I have two 4 ton geocomfort units connected to my old fossil baseboards and new multiaqua fancoils to account for reduced BTU output of the baseboard.  The fancoils are set slightly below the bb temp.  I am playing with the temp settings for the two units and need some advice.  Currently i have set unit 1 setpoint to 120 with a 5 degree swing and unit 2 to 116 with a 5 degree swing.  Unit 2 has yet to come on and unit 1 is running from 1/3 of the time in 30-40 degree weather to 2/3 of the time in colder weather down to teens.  Unit 2 has not been coming on because water temp in the system has not dropped low enough.  Also fan coils have only come on when temps were in the teens and  the wind was blowing outside. 

I am looking for advice in this setup for setpoints, temp differences, and any other advice for setting the controller and or running times. 

I know this is a general post but i am just looking for any advice right now.  Thanks!

What is your contractor's advice?
J

They basically said we (myself and them) can adjust temps and fiddle with it for a while until we figure out where things work best.  We are very close to where we started with temps but i havent seen any real change in anything.  Not that there is a problem I just wanted to see if anyone had and ideas about my current setpoints and differentials to see if they thought they looked good, or if i should be doind something different to start out.  Thanks,

Are the two heat pumps connected to a buffer tank or directly to the baseboards and multiaquas ?

they are connected to an 80 gallon aosmith storage tank.

I would see how low you can go on the tank temp. The efficiency of the heat pump drops of dramatically as the tank temp increases.

Aware as I am that we engineers sometimes over complicate matters, I do want to point out that this system's efficiency and comfort may not be as simple as maximizing COP by minimizing buffer tank setpoint.

It is probable that baseboards provide greater comfort since they are more distributed, better attack loads by being located along outside walls, run almost silently, and use no additional energy (no blowers). Rooms in this house may seem more comfortable at lower room air temps owing to these characteristics of baseboards. It may take a higher room air temperature setpoint to be comfortable in a room heated by a Multiaqua owing to air velocity.

Suppose the Multiaquas can meet design day load with 120 deg water, but baseboards require 160 deg. The simple answer would be to set the buffer tank at 120 deg. A better answer might be 130 or so, to take into account considerations listed above. These values are examples only, just to illustrate the point.

An even slicker solution might be to adjust the buffer tank setpoint automatically according to outside air temp. Such a setup could maximize efficiency during mild weather and comfort during severe weather.