Why is it so hard to relocate a gas furnace ?
Quite frequently I get asked what is involved with moving a electric or gas furnace to accommodate future development for a basement renovation. There are a few challenges that I will point out here. Some of them can be code issues while others will relate to the expected headroom and clearances with the duct system.
There is almost always a way to improve on an existing floor space by relocating the furnace and possibly the water heater, but the overall costs can “blow the budget” pretty fast!
The biggest but not always the most obvious factor restricting the limits to relocate either water heater or gas furnace is the vent or chimney pipe connection. This would not be an issue if the water heater is an electric model with no venting so conversion from gas to electric can eliminate this problem. If the furnace is already a high efficient it becomes less of a vent problem since the PVC venting can be extended or relocated more readily. Extending the metal venting pipe(s) will have its limitations as to how far away and headroom can become a factor since the further away from the main chimney connection you go, the more slope or grade develops with the horizontal portion of the vent pipe. Pipe sizing will need to be recalculated since vent codes for Natural Gas Venting strictly determine the distance based on size and capacity. An increase in pipe size is not usually possible, and a need for a smaller vent pipe will mean installing a chimney liner. This is no more than a smaller new metal vent pipe run up through the old chimney up to the roof termination. This cost for a chimney liner will run from at least $450.00 to as high as $800.00.
The next most difficult obstacle usually involves the ductwork. With basement stairways entering into the middle of the area from an outside wall towards the center beam, the main trunk can restrict headroom at the base of the stairs. Sometimes this main duct run can be moved so that it runs parallel to the beam on the opposite side. If not a custom made trunk run can be made to reduce the depth and increase the headroom. Without reducing airflow the width will of course end up proportionately wider. Eg: 8”x12” = (96sq in) = 6”x 16” = 4”x24”.
Most often if the furnace is located at one end of the basement, the floor area opens up substantially since the main duct runs can follow along the center beam. The main trunk ducts must be large enough to carry the required airflow and get reduced in size as the branch runs use up air. When sized properly the reduction allows for back pressure within the duct and is the determining factor for achieving balanced airflow in all spaces.
Return air ductwork is almost never sized adequately particularly on second floor spaces and in basement rec rooms. A rule of thumb is that the return air duct should be able to remove an equal amount of air from all spaces and deliver it to the furnace keeping a low static pressure (something like your blood pressure) and allow for less air noise and lower operating temperatures in the furnace. This will translate into better more efficient heat transfer in heating and cooling modes and you can expect much longer equipment life from your furnace and Central air Conditioner. Basement return air ducting is not that hard to incorporate especially when the space is just being developed.
Gas lines and electrical feeding the furnace and/or water heater may need to be extended or re-routed. Access to the front of the furnace and water heater must be maintained for servicing. 24” is standard for front access but the installation manuals will have the correct clearances listed. Clearances to vent pipes and furnace plenums are also important. If the chosen location for the furnace is directly under a bedroom, special care should be given to the return air in particular to reduce noise transfer to above.
- Relocating a mid-efficient furnace is probably not a good idea since eventually the replacement for it when it finally becomes obsolete will be a high efficient gas or electric furnace.
- Residential mid efficient furnaces are no longer available in Canada and cannot be installed. The new PVC vent pipes will still need to terminate away from building openings and other vents.
- Conversion to an electric water heater can offer much more flexibility since there is no vent pipe.
- Professional consultation is always recommended.
Tradesman Heating and Cooling can provide you with a complimentary consultation and options for your renovation project in Winnipeg.