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Acceptable electrical load

Rvdude22
Explorer
Explorer
Good afternoon I have recently purchased a 2007 Keystone Cougar 289BHS. I am new to the world of RVs. With this in mind me and my wife are going to be living in the Rv full time. We do not plan on moving the rv for awhile since we have nothing big enough to pull it with. The RV is a 50 amp with a single ac at the moment I am planning on adding a second to help cool the rv. We are needing extra fridge and freezer space which we are planning on running a 4.5 cubic ft in the area where the bunk beds are and 5.3 cubic ft deep freezer that will sit out side. We also want to use a portable washer. The only other electronics that will be used is normal stuff that would be used for entertainment. With all of this information for what I am drawing for power. Will I need to do anything special to prevent electrical damage to anything in the rv? Also what are some tips that I should look for or do while living in the rv? Thank you anything is appreciated. 
18 REPLIES 18

pianotuna
Nomad II
Nomad II
Stickdog,

My peak load, using the OEM 30 amp, auxiliary 20 amp, and auxiliary 15 amp, is 7700 watts. At 120 volts that works out to about 64 amps.

The average load for a 25 hour period was about 5400 watts, or 45 amps (at 120 volts). So the continuous load was less than 80% of total capacity.

Total consumption was about 129 KWH in 24 hours.

120 volts is probably optimistic. I did not have the autoformer at that time.

The high for the day was -30 C (-22 f) and I was heating 100% electrically.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

stickdog
Explorer
Explorer
We have a 50 amp rig, in sig. Two AC, residential fridge, Splendidi 2100xl, 3cu freezer I have never seen a total over 60 amps on both legs combined.
9-11 WE WILL NEVER FORGET!
FULLTIME SINCE 2010
17 DRV MS 36rssb3
17 F350 King Ranch CC DRW 4x4 6.7 4:10 B&W hitch
John
“A good traveler has no fixed plans, and is not intent on arriving.” Lao Tzu

pianotuna
Nomad II
Nomad II
BB_TX wrote:
pianotuna wrote:
Although RV's are classed as plug in devices and so exempt from the National Electric Code, it is best practise to follow using 80% as the maximum continuous load.

For 15 amp service that is 12 amps
For 20 amp service that is 16 amps
For a 30 amp service that is 24 amps
For a 50 amp service that is 30 amps per leg

Try as best as you can to balance the two legs. Any imbalance is sent back via the Neutral wire.

Actually 80% of 50 is 40 amps.


Thanks for catching the typo! Nice to know some one reads my posts, too.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

enblethen
Nomad
Nomad
NEC Article 551 covers recreational vehicles electrical systems. Art 551-20 refers installation back to Parts I-V of the NEC.
Manufacturers don't follow it in many cases.

Bud
USAF Retired
Pace Arrow


2003 Chev Ice Road Tracker

BB_TX
Nomad
Nomad
pianotuna wrote:
Although RV's are classed as plug in devices and so exempt from the National Electric Code, it is best practise to follow using 80% as the maximum continuous load.

For 15 amp service that is 12 amps
For 20 amp service that is 16 amps
For a 30 amp service that is 24 amps
For a 50 amp service that is 30 amps per leg

Try as best as you can to balance the two legs. Any imbalance is sent back via the Neutral wire.

Actually 80% of 50 is 40 amps.

pianotuna
Nomad II
Nomad II
Although RV's are classed as plug in devices and so exempt from the National Electric Code continuous load requirements, it is best practise to follow using 80% as the maximum continuous load.

For 15 amp service that is 12 amps
For 20 amp service that is 16 amps
For a 30 amp service that is 24 amps
For a 50 amp service that is 40 amps per leg

Try as best as you can to balance the two legs. Any imbalance is sent back via the Neutral wire.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

CA_Traveler
Explorer III
Explorer III
BB_TX wrote:
theoldwizard1 wrote:
Just make sure the A/C units are on different "legs" of the 240V feed.
..........

Over simplifying. Balancing is a good idea. But before wiring in a 2nd A/C you need to look at how distribution is already done. If the existing A/C is on hot leg 1; and the water heater, microwave, converter, and that outlet used to operate the DW’s 1500 watt hair dryer are on hot leg 2, then hot leg 2 already far exceeds hot leg 1. Adding the 2nd A/C to hot leg 2 would compound the problem. In that case putting the 2nd A/C on hot leg 1 would make more sense. Or better, move some things from hot leg 2 to hot leg 1 before adding the 2nd A/C to hot leg 2.

