Thread: Screen needed

This is the exhaust for a high efficiency furnace. It is located on the roof. Does it need a screen?

Thanks,

Ryan

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Any info. on needing a cover for this?

You would have to consult the manufacturer, but my first thought is no screen. If it needed a screen, the manufacturer would have provided one. I would guess that any modification to the vent would be prohibited.

I thought the same thing but I wanted to make certain. Thanks

Originally Posted by Ryan Stouffer

This is the exhaust for a high efficiency furnace. It is located on the roof. Does it need a screen?

Thanks,

Ryan

You can check the manufacturers web site.

The PVC should be painted to protect it from UV light

Chuck

Whenever I run into stuff like this I grab the manual (if available) or run the model number through Google and you will usually get right to the manual.

These hi-efficiency furance vents do a vary a lot - Some with openings facing up, some down, some sideways, screened, not screened, etc.

One thing for sure is you can't paint them all with a broad brush. Get the model # and check out the manufacturer's specs. I can't say I do it on everyone. Usually, just if something else with the install or the house makes me suspicious.

I never saw one wearing a hat before.
Just curious where they placed the air intake as you do not have the same concern for it and best practice would be to have it in the same area.

(Hoping it is not in some small utility closet with the water heater.)

Originally Posted by Bob Elliott

I never saw one wearing a hat before.
Just curious where they placed the air intake as you do not have the same concern for it and best practice would be to have it in the same area.

Bob,

I suspect the air intake is taken in under the "hat" and into a concentric space between the inner pipe and an outer pipe.

Originally Posted by Jerry Peck

Bob,

I suspect the air intake is taken in under the "hat" and into a concentric space between the inner pipe and an outer pipe.

Hmmm
Would that not violate a minimum distance between the two.

Originally Posted by Bob Elliott

Hmmm
Would that not violate a minimum distance between the two.

Not if it is listed that way.

Originally Posted by Jerry Peck

Not if it is listed that way.

Jerry every high eff PDF install Manuel I have seen states 18" min space between air intake and exhaust on sch 40.

Haven't seen an HVAC equipment manufacturer yet that doesn't approve that type of concentric vent termination.

Originally Posted by DavidR

Haven't seen an HVAC equipment manufacturer yet that doesn't approve that type of concentric vent termination.

David you may be right as here is an excerpt from a vent install PDF for a high efficiency furnace.
Concentric Vent Termination
Concentric vent termination kits are approved for
use with these furnaces. The kit part numbers
are 904176 (3 inch) and 904177 (2 inch). For
proper installation of the concentric vent termination,
follow the installation instructions provided
with that kit

Guess I never understood how they work in order to not cause pressure imbalance or get around the 18 inch rule.

schedule 40 vent termination.gif

Can someone explain this for a primitive caveman?

Originally Posted by Bob Elliott

get around the 18 inch rule.

Because they have been tested, listed, and labeled for that use.

The testing shows they function in the manner in which they were designed. Which is what the 18" is trying to accomplish for unlisted other installations.

Originally Posted by Bob Elliott

David you may be right as here is an excerpt from a vent install PDF for a high efficiency furnace.
Concentric Vent Termination
Concentric vent termination kits are approved for
use with these furnaces. The kit part numbers
are 904176 (3 inch) and 904177 (2 inch). For
proper installation of the concentric vent termination,
follow the installation instructions provided
with that kit

Guess I never understood how they work in order to not cause pressure imbalance or get around the 18 inch rule.

schedule 40 vent termination.gif

Can someone explain this for a primitive caveman?

I can explain how they are "supposed" to work Bob.
Doesn't mean it will always do what it's supposed to.

The opening is the discharge of the flue gas from the furnace, it is supposed to be exhausted far enough away from the intake air (underneath) that it will have no ill effects on the combustion process.

The standard termination only discharges flue gas down or up and down depending on manufacturers instructions and could short circuit if not for this distance in between.

Wind can also make these termination due some nutty stuff especially if they are near an inside corner of the building.

Originally Posted by DavidR

I can explain how they are "supposed" to work Bob.
Doesn't mean it will always do what it's supposed to.

The opening is the discharge of the flue gas from the furnace, it is supposed to be exhausted far enough away from the intake air (underneath) that it will have no ill effects on the combustion process.

The standard termination only discharges flue gas down or up and down depending on manufacturers instructions and could short circuit if not for this distance in between.

Wind can also make these termination due some nutty stuff especially if they are near an inside corner of the building.

I suppose if ok with manufacturer I can"t put up a stink , but sure will be looking for a good excuse to write them up if if I find one.

what about that exhaust within ten feet of the attic vent

Maybe it's functioning as a storm collar ?

err what I meant was collar is to prevent water from entering outer pipe, no screen if not supplied from the manufacture, overtime the screen can reduce flow b/c of dirt etc. accumulating.

Originally Posted by Richard Pultar

what about that exhaust within ten feet of the attic vent

Richard,

I believe you are thinking of plumbing vent terminals.

Richard makes a good point. If there is a concern about waste gases entering through an attic vent, what about byproducts of combustion from a burner ?

- G2427.8 (503.8) Venting system termination location.

The location of venting system terminations shall comply with the following (see Appendix C):
- - 1. A mechanical draft venting system shall terminate at least 3 feet (914 mm) above any forced-air inlet located within 10 feet (3048 mm).
- - - Exceptions:

- - - - 1. This provision shall not apply to the combustion air intake of a direct-vent appliance.
- - - - 2. This provision shall not apply to the separation of the integral outdoor air inlet and flue gas discharge of listed outdoor appliances.
- - - - - 2. A mechanical draft venting system, excluding direct-vent appliances, shall terminate at least 4 feet (1219 mm) below, 4 feet (1219 mm) horizontally from, or 1 foot (305 mm) above any door, operable window, or gravity air inlet into any building. The bottom of the vent terminal shall be located at least 12 inches (305 mm) above grade.
- - - - 3. The vent terminal of a direct-vent appliance with an input of 10,000 Btu per hour (3 kW) or less shall be located at least 6 inches (152 mm) from any air opening into a building, and such an appliance with an input over 10,000 Btu per hour (3 kW) but not over 50,000 Btu per hour (14.7 kW) shall be installed with a 9-inch (230 mm) vent termination clearance, and an appliance with an input over 50,000 Btu/h (14.7 kW) shall have at least a 12-inch (305 mm) vent termination clearance. The bottom of the vent terminal and the air intake shall be located at least 12 inches (305 mm) above grade.
- - - - 4. Through-the-wall vents for Category II and IV appliances and noncategorized condensing appliances shall not terminate over public walkways or over an area where condensate or vapor could create a nuisance or hazard or could be detrimental to the operation of regulators, relief valves, or other equipment. Where local experience indicates that condensate is a problem with Category I and III appliances, this provision shall also apply.