Best Wiring Solutions for Running Multiple RV Air Conditioners

[JimTheSoundman]

I'm in the middle of planning out a rebuilt project, and I'm trying to figure out the best way to deal with the issue of multiple air conditioners.

I'll have three sources, either shore power, a 3500 watt inverter, or a 6500 watt Generac generator (dual 30 amp)

So I have an automatic transfer switch, but I'm confused as the best way to handle these three sources, plus the four different outputs (120v outlets, A/C 1, A/C2, and A/C3)

My transfer switch/load bank/converter unit only has 5 circuit breakers available. So I could use a sub panel and just wire all three A/C units into a three way rotary switch, and then run that into the 20 amp 120v circuit breaker. That only lets me run one out of the three roof a/c units at a time. Not ideal.

Or I could use one half of the generator to run the a/c units, and bypass shore power altogether. Genny has plenty of power to run all three. But then I'd have to start the genny every time I wanted A/C. Not ideal.

Or put one on the circuit breaker and two on the genny. Again, not ideal.

And my transfer switch is made for only shorepower/genny, factoring in the inverter is another piece to the puzzle. I could A/B switch between inverter and shorepower into the transfer switch, but then we have the circular loop issue, where the inverter could be feeding in like shorepower, then the load bank is using part of that energy to try to recharge the very battery that is supplying the inverter. Definitely not ideal.

I have the skills to set up something like a solid state relay which could sense the inverter being in use and break the charging loop, but I'm certain there has to be an easier way.

Has anyone been through this conundrum before and gotten it solved? Ideally I'd like to use the front or middle or back A/C units and have it be fed through either shore power, inverter, or generator. Even if I ordered a three way transfer switch, that still doesn't account for the fact that I have split phase on the generator, so half of it's output would be wasted.

Anyone have any suggestions for me?

 

[RayIN]

forget about trying to run air conditioners from an inverter. The amperage draw is 10/1; it requires 10A DC from the battery bank to create 1A AC. That would require a HUGE battery bank and/or a lot of solar power, both are expensive to create and maintain.
This website might be useful: The 12volt Side of Life (Part 1)

 

[JimTheSoundman]

forget about trying to run air conditioners from an inverter. The amperage draw is 10/1; it requires 10A DC from the battery bank to create 1A AC. That would require a HUGE battery bank and/or a lot of solar power, both are expensive to create and maintain.
This website might be useful: The 12volt Side of Life (Part 1)

I have a 600 amphour LiFePO4 battery. I have space to add a second one if needed.

 

[Gary RV_Wizard]

I have a 600 amphour LiFePO4 battery. I have space to add a second one if needed.

600AH x 12v = 7200 watt-hours. That's enough AH to run an a/c for a couple hours, but the 3500W inverter will also be a bottleneck. Each a/c draws about 1400W when the compressor is working and the start-up surge when the compressor cycles on briefly doubles that. Running off the 3500W inverter is the same as running from 30A/120v shore power, which is 3600W.

Your problem is the load center (breaker panel). It lacks the capacity to handle the branch circuits needed to run 3 a/c units as well as other appliances and such. Sounds like it is designed for just 30A input. You need to upgrade the load center if you expect to add more high-amperage branch circuits. However, if you only have 30A (3600W) shore power and 3500W inverter, there is little point to that unless you also upgrade the shore cord to 50A/240v.

An alternative would be to add a second load center to handle the second 30A output from the generator. Wire the extra two a/c units to that auxiliary load center, which of course means they only run from generator power. But that's going to be the case anyway unless you add t50A shore as well.

 

[JimTheSoundman]

600AH x 12v = 7200 watt-hours. That's enough AH to run an a/c for a couple hours, but the 3500W inverter will also be a bottleneck. Each a/c draws about 1400W when the compressor is working and the start-up surge when the compressor cycles on briefly doubles that. Running off the 3500W inverter is the same as running from 30A/120v shore power, which is 3600W.

Your problem is the load center (breaker panel). It lacks the capacity to handle the branch circuits needed to run 3 a/c units as well as other appliances and such. Sounds like it is designed for just 30A input. You need to upgrade the load center if you expect to add more high-amperage branch circuits. However, if you only have 30A (3600W) shore power and 3500W inverter, there is little point to that unless you also upgrade the shore cord to 50A/240v.

An alternative would be to add a second load center to handle the second 30A output from the generator. Wire the extra two a/c units to that auxiliary load center, which of course means they only run from generator power. But that's going to be the case anyway unless you add t50A shore as well.

Second load center is a good idea.

 

[Adventurous Traveler]

Second load center is a good idea.

Gary is spot on again!