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07-06-2016, 08:51 PM
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#1
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Member
Join Date: Jan 2016
Posts: 72
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Inverter breaker/ wire size
I recently added a 2000 watt inverter to my rig. The inverter manufacturer recommend AWG 1/0 cable for runs up to 9 feet. I used AWG 1/0 cable and my run is about 5 feet from inverter to battery bank. I installed a 250 amp breaker on this run. My battery bank is 420Ahr.
The inverter runs fine except when I try to run my 1500 watt microwave. The microwave works fine but the 250 amp breaker pops after about 30-40 seconds despite the inverter showing its only at about 75% capacity. It's my understanding a 250 amp breaker should be able to handle up to 3000 watts.
Is my issue the 1/0 cable creating too much resistance? If so I guess I could double up the runs with two 1/0 cables for each leg.
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07-06-2016, 11:11 PM
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#2
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Senior Member
Join Date: Jul 2015
Location: Currently; SW Cali. Sunny & warm!
Posts: 1,323
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Hi,
We only have a 1000W inverter (Magnum) but in reviewing the manual they are requesting the # 1/0 AWG up to 5ft.. Then 5-10ft., #2/0 AWG with a 300A fuse (*rated for DC) protection device.
Best of luck.
__________________
J & J, DRV Suites ES-38RSSA #9679 GM Denali, 3500HD-Max, 4x CC, 8' DRW,
EZGo-TXT, Clubcar Precedent
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07-07-2016, 10:08 AM
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#3
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Senior Member
Ford Super Duty Owner
Join Date: Dec 2005
Location: Buxton, North Dakota
Posts: 3,940
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I suspect that the breaker isn't suited for the application. A fuse may work better for you or a different or larger breaker.
__________________
2003 Winnebago Adventurer 38G F53/ V10 605 watts of Solar
1999 Winnebago Brave 35C F53V10 Handicap Equipped
1999 Jeep Cherokee, 1991 Jeep Wrangler Renegade and 2018 Chevrolet Equinox Diesel
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07-07-2016, 09:32 PM
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#4
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Member
Join Date: Jan 2016
Posts: 72
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Quote:
Originally Posted by John Hilley
I suspect that the breaker isn't suited for the application. A fuse may work better for you or a different or larger breaker.
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Thanks for the input. I think the wire size was too small and creating excessive heat causing the breaker to pop. I doubled up the cables and all seems ok now.
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07-08-2016, 03:18 PM
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#5
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Senior Member
Join Date: Jul 2015
Location: Currently; SW Cali. Sunny & warm!
Posts: 1,323
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Good deal, thanks for the update!
Happy motoring.
__________________
J & J, DRV Suites ES-38RSSA #9679 GM Denali, 3500HD-Max, 4x CC, 8' DRW,
EZGo-TXT, Clubcar Precedent
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07-08-2016, 03:58 PM
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#6
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Senior Member
Join Date: Sep 2012
Posts: 8,055
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FWIW I'm trying to figure out how a warm wire would cause the breaker to pop. 1/0 copper has 0.09827 ohms/1000 ft. so 5 ft is ~0.0005 ohms.
1500 W @ 12 VDC = 1500/12 = 125 A
line drop = 125 x 0.0005=0.0625 V
line drop @ 250 A = 0.125 V
pwr loss @ 250 A = 31.25 W
The line drop does not look like enough to be an issue. OTOH you are dissipating enough power in the wire at a very low resistance to get me looking at the actual connection to the breaker. I would be cleaning and/or tightening up any screw type connectors as the contact resistance could be an issue. That is a good place for a non contact thermometer or an educated finger.
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07-08-2016, 04:08 PM
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#7
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Senior Member
Join Date: Jul 2015
Location: Currently; SW Cali. Sunny & warm!
Posts: 1,323
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"I would be cleaning and/or tightening up any screw type connectors as the contact resistance could be an issue."
Good observation.
This can often be an issue with other RV electrical related problems. Shore power, pedestal connections etc. another example.
