When the intake and exhaust lines run to the exterior for a high efficiency furnace are there regulations as to distance apart or configuration.
Yes, check the make and model installation instructions and here is one picture, that I found, that may help:
There are a few codes to regulate this.
But there is a good article here from BC that helps (they have same code) summarizes well and adds some additional info.
CSA B149.1 Article 8.14.8 states that a vent shall not terminate:
• Where it may cause hazardous frost or ice accumulations on
adjacent property surfaces.
• Less than 7 feet (2.1 m) above a paved sidewalk or a paved
driveway that is located on public property.
• Within 6 feet (1.8 m) of a mechanical air-supply inlet to any building.
• Within 3 feet (900 mm) horizontally of the vertical centerline above
the gas service regulator vent outlet to a maximum vertical distance
of 15 feet (4.5 m).
• Less than 1 foot (300 mm) above grade level.
• Within 12 inches (300 mm) of a window or door that can be opened
in any building, of any non-mechanical air-supply inlet to any
building, or of the combustion air inlet of any other appliance for
gas units up to and including 100,000 BTU/hr (30 kW).
• Within 3 feet (900 mm) of a window or door that can be
opened in any building, of any non-mechanical air-supply inlet to
any building, or of the combustion air inlet of any other appliance
for gas units exceeding 100,000 BTU/hr (30 kW).
Manufacturers will specify distance apart where they terminate outside, usually a foot between intake and the exhaust. Installers will use elbows and a short length to make this happen if the pipes are too close together where they come out of the house. High efficiency exhausts need to be graded back to the furnace, so that condensates will go back to the furnace and be collected in the condensate drain.
I am not aware of any need to maintain separation between the pipes other than where they terminate.
Concentric intakes and exhausts are usually OK (intake is taken through outer pipe, exhaust goes out the inner, there is usually a cone shaped ‘hat’ surrounding the intake so that air is pulled from the back of it).
Not all codes have caught up with the latest furnaces, so consider the manufacturers instruction to be the last word on proper installs.
Thanks guys. I asked because i ran into an installation where the intake and exhuast vents existed at the same level. were 3" apart, were cut off the same length from the wall and neither had any extensions/fittings at the exterior My concern became that could the exhaust be sucked back into the intake.
Do you remember what manufacturer it was? I would just Google for the install manual and see what it has to say.