Furnace/Hot water heater chimney vent question

[Lisa Gardner]

We want to remodel our kitchen, but a large 9" round chimney vent to our roof connected to our furnace and hot water heater runs through one of our cabinets, taking up a fair amount of space. In the remodel, we are putting in a new wall to separate the kitchen area from the dining area that is next to the existing chimney.

A handy friend of mine said that I could convert the round pipe to a rectangle (3 x 10) that could run through the drywall. However, the heating contractors I've spoken with on the phone are saying I can't do this and I need a new furnace and hot water heater to direct-vent the air out.

My concern is that these heating contractors are mostly trying to sell a product rather than really telling me what I could do more economically. I'm also concerned that if I follow my friend's advice, I might not be up to code (and could potentially endanger my family...).

I'm not very handy and would appreciate any advice.

[American Mechanical]

They are correct. I don't believe this would be a safe venture.

Flue venting is very important to your family's safety. Depending on the age of the equipment you're talking about it might be in your best interest to replace the equipment with high efficiency units that use PVC pipe as venting. If not, there may be other venting options such as a power sidewall vent. Check with other contractors and remember that it's not always about selling new equipment, sometimes the recommendation is in your best interest.

- Robert

[Greg O]

I am in the heating and AC bussiness and I belive you "handy friend" is wrong. Sounds like the heating contractors are steering you right. The simplest solution to me would be perhaps two vents instead on one. The diameters could possily be smaller and more readily hidden in a wall. 4" "B" vent would still need a total of about 8" thick wall to conceal it. The water heater would need less yet. Without knowing the specifics of you furnace and water heater I am guessing though. The best bet would be to hire a licenced contractor to deal with this for you. This is not something you want to screw up. If you mess this this up it may cost you your life and/or your home. Greg

[~KJPRO~]

Your friend may indeed be handy, but his level of expertise stopped when he advised you to convert it to 3x10! (just for figures 9" @ .1 wc = 310 cfm, 3x10 @ .1 wc = 95 cfm, no where's close to being the same!)

You need to find a competent contractor that you trust to not only make sure it's up to code, but to insure your safety.

~kjpro~ HVAC owner/tech

[Dr. Hardcrab]

"Lisa Gardner" wrote

Just make sure you have plenty of insurance on the house......

[DT]

Your 'handy' friend is completely, and dangerously, wrong. But no one is explaining to you what he had in mind.

IF, and I mean IF, this was a hot air duct, the ones that distribute the furnace's warm air to the registers in the rooms, you could indeed convert a round duct into a rectangular wall stack (but not a small 3 x 10). But that is NOT what you are dealing with.

You are proposing to move the main vent of the chimney and the hot water heater. This contains very hot combustion products loaded with carbon monoxide. This MUST be ducted through a special, double walled vent pipe called a "B" vent. That is what the pipe in question is.

B vents have many requirements and restrictions to insure a safe installation. A heating contractor is needed for this job, and it may prove very difficult to relocate. You will more than likely NOT be able to reduce the size of the vent, so the alternatives are to relocate it, build around it again, or get a new furnace and water heater with direct, sidewall venting.

Dennis

[Greg O]

Insurance won't do any good when they find out the home owner installed venting for their furnace that is not approved! I can see it now, the insurance company: "Gee, your house burned down because the furnace vent you just installed was not approved? Now you want us to pay to build a new house? LOL!!" Greg