Space between Chimney Pipe and Cap

[MattBOut]

Is there a certain distance there has to be between the exit pipe at the top of the chimney and the rain cap? We just installed a englander insert with insulated 6" chimney pipe. There was a ran cap already on the chimney that covers the fireplace and oil furnace exhaust and i like the look of it. But i want to make sure the chimney is drafting correct and make sure i have the correct space between pipe and cap. Everything seems to be working great, i cant believe i never installed a stove before.

 

[Nick Mystic]

I don't think you've given enough data for a definitive response on whether or not you have sufficient space with your rain cap for efficient burning. I've never heard of an iron clad rule for how much space you need. Your photo doesn't actually reveal how much space your cap provides due to the steep angle of your perspective. I know that most of the rain caps I've seen only allow for a couple of inches or so of venting space, so you're probably okay. After all, the proof is in the pudding and if your are getting good performance, as you said, then you should be good.

One word of warning: I see in your photo of the chimney that you have leaves built up in your gutter right below the chimney. So long as you have a screen in your cap this shouldn't be a fire hazard. However, if the cap is open then you run the risk of hot embers exiting your flue and sliding down your roof igniting those leaves. This is especially true if you ever have a chimney fire.

 

[MattBOut]

It seems to be about 3.5-4 inches from top of pipe to bottom of rain cap. But the cap tapers down on the sides.

 

[Nick Mystic]

I see a couple of things noteworthy in your photo. First, it appears that your flue has a clay tile liner that sticks up an inch or two above the crown of the chimney. Then your SS liner sticks up a bit further. If the 3.5" - 4" you mention is measurement of the wire sides of the cap, then there is only a couple of inches of "headroom" between the top of the liner and the top of the cap. That might be a little on the tight side.

Secondly, it appears that you have a crack in the cement crown that extends down through at least one mortar joint and then into the brick below it. Any cracks like those should be sealed as soon as possible to prevent water infiltration into the chimney. A lot of damage can occur when water seeps into such cracks and then freezes. This makes the cracks larger and starts a cascading problem down the road. It's best to tackle this sort of situation before you start getting leaks inside the house.

 

[MattBOut]

I will be fixing the crack before winter hits. Did know it existed till installing the stove.

The 3.5-4 inches is from the top of the SS liner to the cap. That cap that came with the liner is 5 inches from ss liner to top, so i have about 1-1.5 inches less. Do you think this is ok distance?

 

[Nick Mystic]

The distance you describe sounds okay to me, but I would keep a close eye on creosote build up on the underside of the cap and on the screen. With such a large cap close to the top of your liner you are likely to get an accelerated accumulation of creosote building up there. You can usually detect this by having smoke start exiting your insert on reloads. If you open your door and notice a tendency for smoke to come out you should go check your cap for clogging.

 

[MattBOut]

After some research it seems the consensus is 5" minimum for distance from top liner to cap. Hrrmmmmm i might have to modify my cap just to be on the safe side.

Anyone else have a short chimney cap? Any issues?

 

[begreen]

Looks very smokey. Damp wood?

 

[bholler]

I would say that is to close for me i usually shoot for 5 to 6"

 

[Hickorynut]

After some research it seems the consensus is 5" minimum for distance from top liner to cap. Hrrmmmmm i might have to modify my cap just to be on the safe side.

Anyone else have a short chimney cap? Any issues?

I had a 6 inch liner put down in a 12 inch clay flue and used the old 12 inch rain cap and the liner was within about 4 inch's of the top and didn't seem to effect draft and let the exhaust out okay I think. I have since, just this year put on a higher chimney cap, 10inch high I think. Not sure if it will make a difference or not. One thing for sure, you don't want the cap to high or a slanting rain may get down the flue, maybe....

 

[begreen]

FWIW, I think the average class A cap has a gap of about 4".

 

[fire_man]

Bholler is right as usual. I had a chimney sweep install my liner and rain cap and he looked up the code in his book. I seem to remember the correct distance was equal to the diameter of the flue pipe, which was 6", but any case, there was absolutely a defined code for that clearance.

Yes it might work ok with less, but there was a code.

 

[MattBOut]

Well I have to wait a few months to get the money to buy a taller cap but for now this is what i came up with Seems to work ok. My chimney cap has a chimney cap