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Has not been an issue for me – we haven't used the furnace.  We use a ceramic heater instead to save on propane.

The thing I'm wondering is whether the RV t-stats use the same voltage as house t-stats.  I don't know the answer to this.  If they are compatible, then yes installation should be quite easy.  I just installed a Hunter programmable for my daughter because her existing (electronic) t-stat got wonky and wouldn't shut the AC off when it should.  Just a matter of paying attention to where the 4 wires go on, and the terminals are clearly labeled.

Post edited 8:22 pm – April 27, 2011 by FoCoNoCo

Steve said:The one I linked uses batteries. Most thermostats operate at 12 volts and houses have transformers to convert power for them. Well, from what I've been reading.

A thermostat in your camper may run on 12VDC . Residential thermostats run on 24VAC.  You can find thermostats that run on 120VAC as well.  In general, the batteries in residential thermostats are designed to keep the time/temp settings – most do not run correctly on the 3VDC supplied by batteries.  For a more permanent solution, you can buy a transformer to stepdown the 120VAC to 24VAC and run a length of 18ga thermostat wiring from the transformer to the thermostat and wire the C and Y terminals on the thermostat to the coil leads on a 24VAC coil relay or contactor for cooling, and the C and W terminals for heating– not sure what you are planning to control with the thermostat – you COULD control a window shaker A/C with a wall mount thermostat, but would require rewiring most of the A/C unit.

Steve said:All I know about electricity is how wobbly it makes you feel when you come into direct contact with it. 

Only the first 10 times or so – depends how many amps you got hit with!  I know for a fact that 230vac at 15amps is somewhat painful – 120V shocks don't even bother me anymore….

wrenchist said:I just recalled the digital thermostat closed the ground circuit on the control side of the relay. It did not actualy power up the relay with the 3vdc. I could provide a simple drawing if anyone is interested.

If tyou're referring to the thermostat's internal switching relay, that makes sense.  Relays generally have a coil voltage rating – ie: the voltage needed to energize the coil side of the relay to either open/close the NO or NC contacts, in my field of work, most relays have a coil voltage of 24VAC – sometimes they will close with less voltage, but can weld the coil.

Makes perfect sense now – you're simply switching ground open and closed.  Most thermostat setups normally switch a power source, not  ground.  But that will work – so long as the thermostat side doesn't rub through or short to ground – then the furnace will stay running!  That's good – I wouldn't have even thought to switch the ground leg of the coil.