Special Plumbing Requirements for a High-efficiency Furnace

Codes and Licenses

• Gas plumbing for any furnace must be done in accordance with the local building code, and by a licensed plumber. The finished product is subject to inspection and if it is not done correctly, the project will not gain a final sign-off to allow it to operate until the problems are corrected. New home installation is a little easier than retrofitting a high-efficiency furnace into a older home because different venting is needed.

More Oxygen

• Low-efficient furnaces draw their oxygen to operate from the surrounding air. Some newer 80 percent and all high-efficient furnaces require more oxygen to operate than is safe if they draw only from the existing air in the home. They could rapidly take too much air, creating an unhealthful and unsafe air pressure imbalance. These furnaces need an air intake vent added that older furnaces do not require.

Intake Vent

• The special intake vent goes from the furnace to the roof, and allows fresh air to flow to the furnace without disturbing the oxygen in the home. Because no inside air is consumed, it is less likely that colder, outside air will come in through leaks around doors and windows to replace the missing air. Less-efficient furnaces send a substantial amount of heat up the vent, which requires a galvanized steel metal vent to handle. With high-efficiency furnaces, the heat is moderate enough to be vented through PVC pipe.

Gas Distribution

• The basic gas distribution system remains the same for a high-efficiency furnace. The overall BTUs of all the household gas appliances help to determine the size of iron pipe that feeds the furnace. From the outside meter to the appliance the installation is the same. Because high-efficiency furnaces use different types of built-in gas modulating valves to monitor the flow of gas, the technician has to be trained and certified on that particular appliance to be able to hook the gas to it.