joppa
Massachusetts
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Joined: 09/12/2006
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So when we say 50 Amp... do we really mean three air conditioners?
Anytime I fire up all 3 units I tend to draw more like 55-56 amps. This with very little of anything else going. Wouldn't dare turn on the microwave or coffee maker.
Assuming the CG breaker doesn't go... is there any safe amount of headroom?
Can I draw an extra 10% or am I about to spontaneously combust?
The World is a book, and those who do not travel read only a page. ~St. Augustine
2007 Foretravel Nimbus
Cummins ISM 500HP
Allison MH4000w/Retarder
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javaseuf
Southern Cal
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Joined: 03/30/2005
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At start-up, all three compressors will run and draw around 45-50 amps. Once the room temp is satisfied, the units will begin to cycle on and off depending on room temperature and thermostat setting.
It is probable that all three will come on again at the same time.
Couple this load with other loads such as convertor/battery charger, electric water heater and other loads, you will exceed your 50 amps pretty easily.
Do you have an energy management system that will cycle the compressors on and off? If so, programing this can ease your load.
You may get away with an additional 10% but possibly not.
Steve
2007 Springdale 291RKL
2003 F150 King Ranch
2001 Dodge Van w/Wheelchair Ramp
1991 Palomino Mustang PUP
Eureka Timberline Tent
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marvmarcy
Polson, MT, USA
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The rvs I've seen with three a/cs could only run two at a time on a 50A service. There was a switch in the coach that allowed you to select which two. My last two mhs had a switch which would allow me to run two a/cs or one a/c and the dryer. A 50A service can support up to 12KW, but that doesn't consider motor surges at start up, which can easily be double the continuous draw.
Your point is valid, but you won't spontaneously combust; just trip off the breaker. If the 50A receptacle or your plug are corroded, even a little bit, they can get hot enough to melt the plug or receptacle. I clean my plug frequently to remove any corrosion or evidence of arcing. I've had to replace a few plugs over the years.
Marv
2001 Volvo VNL42T420, ISX450/1650, super 10sp w/GearMaster
2003 Newmar Mountain Aire 38RLRK
Piaggio MP3 400 scooter
RVing since 1979 - Fulltime since 2000 (mostly CO, MT, NC & Key West)
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John S.
Northern Virginia
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I run my three AC units all the time on my generator but on 50 amps I am very careful.. It is rare for them to all kick on at the same time. I do set the temps one degree apart though. I have had all three running but do not do it when you get to the campground as your battery charger will go into bulk charge and draw 14 amp on the Foretravel. I only use the ACs and not the fridge if I am using all three and I am fine for a short peroid to cool it down a bit.. Now if the park has a weak breaker you may trip it and if you do then you will need to back off to two units again. Is your Nimbus all electric. If not you can switch your fridge to propane to save some amps there. I would recommend though that on shore power you just run two and I switch them to the room I am not in.
John
2001 42' Foretravel U320
2007 Bornfree 24 Painted
2001 Jeep Wrangler
2007 Burgman 650 Executive
Susie and Dolly (Cavalier King Charles Spaniels)
Dolly now in our hearts and thoughts 8-27-05
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wolfe10
Texas
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A 50 amp RV outlet/system has TWO 50 amp hots. Open the CG box and look. You will find two 50 amp breakers connected/pinned together (obviously assuming they are properly wired).
So you could draw near 100 amps total assuming the loads are pretty well split between the two hots.
Brett Wolfe
1993 Foretravel 36' U-240
Cat 3116, Allison 3060
Caterpillar RV Engine Owner's Club: www.catrvclub.org
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lightguy48
Tulsa, OK
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Joined: 03/18/2006
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Keep in mind that's 50amps per leg/circuit. I hate to bring up the subject, but your total capacity is actually 100amps (50a x 2 legs). So depending on how your RV is wired and how it is metering that load you could run up to 100a total.
Depending on the size of those AC units you could have 2 on one leg of the incoming power, one on the other leg, and still have reserve capacity.
You would have to have some pretty detailed information on how it's metering and is wired to know with 100% certainty.
R. Brett Gilbert Tulsa, OK
2005 Fleetwood 27' Wilderness Limited
2005 Ford F-250 6.0L PSD Crew Cab
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MI Director
Michigan
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Joined: 03/03/2007
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A 50 AMP 240 volt service is 50 AMP on each leg. If the breaker box is properly balanced with loads you can actual pull up to 100 AMPs. Thats 50 AMPS on L1 and 50 AMP L2.
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Fulltimingman
Livingston, TX, USA
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Joined: 11/29/2003
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As R Brett and Brett W. have said, 50 amps is really 2-50 amp legs. I can run my 4 basement airs off of 50 amp service.
Michael Day
Newell Coach
PT Cruiser Turbo
Patrick the Irish Wolfhound
Native Texans
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Nick Badame Refrig.
Cape May Court House, N.J.
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Joined: 08/23/2006
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Hi Guy's,
Yes, you can pull 50 amps per leg at 115v ac as long as your nutral is strong enough to carry and balance the load if each leg is drawling a different amount of amps. It's called load sharing through your nutral bond.
If you are using 220v apliances the 50 amps is all you will have.
If you can bear it, go ahead and load up the park panel...lol.
Keep in mind folks, your A/C's will draw 3 times the amp rating at start up, then work it's way down. Always stage your A/C's to not trip your curcuit braker. 5 min intervals is good.
Good Luck
Nick-
MCI 102C3 40' 2006' Bus Conversion by Atlantic Custom Coach
Detroit 475hp 8V92t w/Allison Ht750 auto
Master Mason, Cannon Lodge #104 S. Seaville N.J.
FMCA# F-27317-S
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mike4947
N. Syracuse, NY
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Joined: 08/26/2002
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Good information, except the starting currents on motors. While the spec's say the "locked rotor current draw" may be three or more times the running current draw; you'll never see a locked rotor condition unless something has gone wrong.
We tested several dozen AC units when we did out genset testing and the running currents averaged 10-12 amps on the newer power saver units and 14-17 on the old designs. Starting currents ran 11-14 amp on the PS types and between 16-19 amps on the older designs.
If you tend to trip a main breaker in a 50 amp service RV, we first check what's on what leg. Many RV's come with everything on one leg except a second AC unit. Moving some circuits to get a more balanced load in most cases "fixes" the breaker tripping problem.
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