Water Source heat pump system – I have used a boiler for direct heat add (boiler used only for heat add). I have used a boiler for an indirect heat add (heat exchanger). I don’t think I had a system the hot water system was directly coupled to the heat pump loop (hot water used for entry unit heaters and heating ventilation air). I can’t think of any reason I can’t have the loops directly coupled as long as I have a heat trap. Am I not thinking of something?
(I am talking about a regular water source heat pump loop - not a ground source).
If the cooling side of the system is an open tower, the constantly added fresh water can destroy the piping/boiler. I would keep the boiler on its own set of piping, whether a direct add or heat exchanger.