Originally Posted by D.T.
Water heater to heat the workshop? How does that work? Like cirulation to a heat register?
Anyway, I assume the main burner is not coming on? It has a power vent too? I'd make sure all the things are working in the order that they are supposed to. You can try and clean the thermocouple first with sand paper.
There is a circulator pumping the hot water through three 200' loops of hepex (cross linked polyethylene) buried in the concrete floor. There is a radiant barrier under the concrete.
So are there two thermocouples? One for the pilot light and another for the main burner?
The gas supply is good or the pilot wouldn't stay lit.