Drawing 35 amps on a 30amp circuit

AudiDudi · 08-11-2018, 08:10 PM

I had the fridge, 15k A/C and the microwave going all on a 30 amp conneciton. I checked the Progressive Industries EMS - PT30X for usage and was drawing 35 amps. Glad it all worked

Bluepill · 08-11-2018, 08:42 PM

National Electrical Code recommendation is to run no more that 80% of circuit capacity on a continuous basis. That's 24 amps. Short bursts, like A/C startup, are OK to exceed this amount.

AudiDudi · 08-11-2018, 09:47 PM

Quote:

Originally Posted by Bluepill

National Electrical Code recommendation is to run no more that 80% of circuit capacity on a continuous basis. That's 24 amps. Short bursts, like A/C startup, are OK to exceed this amount.

I was surprised the main breaker didn't trip. The A/C was running constant as it was almost 100 deg.

Toyman · 08-12-2018, 02:31 PM

Like Bluepill said...I wouldn’t trust a 30A breaker that carried 35A for more than a second, (maybe 2) to protect anything.

formerFR · 08-12-2018, 02:41 PM

I doubt you were drawing 35 A, continuously - your AC unit running, your microwave, and your fridge, if the compressor is actually on when the other two items are running, still wouldn’t exceed 30 A.

I can run both of my 13.5ac’s, fridge, computers, TV, receiver, and some floor fans, all on 30amp service. : )

llr · 08-12-2018, 03:32 PM

Unless breakers have gotten much better recently it is not surprising.
I worked in the R&D area of a company that made panels and breakers, not my area but I talked to people in that area.

It was common to carry a 50% overage indefinitely and a 100% overage for a number of minutes. Occasionally they would melt together then never trip.
A short circuit would trip almost instantly.

**Bama Rambler** · 08-12-2018, 03:51 PM

Residential circuit breakers trip two different ways depending on the type of overload. They have a bimetallic strip that heats up and bends to trip the breaker. The higher the overload, the quicker it trips. In slightly overloaded conditions they may hold for a while, but will eventually trip.

In short circuits they have a mechanism that will trip the breaker immediately.

So it's possible that it could have seen 35 amps for a little while (A/C Compressor startup) and not tripped.

formerFR · 08-12-2018, 04:41 PM

our experiences, in all our time, miles, and places we've traveled to and stopped at, is that there is nothing 'for certain', whether it's power related, water, sewer, or anything else... but, we've realized that every rv park and campground can have some issues, sometimes voltage, sometimes a 'trigger happy' Shore Power breaker, and sometimes even 'non standard' wiring.... don't ask me how I know(Alaska, but I'll say no more!)
: )

you can find a breaker that might be 'less' sensitive than it might be designed for, but those are hard to determine since nothing is telling you that it's 'going wrong'... while others have an overly 'sensitive' breaker, and you think it's YOUR coach, when it's just the breaker.

**ependydad** · 08-13-2018, 10:31 AM

I happened to read a thread on here recently for the same issue ("http://www.forestriverforums.com/for...-a-164111.html"). In it, user HONDAMAN174 reported that Progessive Industries reported that the amps display on the EMS is an estimate and seems to show high by about 1/3.

cavie · 08-13-2018, 10:57 AM

The only true amp reading comes from a clamp around the wire amp probe. All others a faked estimates. Close but no cigar. Remember. Volts go down, amps go up. Just because you can overload a breaker doesn't mean it ok to do it. Something is going to fail. When it does, bad things happen.

**Bama Rambler** · 08-13-2018, 11:04 AM

Actually the only true amp reading comes from a calibrated donut or shunt and meter movement. Too much application error in a clamp-on. Though it's the best method most consumers or even technicians have and it's much better than anything else.

rlh1957 · 08-13-2018, 01:50 PM

Something more was running than that to draw 35 amps. And if it really was 35 amps you should have an electrician check that main breaker or the pedestal breaker as well as find out everything that is running. Start shutting breakers. Checking inverter converter draw.

I maxed out my rig just to see where it would blow... the 30Amp shore power always kicks first.

bubbles · 08-13-2018, 02:52 PM

I believe circuit breakers are tested to a time based 135% must open.

Larry-NC · 08-13-2018, 04:15 PM

Quote:

Originally Posted by Toyman

Like Bluepill said...I wouldn’t trust a 30A breaker that carried 35A for more than a second, (maybe 2) to protect anything.

I actually specified breakers one year. They are typically specified to trip within one hour at 10% overload and within milliseconds at much higher currents.

I'm not a bit surprised that the OP could pull 35 amps through a 30 amp breaker, not do I believe anything is defective.

Larry

AudiDudi · 08-13-2018, 06:26 PM

Quote:

Originally Posted by Bama Rambler

Actually the only true amp reading comes from a calibrated donut or shunt and meter movement. Too much application error in a clamp-on. Though it's the best method most consumers or even technicians have and it's much better than anything else.

Agree re: shunt/donut. The microwave was only running for a minute. 15k A/C on full time, laptop plugged in, fridge on AC, 2 small fans running and the TV was likely on. The only reason I checked the EMS was I figured I was likely close to maxxing out on a 30amp circuit.

I have no idea how PI measures/estimates amps being drawn. Voltage was reading 126. I was just surprised to see 34-35amps.

CHICKDOE · 08-13-2018, 06:56 PM

there was another post a few weeks ago where somebody was drawing in excess of 30 amps on a PI EMS. he called them and got the response that the amp usage displayed on their EMS units was an 'approximation'.

Ilovemywife · 08-13-2018, 07:07 PM

I blow my 30 amp breaker regularly. In order to run the air conditioner which is on almost 24/7 and the microwave on the same time, I have to unplug the hot water heater or I blow the 30 amp circuit breaker.

I'm thinking up upgrading to 50 amp service. I will run a 30 amp line out of one of the 50 amp service lines to the existing box and use the remaining capacity for electric heaters, heat strips, and other stuff I need to keep stuff from freezing overnight during the winter months.

AudiDudi · 08-13-2018, 07:43 PM

Quote:

Originally Posted by Ilovemywife

I blow my 30 amp breaker regularly. In order to run the air conditioner which is on almost 24/7 and the microwave on the same time, I have to unplug the hot water heater or I blow the 30 amp circuit breaker.<snip>
.

My water heater is propane only. I'd guess that is why it's only a 30amp motor home. Although, my old 30 amp 97 HR Alumascape TT had electric HW heater, microwave and 15k A/C. I never tried to run all 3 at the same time.

You may also like: