furnace venting

eric_48

I have an 80% furnace and i want to vent it out the side of my house with pvc. Is there somthing i can add to the furnace for this application?

Al Letellier_21

PVC venting

I do not believe you can do that with a 80% furnace. Check the manufacturer's installation instructions. Unless it is approved by the manuf. you are not allowed to do so and can create a serious health and safety issue.

scrook_3

Think...

you'll find an 80% furnace's exhaust is far too hot for PVC.

Bob Bona_4

nope.

If it's an 80%er, it needs sealed metal pipe aka B vent-the draft inducer in the furnace produces positive pressure in the vent system-ok for chimneys.

If you are doing side wall venting it must have a power venter to get the exhaust out-the draft inducer in the furnace does not take the place of this.

PVC will NOT work in this application.

Shark

venting ..

PVC is not allowed but using metal vent pipe with a fan inline to assist with getting the flue gasses is okay. The fan is also wired in series to come on when there is a call for heat. The fan has to be running in order for the furnace to fire. Hope this helps.

Unknown

Eric, look at the rating

plate on the furnace and see what venting category it is. The category's are I, II, III or IV. That will determine how it can be vented. Many 80% furnaces are Category I , some are fan assisted. Does yours have a combustion air blower on it? That is a fan that comes on before the system fan comes on.

By the way B Vent is not sealed and can't be used on positive pressure vents, AL294C is a stainless steel vent that can be used on some side wall applications due to the fact that those vents may condense. All 80% furnaces have to be vented into at the least a lined chimney with clay tile liner or liner which was installed as a retrofit to bring the chimney up to code.

PVC can only with stand temperatures up to 140°(F).
CPVC up to 200° (F).

Bob Harper

positive vent pressure

Actually, masonry chimneys are NOT approved for positive vent pressure regardless of fuel. Neither is B-vent or single walled connector as Timmie stated. Cat. I is a negative vent pressure appliance, even with an inducer fan. Those inline blowers are not legal with Cat.I or oil. You can put an exhaust termination on a sidewall vent that puts the entire vent under negative pressure if the appliance is approved for such venting.

Mitch_4

you will

need to add a high (90%+) efficiency furnace to the PVC and all will be well...

Bob Bona_4

Right, Bob (and Timmie).

I didn't clarify my statement. When I said postive pressure, I was speaking in terms of the draft inducer assisting, well, draft, not in the DV sense.. And my error was the term "B vent". I flamed out and couldn't find the term for double wall locking vent pipe most mfrs. say to use on new 80+ers to connect to chimneys.

Do I have it right now?

Unknown

Vents - Bob Bona

The 80% equipment (Category III) which may have a possibility of condensing in the flue will use stainless steel flue such as AL294C, companies such a Fas-N-Seal, Z vent and others make this venting pipe. This equipment can't condense in the equipment.

"B" Vent is for Category I venting only and is your standard double wall gas vent. Negative pressure in the vent, flue gas temp above 275°(F). Single wall pipe in my estimation should be done away with as it can't compare with "B" Vent for drafting and heat loss. Some Category I equipment is fan assisted (negative pressure in the vent) which means its only purpose the (combustion air blower) is to overcome heat exchanger resistance so normal venting can occur. This equipment typically gets its air for combustion from within the room it occupys. Keeping in mind draft is created by temperature difference in the flue and the height of the flue.

Some equipment has a power venter which has as its purpose to create a positive pressure in the vent in order to remove flue gases. Typically Category IV (vent temp below 275°(F)and positive pressure in the vent) condensing equipment.

There is also vent assisting equipment usually retrofitted (Field, Tjernlund) which is installed at the end of the vent on the outside or outside wall which has negative pressure up to the venter therefore can be single wall or "B" Vent.

We also have concentric venting which allows for the hot flue gases to vent through the center pipe and air for combustion is brought in through the outer pipe. This allows for a little heating of the air for combustion by the way.

Hope that helps clear some of the confusion. Venting today is a study within itself. I have a full day course just on venting.

joel_19

80%

If it's an 80% just throw it away and get a variable speed 90% You'll get big utility rebates in most places plus a tax credit of up to 1,500$ it's a no brainer.

joel_19

80%

If it's an 80% just throw it away and get a variable speed 90% You'll get big utility rebates in most places plus a tax credit of up to 1,500$ it's a no brainer.