Pulling more than 50 amps ?

BurbMan wrote:

dougrainer wrote:
BTW, I would keep that Idiot away from my Campsite and RV. Doug

Huh? You just agreed with him now he's an idiot?

Yeah, that made no sense to me. The electrician is absolutely correct that a large all electric RV could possibly pull over 50 amps from either leg of the 50 amp park service and trip that 50 amp 240 vac two pole ganged breaker. (And it has to be a ganged breaker since it is a split phase system and has a common neutral.) An EMS might prevent it. I don’t know. But without an EMS there is nothing to limit the current flow but the circuit breaker itself. And perfectly balanced, the RV could pull 50 amps on both legs of the 50 amp service for a total of 100 amps and still not trip the park breaker unless manufacturing tolerance variations set the breaker trip point slightly below the breaker rating. And that would be minimal. Inversely, it could even be higher than the labeled rating due to those same tolerances. And you can talk about it in amps (pure current flow) or in watts (current times volts). Doesn’t matter. In the end it still comes down to the number of amps flowing thru the breaker that trips it.

TechWriter wrote:
Since many 50A pedestals have 50A, 30A, and 20A outputs, does that means the pedestal could safely output 150A total?

I don't like the way it is stated but to the electrician in question... Yes you could get all that power safely.

Most RV parks are wired on a 200 to 400 amp loop so nothing will trip at the main panel.

Could each and ALL pedestals in the loop draw that power at the same time? Not even close.

dougrainer wrote:
BTW, I would keep that Idiot away from my Campsite and RV. Doug

Huh? You just agreed with him now he's an idiot?

Since the 30 and 20 amp are often wired daisy chained from the main supply, No. Again surge for a millisecond would be fine.

So to sum up, my park electrician was indeed correct: an RV could draw up to 100A on a 50A pedestal -- 50A on L1 and 50A on L2, so long as neither leg exceeded 50A.

Next . . .

Since many 50A pedestals have 50A, 30A, and 20A outputs, does that means the pedestal could safely output 150A total?

WATT ARE YOU FOLKS TRYING TO SAY?



Each phase to neutral has its limit expressed as AMPS because that is the electrical limit imposed by the circuit breaker.

There are two breakers limited to 50 amperes each.

One breaker has nothing to do with the other. Except if one breaker gets overloaded like a drowning person it'll take the other leg with it should it start to drown (amperage overload)

It would be expressed better as two circuits each in WATTS capacity. Saw the parallel bar that joins the two breakers together and that would explain the function better. An RV would be better protected by 2 individual 50 amp breakers instead of a single ganged 50 amp breaker.

Total power is always expressed in WATTS. Like an 8 cylinder engine is never expressed as 50 horsepower per cylinder.

Expressing an RV connection as 240 volts would help only if there a 240 volt accessory on board, I know of no such accessory because many facilities are wired for 120 volts.

Two ammeters and two voltmeters should be required on every 50 amp RV.

Ask what conditions are necessary to cause a breaker to trip.

There are two ways for breakers to trip. One is thermal where the heat build up from running near or at full capacity for some time causes the trip. The other is a "magnetic" trip where the amp rating is exceeded for a time. We don't want nuisance trips from, for example, start up surge from the air conditioner.

So yes, for brief periods of time, a 50 amp service may exceed the rated values.

Charlie D. wrote:

Lynnmor wrote:
Calling the guy an ignorant idiot is just plain wrong. It is entirely possible that a large RV with 3 AC's to draw more than 50 AMPs on one leg. An RV with 3 AC's probably has a laundry, large refrigerator and possibly a dishwasher and numerous other appliances. It doesn't matter how much the other leg is drawing, the breaker trips if just one exceeds 50 AMP.

Would not the AC be divided and not all on one leg?

Of course, but there will be at least two on one leg.

12,000 watts sure. 100 amps on any wire would trip the breaker.

Otherwise you may as well talk in battery power and say it pulls 1000 amps ;)

Or perhaps the park electrician was attempting to explain why a 50 amp breaker was tripping and he didn't use exactly correct grammar. It is entirely possible for large rigs to have appliances and systems that would draw over 50 amps if all the appliances were operating at the same time and the breakers (either the park's or the coach's main) did not trip. Saying that those rigs can draw more than 50 amps is entirely correct. However, if the breakers are working correctly the coach cannot draw more than 50 amps for more than a few seconds. (subject to the tolerances allowed in manufacture and the delays built into the specifications of the breaker). The campground electrician was probably correct in what he was attempting to communicate, even if his verbiage was less than 100% accurate.