30 amp shore power Run both Airs

[yeloduster]

So you have an RV with two Air Conditioners, a 30 Amp shore service and a 5500 Watt Generator. You can run both Airs at the same time on the generator and switches let you choose to run either Air on shore power but not both! How frustrating is that!

I’ve seen this addressed in other threads on IRV2 and some have posted that they added an additional power cord to shore power to run one of the Air Conditioners while the existing 30 AMP shore power cord runs the other. Searches of the forum didn’t produce any details of how they accomplished this.

Although I boondock on most of my trips and rarely park anywhere that has any hookups but I decided to make this modification to my MH…just because I could!

Investigation revealed that when on shore power the Air Conditioner selection switches allowed operation of either of the Air Conditioners as expected. I discovered that the 20 Amp output of the generator was connected directly to the Air Conditioner selection switches. The switches only allowed the front air to connect to the generator and the 20 Amp generator circuit powers nothing but the Front Air Conditioner. The 30 Amp output from the generator powers the rear Air Conditioner and everything else in the MH. I saw where other people stated that their rear Air Conditioner was connected to the Generator 20 Amp. That does not change my design.

The 20 Amp generator circuit is diagramed in the first attached drawing.

I determined that I could cut the circuit between the generator and the Air Conditioner selection switches. I could then add a 20 Amp power cord from shore power and insert another selection switch in between the generator and the Air Conditioner selection switches.

The only circuit protection when the generator is running the Front Air Conditioner is the 20 Amp circuit breaker mounted on the generator. I needed circuit protection for my added power cord so I also added a 20 Amp circuit breaker for the 20 Amp shore power service that I added.

See the second drawing. It is a diagram of the circuit after modification. The switch in the diagram is set in the shore power mode. I tried to indicate where I used existing wiring and where I added new on the drawing.

Here is my material list:

• 30 Amp DPDT switch

• Circuit breaker receptacle and 20 Amp circuit breaker

• 2 deep junction boxes I used 2 different types depending on mounting.
  The boxes need to be deep because there are a lot of wire and wire nuts in them.

• Approximately 20’ of 12 2 with ground Romex

• Wire nuts

• External service extension cord with 12 gauge wire.

I won’t go into detail about the specifics of installation other than to say that I cut the receptacle end from the extension cord and routed it beside the existing 30 AMP shore service cord. Installation will vary from RV to RV depending on how the wiring is routed.

The pictures are as follows:

• 30 Amp DPDT switch

• Circuit breaker receptacle

• 20 Amp circuit breaker

• Circuit breaker junction box after installation under bedroom cabinet drawers

• Switch junction box mounted to wall below a closet

• Generator/Shore power selection switch alongside of existing Air Conditioner selection switches

• Everything finished and buttoned up

The bottom drawer in the cabinet would not close all the way after I added the circuit breaker junction box. I cut the drawer down as shown in the last 2 pictures.

When the new selector switch is set to Generator everything works exactly as it did before the modification. When the new selector switch is set to Shore everything is still the same except the new 20 Amp power cord must be connected to 20 Amp shore power for the front Air to work.

If anyone decides to do this I hope my post helps.

Maybe next I will make an adapter so I can plug my 2 shore power cords into a 50 amp service! I will then almost have a 50 Amp service motorhome!

[Waiter21]

Looks like you solved the problem.

I did it in a similar way. My Generator has two circuits, a 30 amp feeds the normal circuit breaker panel. then a separate 20 amp circuit feeds the rear A/C unit when on generator power.

I cut the 20 amp circuit open and added a receptacle and a plug. I normally leave rear A/C unit plugged into the genny, but when on shore power, I can use an extension cord and plug it into a 20 amp receptacle on a pedestal.

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


..

[creativepart]

Our 2017 Adventurer has a Precision Circuits Power Control System that allows both ACs to run on 30-amp. The PCS controls all electrical loads and sheds loads when there are not enough amps coming in to the RV.

For us, the PCS starts one AC fan, and then the compressor and after that compressor start happens the AC uses less amps to keep it running. Then assuming that no other large electric loads are needed it starts the fan on the second AC and then it's compressor as well.

There are times when it's running both ACs and both compressors at the same time, and others when it runs the fan and compressor on one AC but only keeps the fan running on the other AC. And when this happens it goes back and forth between the two ACs every few minutes running this way.

Use the microwave and all ACs drop to FAN only or off completely.

Also, the PCS is connected to our Magnum MS2012 Inverter and when the inverter is idling in the ON position it will barrow some amps from the inverter via the battery bank. The inverter is also our charger so it can lower the charge rate based on the power needed to run the ACs.

We try not to rely on 30amp service when it's in the high 90's and above (because Texas) but we find this system works great. We have a 30-amp outlet in our garage and when we bring the RV home to get ready for a trip or for cleaning upon return we use it to keep the RV cool at our San Antonio home and find it quite adequate.

[twinboat]

Originally Posted by creativepart

Our 2017 Adventurer has a Precision Circuits Power Control System that allows both ACs to run on 30-amp. The PCS controls all electrical loads and sheds loads when there are not enough amps coming in to the RV.

For us, the PCS starts one AC fan, and then the compressor and after that compressor start happens the AC uses less amps to keep it running. Then assuming that no other large electric loads are needed it starts the fan on the second AC and then it's compressor as well.

There are times when it's running both ACs and both compressors at the same time, and others when it runs the fan and compressor on one AC but only keeps the fan running on the other AC. And when this happens it goes back and forth between the two ACs every few minutes running this way.

Use the microwave and all ACs drop to FAN only or off completely.

Also, the PCS is connected to our Magnum MS2012 Inverter and when the inverter is idling in the ON position it will barrow some amps from the inverter via the battery bank. The inverter is also our charger so it can lower the charge rate based on the power needed to run the ACs.

