's insert and it can on occasion push smoke into the room. the problem is that you have a large column of cold air that you need to push up and away through the chimney before the draw starts to work properly. You need to get some heat up there before you start burning the coal/wood. can't you just hold a lighted piece of paper up there to heat the cold air up? if not I agree with Nige.

 

[stuart45]

Tall chimneys usually have a better draw, but yours has a lot of the stack exposed to the cold which takes longer to heat up.

 

[Nige F]

I`ve got an old weed killer - like a gas blowlamp on a long stem - I use that for lighting our fire , and warming the flue first . got it cheap from a boot sale

 

[Lower]

Obviously deep throat would be very pleasant. It would certainly warm me up, but not help too much with the fire smoking issue

Good point about using some lighted paper or a weed burner to warm the column of air in the chimney before lighting the fire.

I'm still concerned about how important the throat is in the performance of the fire. The insert appears to have been fitted properly with a cement capping behind the insert in the chimney sloping down to the actual opening.

What sort of throat should there be with this sort of insert? Or does the damper/flap itself form the appropriate throat? Is there any benefit to having the old throat removed?

I'd get the appropriate trade in to do the work, but i'd like as much background info as possible before getting a tradesman round.

 

[Nige F]

Youre best bet is a HETAS registered bod . have a look @ their website
www.hetas.co.uk