Add second air conditioner to 30 amp RV

[rickfraza]

I'm looking for advice from either a Master Electrician or Electrical Engineer on this question. I've seen a video showing how to add a second air conditioner to a 30 amp RV. The video shows wiring a 13.5 BTU unit to an outside 15 amp plug and then connecting to the 20 amp outlet on the RV pedestal with a short (25') 10 awg extension cord. That would leave the RV on the 30 amp service, while powering the air conditioner using the 20 amp outlet. Power consumption for the air conditioner is stated as 1670 watts which should be between 13.9-14.6 amps. The 20 amp breaker should handle 16 amps continuously. I know when air conditioners first start that they pull more amps (~16A) very briefly before they drop to their "run" amperage. Would it be smarter to use the 50 amp service with one of those 50A pigtails that provides 2 x 30 amp outlets? The RV would be plugged into one of the 30 amp outlets with a surge protector and the other outlet would be plugged into the second air conditioner using a 30->20 amp dog bone adapter. Or would it be better to plug the 30A service in as always, and only plug the air conditioner into one of the 30A outlets with that 30-20 adapter? Or should I just plug the A/C in directly to the 20A outlet and the RV into the 30A outlet? If this doesn't work, I'm afraid my wife will insist on either only using the RV when it's cold, or getting rid of it altogether.

[dougrainer]

CA Traveler wrote:
Yes the dealer orders the units but it's the buyers who want a cheaper unit probably believing the salesman. ie The inexperienced buyers or those buying cheap with prior knowledge.

BINGO:B Doug

We TRY to educate the customer, but they run to that $1000 cheaper unit with the one AC.

[CA_Traveler]

Yes the dealer orders the units but it's the buyers who want a cheaper unit probably believing the salesman. ie The inexperienced buyers or those buying cheap with prior knowledge.

[map40]

1) You can use a 50 splitter, that would work great.
2) You can install an Atwood air command, it will work on a 15 amp plug on its own with no problem (I have 5 RVs configured like this and they have been running for 4 years as rentals)
3) You can install 2 Atwood air command or 2 Power Saver ACs and run them on the 30 amp. It will be tight, but it will work if you know how to manage them
Hope it helps.

[dougrainer]

myredracer wrote:

rickfraza wrote:
.BTW - I don't understand why manufacturers are still building larger RVs with 30A service.

Up until 2005, the NEC only required 5% of a CG/RV park to have 50 amp sites. Then in 2002, it was changed to 20%. In 2017, it was increased to 40% of CGs required to have 50 amp sites. Finding 50 amp sites can be very difficult. Some CGs and RV parks may have built above the min. code requirements such as casinos and some gov't facilities for ex.

Unless we had a larger RV, I'm quite happy with 30 amps. There's been a few times when one AC unit hasn't been quite enough but wouldn't want 50 amps and have to plug into 30 amp pedestals with adapters most of the time. I see 50 amp RVs all the time using 30 amp pedestals including very expensive large MHs. One thing for sure, you won't find dealers or RV manufacturers telling potential buyers that 50 amps may be hard to find.

COST, Plain and simple. Just like when Car dealers advertise a CHEAP entry level Auto at the cannot believe the price. They order those cars with NO AC systems. Drops the cost and then they attempt to get you to upgrade to the higher price car. This is not Bait and switch. They DO HAVE the car as advertised, just not with the normal required equipment. Look at various posts on this forum where people have large RV's that have both 30 and 50 amp. The ones with 50 amp and over 28 foot long and have 1 AC unit complain that the unit cannot keep the unit cold when it is hot outside. The Dealer ordered that unit with 1 AC to keep the cost lower. Units with 30 amp service with 1 AC are built and sold to keep that advertised price a few thousands dollars less than the competition. Manufacturers do NOT dictate this. It is the Local dealers that drive the practice. Doug

[htwheelz67]

I added one to my fs3000 ww, it was already wired but there was no space in the panel for an additional breaker, so I added a small circuit breaker box with 10g pigtail, it was also wired for another outlet next to my 30A plug so I added one for use with the genny, I use a 50a ext cable plugged into a splitter that gives me a 30A rv plug and a 20 amp regular plug, it works perfect and I can still use my 30A cord if there is no 50A available. I cut my long 30A cord and made an ext cord out of it, the 50a ext cord goes right up to the trailer then splits at that point. one last point, I had to replace my existing ac as well so I bought 2 of the Dometic Brisk Air II High Efficiency ac's which only pull 11.4 amps and can be used with a 15a breaker. you can easily run 2 of a 4k genny.

[MEXICOWANDERER]

Manufacturers asssssssssssume or refuse to ponder the fact that a customer would buy their product and -not- drive it to a power pedestal where it will spend the rest of its life connected until the wrecker comes for the remains 15-years later.

