I previously posted about a design I was working on for a client, and got some helpful responses here, so I wanted to ask a couple more questions of the group: I am looking at a design where I use a single W-W heat pump (say 'HP-1') to supply a radiant floor heating system, as well as the domestic hot water for the building, utilizing a stiebel-eltron dual coil tank for the DHW. The geothermal loop will also have 2 other W-W heat pumps ( say 'HP-2' & 'HP-3')utilized for other system in the building. My question: Looking at WH-1, there will be times in the year when we want 'cooling mode' for the radiant floor system, but we will always want 'heating mode' for the DHW production. How is this accomplished? I'm looking at a system like this: http://welserver.com/WEL0383/, and am unclear how 100% of the domestic hot water load can be met, if all summer the radiant zones are dumping heat to the ground loop. Do controls for the 3-way diverting valve (for when DHW is needed) also switch the reversing valve at the heat pump? Additionally, does this get further complicated when I consider I have 2 more heat pumps coming off the ground loop (a scaled down version of this: http://welserver.com/WEL0714/)? Do the other heat pumps (presumably in cooling) need to get isolated off once the DHW is needed? Any insight would be great. Maybe someone has a controls spec/sequence of operations for these?