We try not to rely on 30amp service when it's in the high 90's and above (because Texas) but we find this system works great. We have a 30-amp outlet in our garage and when we bring the RV home to get ready for a trip or for cleaning upon return we use it to keep the RV cool at our San Antonio home and find it quite adequate.

Wow, that would be a lot of $ and work, rewiring most of the electrical system and installing all of that equipment into a 2003 gas Motorhome.

I like his fix better.

[yeloduster]

Originally Posted by twinboat

Wow, that would be a lot of $ and work, rewiring most of the electrical system and installing all of that equipment into a 2003 gas Motorhome.

I like his fix better.

I didn't mention because I was unaware of the system that juggles power to make things work on 30 Amp circuit. With my fix everything works all the time provided you have a 30 Amp and 20 Amp circuit to plug into.

Most 30 Amp power pedestals in RV parks have a 20 Amp circuit to plug into as I do at home.

[yeloduster]

Originally Posted by twinboat

Wow, that would be a lot of $ and work, rewiring most of the electrical system and installing all of that equipment into a 2003 gas Motorhome.

I like his fix better.

I didn't mention because I was unaware of the system that juggles power to make things work on 30 Amp circuit. With my fix everything works all the time provided you have a 30 Amp and 20 Amp circuit to plug into.

Most 30 Amp power pedestals in RV parks have a 20 Amp circuit to plug into as I do at home.

I forgot to mention that the DPDT switch should have a center OFF position. This precludes accidentally connecting Generator and Shore power together.

[RKins]

There's one plus to having an old coach with 13.5kbtu ACs. Making sure to have WH and Frig on gas, I can actually run both AC on a 30 A ckt. Don't try to run any other heavy load though, unless you turn off one or both AC.

[CJ7365]

Pretty retarded for a manufacturer to just put in 30amps and then install 2 A/C units, are they still doing this?

OP way to over come the manufacturer incompetence

[96 Wideglide]

Have a friend with a 30' Tiffin gasser, which came with only one ac, but the MH is 50A!

[sibe]

The setup provided by the OP is pretty good my only concern is that is may not be universal to all units..

That swtich will be a weak link IMO,, and can get warm when AC is cycling on hi fan.. especially a 13.5, a smaller may be OK..

I have run both a 13.5 and an 11K on a heavy duty cord with 20AMP ends or a twist lock.. The 10/11K is OK..

Most recepticles on the RV pole are 15amp or maybe a basic 20,, then you stretch a 25 foot cord.. the ends may get warm.. I fried a recpt in a 2200w genny.. or the cord fried... either way, NO AC until I did a fast hard wire with wire nuts LOL.. 0nj my 11K powersaver AC in trailer..

AGAIN a well thought plan, I like HD over kill wiring with AC Loads , compressers etc..

[RKins]

For me I should have clarified, my old coach is a 50A service but I have to use 30A dog bone at State parks.

[EJW]

Originally Posted by CJ7365

Pretty retarded for a manufacturer to just put in 30amps and then install 2 A/C units, are they still doing this?

OP way to over come the manufacturer incompetence

Our 2019 Jayco Chateau is this way - 30amps, 2 A/C's. We have a Precision Circuits PCS (MIDI PCS?) that does load shedding if the 2 A/Cs are on together.
The coach is new this year and we haven't put it through all it's paces yet.

Used it for 5 days during some hot, A/C weather. Worked well. But that was just 1 time.

Kinda weird letting the system do the shedding (I think up to 5 loads). Coffee was no problem in the morning.

It reminded me of how strange autopilot was at first and learning to trust George.

Still being vigilant and watching the total load.

50AMPs would be nice to have, but this will do.

The OP solution is impressive. The older I get the more I wish I went to our county vo-tech. Sociology isn't too helpful with RVs.

[yeloduster]

Originally Posted by sibe

The setup provided by the OP is pretty good my only concern is that is may not be universal to all units..

That swtich will be a weak link IMO,, and can get warm when AC is cycling on hi fan.. especially a 13.5, a smaller may be OK..

I have run both a 13.5 and an 11K on a heavy duty cord with 20AMP ends or a twist lock.. The 10/11K is OK..

Most recepticles on the RV pole are 15amp or maybe a basic 20,, then you stretch a 25 foot cord.. the ends may get warm.. I fried a recpt in a 2200w genny.. or the cord fried... either way, NO AC until I did a fast hard wire with wire nuts LOL.. 0nj my 11K powersaver AC in trailer..

AGAIN a well thought plan, I like HD over kill wiring with AC Loads , compressers etc..

The switch I chose is a 30 Amp DPDT switch. The extension cord is 12 guage rated at 20 Amp. The circuit is protected with a 20 Amp circuit breaker. After several hours of running I couldn't detect any warming of the extension cord or its plug. It is possible to plug my extension cord into a 15 Amp socket although I've never seen 15 Amp service on an RV park pedestal. They all seem to be 20 Amp.

I measured the current draw while running the air conditioner. It draws 10 Amps. I'm sure that start up current is considerably higher than 10 Amp but the surge current doesn't last long enough to heat any of the system components and it is not high enough to trip a 20 Amp breaker. In every case the current is well below the limits set by the system components. Consider, when running the A/C on generator the circuit is protected by a 20 Amp breaker on the generator. In my design the circuit is also protected by a 20 Amp breaker. From a safety perspective nothing is different.

In my design the only thing the extension cord runs is one air conditioner all the rest of the MH is the original wiring. I've added no additional burden to the MH manufacturers electrical circuits.

I agree, what I've done may not be universal to all units. I say with a smile proceed at your own peril!

Thanks for your comments sibe. They help identify issues that need to be addressed if anyone should they consider doing this.