Have any experience running both AC units on 30 amp

[Lee Bode]

We are currently on a 30 amp service for the first time in any real heat and were wondering has anyone had any experience (success) running both AC units on that? We are working today and tomorrow and have the master cat watching the camper while we are out and do not want the two units to kick the breaker and leave him in a proverbial hot box. I did a search but couldn't find this specific question and I believe I have read that the 30 amp will not support both of my AC units on the 303.

Thanks in advance

[ncitro]

No experience but I would not trust this to work especially if you won't be there to reset the breaker if it trips. I think each A/C pulls around 12 amps. If they both cycle on at the same time the inrush could easily trip the breaker.

[SouthTX]

^^^^x2

I'm good until both start up at the same time. Be sure to turn off the converter and put the fridge on LP. I think I'd just turn on one AC and close the door so it only has to cool half the RV - might be better odds of keeping the cat cool than running both on 30 amps.

[Aridon]

You can run 2 ac on 30 amps.

Turn fridge and water heater on propane.
Turn off converter.
Turn off everything else on the electrical panel that is 120v

Start one air, set it for 55 or whatever the lowest setting is. Let it fire up and run for a few minutes.

Start the second air, if you followed the above it should fire up and run. Set this one for 55 as well and let them both run. The problem is starting and stopping of the units. Once they are running you should be ok.

Once they are both started and running, there is enough amps left over for your TV.

2 15k will run at around 13 amps each, that is 26 total and leaves you with 3 or 4 amps left over. Breakers don't magically trip at 30 amps either, they usually have an extra amp in there or so temporarily.

[steve gravelle]

I am working part time at our local Lowe's in the electrical department. I am NOT an electrician. But a professional electrician I believe knows his stuff told me that a breaker will carry 80 percent of its rating on a continuous basis, which to me means 15 amp breaker=12 amps continuous. Any input from fellow RVers? Just learning.

[Aridon]

Continuous loads are calculated at 80% of a higher actual max load to get the rating you see on the breaker. Breakers don't trip at their rating, there is buffer.

Same thing with wire size.

125% of continuous which means if you take 80% of that you'll get the rating.

You can't take 80% from 30 and say that's your max on 30 amp, it's not designed that way and you'd be flipping breakers all day if it was. The 80% is already figured on the breaker rating.

I'm not an electrician, that is how I understand it

[gbkims]

It's complicated, it's the mind bender thing that is the National Electric Code.

https://blog.schneider-electric.com/...cuit-breakers/
2011 National Electric Code. Section 210.20(A) of the code basically says that a circuit breaker for a branch circuit must be rated such that it can handle the noncontinuous load plus 125% of the continuous load. (A continous load is one where the maximum current is expected to continue for 3 hours or more.) In other words, the breaker needs an extra 25% capacity of the continuous load for headroom. That, of course, means you need a larger, more expensive breaker.

http://www.cliffordpower.com/stuff/c...rated_ats1.pdf


1.0 Introduction:
Circuit breakers (CBs) are designed to carry 100% of their rated current, yet the National Electric Code (NEC) dictates an 80% application.
This information sheet discusses the difference between 80% and 100% rated circuit breakers.

2.0 Circuit Breaker Design:
A CB is designed and evaluated to carry 100% of its rated current for an indefinite period of time, under standard test conditions.
Underwriters Laboratories (UL) 489 Standard for Safety for Molded-Case CBs (MCCBs) and CB Enclosures include mounting the CB in free air, i.e. without an enclosure, where the ambient temperature is held at 40ºC (approx.104ºF).
Under these conditions, molded-case CBs are required not to trip at rated current.
However, a CB most frequently is applied in equipment at 80% of its rated current under NEC Sec. 384-16 (c)

3.0 CB Characteristic Trip Curves:
These curves document how long it takes for specific CBs to trip depending on the level of current. For a typical thermo-magnetic CB, the manufacturer’s published curves will indicate the time it takes CB to trip on overload. An overload condition will cause heat build-up around the current path within the CB, as well as along the power conductors. This heat (generated by the current flow) is actually what causes the CB to trip – not simply the magnitude of the current flow. This portion of the curve is said to have an inverse time characteristic, meaning that the CB will trip in less time at higher levels of current flow.

Since both the CB and conductor react to heat, the overall operating temperature of the equipment becomes a factor in sizing a CB in an enclosure. Other factors that may affect this operating temperature include:
• Size and location of the enclosure
• More than one current carrying device, housed in same enclosure
• Level of current that each device is carrying
• Environmental conditions in the area of the equipment

This means that simply designing a CB to hold 100% of its rated current only addresses part of the concern.
The equipment must be able to safely sustain the heat generated by all the sources without exceeding the temperature limits in the product test standard. Both of these factors are accounted for by the sizing rules imposed by the NEC.

[Lee Bode]

10-4, I appreciate the responses and the info most of which is well above my electrical pay grade (can you believe I once considered Electrical Engineering as my major at NCSU?). Have the main unit in the living area running during the day while we are at work. I will try both units this weekend while we are there and unfortunately according to the weather forecast will be inside the majority of the days. Have a safe and enjoyable Memorial Day and honor those that gave all for us to enjoy.

[Ghdorn]

I have a 3000qb with two ac units. Is a 50 am system. Plugged into a 30 amp circuit at a house and both across units run fine . Been running for several hours, cooling ok and it is lower or mid 80s but feels hotter all is well inside trailer.