Trailer Life Magazine Open Roads Forum: Add second air conditioner to 30 amp RV
Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Tech Issues

Open Roads Forum  >  Tech Issues

 > Add second air conditioner to 30 amp RV

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 3  
Next
Sponsored By:
rickfraza

Texas

New Member

Joined: 10/23/2015

View Profile



Good Sam RV Club Member

Offline
Posted: 07/13/19 06:22pm Link  |  Quote  |  Print  |  Notify Moderator

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.

1492

Arlington, VA

Moderator

Joined: 04/08/2005

View Profile



Posted: 07/13/19 11:31pm Link  |  Quote  |  Print  |  Notify Moderator

Moved from Forum Posting Help and Support

wa8yxm

Wherever I happen to park

Senior Member

Joined: 07/04/2006

View Profile


Offline
Posted: 07/14/19 06:02am Link  |  Quote  |  Print  |  Notify Moderator

Always smarter to use 50 amp if you got it (My opinion)

BUt I have a 50 amp rig. I "Broke out" (Technical term) the bedroom A/C so that when I'm on a 30 amp site I open a door pull a plug and now the Rear A/C is independent of the RV. I use a 12ga cord to the park's 20 amp breaker

Suggest the following hookup for the added A/C also suggest you go 15000 BTU I mean for a few dollars more you get more cooling and as the world warms. YOU WILL NEED IT.

A/C----Single breaker box, 20 amps----- 20 amp (Twist lock) Inlet

20 amp (Twist lock) 12ga cord----------- Park 20 amp outlet .


ON a 50 amp site you have choices

1: will need to buy or build a "Break out" box 50 amp male plug. Two breakers (1-20 1-30) TT-30 outlet and a 15/20 Duplex receptacle

I'd add a few neon Lamp indicators to show things like good safety ground and such but hey that's technical stuff.

The other.. Use the park's 20 amp outlet for the A/c
Feed the RV by either using a 30-50 Dogbone or off the park's TT-30

You won't overload the circuit using any of those methods.


Home is where I park it.
Kenwood TS-2000 housed in a 2005 Damon Intruder 377


CA Traveler

The Western States

Senior Member

Joined: 01/03/2004

View Profile


Offline
Posted: 07/14/19 08:11am Link  |  Quote  |  Print  |  Notify Moderator

rickfraza wrote:

Would it be smarter to use the 50 amp service with one of those 50A pigtails that provides 2 x 30 amp outlets?
The cheater cord does not work with a 20A GFCI plug. There are also safety issues that need to be considered. But RV stores are happy to sell you one anyway.

Knowledgeable CGs will not allow it even though most really don't understand why.

With some panning it's straightforward to modify the A/C with a plug so you can connect it to a 20A pedestal plug.


2009 Holiday Rambler 42' Scepter with ISL 400 Cummins
750 Watts Solar Morningstar MPPT 60 Controller
2014 Grand Cherokee Overland

Bob


Chris Bryant

Arden, North Carolina

Senior Member

Joined: 03/26/2003

View Profile



Posted: 07/14/19 09:03am Link  |  Quote  |  Print  |  Notify Moderator

I would not use a 50-30/30 adapter, as that would be running that cord and air conditioner on a 50 amp breaker- not safe. If you like, you can build a breakout box with breakers like John said.


-- Chris Bryant
My RV Service Blog
The RV.net Blog

CA Traveler

The Western States

Senior Member

Joined: 01/03/2004

View Profile


Offline
Posted: 07/14/19 09:21am Link  |  Quote  |  Print  |  Notify Moderator

Chris Bryant wrote:

I would not use a 50-30/30 adapter, as that would be running that cord and air conditioner on a 50 amp breaker- not safe. If you like, you can build a breakout box with breakers like John said.
Basically agree but would say not as safe. The chance of drawing say 49A on one leg is very slim. But a defective cord etc could cause a problem. Ditto for a 50/30 adapter.

