750mv vs 12v Thermostat Question UPDATE 2
Updated 29 Nov-- Update 2--29 Nov: got it to work. Not clear on the thermostat voltage for these things whether I can use the cheaper version or what. I want it for my furnace only set-up in the R...
Forum Discussion
BFL13 wrote:
I decided to put the blue wire that was on the old Thermo R Common onto R on the new one, and put the other blue wire from old W to new W.
I still think that must be backwards (isn't "common" negative?)
Anyway, it worked. With it set to "heat" I set target temp at 17C and the display (yes you can see it without any back lighting) showed ambient at 50C so the furnace fired up blower first then heat--all good.
When the ambient got to 17 it kept heating away but then there was a click and the "heat on" went out and the heater stopped and then a bit later the blower. By this time ambient was showing at 18C--confirmed by another thermometer nearby as a cross-check. Good!
So I waited to see if it would stay like that for a while, it did, so I opened the RV doors and a window to cool things down and waited to see if it would come back on and at what temp.
It came back on with the ambient reading 17C but this took a while because it stays warm inside the RV (which is good) So it cycled.
I don't know if that one degree C drop counts as a "short cycle". It would be ok by me if it dropped to 16 or even 15, which is how the old slider temp Duotherm in the 5er acted. But it is ok as is where it would have stayed off longer if I had not opened the doors and a window to cool it down inside. Should be able to live with that action as is.
So another day of adventure completed! Can't say all that was much fun, but it was "interesting" for sure. Thanks again for all the advice, some of which I actually took! :)
in reality, for a RV setup which wire goes to W and R really doesn't make any difference.
and how much temp swing you get between on and off is determined by the thermostat. some are adjustable some are fixed. a typical fixed system has about a 2-3F or 1-2 C swing between on and off.
and often they have an "anticipator" circuit that determines when to shut off knowing temp will keep rising for a while. often those are set by what type of heating you have. on the mechanical systems that often is a heating element on the bimetallic coil. But those are designed to run from the 24VAC, so 12V DC won't give the same result.
the ones that are electronic often let you set the swing anywhere from 1F to 5F or so.
