High and low limits for slab sensor thermostat?o

[Blk88GT]

This is my first time setting one up.

Let's say I want the ambient temp to be 55-57, how do I figure out what my high/low limits should be?

I'm running 80 degrees for feed temperature, 60 degree return.

Thanks in advance.

 

[tdkkart]

Floor temp vs room ambient temp is dependant on your heat load. The more your building leaks, and the colder the outside temp, the warmer your floor will have to be to keep up with the demand.

Start with your floor temp 5* above your desired room temp and see how it goes from there.

 

[goneflyin2002]

^^^What he said.
My floor runs at 63-64 degrees when I have the room set at 62, if it's averaging around 32 outside.
However a while back when it was about 15 outside, the floor was running at about 65-66 for the same room temp, 62.

Don

 

[Blk88GT]

Thanks, I've got it set 4 degrees (celcius) on either side of the desired room temp for now and will monitor it over the next few days to see how it behaves.

I guess many people aren't running a thermostat that monitors slab temp?

 

[Highbeam]

No. The stat that measures floor temp is much more expensive and since the goal is to maintain a certain air temp, the slab temp really isn't that important.

 

[BadgerBoilerMN]

Well...

The ambient sensor is controlling all. The heat load is heat loss over time. An ambient thermostat will handle most residential applications and little else is needed. The slab is simply a radiator. Like any radiator, the temperature of the water will effect output and the difference between the surface temperature and the ambient air temperature will determine the slab (radiant panel) output and ultimate the surface temperature. When the ambient design temperature is reached (we design for air temperature) the slab surface has reached it's design temperature as well and the system cycles off.

Slab sensors should not be set too close the ambient setting as they act as "book ends" keeping the slab in certain range determined by the designer. Where two heat sources are used and a significant eccentric load e.g. "extreme" glass must be overcome, the slab sensor acts as an early warning system shutting down flow when it's gets a lot of solar gain for instance and starting flow ahead of the air stat when the sun goes down and heat is quickly lost through the glass. In typical construction the limits should be set wide for comfort and efficiency.

There is never a time when a slab sensor should be used exclusively without the benefit of a room-by-room heat load and proper control logic.