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07-08-2016, 04:14 PM
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#8
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Senior Member
Tiffin Owners Club Freightliner Owners Club
Join Date: Aug 2014
Posts: 1,899
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Agree that it is not a wire problem.
By adding cable, you actually reconnected the breaker, probably a poor connection the first time.
Be sure you use copper wire.
Dan
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2014 40QBH Phaeton DP Cummins 380HP ISL, Freightliner XC, 2019 Jeep Grand Cherokee Trailhawk TOAD
Blue Ox Aventa tow bar, SMI Air Force One -Cave Creek, AZ.
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07-08-2016, 07:55 PM
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#9
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Member
Join Date: Jan 2016
Posts: 72
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All new wires and connections so corrosion wasn't an issue. I can confirm all connections were tight and solid. I also ran the math and would have thought a single 1/0 wire was sufficient but all I know it wouldn't work. In hindsight I should have just used 2/0 or 3/0 cable as my starting position.
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07-09-2016, 07:13 AM
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#10
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Senior Member
Join Date: Jun 2016
Location: South Jersey
Posts: 113
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My 2000W inverter requires 2/0 cable.
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07-09-2016, 09:08 AM
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#11
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Community Moderator
Join Date: Sep 2011
Location: Between the Oceans
Posts: 8,034
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typically a 2000 w inverter requires 2/0 wires with 300a class t fuse. mine is that. i'd rewire if i were you.
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Steven & Polly
2000 Country Coach Intrigue 40' ISC 350
2018 Ford Explorer 4WD
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07-09-2016, 07:33 PM
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#12
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Senior Member
Tiffin Owners Club Freightliner Owners Club
Join Date: Aug 2014
Posts: 1,899
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Darn...I don't want to start an argument...
But the reason you would use a larger wire is to have less voltage drop across the wire. Having too small of a wire will also cause the wire to heat up because of the power dissipated (P=E x I)
A circuit breaker actually has a bi-metal strip inside which heats up as current increases through it. When the current gets high enough, the Bi-Metal strip bends enough to trip the switch (breaker).
The resistance is given as ohms/foot, so this is why you would pick a larger wire if it was a longer run.
There may be other factors at play here on your installation, and a larger wire can't cause any problems.
It is possible the breaker is a little weak, and the larger wire is acting more like a heat sink and keeping the breaker cool. However, the coffee maker was still well below the trip point of the breaker.
But if you ask any electrician, they would never say you can fix a tripping breaker by using a larger wire....it is just ohms law stuff.
Important thing is it is working
Regards,
Dan
__________________
2014 40QBH Phaeton DP Cummins 380HP ISL, Freightliner XC, 2019 Jeep Grand Cherokee Trailhawk TOAD
Blue Ox Aventa tow bar, SMI Air Force One -Cave Creek, AZ.
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07-09-2016, 09:34 PM
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#13
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Senior Member
Tiffin Owners Club Freightliner Owners Club
Join Date: Aug 2014
Posts: 1,899
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A few other numbers.
The average efficiency of an inverter is 10% or better.
Assuming 10%, supplying 2000 watts, would be using 2200 watts from your batteries.
2200 watts from 12V requires 183.3 amps
Dan
__________________
2014 40QBH Phaeton DP Cummins 380HP ISL, Freightliner XC, 2019 Jeep Grand Cherokee Trailhawk TOAD
Blue Ox Aventa tow bar, SMI Air Force One -Cave Creek, AZ.
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07-09-2016, 10:45 PM
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#14
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Senior Member
Newmar Owners Club
Join Date: Jun 2012
Location: Spicewood Texas (West of Austin)
Posts: 4,514
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The Magnum MS 2012 recommends 2/0 up to 5 feet and 4/0 from 5'-10". I would say that 1/0 is too small for any 2000W inverter.
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Scotty and Kristen, Airedales Dagny and Wyatt
2007 Newmar Mountain Aire 4528, 450 HP ISM, Allison 4000, 8 Lifeline AGM's
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