Thread: high efficiency furnace venting thru chimney

I recently purchased a house with a Carrier WeatherMaker 9200 Ultra Efficient furnace. Both the exhaust and air intake pvc pipes run together up the same chimney flue. I have multiple questions about this arrangement and changes I'd like to make.

-I've been told that my wood burning fireplace, using the same chimney but different flue, is not to be used because of the furnace venting (assuming that comment refers to the possiblity of the intake sucking in smoke/etc from the burning fireplace?)

-With that in mind, I'd like to remove the air intake pvc pipe and simply allow the furnace to draw it's air intake from the basement. The furnace shares an approximately 12x15 room with an older water heater that vents with galvanized pipe thru a third flue in the chimney. The only other itmes in the room are the gas meter and the water meter. This room also has a louvered door leading to the rest of the basement. Would this be an acceptable solution?

-Is it safe/correct to have just the exhaust left in the chimeny and use my wood burning fireplace?

Also, is it possible to download from somewhere the installation instructions for my Carrier furnace? So far, all I've found is owner's manuals.

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Hi Michael. If I am understanding this correctly, somebody installed a high effiency furnace but ran the PVC intake and exhaust pipes up the old flue the previous furnace used? If that is the case, it does not sound like a good idea to use the wood burning fireplace with the current configuration to have now. One, the heat buildup in the fireplace flue could possibly have an impact on the PVC pipes for the furnace in the adjacent flue (two flues in one chimmney structure, correct?). Two, depending upon where the inlet for furnace combustion air intake pipe is located in relation to the fireplace chimney, it could pull fireplace combustion gases and smoke into the furnace.

You may want to look into simply having the PVC intake and exhaust pipes for the furnace rerouted to go through a sidewall in your basement to the exterior. I've never seen a high efficiency furnace have it's intake and exhaust installed in the manner you described. And you're better off pulling the combustion intake air for the furnace from the exterior of the house as opposed to the from the basement.

Any pics you can post up to help illustrate the installation of the furnace PVC pipes?

I've attached a picture of the top of my chimney. House was built in 1957. Current Carrier WeatherMaker furnace model 58MXA060-12 and A/C model 38TXA030300 was installed in 2000.

There are four clay flues in one chimney. From left to right they are...non-HF water heater/unused/fireplace/furnace intake and exhaust.

I'm not going to use the fireplace until I make changes, so I'm trying to decide what changes to make.

In the photo of the bottom of my chimney you'll see a square vent in the wall. This is a fresh air intake that runs thru duct pipe straight into the plenum above the furnace. It is currently closed via a damper. That is my driveway that runs along the house.

The chimney is on the end of the house. The third picture shows the area just round the corner to the back of the house where the A/C unit is. The last photo shows the setup in the furnace room.

Ideally, I'd like to leave the exhaust in the chimney flue (where it currently is, maybe shortening the pipe). And ideally I'd like to have the fresh air intake not run to the outside.

I've read enough to know what the 'perfect' answer is (run both pipes to the back of the house near the A/C unit), but what other options are also safe/good considering my circumstances?

Look up a "Carrier" authorized dealer for your location. Request installation instructions, ask questions, etc. They are your best resource and should have Carrier trained technicians to give you options, and/or correct your particular situation.
Any records available who installed/serviced the system? Don't call them . . .

Jess,

You said not to call the people who installed the system....what was done incorrectly? I'm very curious to learn.

I have different preferred company that I've dealt with before. They do excellent work.

I am not a qualified HVAC contractor or a "Carrier" authorized technician nor can I tell you specifically what is incorrect without further research, such as reading installation instructions, physically inspecting, etc, etc. . . . I do know a gas furnace exhaust contains alot of moisture. Cold weather can freeze/restrict the exhaust pipe opening, especially with a long vent pipe exposed to cold outside temperatures. It is difficult to see from your pictures, but it looks like one of the PVC pipes has a 45 or 90 degree elbow? . . . Again, it is best to have a qualified HVAC technician assess the situaition and correct as needed. I think it is best to get a different assessment other than the original installing company. Just my opinion.

How on earth is anybody supposed to be able to service that furnace? It appears the unit is installed with the access panels facing that rear wall and corner.

Possible problem with current installation - The furnace exhaust pipe above the chimney will put out condensate vapor that will condense further and drip onto the masonry chimney structure in the winter. You live in Ohio where you will get below freezing temps in the winter. As that moisture from the exhaust pipe drips onto the chimney, the water will freeze and expand and depending upon where it drips, it will deteriorate the top of the masonry chimney.

Nick you are correct, it was installed 'backwards'. There is about a 2 foot gap between the furnace and the back wall. Genius isn't it? It's just exactly enough room to pull out the filter to change it. Previous owner didn't seem to mind it. If it had been my money, I wouldn't have allowed that. It's workable though.

I'm willing to run the intake to the outside if that's what I need to do. I was just hoping that wouldn't be necessary, but it looks like it is.

I'd like to attach pvc to the back of that metal louver to the right of the chimney for the intake. Do you guys see any problem with that?

Without the installation instructions, I'm not certain what the distances should be between the intake/exhaust and the exhaust to doors/windows. Also, how far off the ground/driveway should they both be?

