Thread: Who needs combustion air?

As I keep telling clients, I see something new at every inspection.

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• Combustion Air in Crawl Space
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That's a great filter did you tell them to change it often. It's funny when installing these systems they can get away with such issues. Look at this furnace I just saw.

Originally Posted by Paul Sew

That's a great filter did you tell them to change it often. It's funny when installing these systems they can get away with such issues. Look at this furnace I just saw.

At least they used the metal dryer vent rather than the vinyl type. Also changing the filter will be easy.

Also, is it ok the vent to masonry chimney? A wood burning or gas burning fireplace?

Originally Posted by Peter Louis

Also, is it ok the vent to masonry chimney? A wood burning or gas burning fireplace?

Fine to vent through the chimney, but the issue is improper material used to vent from the furnace. It was a very shady job on the furnace with the supply plenum cut off and funky vents all over the basement for heat. The chimney was also a good clue for an oil tank.

Originally Posted by Paul Sew

Fine to vent through the chimney, but the issue is improper material used to vent from the furnace. It was a very shady job on the furnace with the supply plenum cut off and funky vents all over the basement for heat. The chimney was also a good clue for an oil tank.

Was the vent just some Class 0 flexible duct or was it a Metal-Fab B-vent?
http://www.mtlfab.com/media/L1940.pdf

Corey

Originally Posted by Corey Friedman

Was the vent just some Class 0 flexible duct or was it a Metal-Fab B-vent?
http://www.mtlfab.com/media/L1940.pdf

Corey

Corey, thanks for the insight of that bvent material, I'll have to go back and have a closer look. It does look like that flex b-vent.

It is not okay to vent an 80% furnace to a masonry chimney unless it has a metal liner according to most manufacturers because of the cooling and condensation issues

Originally Posted by Steve Duchene

It is not okay to vent an 80% furnace to a masonry chimney unless it has a metal liner according to most manufacturers because of the cooling and condensation issues

The primary reason for this is that when the chimneys were designed, the gas appliances connected had standing pilots which constantly provided minimal heat source to the chimney keeping it warm allowing good draft. When you remove a standing pilot device and install an intermittent pilot device, the chimney cools during the off cycle. When the device then starts its cycle, the combustion gasses cool in the chimney preventing proper draft.

Originally Posted by John Arnold

As I keep telling clients, I see something new at every inspection.

Dang that's down right scary. Not enough air would mean incomplete burn which could crate very high CO.

Here they require a 90 ell on the intake to prevent something from accidentally falling and restricting the intake. But in this case the HO might have still stuff a rag in it

Originally Posted by John Arnold

As I keep telling clients, I see something new at every inspection.

Are you sure that's a rag? It looks like religious head gear to me.