Gas and Oil Home Heating Furnaces - Combo Venting 2 Appliances

I am going to be installing a new gas furnace and water heater in the near future. The furance will be high efficiency and will be vented out the side of my house instead of through the chimney. The water heater will be of the powervent variety so it can also be vented out the side of the house (due to a remodeling project I no longer want these two items venting through the chimney). Both the furnace and water heater require 3" pvc venting. Are there any codes or restrictions that prevent venting both the furnace and water heater out the same pipe? I would equate this to the current set-up in which there is a "Y" connecting both units to the same exhuast vent pipe. Thanks!!

Since you are doing the installation, Read the installation manuel. It will give you all the venting info you'll need. Although I do believe they can not be vented together.

Hello Cander. Welcome to the Heating and Cooling forum and the Do-It-Yourself Web Site.

Generically speaking, if the OEM appliance manufacturer does not reccomend combinding vents [combo venting} it should not be installed in this manner.

If the OEM manufacturer makes no reference to combo venting, I suggest you still avoid it, especially with power vented appliances.

Another possible reason to avoid installing two appliance in the combo venting manner is local codes. Another factor could be voiding the warranty and or power venting some of the fumes back into the room or enclosure the appliances are installed in.

Worse yet, forcing air backwards thru the vent of one burning appliances flames will distort the flames causing severe levels of carbon monoxides to be created.

These fumes will be forced out of the flue and or out of the appliances firebox. This is a highly likely and probable possibility, if two vents are installed in combo and installed incorrectly. It's a deadly and disastrous condition in the making.

I highly suggest you seek professional advice before starting this project. Also have the entire system inspected several times during the installation, upon completion and initial firing up of the appliances. It's that critical.

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Thanks for your advice! I'll just vent separtely and avoid any potential problems.