My gas furnace won't turn on when the low temp should be turning on the heater. My thermostat is a LUX 500 series (I had an extra brand new one, that I switched to, but no change), I don't know the brand of heater, it came w/Trane AC unit (2 ton). When the thermostat hits the hi temp, the heater turns off fine and I can set it on hold and the unit seems to work properly. I can also manually override the temp up/down and the heater turns on. So it seems that only the low temp is have trouble telling the heater to turn on. I have the setback thermostat on default 4 degree swing. Any ideas, my heating guy has blown me off the last 2 days, I'm out of town and won't return until midnight Thurs, so wife and child are there.

I'm building a small shop whose hot water requirements will be two sinks and a washing machine. Just me and my wife, so even washing clothes will be minimal, so we dicided to go with a porpane tankless hot water heater. 1.) For the application above, what kind of gallons per minute am I talking about? 2.) I'm building this shop myself. What type of pipe is required for propane? 3.) Originally, we were going to go quick and dirty with a 20 LBS. propane bottle until someone said it's illegal to put one inside the house. Would it be unsafe to have one sitting in the rafters of an open air carport? 4.) Any comparisons anyone wants to make on electric vs propane for this application?