Where should the air conditioning coil be installed on an electric furnace? Is this different if it is a heat pump?
You should always check the installation manual of the electric furnace. Usually a standard AC coil can be installed downstream, on the supply side, above the heating elements. The electric furnace manual may require a certain distance between the elements and coil.
A "packaged" heat pump coil is usually installed upstream, located beneath the blower and elements, on the return air side.
With fossil fuel furnaces the heat pump coil is usually installed downstream, above the burners, on the supply side. A heat pump coil installed upstream, on the return side, could cause the heat exchanger to rust and potentially leak flue gases, however the gas code does allow an AC coil to be installed in the return side if the furnace manufacturer allows it.
QuoteClause 7.12.4 - A forced-air furnace installed in series with a cooling unit and downstream of a refrigeration coil shall be designed for such use.