50 amp MH, plugged into 30 amp, ok to run 2 ac units??

wa8yxm wrote:
...I have run two 13,500 BTU 13.5 Amp A/Cs on 30 amp, With the batteries fully charged and no other loads. Measured draw 27 amps As a TEST...

And what were your results? Did the breaker trip? If not why do you not recommend it? The breaker is rated for 30 amps and you think 27 amps is too much. I guess I'm missing something. Seems some are looking at the NEC spec related to continuous loads and applying it to all branch circuits. Also, I don't care where the breaker was made. If a 30 amp breaker trips at 27 amps it needs to be replaced. What amperage would you suggest, apparently you feel 27 amps is too much? Maybe 25 amps or say 24 which would meet the NEC spec for continuous loads. What if it's a cheap Chinese made breaker and trips at 24 amps or 20 amps? What do you do then, limit your load to 19 amps. If a 30 amp breaker can't handle 30 amps there's something wrong with it. Now I'm not talking about continuous loads as described in the NEC spec, I'm referring to our RVs or homes.

Hank MI wrote:
Circuit breakers are designed to handle their rated current indefinitely at an ambient temperature of 104 degrees in open surroundings if manufactured to meet UL standard 489.

I will point out only that there is a big "IF" there.. not all manufactgurers are that good.

And 2nd. there is also a "Margin of error" as I recall. So yes, if it is properly designed and built and brand new.. It should perform as you cite, but if it's older, or has been abused, or was made in china.. I'd not bet on it.

I have run two 13,500 BTU 13.5 Amp A/Cs on 30 amp, With the batteries fully charged and no other loads. Measured draw 27 amps As a TEST.

But I9 don't recommend it. Oh yes, and I'd JUST cleaned the condensers (like 5 minutes ago just).

dezolen wrote:
Wow 5 pages of posts to say no.

If you got a resounding "NO" out of these 5 pages, I'm not sure I've been reading the same thread??? ;)

Wow 5 pages of posts to say no.

dougrainer wrote:
For ScottG. I looked up the breaker info at work from the NEC. Doug

Circuit Breaker Ampere Ratings

Circuit breakers have an ampere rating (typically marked on the end of the operating handle). This is the maximum continuous current that the breaker can carry without exceeding its rating. As a general rule the circuit breaker’s ampere rating should be the same as the conductor’s ampacity.

Circuit breakers are designed to handle their rated current indefinitely at an ambient temperature of 104 degrees in open surroundings if manufactured to meet UL standard 489. Breakers are seldom mounted in open air. Mount it in a breaker panel with a cover, surrounded by other breakers generating heat and everything changes. Hence the NEC 80% load rating for continuous loads. Now an RV is not considered a continuous load. It's expected that A/C compressors, fridges, water heaters will cycle on and off. Certainly in hot weather 2 A/C compressors may run continuously for more than 3 hours. Does that mean the breaker will pop, maybe, maybe not. You have to account for the other factors. Temp, other breakers in the panel and what their load factor is and the type of enclosure.

So you can't make a blanket statement that a breaker can only be loaded to 80% of it's rated capacity because it's just not true. If you run at full capacity and exceed the '3 hour continuous load' does that mean the breaker will trip? Again, maybe, maybe not.

I have never thought there was a solid "Yes" or "No" answer to this, as you can see by the various answers above. Not all RVs and electrical circuits are made equal.

Now my opinion. the 30 amp CB will do what it is designed to do. Overload it in Amp draw and it will pop. That's a good thing. Now, if the volts start drop, the CB will not trip. That is a problem as many AC are rated at 115 volts +/- 10%. That means low side is 104 volts. Once volts drop below that, heat rises, you start causing damage to the AC (and other items, if in use).

I have had success in running my 15K and 13.5K at the same time, but only in pristine conditions, like a 30 amp CB with nothing else on it, including that 20 amp socket that should not be but sometimes is drawing from the same source. Also, as some mentioned, you need to turn everything else off.

This weekend, I was at a CG, with some friends, which had very old wiring. There were a few of us, which had 30 amp circuits, but we did not know where that went and if there was truly a 200 amp or 400 amp CB down the line. Well I have a PI 50 Amp EMS, I heard my 1 AC kick off and sure enough the whole coach was dead. While I was checking the Kill-A-Watt, the power came back on. I watched the volts start at 113 volts and then drop to 70.9 when my AC came on. My EMS did it's job again, by shutting off the source. Thank you PI for saving me.

I turned of the one AC I was running, started the genny and then turned on both AC for the afternoon heat.

I told the others of what I saw but they insisted that they were fine. One guy had a Fluke and checked his a couple of times but said it was staying at about 113 volts.

MH is at home and I can run both AC and the volts never dip below 118 volts.

I suggest a PI 50 EMS. With that you do not need a Kill-A-Watt (or voltmeter) to detect the problem. It will tell you about it. The Kill-A-Watt is still a good, live tool.

To address a couple things

The "30 amps is only rated for 24, (I thought it wazs 27) amps continous applies to the circuit breaker.. But though the plug is rated for 30 full time.. Darn few can survive that.

Second: To answer the O/P's question

The only danger in running both A/Cs at the same time is the click of darkness.

That is. Tripping the circuit breaker.. If it does not trip.. you are good to go

DO, however, monitor voltage and check the plug for signs of melting.

doug i appreciate all the time and knowledge you are willing to share.
i am not a sparky but sold and repaired electric motors for about twenty years.
and agree with you.

Doug you are kinda talking out of both sides of your mouth. You started with the "the simple answer is NO". Now you continue to say drawing right at 30 amps continuous will not be an issue. So what is it?

ScottG wrote:

dougrainer wrote:
For ScottG. I looked up the breaker info at work from the NEC. Doug

Circuit Breaker Ampere Ratings

Circuit breakers have an ampere rating (typically marked on the end of the operating handle). This is the maximum continuous current that the breaker can carry without exceeding its rating. As a general rule the circuit breaker’s ampere rating should be the same as the conductor’s ampacity.

Pure nonsense Doug. You found all the same information I did on the subject and you post BS to back up your side. But your problem runs much deeper.
Your problem starts with not being able to have a civil conversation without going into attack mode. I see you do this quite often. For that reason I feel no need to prove anything to you. Your just not worth it.

You are wrong about ampacity ratings for breakers. Plain and simple.
My EMS shows amp draw and I have run both ACs, fridge and inverter at 28-29 amps for HOURS in the Florida heat never popped a breaker.

As far as Doug's knowledge, he has forgotten more than most people know.

He is an excellent and accurate source of quality answers on the site.