Shem controller for Radiant pump control

I am looking to set up a new solar system and want to tie solar water from the SHEM 120 tank to my existing radiant floor. We heat with wood so I would love to reduce our wood consumption but that will be our backup if there is not enough solar gain. Because the tank is so small compared to the 8 4x8 flat panels on the roof I want to dump all of our excess winter heat into the radiant floor. Naturally this will be turned off in the summer.

The question is regarding the SHEM 32 controller which I see has a third temp sensor and second pump control. I just read the manual and from what I can tell it does not look like the SHEM 32 controller will let me set the second pump settings like I want. It only allows for a temperature differential temp settings rather than set temperature settings.

I would like the radiant pump to kick on when the tank reaches 140* and off at 130* I don't want the radiant to drop the tank to go below 130* and rob us of our domestic hot water! Is there anyway of achieving this with the SHEM controller?

My current non solar system has a thermostat linked to an "I-link sp81" which turns the floor pump on and draws domestic hot water through an on-demand water heater. I want to separate the radiant floor from the domestic water and naturally this system won't take into account the solar tank temperatures so I was originally thinking that I could put an Aquastat on the tank to control the floor but it would be sweet if the SHEM32 could do the job.

Thanks
Ryan

Excellent question! The SHEM 32 differential controller has 3 temperature sensor inputs, and two pump outputs. The key descriptor is "differential". The controller activates two different 110 motors given temperature differentials, rather than temperature settings.

For a two tank configuration, the second (recirculation) pump would activate when a set temperature differential is exceeded, and shut down when the temperature differential ceases.

For floor loops, the second pump would activate a floor loop, but not as you wish. A separate temperature sensitive control would be needed.