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Howdy all,I've been watching Brian's project for a couple of years now. My 32 x 16 greenhouse with in-ground plantings is up and running, though I went for pressure treated and redwood construction, glazed with operable glass units for the walls and uv transmitting double walled acrylic for the roof.I'm in zone 3/4 and when it's -20°F out two 30K btu heaters keep temps well above freezing. My goal is just to keep things just above freezing. Here's my dilemma: I went with one Southern Burner ventless heater which needs no electricity to operate, not even a battery for the thermostat. (The other is a direct vent propane heater which requires an electric thermostat.) When I bought the SB it was advertised as coming with a thermostat that would go down to 35F. Just above freezing so I was fine with that. I want the SB to be the primary heater. Well, when it arrived it came with a RoberstShaw millivolt thermostat that could only be set down to 39F. When I called to inquire/complain I was told that RobertShaw thermostats now only go as low as 45F. and SB was aware of no other millivolt thermostat that had a lowered set temperature. I found another 39 F stat on ebay so I have a backup, sort of. I'd rather not heat to 39, let alone 45. Is my SB furnace soon to be useless? I like the reliability of needing no electricity.The best suggestion SB could offer was to try to find an old millivolt thermostat wit a mercury switch and mount it on a slant. My, what a helpful suggestion that was. How can I operate the SB at near freezing temperatures? Or is my desire to heat without electrical back up doomed?Any ideas? Thanks! Steve H SW WI USA USDA Zone 4.
The best suggestion SB could offer was to try to find an old millivolt thermostat wit a mercury switch and mount it on a slant. My, what a helpful suggestion that was. How can I operate the SB at near freezing temperatures? Or is my desire to heat without electrical back up doomed?