Home » Public Forums » GMCnet » Minimal extension cord (Need to figure out how to run one A/C unit at home)
| Minimal extension cord [message #284580] |
Tue, 11 August 2015 13:29  |
habbyguy
Messages: 896
Registered: May 2012
Location: Mesa, AZ
Karma: 3
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I've tried to run one of my rooftop A/C units using a "regular" (probably 14g) extension cord, with predictible results (the cord got hot, and there really wasn't enough power at the coach to reliably run the A/C). I was recently camping in Mexico, and one of the campsite residents said he had a "30 amp cord" that he'd hook up to my coach so I could use my A/C. After he hooked it up (I was elsewhere), I flipped on the A/C and it worked great. Only later did I notice that the "30 amp cord" was a "regular" though thicker, three-prong extension cord. Seemed to work just fine - the A/C ran for five days without anything getting hot.
My question is - what gauge extension cord have you gotten away with on a 25' or 50' extension cord (running one original A/C unit)? I'd really like to get a three-prong (non-twist-lock) extension cord since I don't have a 30A outlet anywhere near where I store or work on my coach, and it would be nice to have A/C when working inside the coach (hey, I live in Arizona!). Yes, I know a 30A or 50A cord is better, but I'd need a really, really long (and expensive) cord to make that work - I'd never be able to put it in the coach, either... a 50' 10 gauge cord would be about the max I have room for without giving up storage space for something else.
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen
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| Re: Minimal extension cord [message #284582 is a reply to message #284580] |
Tue, 11 August 2015 13:41  |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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I use one of the heavy flat yellow ones to power my coach when it's at home, I put a 30A socket on the end of it, and plug it into an outlet in the house. I think it's a #10 conductor, might be #12. Doesn't run hot anyway. They havfe them at Lowe's, get the heavy, <not> the lightweight.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Minimal extension cord [message #284584 is a reply to message #284580] |
Tue, 11 August 2015 14:03 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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I messed with the same issue for the first 4 years of ownership. It was not the cord, so much as the plug end. either you melt the one at the coach, or the one into the wall gets hot.
however, for $650 I ended this whole heating up the cord problem by replacing my roof air with an Atwood 15.5k unit. It draws less then 12 amps, and will run on a 100' 12-2 cord plugged in to a 15 amp GFI with no issues.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Minimal extension cord [message #284585 is a reply to message #284580] |
Tue, 11 August 2015 14:24 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Lemme point out, I run a Dometic heat pump - three years old, low current draw also.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Minimal extension cord [message #284586 is a reply to message #284580] |
Tue, 11 August 2015 14:37 |
habbyguy
Messages: 896
Registered: May 2012
Location: Mesa, AZ
Karma: 3
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Senior Member |
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I suppose the intelligent question I should have asked is - how much current does one of the original rooftop A/C units draw? I agree a new, more efficient unit would be great - but as long as the two I have work as well as they do, it's hard to justify tossing them (or more importantly, spending the money on a replacement).
Interesting idea to replace the coach end plug with a 30A twist-in plug... I'll have to consider that. And heck, I could always splice in two male three-prong plugs on the house end so each of them would only have to deal with half the current.
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen
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| Re: Minimal extension cord [message #284588 is a reply to message #284586] |
Tue, 11 August 2015 15:09 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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I wish I could answer your question on the amps that the orignial A/C units pull, I never tested that.
What I found though, is the shorter the cord the better. I could run my A/C unit on the outlet that was close to my panel with a 25' 12-2 cord without it melting off, and really not getting hot. But When I plugged into the original A/C into the outlet that is furthest from my panel, using that same 25' 12-2 cord, that added about 45' more of 14-2 house wiring, it would melt off the cord end.
so longer, smaller AWG cords, cause a voltage drop to the A/C, and the A/C will pull more amps to make up the difference.
so there is a lot of variables in it. I understand your thinking on the cost and hassle of upgrading A/C units. I was in the same mindset, because my originals worked, but all too often I found myself being cooked out of my coach, because I did not have adequate power available. Also about the 4th $30 electrical cord that the end burnt up on because I tried running the A/C, got em a little worried about fire. