Inverter Installation

A 115 vac inverter can be permanently installed in an RV, and connected through an automatic change-over relay.  The relay is wired in such a way that the normally closed contacts are used for the inverter output, and the normally open contacts are used when external power is available.  By connecting this way, inverter power is not used to energize the relay coil, saving battery power.   You will most likely need to do some re-wiring in the RV to isolate the wall receptacles that will be powered by the inverter from built-in appliances that require external power. 

Schematic of automatic change-over relay installation (including ATS-30 Installation Instructions).


  • Camping World sells a 30 amp automatic change-over relay for generator use that can be used as an inverter change-over relay.  The relay is the ATS-30 from Parallax Power Components.
  • The 12 VDC converter must not be powered from the inverter because it will just burn up energy trying to charge the battery while running on the battery.
  • Unless you are installing a very substantial solar electric system in the RV, you do not want to run high power appliances like the microwave, air conditioning, etc. from the inverter.  Therefore, those appliances must be isolated from the inverter output, and powered directly from the 115 vac external power bus (see schematic).
  • There is no point in running appliances from the inverter that can be run from propane.  Examples are the water heater, refrigerator, and electric space heaters.
  • It is not necessary to connect the 115 vac inverter output through a circuit breaker because modern inverters have overload protection built into them.  The inverter will shut down if overloaded.
  • If the inverter is more than 150 watts or so, the inverter should be installed as close to the battery as practical.
  • Connect the inverter to the battery and RV ground with adequate gauge wire.  DC current draw by the inverter will be approximately 10 times the AC current it is delivering.   A 1000 watt inverter will require 4 - 6 gauge wire.
  • Power from the battery to the inverter should be fused if possible.  A 1000 watt inverter can draw close to 100 amps, so do the math when selecting wire gauge and fuse size. 
  • If it is not practical to install a fuse, be very careful that the wiring cannot short to ground or chafe.  RV batteries can deliver hundreds of amps of current through a 6 gauge wire shorted to ground.  Fire or battery explosion could result.
  • The Xantrex RS-400 inverter that I installed in my RV has provisions for a remote on-off switch, allowing the inverter to be turned off when not being used.  If the inverter you select does not have this option, you can: leave the inverter running all the time as the idle current is less than 300 ma, install the inverter in a location where you can access the on-off switch on the inverter, or finally, install a relay in the 12 VDC power wire to the inverter.  The last option is not very desirable since the relay will need to handle high DC currents, and DC power is required to energize the relay when in use, thereby using more of the power you are trying to conserve.
  • Warning:  Installing an AC inverter must be performed carefully as connections are made to high current DC sources and high voltage AC systems.  Be sure to comply with all electrical codes and utilize high quality workmanship.  If you are not sure if you are qualified to perform this installation, seek professional assistance.

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