On an RV furnace? My current furnace thermostat is one of the mechanical ones, and the problem is that the temperature swing is too dramatic between off an on. I want something that will cycle the furnace quicker.
I have a regular "5-wire" electronic heating and air thermostat that came out of my house when I upgraded to a heat pump. Will this connect up to the furnace? I don't have thermostat wiring for the AC side, but if it will work just off the heat side, that will be perfect. It doesn't need to be level because it is electronic, but I didn't know if the wiring is any different between a home thermo, and an RV thermo.
Here's the pinouts for the home thermo:
When the unit is in heat mode, the thermo only switches on the burner on line when heat is called for. The fan unit in the furnace is activated by a heat sensor inside the furnace...when the heat exchanger is warm enough, the fans come on. RV furnaces seem to work the exact opposite...the fan is started, and then when the furnace sees that the fan is OK, then it lights the burner.
When in AC mode, when cooling is called for, both the compressor on, and the fan on leads are switched at the same time, activating both.
Home thermostats are designed to switch only a few hundred milliamperes at 24 volts. Do RV thermostats carry the full 12 volt load of the furnace through the thermostat? I imagine running the thermostat at 12 instead of 24 will be fine since the actual temperature sensing electronics operate off a battery, but if it's carrying too much current, it could damage the relay switches inside.
Take a look at your old one. Many have what is called an anticipater. Has a small scale and a movable pointer with something like .2-3 or something like that. Moving the pointer toward a lower number sets the on-off temperature closer.
The furnace draw will be just about 1 amp, which should be fine for most thermostats.
Coleman air conditioners send +12 volts to the control circuits, DuoTherm units ground out the relays, so the hookup will be different.
If you search the forum for "hunter thermostat" you will find lots of info, along with a link to Les Adams article and diagrams.
Not quite as far as millivolts go.
First of all, a millivolt thermostat is designed for gas valves that are self-powered using a pilot generator, which the new RV furnaces do not have. They will not work on a 12-volt furnace.
The mechanical thermostats used on a RV furnace are rated for 12-volts DC.
Second, even though residential thermostats operate with 24 volts AC, you CAN use them in a RV as long as the thermostat uses power from the internal thermostat batteries. The Hunter does this.
Most residential digital thermostats do this but some do not, these taking power for operation from the 24-volt transformer in the heater. The latter will NOT work in a RV.
BTW, a millivolt thermostat is used for heating only, not air-conditioning and most will NOT work on a 12-volt RV system due to the current limitation of the heat anticipator.
Sorry Steve but your last comment is incorrect. A millivolt Tstat will work for AC and it will work with a 12V RV system. You simply dont connect the 12v feed wire to anything when you wire it up. As for the AC part, they are indeed designed to run them and even have seperate programming for both heat and AC if they are of the programable type. A common residential millivot Tstat works great in both my TT and my house, which also has AC.