Max distance on a rear vent (F500)

[CarbonNeutral]

I m intending to rear vent a Jotul F500.

I was in a fire shop discussing this, and they said that my draft would be negatively affected because I had a longish initial horizontal run. There is a picture attached of what I am doing - the stove will sit outside the fireplace box with the vent making its turn 16-18" from the stove.

Is this something I should be concerned about?

Intuitively I feel there would be some effect, but as the shop was suggesting a 5.5" uninsulated liner because of flue size, I'm not convinced they actually 'knew'. I will be using an insulated liner with a cross section equivalent to a 6" pipe so maybe that will offset the slightly longer horizontal run?

Note the picture doesn't show the elbow that will be between the stove pipe and liner.

 

[BrotherBart]

Just maintain the 1/4" per foot vertical rise and it will be fine. Actually I think it will be fine as is but all of the gurus preach the rise. Don't know why because there isn't a mason on the planet that doesn't install chimney thimbles dead level. Like mine in the office.

All I can offer is my experiences. My Jotul F3 down in the office has four feet of vertical pipe into a 90 degree elbow into two feet of horizontal pipe into two feet of 5.5" horizontal liner in the thimble that then turns 90 degrees toward the sky. That is four feet of horizontal pipe with two 90 degree turns and the draft on that thing will suck paint off a wall. In a exterior masonry chimney with an un-insulated liner.

Yours is gonna work just fine.

 

[CarbonNeutral]

Just maintain the 1/4" per foot vertical rise and it will be fine. Actually I think it will be fine as is but all of the gurus preach the rise. Don't know why because there isn't a mason on the planet that doesn't install chimney thimbles dead level. Like mine in the office.

All I can offer is my experiences. My Jotul F3 down in the office has four feet of vertical pipe into a 90 degree elbow into two feet of horizontal pipe into two feet of 5.5" horizontal liner in the thimble that then turns 90 degrees toward the sky. That is four feet of horizontal pipe with two 90 degree turns and the draft on that thing will suck paint off a wall. In a exterior masonry chimney with an un-insulated liner.

Yours is gonna work just fine.

Thank you. They said that it was the fact that the first section was horizontal - that was the problem, Don't believe them. Anyone else rear vent have any problems?

 

[BrotherBart]

It will impede the start-up draft a little more than a run of vertical. But not much. It will be interesting to hear from people with straight rear exits. There are a lot of them into exterior Class A chimneys.

 

[Stephen in SoKY]

I didn't reply until I had a chance to measure, but, my stove rear vents into a 37" long piece of 6" black pipe, then nineties straight up to the cap. I maintain the requisite 1/2" per foot of rise and I've never had any issues with draft. I do light off a piece of newspaper on top of my wood to establish draft at startup, although it hasn't been an issue when I've forgotten to do so. I don't recall ever having any issue with backpuffing when reloading either. Hope this helps.

 

[CarbonNeutral]

I didn't reply until I had a chance to measure, but, my stove rear vents into a 37" long piece of 6" black pipe, then nineties straight up to the cap. I maintain the requisite 1/2" per foot of rise and I've never had any issues with draft. I do light off a piece of newspaper on top of my wood to establish draft at startup, although it hasn't been an issue when I've forgotten to do so. I don't recall ever having any issue with backpuffing when reloading either. Hope this helps.

That's twice as long as mine will be. Answers my question. My chimney may be colder than yours at times, but can't figure that will make a difference with half the distance.

Thanks for measuring.

Out of interest - where does the 1/2" per foot come from - it's not in the manual is it?

 

[Stephen in SoKY]

Actually, as I recall it came from here. I more often see 1/4" per foot, but the 1/2" works great for me without looking wierd. BTW, I have my manual damper in this horizontal run and it works out quite nicely.

 

[CarbonNeutral]

Just to close off this (old) thread - my stove is in, and though I have little to compare it to, it pulls well - no trouble starting, no smoke back in room when I open it. It doesn't have much of a rise on it - maybe 1/2" over the 18" or so. It is clear when I add a piece of wet wood by mistake - takes a while to get going, but I guess that's true of most modern stoves.