Questions about a two flue chimney

[Littleboomer]

I am preparing to become a wood burner, but have run into a question that I can't seem to find an answer for; in my chimney I have one flue for my oil burning furnace and another for my fireplace. The fireplace flue will soon be lined with 6" rigid SS, but the question is even if I insulate the the liner is it going to heat up the masonry around it enough to where it will create a draft problem for the adjacent flue? The chimney is exterior with three sides exposed to the cold and the oil flue is not lined all the way to the top.
Has anyone had any experience with this type of setup?

 

[bholler]

It should not cause a problem i have never heard of that if anything warming it would increase draft but the baro damper on your furnace will fix that. The only potential problem which i have not seen often is the wood stove backdrafting into the furnace chimney

 

[NinjaTech]

Did you ever have any draft issues while using the fireplace without a stove in it? That would heat up the brickwork a lot more than an insulated liner will, and would be pulling much greater CFM worth of air up the flue. If you didn't have any issue like that, I don't see how you would have any issue with a liner/stove. Mine is a double flue like that also, no issue with the natural gas water heater either before or after the stove.

 

[Littleboomer]

I haven't used the fireplace yet as it currently has an old VC insert in it from the late 70's and the install is nowhere near code compliant, so for now the damper is closed off. But it is encouraging to see others have a similar setup with no issues concerning the other appliance's draft

 

[bholler]

It is a very common setup and i have never heard or seen of any issues like like what you are worried about. And i see many hundreds of chimneys a year

 

[Littleboomer]

Awesome, thank you! Glad to know I don't need to worry about that

 

[AnalogKid]

I have a triple-flue chimney; open fireplace, woodstove insert (w/ insulated SS liner), and oil furnace. My chimney too has 3-exterior sides as well. Zero issues.

 

[Littleboomer]

Thanks Analogkid, good to know other people have a similar setup

 

[cheechblu]

I have my wood burning Jotul on the ground floor and my coal burning Marathon in the basement going up the same chimney. Never had a problem. Rest easy.

 

[mellow]

I have my wood burning Jotul on the ground floor and my coal burning Marathon in the basement going up the same chimney. Never had a problem. Rest easy.

As per the Jotul F600 user manual: "• No other appliance can be vented into the same flue."

OP do not do something like this.

 

[cheechblu]

I apologize if I'm using the wrong terms. When I wrote chimney, I mean the chase. Inside the chimney is the flue pipe.
I have 2 separate flue pipes from 2 separate stoves going up the same chimney. I'm not saying to run 2 appliances up the same flue. I'm sorry for not being clear on that.

 

[velvetfoot]

The only problem I have is when a flue gets too cold and then the draft reverses. I have a motor operated oil vent damper for the oil burner that helps. I think taping the oil connector pipe joints would also help, but I haven't done that yet. I noticed a bit of a wiff today when the damper was open, unintentially (oil burner off and cold). Anyway, cold is the issue for me. The oil burner and its fan overcomes it, I believe.

 

[newatthis]

I am a newbie, but we have an insert in an interior chimney that has a separate flue for the furnace in the basement, which is about 3 feet lower (split level house). The furnace vents at about the same level as the insert on the (slightly) higher floor. Never had any problems at all with the draft when the insert was just a fireplace.

Surprisingly, we found there was backdraft coming down the chimney, such that the basement smelled of smoke with the insert running. This was just a couple of weeks ago, when the weather was considerably warmer, and we were still doing the test fires on the new Morso. The problem did go away when we lit the pilot light on the gas furnace. (Still haven't turned the furnace on). No hint of any smoke smell now. I was only able to quickly figure out what the reason for the smoky smell thanks to this board.

 

[velvetfoot]

The pilot light would do the trick to keep the draft moving in the right direction. I initially figured out where it was coming on the oil from when I put a bag over the baro damper and that stopped it. I've also fooled around with changing the heights of the three flues, but that makes assumptions about what appliances are likely to be running an the prevailing winds.

 

[bholler]

As per the Jotul F600 user manual: "• No other appliance can be vented into the same flue."

They all said it right they are multi flue chimneys the chimney is the containing structure the flue is the interior passage you can run as many appliances through the same chimney as you want as long as you have a flue for each of them. The only issues that i have seen with it is that occasionally like newatthis said under certain conditions with certain setups you can get a backdraft down one of the other flues

 

[cookin2night]

I am preparing to become a wood burner, but have run into a question that I can't seem to find an answer for; in my chimney I have one flue for my oil burning furnace and another for my fireplace. The fireplace flue will soon be lined with 6" rigid SS, but the question is even if I insulate the the liner is it going to heat up the masonry around it enough to where it will create a draft problem for the adjacent flue? The chimney is exterior with three sides exposed to the cold and the oil flue is not lined all the way to the top.
Has anyone had any experience with this type of setup?

What is the hight of your chimney from your fireplace? I have the same configuration with the two flues in the same chimney. My hight is roughly 25 feet which gives me very good draft. I think if you have good draft there won't be any problems. However if you have poor draft from your fireplace you might get back draft into your boiler flue.