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valhalla360

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Posted: 07/28/20 11:03am Link  |  Quote  |  Print  |  Notify Moderator

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.


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BB_TX

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Posted: 07/28/20 12:20pm Link  |  Quote  |  Print  |  Notify Moderator

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.

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Posted: 07/28/20 01:27pm Link  |  Quote  |  Print  |  Notify Moderator

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.


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Posted: 07/28/20 05:08pm Link  |  Quote  |  Print  |  Notify Moderator

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.

* This post was last edited 07/28/20 06:43pm by pianotuna *   View edit history


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BB_TX

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Posted: 07/28/20 05:29pm Link  |  Quote  |  Print  |  Notify Moderator

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.

enblethen

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Posted: 07/28/20 06:03pm Link  |  Quote  |  Print  |  Notify Moderator

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.


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pianotuna

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Posted: 07/28/20 06:35pm Link  |  Quote  |  Print  |  Notify Moderator

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.

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Posted: 07/28/20 11:37pm Link  |  Quote  |  Print  |  Notify Moderator

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.


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pianotuna

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Posted: 07/29/20 02:13am Link  |  Quote  |  Print  |  Notify Moderator

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.

* This post was edited 07/29/20 02:26am by pianotuna *

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