RLS7201

Beautyful Downtown Gladstone, MO

Senior Member

Joined: 10/26/2002

View Profile


Offline
Posted: 07/14/19 09:38am Link  |  Quote  |  Print  |  Notify Moderator

I do just as you describe, with my 2 A/Cs on a 30 amp coach. A 20 amp cheater cord WILL work with a GFCI if you make sure the ground and neutral are not bonded. Much easier than rewiring your coach for 50 amp.

Richard


If I had a dollar for every girl that found me unattractive,
they would eventually, find me attractive.

95 Bounder 32H F53
460/528 stroker
Web Master
MWPSchooners.com

CA Traveler

The Western States

Senior Member

Joined: 01/03/2004

View Profile


Offline
Posted: 07/14/19 09:51am Link  |  Quote  |  Print  |  Notify Moderator

RLS7201 wrote:

I do just as you describe, with my 2 A/Cs on a 30 amp coach. A 20 amp cheater cord WILL work with a GFCI if you make sure the ground and neutral are not bonded. Much easier than rewiring your coach for 50 amp.

Richard
What is a 20A cheater cord? I'm familiar with 50-30/30 and 50-30/20 cheater cords which will trip a GFCI. Nothing to do with neutral/ground bonding which occurs in a service panel.

Are you referring to incorrect ground/neutral bonding in the rig?

myredracer

Langley B.C.

Senior Member

Joined: 04/27/2013

View Profile


Offline
Posted: 07/14/19 12:55pm Link  |  Quote  |  Print  |  Notify Moderator

Some comments:

- Running two AC units on 30 amps is a bad idea. You're looking at 2 units at 13 amps, plus at least a few amps for the converter, plus whatever else might be running on 120 volts. While a 30 amp breaker (in your RV or pedestal) technically speaking can run indefinitely at 30 amps, it will get very hot due to the thermal elements in breakers. To make it worse, RV panels have the 20 amp AC breaker right below the 30 amp main breaker. Besides the heat, the breakers can eventually trip.

- AC units have a 20 amp breaker which is sized to ensure it won't trip on the momentary startup inrush current, it's not based on the full load running current.

- Momentary startup inrush current is in the 50-60 amp range.

- Voltage is extremely important when running AC units. If the voltage gets down to 105 volts or less, that will cause damage to the motor windings. AC units will draw more current as the voltage goes down which will exacerbate voltage drop.

- Voltage may *look* okay when running, but can drop very low during startup and lead to AC damage.

- AC unit damage is cumulative over time and it can fail prematurely one day for no apparent reason. AC units are expensive to replace.

- Running a 2nd AC unit off the 20 amp breaker in pedestal may or may not work. "Modern" CGs have loop-fed pedestals on large amperage wire (like say 200 amps) and the possibility of excessive voltage drop is significantly reduced. Older CGs have distribution panels spread around the property with small gauge wire to pedestals, which can be as small as #10 wire and thus voltage drop can be high plus wiring runs to the pedestals can be long, further increasing voltage drop.

- If you plan to travel around a lot and not stay exclusively at newer CGs/RV parks with loop-fed pedestals, do not expect running a 2nd AC unit off the pedestal 20 amp breaker to work.

- Installing a permanently mounted voltmeter inside an RV is highly recommended. An EMS unit is also recommended.

- Choosing a site close to a pad-mounted transformer in a CG can help in some cases.


Gil, Deb & Dougal a 15 year old Springer Spaniel
2014 KZ Spree 262RKS, Reese DC WDH, shocks and Endurance LRE tires
2012 GMC Sierra 2500HD crew cab, Bilstein shocks, heavy duty trailering option


MEXICOWANDERER

las peƱas, michoacan, mexico

Senior Member

Joined: 06/01/2007

View Profile


Offline
Posted: 07/14/19 01:09pm Link  |  Quote  |  Print  |  Notify Moderator

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.

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 3  
Next

Open Roads Forum  >  Tech Issues

 > Add second air conditioner to 30 amp RV
Search:   Advanced Search

Search only in Tech Issues


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:

© 2019 CWI, Inc. © 2019 Good Sam Enterprises, LLC. All Rights Reserved. | Terms of Use | PRIVACY POLICY | YOUR PRIVACY RIGHTS