By the way, WFCO offered me a warehouse distributorship an agreement in which said if I purchased 50 units annually the price would be 30% of retail but I must not under any circumstances sell the unit retail. This meant a -70% discount. Out the window and into the dumpster.

I did get OEM pink sheet on Dometic primarily for their FC540 chest freezers.

[CA_Traveler]

rickfraza wrote:
I understand that the 50A service actually provides 2 legs of 120V (L0-L1 & L0-L2) @ 30A and this is why I asked if using the 50A pedestal outlet would be a better option than plugging into the 20A outlet.
The 50A service is 50A on each leg at 120V or 50A at 240V or a combination of both 120V and 240V not to exceed 50A on either leg. Very few RVs have 240 appliances.

I have not been able to find a 20A EMS unit.
The 30A EMS will work. They ignore amps except for the display.

BTW - I don't understand why manufacturers are still building larger RVs with 30A service. The additional cost must be less than $1000, and anyone who wants to install a second A/C unit is forced to jerry-rig something that should have been a straight forward modification.
The buyers don't want to pay for something they are clueless about.

[myredracer]

rickfraza wrote:
.BTW - I don't understand why manufacturers are still building larger RVs with 30A service.

Up until 2005, the NEC only required 5% of a CG/RV park to have 50 amp sites. Then in 2002, it was changed to 20%. In 2017, it was increased to 40% of CGs required to have 50 amp sites. Finding 50 amp sites can be very difficult. Some CGs and RV parks may have built above the min. code requirements such as casinos and some gov't facilities for ex.

Unless we had a larger RV, I'm quite happy with 30 amps. There's been a few times when one AC unit hasn't been quite enough but wouldn't want 50 amps and have to plug into 30 amp pedestals with adapters most of the time. I see 50 amp RVs all the time using 30 amp pedestals including very expensive large MHs. One thing for sure, you won't find dealers or RV manufacturers telling potential buyers that 50 amps may be hard to find.

[rickfraza]

Thanks for all your comments and help. My intent is to not disturb the existing RV 30A wiring system. Rather, the new A/C unit would be on a completely separate circuit wired to a plug mounted on the outside of the RV. To power the A/C, a 10awg extension cord would be run between that plug and the 5-20A outlet in the pedestal. I understood this could possibly cause the circuit breaker to pop, so I wondered if there was a better method. I am neither an engineer or an electrician, but I have experience with electrical circuits. I understand that the 50A service actually provides 2 legs of 120V (L0-L1 & L0-L2) @ 30A and this is why I asked if using the 50A pedestal outlet would be a better option than plugging into the 20A outlet. I have not been able to find a 20A EMS unit. BTW - I don't understand why manufacturers are still building larger RVs with 30A service. The additional cost must be less than $1000, and anyone who wants to install a second A/C unit is forced to jerry-rig something that should have been a straight forward modification.

[MEXICOWANDERER]

My aim was to avoid Mississippi riverboat grade workarounds. I've seen some real off-the-wall

"But if we..."

[myredracer]

I would add that ALL pedestals require a 20 amp receptacle by code. But the NEC does NOT require the wiring to a pedestal to be sized for the 20 plus 30 amp receptacles to be used simultaneously and may be only #10 wire protected by a 30 amp breaker in a CG panel. You won't have 50 amps (30 + 20 @ 120 volts) available unless you're in a newer CG with loop-fed pedestals or a pedestal has 50 amps.

You would have no problem using a 30 to 50 amp adapter along with a separate connection to the 20 amp recept. other than monitoring the voltage.

[CA_Traveler]

MEXICOWANDERER wrote:
Running a pair of A/C means every so often in a hot climate they BOTH will want to high head pressure re-start simultaneously.

That's when compressor motors will fry and other electrical has to deal with an 80-volt brownout.

Mex That's changed for some rigs. Since 04 my rigs A/Cs have a 12V controller connected with a data cable to the thermostat. They controls won't allow multiple starts at the same time in addition to other functions.

[Boomerweps]

Your basic plan is solid. An EMS, as suggested, is a good thing to have but would not cover a separated, add on power supply. I added a seperate 15/20 amp inlet on my TT that supplies one duplex outlet inside. So I can separately run a power hog off that while running my Air Conditioning or microwave (not at the same time). I can run an electric heater, toaster, electric fry pan, or coffee maker off the new power supply and not drag down the main power.

[MEXICOWANDERER]

Running a pair of A/C means every so often in a hot climate they BOTH will want to high head pressure re-start simultaneously.

That's when compressor motors will fry and other electrical has to deal with an 80-volt brownout.

Use a pair of 30-amp relays in the feed line. And an ON/ON toggle switch. Either or. This is the only safe way when a single 30-amp service is the only power available.