Shared Flue?

[bjohnson]

Doe anyone out there have a gasification wood boiler vented into the same flue as your oil boiler? I realize that this is not the optimal scenario but I have no other option if I install a wood boiler. Power venting is not a possibility, nor is an additional liner or chimney. With little to no creasote emmision, it seems very unlikely that the flue could become clogged. It also seems that the current codes were generated when oil boilers had much higher vent pipe temps than are current with new technology. I can't imagine what the possible danger could be if only one appliance is firing at a time. Anyone with hands on experience, please share your experiences. Thanks.

BB

 

[Michael6268]

Two appliances in the same flue is not allowed. Dont think it is as much about "clogging" but more so if you ran both the flue cant handle the volume and the possibility of the idle appliance allowing gases to enter the home through it. Code doesnt allow it.

 

[flyingcow]

know quite a few people that do it with an old fashioned wood boiler or stove sharing chimney with oil furnace. Correct that it's against code, or at least I think national code, and if insurance company found out, they might get upset too.

One question I have , and somebody here should be able to answer. What problems will the "pressure" from the fan driven draft have on the oil flue? i.e. will this force fly ash into/around thimble? or into boiler room, with the oil burner having a baro damper. I'm assuming that it has one.

For only turning my oil boiler on once this winter(after hooking up my tarm) I suppose(if I had to share a flue) I could disconnect the oil side and put back in when necessary. Wouldn't be a huge problem. Just a thought.

 

[CrappieKeith]

If both units were connected by a common manifold....as per NFPA you could vent through the same flue.
Otherwise it's a no-no.

 

[firefighterjake]

know quite a few people that do it with an old fashioned wood boiler or stove sharing chimney with oil furnace. Correct that it's against code, or at least I think national code, and if insurance company found out, they might get upset too.

One question I have , and somebody here should be able to answer. What problems will the "pressure" from the fan driven draft have on the oil flue? i.e. will this force fly ash into/around thimble? or into boiler room, with the oil burner having a baro damper. I'm assuming that it has one.

For only turning my oil boiler on once this winter(after hooking up my tarm) I suppose(if I had to share a flue) I could disconnect the oil side and put back in when necessary. Wouldn't be a huge problem. Just a thought.

What isn't well known however FC is that there is some talk about the Maine politicians doing away with the two-in-one "rule" . . . it still hasn't come out yet, but there has been some talk about doing so . . . for better or for worse.

Moreover, it is interesting to hear the reasoning for this requirement as there are a number of guesses for the reasoning . . . but even some folks who deal with this stuff all the time and are even on national committees aren't quite sure of the real reason it was placed in the code in the first place.

 

[CrappieKeith]

It seem appearant to me why.
If you had issue with a burner lets say and there was a lot of fume in that flue then you tried to light a wood unit. There could be an explosion.
Regaurdless of what some may think. For the most part our heating code is there to protect us from ourselves. In the late 70's to mid 80's there was a rash of home fires because of the lack of code.

 

[flyingcow]

I was under the impression it had to do with a few cases of thew chimney plugging up with creosote and the oil unit firing up and co2 killing people. But seems like this was a few and far between and somehow this translated into what we have now. Again, not sure how it happened.

 

[BrotherBart]

The reason I wouldn't have two appliances connected to the same flue is that when one isn't burning and the other is then cold air is going to be drawn through the idle appliance and not only cool the flue gases and crud up my chimney but also make a mess of my draft.

Not much different than leaving a clean-door open or a tee un-capped.

 

[SlyFerret]

Yup! The chimney isn't just a vent. It's a critical part of the draft "engine" that drives the system.

It would be sort of like trying to drink a Coke through a straw with a hole poked in the side of it.

-SF