I moved into a house about 2.5 years ago, and the previous owners had a heat pump installed, together with a gas furnace. Recently I had my furnace repaired (faulty igniter) and the HVAC technician said the installation was done against code because the heat pump was connected to the return air pipe, instead of on top of the furnace. He said I could be "red tagged" with a B-type warning and be required to fix this within 45 days.
Is that true? Why would they have installed it into the return air pipe if that's against code? are there health risks with this? I use the heat pump (hot mode) when it's between 0 to 15 degrees C outside, just the furnace when it is below 0, and the cold mode heat pump when it's above 35 C.
What are my alternatives for fixing this? Can a contractor just fix the pipe to go to the right place?
I am located in Toronto, Canada.
Best Answer
The tech made it sound worse than it is. It's not in the wrong air flow, just the wrong order, so moving the pipe will not help. It's a fair sized duct, not a pipe.
There is a restriction in at least the International Mechanical Code about heat exchanger coils being before the furnace. It is because in cooling mode, the resulting condensate can be corrosive. In heating mode the physics involved are not really a problem, but that doesn't change the code.
There is an exception to this requirement, it is OK to configure the system this way if the appliances are listed for such configuration. You would need to obtain the installation instructions and see if this is indicated as an option.
The only practical way to fix this if you cannot prove the current configuration is allowable is to relocate the heat pump coils upstream of the furnace.
Note that the direction of airflow is the criteria for placement, not above or below.