Two A/Cs are 30 running amps or less. That is only 60% of the full 50 amps available for one leg if no other high current device is also connected to that hot leg.

Need to look at the big picture.
Great advice. Absolutely no reason why 2 A/Cs can't be on the same leg. Take this advice and look at the big picture.
2009 Holiday Rambler 42' Scepter with ISL 400 Cummins
750 Watts Solar Morningstar MPPT 60 Controller
2014 Grand Cherokee Overland

Bob

BB_TX
Nomad
Nomad
theoldwizard1 wrote:
Just make sure the A/C units are on different "legs" of the 240V feed.
..........

Over simplifying. Balancing is a good idea. But before wiring in a 2nd A/C you need to look at how distribution is already done. If the existing A/C is on hot leg 1; and the water heater, microwave, converter, and that outlet used to operate the DW’s 1500 watt hair dryer are on hot leg 2, then hot leg 2 already far exceeds hot leg 1. Adding the 2nd A/C to hot leg 2 would compound the problem. In that case putting the 2nd A/C on hot leg 1 would make more sense. Or better, move some things from hot leg 2 to hot leg 1 before adding the 2nd A/C to hot leg 2.

Two A/Cs are 30 running amps or less. That is only 60% of the full 50 amps available for one leg if no other high current device is also connected to that hot leg.

Need to look at the big picture.

valhalla360
Nomad
Nomad
BB_TX wrote:
If you exceed the amp rating of any of these that circuit breaker will trip before damage is done.


That's the theory...but if you are constantly pushing right up to the limits, it very much can still do damage without tripping the breaker, so if you have breakers trip once or twice a week, good chance you are pushing the system too hard.

It's not as common with 50amp rigs (compared to 30amp rigs) but if you are running a bunch of stuff, it's still a possibility.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV

pianotuna
Nomad II
Nomad II
Add the new items as much as possible in a balanced manner.

i.e. air conditioner 1 on one leg, the other on the other leg.

Monitor voltage. Campgrounds are endemic for low voltage. I shut down at 107 or add my autoformer to boost voltage.

It is good to check polarity and voltage under load before plugging in your RV.

The best of the add on energy management devices may be the Hughes PWD50-EPO-H Power Watchdog Smart Bluetooth Surge Protector Plus EPO with Auto Shutoff - 50 Amp Hardwire Version. The one thing I do not like is the cut out voltage which is at 104--to low for my comfort zone.

https://hughesautoformers.com/wp-content/uploads/2019/02/PWD-EPO-H-instructions.pdf
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

theoldwizard1
Explorer
Explorer
Just make sure the A/C units are on different "legs" of the 240V feed.

Before you pull the trigger, you might want to consider installing a mini-split heat pump with dual ceiling cassettes.

Flute_Man
Explorer
Explorer
I would recommend getting an energy management system from progressive industries. It monitors the power at the pedestal and if anything happens high-voltage etc. because of some fault in the underground cabling The Progressive Industries unit will cut the power to your trailer. Get the best one that you can find. It is cheap insurance compared to the appliances that could be damaged if there is a fault in the pedestal.

I do not repeat do not recommend your freezers be on a GFCI circuit. They are very sensitive units and if it would trip your freezer would shut off.

You may call me if you wish and we can talk about a lot of other things as well.
Jerry Parr
05 Mandalay 40B
Cat C7 350
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Ham Radio K7OU
Retired EE
Jrparr32@gmail.com
602-321-8141
Full-timer

GordonThree
Explorer
Explorer
Only problem I could see you running into is weight issues, two large freezers loaded up, how many pounds is that?

Otherwise, can the park provide adequate amperage service? I've seen low voltage fairly often at busy parks. Low voltage is an equipment killer.
2013 KZ Sportsmen Classic 200, 20 ft TT
2020 RAM 1500, 5.7 4x4, 8 speed

time2roll
Explorer II
Explorer II
With a 50 amp RV you should not have any issues. Although you may want to check voltage is good (108+) in the hot afternoon when all the neighbors are running air conditioning.