This modification makes RV-style roof air conditioners (that normally run continuously) turn on and off like a normal home air conditioner, and replaces the Suburban propane furnace
thermostat with a modern digital one. It was recommended by Gene at the Casita
Forum, and you can find his extensive writeup here: http://www.casitaforum.com/invboard/...?showtopic=379
An annoying problem with the Coleman R/V roof air conditioners that are installed by Scamp
and others is that they run continuously, shutting the compressor off but not the fan when the selected temperature is reached. This modification adds a heat/cool thermostat and a relay that turns the A/C completely off, and provides a central control for both heating and cooling.
Gene has verified with Coleman that this is not harmful to the A/C, and I noticed in my testing that the Hunter brand thermostat even has a time delay for the A/C to avoid compressor problems from stopping and re-starting too close together.
Two main items are required for this mod:
1. Thermostat - Hunter Digital #42995B or #42999B - WalMart $20. See Photo #1
2. Relay - Omron #G8P-1A2T-F12VDC, (12 volt, switching 120 volt) - Mouser Electronics $4 + $6 shipping - http://www.mouser.com/index.cfm?&handler=d...*&N=0&crc=false
. See Photo #2
3. Assorted wire, crimp-on connectors, screws and enclosure for the relay.
The simple explanation is you replace the existing furnace-only thermostat with the new one and install a relay controlled by the thermostat that acts as a switch on the A/C power line. To operate you leave the A/C turned on, with A/C thermostat turned up to maximum cooling. The new thermostat and relay then control it, and turn the A/C on and off using the setting on the new thermostat. As a bonus, the propane furnace
is also now controlled by a digital thermostat. A wiring diagram is shown in Photo #3.
Some roof A/C's have heat strips and those can also be controlled by adding a switch and a jumper as mentioned in the instructions below. Gene covers this in detail as that is what he had.
This is a relatively simple process but involves some contorting in the 13' to mount the relay. Be sure to disconnect the power cable while doing the installation.
The process is described starting in the next post.