I've done this type of work before when I installed a high efficiency water heater in my last house, so I'm not concerned about being able to do the work. I'm always trying to be very aware of doing things correctly though.

Thanks in advance for your help.

What is that metal louver vent currently being used for? It appears it may be a combustion air intake vent for the fireplace.

The A/C condenser unit is installed directly in front of the electric meter without proper clearances.

The metal louver has a round duct pipe attached to the inside of it and, if the damper is open, allows outside air into the furnace plenum. I've kept the damper closed.

Originally Posted by Michael Braun

The metal louver has a round duct pipe attached to the inside of it and, if the damper is open, allows outside air into the furnace plenum. I've kept the damper closed.

The supply plenum? If that's the case, even if you keep that damper closed, you'll still lose treated air (heat and AC) to the exterior.

I think you need a good HVAC pro to come in and get everything squared away. There's too much wrong with the entire setup.

Did you have a home inspection done before you bought the property Michael? Assuming you did, what did your HI say about this setup?

This install has many issues that are code related. I would first have the local code enforcement officer show me the signed off paperwork for this install. Second, assuming there are no such documents, I would contact a knowledgeable real estate attorney and go after the installing offender. I find it very hard to believe that the chimney was the best chase for the direct vent pipes, when 12" above ground on most sidewall install will do. I haven't even touched on the condensate issues,,

I was all along planning to loose the outside vent to the plenum. Is the termination to that existing louver grill and acceptable exterior termination for the intake re-route?

Is the exhaust for the furnace acceptable running up thru the chimney (after the intake is re-routed) or should it definitely be changed to side wall?

I know these issues are incorrect, but they're relatively simple fixes to remedy. I just want to make sure I don't overlook details.

The furnace install is a clearance issue being too close to that wall and that's no simple detail to correct. You really need a good HVAC pro at this point Michael. Whoever did this install has no business doing this type of work. Like David said, there appear to be issues with the condensate drain lines that haven't even been discussed yet. And this is just what we've been able to pick up based on four pics and what you've described. Who know what else is wrong that can't be seen. You really need a good HVAC pro to sort all this out (this is what I would say to a client if I inspected this set-up).

I'm guessing you did not have a home inspection.

What about the condensate drain line?

Michael, your first two photos reveal the real problem. Your house is upside down!

Originally Posted by Nick Ostrowski

I'm guessing you did not have a home inspection.

This is obvious.

NO you canNOT have PVC Cat III or IV venting in a masonry chase of a common masonry chimney with a solid fuel fireplace and a Cat I water heater vent.

You have described a DANGEROUS condition. Dangerous to life and property.

Get a F.I.R.E. or CSIA certified individual in PRONTO for a minimum Level 2 inspection. They can advise you of your best direction regarding remediation to a SAFE conditon, PRONTO regards your DANGEROUS CHIMNEY situation.

Everything else you have shown and described is further evidence of unsafe and (obviously unpermitted and uninspected) unqualified work.

This is not a DIY site.

Had you had a qualified paid home inspection done all of your issues/questions raised so far would have been covered in your inspection report.

Originally Posted by H.G. Watson, Sr.

This is obvious.

NO you canNOT have PVC Cat III or IV venting in a masonry chase of a common masonry chimney with a solid fuel fireplace and a Cat I water heater vent.

You have described a DANGEROUS condition. Dangerous to life and property.

Get a F.I.R.E. or CSIA certified individual in PRONTO for a minimum Level 2 inspection. They can advise you of your best direction regarding remediation to a SAFE conditon, PRONTO regards your DANGEROUS CHIMNEY situation.

Everything else you have shown and described is further evidence of unsafe and (obviously unpermitted and uninspected) unqualified work.

This is not a DIY site.

Had you had a qualified paid home inspection done all of your issues/questions raised so far would have been covered in your inspection report.

I have a high efficiency furnace and tankless water heater being installed. The installer has combustion air PVC and exhaust PVC pipes (4 pipes total) running up a chimney flue which is a separate flue next to two wood burning fireplace flues. Is this an acceptable installation? If not, what code should I reference?

PVC Sch. 40 pipe is not approved as a venting material for CAT III or IV by the pipe mfrs. nor as a chimney liner. In fact, most mfrs. state NOT to use their pipe for combustion venting. It is considered combustible. Therefore, if you install it into one flue where an adjacent flue is being used for a heating appliance, it technically violates the clearance requirement. Being captured in the flue, it may experience sufficient heat for the PVC to fail. There is no recognized way to support this pipe vertically inside a flue.

You can use polypropylene listed venting IF the other flue is not used.
HTH

Thanks Kevin and Bob. We're coring the basement wall today (above grade) and running everything directly out.

You'll need to have protective sleeves between the bored foundation wall/exterior wall and the plastic special gas vent pipe to allow for contraction/expansion, and to properly weatherstrip/seal/fire block, rodent/pest-proof, properly support, protect from damage, etc.A number of mfg's systems provide concentric systems (then you'd only require one wall opening per appliance). Be aware of clearances between the intake/terminations for each appliance and other intakes, walkways, property, and other equipment, etc. adequate air, avoidance of direct prevailing winds, and protection from corrosive condensate.This type work requires a permit, and a qualified professional (who would already be aware of the myriad code references and mfg listed instructions for the equipment and special gas venting system(s).