Hydronic radiant heat stat

crater said:

With a 30* Delta-T, I would think I would need to have the Aquastat set at 110* to maintain the thermal mass(concrete floor) at 80*
So I could regulate floor temp at the return line. Setting return line stat to be satisfied at 80* and if I wanted to heat with the floor then set a air temp stat at say 72* then if the floor was 80* but the room was 70 system would be running and if the room temp was 73* but the floor temp dropped below 80* the system would start and heat the floor back up to 80* but would't that require a constant flow to get a real floor temp. not just a drop in temp at the sensor?

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I guess I was assuming a continuously on pump. The Delta-T would drop as the pump continues to run with the resulting Delta-T being dependent on how much heat the slab looses.

I would think a embeded floor sensor could do the same thing without have a pump running continously

The way my system is set up is as such:
Stat--->24v 3 zone control panel--> low voltage to boiler and high voltage to corrisponding zone pump
so when zone 1 calls for heat the zone panel sends low voltage to boiler to start it and also high voltage to the #1 zone pump to start the flow

I am using 3 zone pumps instead of zoning valves and 1 pump

I know this is not an answer to your question but comments on the overall system fundamentals and assumptions. I hate it when people do that.https://terrylove.com/forums/images/smilies/biggrin.gif Anyway, there are several issues.

You should not need radiant and air. Radiant just makes you feel warm. No source, no breezes, etc. I have it; I feel no need at all to have any additional system. Most everyone that walks in comments about the absolutely uniform and sourceless comfort. I have never seen a recommendation for dual systems.

Heat pumps tend to be poor sources for hot air heating because they do not get the air comfortable enough for the draft the system causes. Geothermal pumps can be better than air based systems. The temperature available from the geothermal system is very well matched with radiant floor; not so well with air heating systems.

Some assumptions include, sufficient insulation under a slab. Floors that are ceilings of other heated spaces need to be insulated from each other. You should have had a heating calculation before building things. If you can supply the full loses from the heat pump, you could go that route. If there is a backup resistive heater in the heat pump system, you would be no worse off than you are now for capacity and cost to operate.

There is probably nothing you can do with your existing heat pump if has a direct air exchanger in the furnace. You might ask the manufacturer if it can be converted to provide only hot water. If it could, use the radiant as you only heating source. Do a heat loss analysis of the house. Find required fluid temperatures, required flow, if you tubing is adequate in layout and flow capacity. The floor tubing is the only imutable given.

I know "you should have done it this way" is annoying. Just think over what you have and how you might be able to use the pieces. A single system would most likely give you much better comfort. Certainly couse less headaches for controlling things.

The thermostat for the floor should be capable of dealing with the thermal mass of the floor. I suspect thermostats not designed to be smart will not be real helpful. I had one of those systems a long time ago. Constant over and undershoot.