Thread: Single or double wall flue pipe?

I am having one of those days! I am reviewing pictures from an inspection I performed yesterday.
I am looking at this one and wondering why I took it.
It looks like it is single wall pipe coming off the furnace, but I am not sure. Can anyone tell by looking at the picture. Does type b flue always have the thick seam at the ends?
Also, is the 180 bend permitted. On down the line, the pipe turns 90 degrees up and through the roof.
This is a newer gas rheem furnace located in an attic.

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Looks like single wall to me. That insulated refrigerant line looks too close to the vent.
And I'd also be leery of the 180 bend. I've never seen that done.

You are in WV where the Winter Design Temperature is below 32 degrees F, thus, single wall vents are not allowed outdoors (outside the thermal envelope).

Additionally, single wall metal pipe vent is not allowed in the attic.

To my knowledge, that elbow would be permitted in the correct installation, but this is not a correct installation (first and foremost because it is single wall vent and is in the attic and outside the thermal envelope.

From the 2006 IRC. (underlining is mine)

- G2427.7.2 (503.7.2) Cold climate. Uninsulated single-wall metal pipe shall not be used outdoors for venting appliances in regions where the 99-percent winter design temperature is below 32ºF (0ºC).

- G2427.7.6 (503.7.6) Installation.Single-wall metal pipe shall not originate in any unoccupied attic or concealed space and shall not pass through any attic, inside wall, concealed space, or floor. The installation of a single-wall metal pipe through an exterior combustible wall shall comply with Section G2427.10.15. Single-wall metal pipe used for venting an incinerator shall be exposed and readily examinable for its full length and shall have suitable clearances maintained.

Plus, as John said, that insulation is too close too the vent - single wall vent requires 6" clearance to combustible material.

Thanks for your input. I am aware of the requirements and limitations of using single wall pipe. My question was really concerning the indentification of single wall pipe. (by looking at the picture only). This was a very large house (8,000 sq ft) and I had taken lots of pictures and notes and when I was reviewing this particular picture I was trying to remember why I took it. I then questioned whether or not the pipe was single or double wall and was asking if you can always identify double wall pipe by the ends of the pipe.
Greg

Yes you can. The dbl wall pipe has an indention that looks like a depressed ring around it! That is where they twist and lock together.

if that is the flue, no way is that right.'
aj

Isn't a 180 bend just a straight pipe or is the new math enforced in 2009 along with the metric system?

Originally Posted by RANDY NICHOLAS

Isn't a 180 bend just a straight pipe or is the new math ...

.

That "new math".

You know that "new math" stuff where you are going in one direction and make a 'U' turn and go in the other direction?

Yep, 180 degree turn.

(I think you are thinking of a 360 degree bend. However, a 360 degree bend is still not a "straight pipe", it just has a loop in it. )

What is the orange cord at the top of the picture?

Greg,
Is it possible that 180 bend is for combustion intake air?

Jim Weyenberg
HouseMaster Inc.
WI.

Originally Posted by Jim Weyenberg

Greg,
Is it possible that 180 bend is for combustion intake air?

Jim Weyenberg
HouseMaster Inc.
WI.

I second Jim's motion...
aj

Originally Posted by adkjac

I second Jim's motion...
aj

That looks like a standard Cat 1 appliance. I doubt there's a dedicated combustion air intake for that furnace.

Originally Posted by neal lewis

That looks like a standard Cat 1 appliance. I doubt there's a dedicated combustion air intake for that furnace.

Not being a gas furnace guy (I did not see many gas furnaces in South Florida), is a dedicated combustion air intake required for a Cat 1 furnace installed in an attic, which is already considered 'outside the thermal envelope' and which is considered to contain 'outdoor air' because of its ventilation to the outdoors?

The elbow I see is a 90 Degree In my area a single wall flue is allowed as long as there is 6" from a combustionable material. Insualtion on the sunction line for the condenser may qualify as combustionable material

Originally Posted by Chuck Melocco

In my area a single wall flue is allowed as long as there is 6" from a combustionable material.

Even in an attic?

Ran across this elsewhere (not an HI board), but felt it was a true classic:

The furnace is an induced draft 80% efficient unit. The pipe is question is the flue pipe. Combustion air would be brought in via vents in the roof or a gable wall. The picture indicates a single wall pipe as there are no twist lock rings.

(c) Chuck Jones Enterprises

Meanwhile, I got curious about if/how you patch that properly, and Simpson DuraVent sent me this:

Well.... I followed up further with Simpson DuraVent, and was told:

"If the hole is for any other purpose or size than to test the draft with a probe then the hole is not allowed."

Likely, every B-Vent manufacturer is going to say something similar, so there is a good chance that if you want to be in compliance with the manufacture's requirements (and thus with code, which incorporated these) that section of B-Vent would have to be replaced.

Originally Posted by Greg Jenkins

Does type b flue always have the thick seam at the ends?

No. I have some pics from today's inspection. It is a B-vent, but the big seam is not present. This is from the early '70s.

Originally Posted by Inspector 3500

What is the orange cord at the top of the picture?

Looks to be t-stat wire. I also noticed the secondary A-coil drain is pluged.

To me it looks like the A/C line was run and later they did the furnace vent so that force them to mount like so. The vent should have 90 up and then less then 90 to go back over the furnace and not in front of the access panel