Buffer Tank for Air to Water Heat Pump - 2 pipe - in series connection with the supply line

gm332

I was studying the different design configuration when connecting a buffer tank to an air to water heat hump (2-, 3-, 4-pipe). I was wondering what would be the disadvantage if a 2-pipe buffer tank is connected in series with the supply line (i.e. hot water from the heat pump to the bottom of the buffer tank, hot water outlet to the heating load / return line not connected at all to the buffer tank).

fentonc

It makes the controls for it kind of weird, doesn’t it? With that setup it seems like the heat pump can’t run at all unless a zone is actively calling for heat. I think most of the setups want to let the heat pump maintain temperature in a large buffer tank, and then the zones pull heat from the tank in an uncoupled way as needed. 

hot_rod

Like this? You are one important connection swag from a 3 pipe🥴. As @fentonc mentioned what controls the HP? Hi do you load the tank after the heat call is over?
How do you pull from the buffer without flow through the HP?