Power Available vs. A/C Performance

[JimGolden]

Hi all,

I made an observation today and wanted to see what you all thought.

Finally got my RV plugs wired into the side of my house. So instead of running on a 20amp circuit, I'm now plugging directly into a proper 30amp circuit for my '77.

Well, the air conditioner on my Excella always seemed marginal. And if any kind of storm kicked up, it would trip the breaker.

But, with the added juice available of the 30amp circuit now, that sucker was like a deep freeze inside! It was mid 80's pushing 90 degrees out, and it was more like high 60's inside the coach. I couldn't believe the difference.

Is it because I'm on the 30amp circuit vs. the 20amp? Was I so marginal before that it would barely power up the a/c? Am I all wet here in my logic?

All I know is that the old armstrong unit seems to work like a champ when plugged into the real feed, versus using the adapter and plugged into one of my normal outlets (I know they're 20amp rather than 15amp because we wired them ourselves...all on 12 wire...got 10 wire on the 30amp circuit).

Anyway, the difference was amazing. Just wondered what you all thought.

Thanks!

[Druupy]

Yep, did the 20 amp to 30 amp trade last week.

With 20 amp and the plug adapter we could run one (1) major appliance. This was a learning experiance, if you run the blow drier and the microwave, you get to decide who gets to walk around the house, downstairs in the dark, and trip the breaker. Usually it was me.

With the 30 amp RV plug, fine with A/C, microwave, TV, computer, coffee pot. All at the same time and it works fine. I think it is the "reserve capacity" of the bigger wire that can take the starting load of the appliances.

[CanoeStream]

Did you really have a 20A outlet? (see image below) I've got one in my basement for a 3-horse planer motor. Otherwise a 2-vertical-slot with ground would be 15A -- low enough amperage to strain on startup and prematurely burn out an A/C compressor from what I've read. Can't really say where 20A would fall in regard to that problem.

[dwightdi]

If you have a voltmeter, check the voltage at the internal box on the trailer. You house may use wiring which is not adequete to run an air conditioner as big as the Airstream. Running the air with less than 100 volts at the box will give poor performance and may damage the air conditioner. Proper wiring is a must.

[crowbar68]

you got the juice now. w/ all the appliances running 30a is better than 20a. it's difficult to say exactly what your camper draws w/o putting a amp meter on the line. and even then if all the items turn on simultaneously you could pop your 30a. not likely though,and it's probably a dedicated circuit. your 20a may be shared w/ other things causing problems.

crowbar

[pamelake]

Originally Posted by dwightdi

If you have a voltmeter, check the voltage at the internal box on the trailer. You house may use wiring which is not adequete to run an air conditioner as big as the Airstream. Running the air with less than 100 volts at the box will give poor performance and may damage the air conditioner. Proper wiring is a must.

Oh man! I thought I had this figured out! By the advice from several different people I was to understand that I shouldn't run my AC on the 15 amp plug outside of my house. I was told I needed 30 amps and have the electrician on the way to add a 30 amp plug. This is the first time I have ever heard of 100 amps.... is this what you would find at RV campsites? I thought those were 30 amp. Can you clarify? Thanks, Pam

[JimGolden]

Canoe Stream,

Are you sure about that on the outlets? I got mine at a supply house (Hagemyer/TriState Electric) and they were all supposed to be 20amp outlets, although the faces look like the ones at Lowes, they seem to be of heavier construction. I ran 12 wire which is 20amp wire, and used a 20amp breaker in the panel. The circuit is a dedicated one for wall outlets and is one side of my garage. I have another like it on the other side.

The RV plugs (one on each end of the garage for if the RV I own at the time has a plug in front or out back) are on a dedicated 30amp GFCI circuit, using 10 wire. I park the Airstream parallel to the garage and can plug right in now.

All I can say is, wow, the difference in the a/c performance! I hope I didn't harm it before when on the 20amp line. It seemed to work OK, but didn't have the "cooling horsepower" that it's got now. The trailer isn't roadworthy right now and so I've not used anything other than the a/c and the lights at the same time. They never conked out. During storms though, the breaker in the trailer would sometimes flip. I've not had a storm yet since the 30amp circuit (just hooked up yesterday) so not sure if that'll make any difference.

Anyway, there's something to be said for having enough juice. I wired the house very conservatively. Never undersized anything, always erred on oversize wire. Got two 200amp panels, so I've got enough capacity to light up Vegas. The power company loves me Nah, house has 12" thick R38 walls so is very energy efficient. I just wanted the capacity there if I needed later...

Anyway, I can be cool in the Stream now

[JimGolden]

Pamelake,

I think he meant 100 volts, rather than 100amps. It'd be 100 volts at 30 amps. Voltage drops with wire run length.

I think Watts is the real thing here; how much power you actually have.

Amps * Volts = Watts

120 volts at 30 amps gives you 3600 watts available (theoretically) from the circuit. So if the a/c draws 15amps at 100 volts, it's taking 1500 watts to power it. That would be maxing out a normal household circuit, counting for voltage drop across the wires. So if you're running the a/c and turn on the 1000 watt microwave, and you're plugged into a 15amp circuit, you'll probably pop the breaker.

Best thing is to run a dedicated circuit from your panel. Get a 30amp GFCI breaker, #10 wire, and an RV plug, and you're set.

[Pick]

When running on 2 Honda Eu2000i's, with the A/C on high, my voltage, read from the outlet over the stove was 122 volts. At my house, on a 30 amp RV outlet, 70 feet from meter box, I get a reading of 116-119 volts, on high. From my normal parking spot under the shade tree, about 250 feet from meter box, fed with #10, I get a reading of 105 to 109 volts, with A/C on high. I do not run the A/C with that low a voltage.

[crowbar68]

you are better off w/ 30a breaker. i woudn't think voltage drop would factor in if your by your house ( 100' or less). the 20a plugs look like 15a plugs except they have a little extra horizontal slash inwards for the special 20a plug shown previously. that is so you can plug 15a items into 20a plugs. but you can't plug 20a items into 15 a plugs. as far as plugs go you can buy 78cent plugs or 5 dollar plugs which are much heavier duty, all the same ampere rating. you get what you pay for. 2 dollar range is decent. especially for kitchen/bathroom and garage.

[acrane]

Neewbie here. How would that effect you plugging in at a campground. Would your a/c cool enough?

[JimGolden]

Acrane,

I've only been to a few campgrounds so far, but they all had 30amp plugs. No need to worry there.

Some of the bigger RVs now have 50amp plugs. Not our "little" Airstreams though.