As outlined in my new Garage Build thread, we added a boiler to heat the new garage with hydronic in floor heat. The Lochinvar boiler we went with has up to 4 zones (thermostats) that we can hook up to it. I buried an insulated PEX loop out to my pole barn where I have my main shop. So one end (with a pair of 1" PEX lines) comes up in my mechanical room in the new shop, the other in the pole barn. Today I am heating the pole barn with a forced air NG hanging style shop heater. I will likely leave that in place for the time being but am looking at heating the shop with a water to air heat exchanger. This is the one I think I will buy.
So to operate something like this I will need a way to call for the boiler to kick on and generate heat as well as trigger the pump to pump glycol out to the pole barn. I will also need to trigger the fan on the water to air heat exchanger to kick on. I will run a thermostat wire from the boiler to the pole barn via conduit that will be shared with the fiberoptic cable for internet. Shouldn't be an issue mixing low voltage with glass in the same pipe. That will allow me to install a thermostat out there to trigger the boiler and pump however how do I trigger the fan? Am I going to need two thermostats? My thought is to put a probe on the return loop or in the heat exchanger somewhere to detect a temp warmer than say 80F and kick on the fan. This way the call for heat controlling the boiler/pump will start circulating warm fluid, once it gets to the heat exchanger it detects it or the return loop heating up and kicks on the fan. Once the air temp hits my target the boiler/pump cuts out but the fan would keep running until either the return loop or heat exchanger drops in temp below whatever it is set at. The only problem is that the fan would try and run all summer unless I set it to something like 110F or just turn it off in the summer which is likely what I would do. Might as well keep using the warmth in the exchanger for a bit even though the boiler/pump kicked off. The boiler will send 160F to the pole barn and I expect some heat loss but it will be very minimal the majority of the run is under the new garage which has a heated floor, and it is about 15' from the new garage to the pole barn where it would be in frozen ground. I think the PEX is rated to 1F loss per 100' Total run is probably just shy of 70'. So I expect to basically have 160F liquid.
So, my question is if anyone has a setup like this and if so, how do you control both the boiler/pump and line voltage to the fan? Is there a single thermostat that will do this or am I better off going with two thermostats with a probe on the heat exchanger and a separate air thermostat to trigger the boiler/pump.