Rear heatshield clearance question - code interpretation

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KeithO

Minister of Fire
Aug 8, 2007
592
Jackson, MI
I'm busy installing my Morso 7110 in the living room at present. One of the reasons for choosing the 7110 was the small rear clearance required (6.5"). What I'm curious about is from where one measures the 6.5 " ? The stove is shipped with a rear heatshield as standard. Does the 6.5" count to the back of the stove or to the back of the heatshield ?

I ask this question because if I set the back of the heatshield 6.5" from the wall, I run out of clearance on the radiation shield on the rafter that is on the front side of the stove. I am using a square "cathedral ceiling" box to pass the class A through the ceiling and it is exactly 12" square on the outside. This puts the centerline of the class A 6" from the face of the rafter. I can only achieve this position with a vertical run of double wall pipe if the 6.5" requirement is to the back of the stove (in which case it will actually be a little more than 6.5" but not 6.5"+2" which it is to the back of the heatshield). Worst case scenario I could have the pipe angled up ever so slightly, but I'm sure someone could see 1/2 " out of vertical in 12 ft and I would like to avoid that.

Any inspectors want to chime in on this one ?
 

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begreen

Mooderator
Staff member
Nov 18, 2005
92,798
South Puget Sound, WA
How about rear venting the stove into an elbow (or cleanout tee)? Would that make the close clearances a non-issue?

edit: rereading - is your concern with the 6" clearance for the class A? I thought class A needed 2" clearance? Maybe I am not visualizing the issue correctly yet.
 

KeithO

Minister of Fire
Aug 8, 2007
592
Jackson, MI
Here is a plan view on the stove.

I have a restriction to the rear of 6.5" (question is to which surface). Normally when using metal heat shields to protect combustibles, one does not measure to the heat shield, but rather from the combustibles directly to the radiating surface.

I have a restriction on the front imposed by the clearance required for the class A on the nearest rafter. I meet the rafter clearance when I fit the 12x12 radiation shield flush to the closest rafter. This puts the center line of the class A 6" away from the face of the rafter. This position transfers to the stove connector directly below. If I am required to be 6.5" from the back face of the stove, all is good and well. If I have to be 6.5 " to the back of the heat shield, I have a problem.
 

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begreen

Mooderator
Staff member
Nov 18, 2005
92,798
South Puget Sound, WA
I think it's from the heat shield which is built onto the stove, at least that is the way I measured from my Castine. I'll let the code experts comment here.

What is the distance from the flue collar on the stove to the back wall? It looks like it should be 10". The front beam doesn't appear to be an issue if that is class A pipe adjacent to it. 6" just meets the clearance for double-wall.

If you are that close to the back wall you might want to consider rear exit with a 90 for better peace of mind. That will give you a generous margin of safety. 6.5" is pretty close. Canada requires 9.5"
 

rdrcr56

New Member
Sep 8, 2006
216
When I installed our stove the manufacturer said the measurement was to the back of the stove not the heat shield, why don't you call Morso tech line and ask them, that way you get it straight from the horses mouth.
 

KeithO

Minister of Fire
Aug 8, 2007
592
Jackson, MI
BeGreen: If I went with a rear exit it would push the stove further into the room. In that case my front clearance to the coffee table becomes too close, both in terms or radiant heating and clearance to walk past without getting too close to either the table or the stove.

Its just a small amount that is at stake here. The double wall pipe itself has a clearance to combustibles of 6" and I am way in the clear with that. If I remember correctly, the "general clearance" for unlisted stoves was 18" and this was reduced to only 1/3 (6") if one fitted a steel heat shield to the wall. If this memory is correct, then Morso may be a little conservative with their 6.5".

BeGreen said:
I think it's from the heat shield which is built onto the stove, at least that is the way I measured from my Castine. I'll let the code experts comment here.

What is the distance from the flue collar on the stove to the back wall? It looks like it should be 10". The front beam doesn't appear to be an issue if that is class A pipe adjacent to it. 6" just meets the clearance for double-wall.

If you are that close to the back wall you might want to consider rear exit with a 90 for better peace of mind. That will give you a generous margin of safety. 6.5" is pretty close. Canada requires 9.5"
 

mayhem

Minister of Fire
May 8, 2007
1,937
Peru, MA
My Morso 3610 instalaltion manual illustration shows the rear clearance is to the stove body, not the heat shield. Check their website for the most up to date version of the specific manual for your stove and if you look carefully at teh heads of the arrows they use to indicate the clearances it should answer your question.

If it is in fact clearance to the stove body, make sure you have all your documentation very clear for the inevitable inspector questions.
 

KeithO

Minister of Fire
Aug 8, 2007
592
Jackson, MI
Mayhem: Unfortunately, the diagram in the manual is so non explicit that it leaves a lot open to interpretation. See the diagram below:

Note that they do not have different callouts for single wall and double wall pipe. Both are listed as a rear clearance of 6.5". Obviously, if single wall requires 18" clearance this would not be valid. They show a clearance to connector of 10" which is OK for double wall, but 8" too little for single wall. They show no heat shield whatsoever in the diagrams.
 

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JohnnyBravo

New Member
Oct 15, 2007
169
Calgary AB Can
Just a thought, what does it give for stove dimentions? if it measures to the heat sheild i would assume that mesurements should come from there. if it gives stove body size, one could assume that mesurements are from there.
 

Gooserider

Mod Emeritus
Nov 20, 2006
6,737
Northeastern MA (near Lowell)
I would second the suggestion to double check w/ Morso tech support, but AFAIK, the heatshield doesn't change anything but the clearance distance, the measurement is taken from the same place, namely the stove body.

Gooserider (not an inspector)
 

mayhem

Minister of Fire
May 8, 2007
1,937
Peru, MA
KeithO said:
Mayhem: Unfortunately, the diagram in the manual is so non explicit that it leaves a lot open to interpretation. See the diagram below:

Note that they do not have different callouts for single wall and double wall pipe. Both are listed as a rear clearance of 6.5". Obviously, if single wall requires 18" clearance this would not be valid. They show a clearance to connector of 10" which is OK for double wall, but 8" too little for single wall. They show no heat shield whatsoever in the diagrams.

My 3610 manual has an additional diagram that very clearly shows the specific stove and differentiates between the stove bodya nd the heat shield.

I agree, call Morso.
 

backpack09

Minister of Fire
Sep 10, 2007
554
Rochester, Mass
I interpreted their instructions as being to the back of the stove not the back of the heatshield. If you use the difference in offsets from the stove pipe to the wall vs the stove to the wall, you end up with 3" which puts you at the back of the stove, not the heatshield. If that made any sence. I am off to lunch :)
 

webbie

Seasoned Moderator
Nov 17, 2005
12,178
Western Mass.
KeithO said:
Mayhem: Unfortunately, the diagram in the manual is so non explicit that it leaves a lot open to interpretation. See the diagram below:

Note that they do not have different callouts for single wall and double wall pipe. Both are listed as a rear clearance of 6.5". Obviously, if single wall requires 18" clearance this would not be valid. They show a clearance to connector of 10" which is OK for double wall, but 8" too little for single wall. They show no heat shield whatsoever in the diagrams.

I saw that too......

But remember that the 18" is a generic measurement and does not pertain to listed stoves - listed stoves can be more....and they can be less. In other words, unless the manual says to keep the pipe out 18", and since this is a top vent only stove, that means when the stove is right, the pipe is right!

If that is NOT the case, it is a mistake in the manual and/or label. Let us know what Morso says.

I have seen other clearance charts which clearly say the measurement is to the top plate of the stove - but you should get this confirmed by Morso......
 
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