I just closed on a home that has a 2001 vintage 5Ton Trane GSUF060 heat-pump hooked up to vertical loops. During my walk-through a couple of days before the closing, I found that the heat output of the system wasn't sufficient to raise the temperature of the home without kicking the heat-strips on. The differential between the return and the main output was about 13F. Upon further investigation, it turned out that one of the Grundfoss pumps on the pump module wasn't running due to a wire-nut that had backed off. Also, the 'IN' and 'OUT' connections on the loop side of the system had been switched during installation. After getting the second pump online, the differential increased to 16-18F in heating mode. The sellers contractor has the hose kits on order to switch the loop to the correct configuration and I have a holdback on the purchase price that covers potential repairs. Now I am looking for a data source that tells what this system is supposed to put out. Trane has been less than helpful. The sellers contractor tells me that 'it's supposed to do that' The only manual I can find from Trane is a generic users manual that doesn't have performance tables. So if someone has experience with this particular system, could you please give me some pointers towards: - what GPM flow does this unit require on the loop side ? - what temp differential should I see on the loop side ? - what temp differential should I see in heating mode on the air side if my return is around 70F ?