Front/Rear Air Conditioner Switch

[RStrickler]

Howdy all, I'm back with more A/C wiring questions. For those who didn't read my last post a couple months back, I offered to help a neighbor with some RV wiring and landed in the middle of a nearly worse case scenario. Someone else had dismantled the the electrical control panel, didn't document anything, and threw away a couple of key parts. We knew how the system operated when new, but not how it had been put together.

Fast forward to now, and thanks to help I've gotten here, we've figured out that the system should be laid out roughly as shown here:



Now the part that I'm trying to figure out is how to wire the Front / Rear A/C switch. The owner insists that everything was done through a switch similar to this one (please ignore the jumpers, that's the remnants of someone else's work):



I've tested this switch and its operation is fairly simple. When switched to "F(ront)", all of the bottom connections are on and the top are off, when it's in "R(ear)" all of the top connections are on and the bottom are off, and when it's in "0" everything is off. Also, the original switch apparently only had twelve connections instead of sixteen. The owner of the rig also swears up and down that all the connections were made through this switch, that there was no second isolator anywhere (as shown in my diagram), and that somehow this switch alone was capable of selecting front vs. rear, and isolating the 30A and 20A lines from the generator when it is supplying the power.

I don't know how this would be possible with nothing but this switch. I feel like there has to be more to the switching setup than just this switch. The owner has forgotten about a couple of major pieces of the puzzle so far (for example the second 20A line coming off the generator), so I can't really trust the accuracy of anything I'm being told.

Has anyone wired one of these switches up? Is there another isolator? Is there something else? Help!

Thanks in advance everyone.

[Waiter21]

On my Southwind, there are two automatic changeover solenoids:

#1 The main one switches the 30 amps between shore power (normal) and the generator (priority), i.e. if the generator is started, it will automatically energize and switch over to the generator. This isolator is mounted inside the main power panel

#2 The second ACO controlls where my rear A/C unit gets its power. In its de-energized position, it gets it from shore power via the power distribution panel. However, if the generator is started, it energizes and the A/C unit now gets its power from a separate 20 amp circuit on the generator.

You can see a diagram and several photos on my site:

Rear A/C unit can be run on separate 20 amp shore power circuit – 1999 Southwind 35S


..

[RStrickler]

Originally Posted by Waiter21

On my Southwind, there are two automatic changeover solenoids:

#1 The main one switches the 30 amps between shore power (normal) and the generator (priority), i.e. if the generator is started, it will automatically energize and switch over to the generator. This isolator is mounted inside the main power panel

#2 The second ACO controlls where my rear A/C unit gets its power. In its de-energized position, it gets it from shore power via the power distribution panel. However, if the generator is started, it energizes and the A/C unit now gets its power from a separate 20 amp circuit on the generator.

You can see a diagram and several photos on my site:

Rear A/C unit can be run on separate 20 amp shore power circuit – 1999 Southwind 35S


..

Hey, thanks for the reply. I'd actually stumbled on your diagram previously in my searching. That's exactly what I'd expect to see, and how I'd like to proceed. I have to convince the owner that it's the right way to go though. The ACO in the electrical panel is present, accounted for and functional.
If there was an ACO for the rear (and I'm sure there must have been), it's been lost or misplaced. What's the actual part that you're using for the rear ACO?

Thanks again!

[Gary RVRoamer]

Are you sure your Coronado originally had a separate feed from the generator that enable both a/c to be powered? That implies a generator with two seprate power outputs, typically a 30A for the main power and a secondary 20A that could feed a second a/c unit. Not all coaches were set up that way.


Ignoring the secondary generator feed, you only need to switch three (3) wires to route main (shore 30A) power to front vs rear a/c. Hot, Neutral and Ground. Furthermore, the ground wire doesn't actually need switching, since it is legitimate and safe to have both grounded at all times). That means a standard double pole, double throw switch can do the basic job. Six (6) wire connections total.


If there was some fancy 12 or 16 terminal switch previously, it may have had the secondary isolation built in somehow, but that would take some study to figure out. I think it would be a whole lot easier to re-wire with two simpler switches, with another double pole, double throw (DPDT) switch to change the rear a/c from the main power side to the generator secondary. As you show in your diagram.

[Waiter21]

My A/C unit ACO is buried under the frig and very difficult to get to.

However, Its similar to this item:

https://www.boatandrvaccessories.com...ransfer-switch


Its wired so that one source (the shore power source) is from a 15 amp circuit breaker on the circuit breaker panel. The other source is the 20 amp feed from the generator. Whenever the generator is running, it switches over to the generator. I added a Receptical/plug in the 20 generator circuit so I can run my rear A/C unit on a separate shore power

IMPORTANT:

My Southwind has a current sensing circuit that senses how much current is being drawn from shore power. When both A/C units are running, it measures this current, if its more than about 28 amps, it will automatically "shed" one of the A/C compressors to prevent an overload on shore power

[RStrickler]

Originally Posted by Gary RVRoamer

Are you sure your Coronado originally had a separate feed from the generator that enable both a/c to be powered? That implies a generator with two seprate power outputs, typically a 30A for the main power and a secondary 20A that could feed a second a/c unit. Not all coaches were set up that way.


Ignoring the secondary generator feed, you only need to switch three (3) wires to route main (shore 30A) power to front vs rear a/c. Hot, Neutral and Ground. Furthermore, the ground wire doesn't actually need switching, since it is legitimate and safe to have both grounded at all times). That means a standard double pole, double throw switch can do the basic job. Six (6) wire connections total.


If there was some fancy 12 or 16 terminal switch previously, it may have had the secondary isolation built in somehow, but that would take some study to figure out. I think it would be a whole lot easier to re-wire with two simpler switches, with another double pole, double throw (DPDT) switch to change the rear a/c from the main power side to the generator secondary. As you show in your diagram.

Hi Gary, it's definitely got two legs from the generator.


-Rob

[RStrickler]

Originally Posted by Waiter21

My A/C unit ACO is buried under the frig and very difficult to get to.

However, Its similar to this item:

https://www.boatandrvaccessories.com...ransfer-switch


Its wired so that one source (the shore power source) is from a 15 amp circuit breaker on the circuit breaker panel. The other source is the 20 amp feed from the generator. Whenever the generator is running, it switches over to the generator. I added a Receptical/plug in the 20 generator circuit so I can run my rear A/C unit on a separate shore power

IMPORTANT:

My Southwind has a current sensing circuit that senses how much current is being drawn from shore power. When both A/C units are running, it measures this current, if its more than about 28 amps, it will automatically "shed" one of the A/C compressors to prevent an overload on shore power

Excellent, thanks for the link. I'll check it out in a bit.