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Topic: Adding Second Transfer Switch to Power only one A/C unit? (Read 599 times) previous topic - next topic

Adding Second Transfer Switch to Power only one A/C unit?

Greetings from Lake Conroe - This is a bit difficult to communicate accurately as I do not understand how this may or may not work, but wondering if anyone knows how to make this work, if it will work...  I heard there is a way to run a second rooftop rv A/C unit in a campground that only offers "30 amp" service by separately plugging the 20 amp receptacle in the same campground pedestal power supply box to a second, added single-circuit manual transfer switch that would some how provide power from the 20 amp campground pedestal receptacle straight to only one of rooftop A/C unit via a 20 amp extension cord from the campground pedestal to the additional single circuit manual transfer switch.  The regular 30 amp plug would of course provide enough power through the factory installed coach automatic power transfer switch for one ac unit and other items, except for a second ac unit.  Anyone ever heard of such a solution to be able to run two ac units in such a manner?  Thank you!

Jeff on Lake Conroe
1997 Eagle
2013 FJ Cruiser 4x4 Toad
Jeff & Sandy
1997 American Eagle 40' Slide-less
2013 Toyota FJ Cruiser 4X4 Toad
Interested in Foretravel Coaches

Re: Adding Second Transfer Switch to Power only one A/C unit?

Reply #1 –
Quote from: JeffOnLakeConroe –
Greetings from Lake Conroe - This is a bit difficult to communicate accurately as I do not understand how this may or may not work, but wondering if anyone knows how to make this work, if it will work...  I heard there is a way to run a second rooftop rv A/C unit in a campground that only offers "30 amp" service by separately plugging the 20 amp receptacle in the same campground pedestal power supply box to a second, added single-circuit manual transfer switch that would some how provide power from the 20 amp campground pedestal receptacle straight to only one of rooftop A/C unit via a 20 amp extension cord from the campground pedestal to the additional single circuit manual transfer switch.  The regular 30 amp plug would of course provide enough power through the factory installed coach automatic power transfer switch for one ac unit and other items, except for a second ac unit.  Anyone ever heard of such a solution to be able to run two ac units in such a manner?  Thank you!

Jeff on Lake Conroe
1997 Eagle
2013 FJ Cruiser 4x4 Toad

I have done it and it is the best modification I could have done. I always have both air conditioners available even when I have a 30 & 20 amp plugs . There was a company that sold the kit (PSRV dual power adapter) but unfortunately I think they are out of business. I have the wiring diagrams and instructions that anyone should be able to put this together on there own. DUAL POWER ADAPTER It was set up so you have a 20 amp female outlet installed by the electric reel. When you plug in the second extention cord the circuit breaker with the rear A/C was now powered by the 20 amp breaker. When you unpluged it there was a bypass plug that put that circuit back on the original wiring.
The selected media item is not currently available.Barry BEAM #16014
2003 U320 40' AGDS
Beamalarm, Foretravel technical help and specifications
"Whatever the mind can conceive and believe, it can achieve"

Re: Adding Second Transfer Switch to Power only one A/C unit?

Reply #2 –
Quote from: Barry Beam –
It was set up so you have a 20 amp female outlet installed by the electric reel. When you plug in the second extention cord the circuit breaker with the rear A/C was now powered by the 20 amp breaker. When you unpluged it there was a bypass plug that put that circuit back on the original wiring.
I am not sure exactly what you are describing here, but I would certainly want folks to clearly realize that you would NEVER have a female 110 V. outlet waiting for an extension cord with a male plug to plug into it.  That would not be safe, as of course the end to be plugged in to a female socket would be male, with the HOT pins of the male plug exposed.  I'm sure that isn't what you meant, but the original poster indicated he didn't understand how it would work, and the post could be read that way.
The selected media item is not currently available.Brad & Christine Slaughter
Was:  1990 U280 36'
Was:  2002 U270 36' (With a bathroom door) Build #5981
Is:  2021 Leisure Travel Van Wonder 24RL
2015 Jeep JKU, 2003 S10 QC 4x4 or 2017 C-Max
Lake Havasu City, AZ (or Gillette, WY)

Re: Adding Second Transfer Switch to Power only one A/C unit?

Reply #3 –
Good Morning!  This is exactly what I would like to install!  THANK YOU!  Since the original device is not available, can you tell me what specific parts I need to purchase so I can build one?  Would it be a single-circuit 20 amp manual transfer switch?  THANK YOU SO VERY MUCH :)
Jeff & Sandy
1997 American Eagle 40' Slide-less
2013 Toyota FJ Cruiser 4X4 Toad
Interested in Foretravel Coaches

Re: Adding Second Transfer Switch to Power only one A/C unit?

Reply #4 –
Quote from: JeffOnLakeConroe –
Good Morning!  This is exactly what I would like to install!  THANK YOU!  Since the original device is not available, can you tell me what specific parts I need to purchase so I can build one?  Would it be a single-circuit 20 amp manual transfer switch?  THANK YOU SO VERY MUCH :)
It is all in this connection box. It has a ckt breaker and the outlet with a pigtail.
The selected media item is not currently available.Barry BEAM #16014
2003 U320 40' AGDS
Beamalarm, Foretravel technical help and specifications
"Whatever the mind can conceive and believe, it can achieve"

Re: Adding Second Transfer Switch to Power only one A/C unit?

