Puzzling out a hydronic in-floor system

[spamTHISbrp]

I'm helping someone puzzle out a system-

Radiant hydronic in-floor, gas boiler, circulator pump located near the loop, not at the boiler:

- room thermostat is paralleled with a thermostat in the mixing valve

- room thermostat 'sends' a call for heat to the boiler

- circulator pump is controlled by a goldline SP32D, set to turn on the circulator when the sensor (don't know for sure where it is) is below 60 deg. F.

Does this sound like I've puzzled it out somewhat correctly?

Is it normal to leave the circulator pump on below some sensed temperature (sensed in the slab? outdoors?), and just use the call for heat to modulate the water temperature?

Dave

[Doug Miller]

Pretty much, but (I think) not quite...

More precisely, it's normal for the circulator to run when there is a call for heat. If the water is hot enough already to satisfy the demand, there is no need to light up the boiler. If the water is not hot enough, there is. Some controllers are sophisticated enough to "know" when they need to light up the boiler and when they don't, and some are not. I don't know which category your SP32D falls into.

[spamTHISbrp]

(I think) not quite...

circulator to run when there is a call for

The SP32D just looks at its setpoint (60), compares it to the remote thermistor, and activates the relay when the thermistor is below the setpoint.

It doesn't seem quite right to me, either, I've dealt with oil forced air, gas forced air, oil-boiler hot-water baseboard, and figured this would be the same.

Well, I haven't exhaustively traced the leads off the relay, so since the way it seems to be hooked up doesn't seem likely, I'll dig into it some more.

Thanks-

Dave

[spamTHISbrp]

I have confirmed that the thermostat (paralleled air thermostat and water loop temp thermostat only does the call-for-heat to the boiler, and that the circ. pump runs whenever the outside temp. is below the goldline setpoint.

Dave

[spamTHISbrp]

Ahhh, finally some info. Mid-late '90s Stadler was a fan of installing systems where the circ. pump always runs below the outdoor reset temp., and the thermostat just does the call-for-heat.

Dave