I recently had a heat pump installed. They placed the heat pump coil downstream (warm side) of furnace. Had issues with clanging pipes at times (I think due to pressure). I called the company and they disconnected a wire so my furnace doesn't heat during defrost cycle. The result is I have freezing cold air during defrost cycle. I've read that having coil upstream (return side) of furnace is more efficient. Is my installation wrong?
I would refer to the electric furnace installation manual to see if a coil is approved on the supply side. You're right, usually a heat pump coil would be on the return side of an electric furnace.