Reply #5 –
Quote from: Barry Beam –
It is all in this connection box. It has a ckt breaker and the outlet with a pigtail.

This is how my two previous motorhomes were connected to shore power, except that the male connector was at the end of a long cord and the female connector in the electrical box.  Standard practice in the days before automatic transfer switches.  In those cases, the female end wired to the generator and the male end to all 120 volt circuits in the rig.  Connect the two together, and the generator powers everything.  Disconnected, the male end gets connected to the power pedestal.  This device is the same, except the female end is connected to the ATS output, carrying either generator or shore power, and the male end only connects of one AC unit.
Tom Lang K6PG (originally  KC6UEC)
and Diane Lang
2003 38 U295 build 6209
2016 Jeep Grand Cherokee Summit Ecodiesel
still have tow-ready 2006 Acura MDX 
Temple City, California
Motorcade 16681 California Chapter President
SKP 16663 member of SKP Park of the Sierra, Coarsegold California
FMCA F071251
Retired electrical and electronic engineer

Re: Adding Second Transfer Switch to Power only one A/C unit?

Reply #6 –
The unit in the picture should be considered a MALE end.  The female part of the connection is always the power end.  If you can't touch the connectors it should be considered female.  The un-powered end is always MALE and has the pins exposed.  Things should never be wired so that powered contacts are touchable.

Keith
Keith, Joyce & Smokey the Australian Cattle Dog
1995 U320 SE Extreme 40' WTBI Build # 4780, with a Honda CR-V hopefully still following behind.
Motorcade # 17030
FMCA # F422159

Re: Adding Second Transfer Switch to Power only one A/C unit?

Reply #7 –
We connect to campground pedestal 30 amp + 20 amp two different ways. Both ways allow us to run both roof air conditioners.

We have a 'Y' cord that has two 30 amp male and one 50 amp female. They are available to buy and are easy to make. But because this arrangement shares a common neutral it will not work if either of the campground 30 or 20 is a GFCI socket. Most campground 20 amp sockets are GFCI. But this 'Y' cord has been quite handy if there are two 30 amp outlets available, as 30 amp is seldom GFCI protected.

The other way is basically simple and will run our rear AC during very hot weather on a campground 20 amp GFCI outlet because it can plugs the rear air directly into a campground outlet. When not using a separate campground outlet, the rear air is connected right back to breaker box for normal campground or generator operation. We just used this method again for several days in 100 degree temps and we were comfortable inside.

We went into main breaker box and disconnected the original Romex from rear air conditioner from circuit breaker (black wire), common neutral bus bar (white wire) & ground bus bar (green wire). We have two new short pieces of

12 Romex extending outside of breaker box near bedroom floor.

Inside the breaker box we connected one the new Romex cables to the connections where we just removed the rear AC wires, breaker, neutral & ground. The other end of this wire has a Romex compatible female socket.

Inside the breaker box we connected the 2nd new Romex to the original rear AC Romex cable using wire nuts & electric tape. The other end of this wire has a Romex compatible male plug.

Just plug the male into the female for normal operation. This connection is near our floor in front of bed.

To run the rear AC on campground GFCI outlet, plug the new male Romex plug into a #10 extension cable that has its male end plugged into the campground GFCI outlet. How the extension cable gets from the bedroom floor is a matter of personal creativity. It could be a simple as running the extension cable out a window.

We wired a new household kitchen 20 amp duplex outlet to a male plug in the water bay. For normal operation the outlet's male plug is in a motorhome bay outlet. To run rear air on GFCI, we plug the bay plug into an extension cord that is plugged into GFCI. Then we run a #10 extension cable from kitchen outlet to bedroom floor rear AC plug. This way we don't rely on running cable through a window.

Another way would be to permanently run a new Romex from a bay into bedroom. BarryBeam did a different way by running two new Romex cables from breaker box to bay, and for normal operation the two Romex's are connected together. To connect to GFCI the Romex's are separated with the rear AC connected to GFCI.
No reason why a 2nd transfer switch would not work, but the same cables would have to be run.

Re: Adding Second Transfer Switch to Power only one A/C unit?

Reply #8 –
THANK YOU VERY MUCH!  I am going to wire mine up using the 20 amp plug and receptacle pictured in post #7 :-)
Sure wish I had known about it four years ago after purchasing my coach, but better late than never! 
Jeff & Sandy
1997 American Eagle 40' Slide-less
2013 Toyota FJ Cruiser 4X4 Toad
Interested in Foretravel Coaches

Re: Adding Second Transfer Switch to Power only one A/C unit?

Reply #9 –
If #7 is our posting with the plugs on the foot of the bed near the floor, there is an additional benefit of having the new permanent kitchen outlet with bay plugs:

We once stopped at an Elks Lodge that had a bunch of 15/20 amp duplex outlets on a central common pole. We found we can plug our motorhome cable in to one outlet and plug our bay plugs into another so we could plug in a toaster or heater into the new kitchen outlet and in affect not be limited by the one 15/20 amp outlet. And now we use it for our rear air, too.