750mv vs 12v Thermostat Question UPDATE 2

BFL13 wrote:
This digital one says no to 12v--scroll down to the questions--one guy asked about 12v.

http://www.canadiantire.ca/en/pdp/honey-non-programmable-thermostat-0529214p.html#spc

Answer says it is for "24v" but not for Direct Voltage. What's that supposed to mean?

well, there are two typical house thermostat systems.

The oldest one is the 750mv system, which is designed to work with systems that do NOT have any other power going to them. the 750mv comes from the thermopile heated by the pilot light and when the thermostat contacts close, the 750mv is routed to the gas valve, turning it on and turning on the heat. Note, these systems, usually not having any other power, 120V or otherwise don't have a blower motor, completely convection heat. E.G. a really old system.

A 750mv thermostat should work with a rv furnace, instead of connecting the 750mv to the furnace it will route the 12V dc to the furnace, and on comes the furnace.

The other typical system is 24V high impedance AC. there is a 120V to 24V transformer in the furnace routing 24VAC through an impedance limited transformer to the thermostat. The thermostat then routes this 24VAC back to the furnace controller.

Common with current furnaces and support programmable thermostats.

Now one of these thermostats without any progamability should also work with a RV furnace.

But using one with a programmable feature is hit and miss. First, you only have 12VDC, not 24VAC, so often the programming won't work. However, if it has battery backup, very typical, they then will often work, but batteries will run down faster, months or more is still common though. And any backlighting may not be very bright.

Sometimes these won't work at all with 12VDC depending on how they actually do the temperature sensing and if that works with 12VDC.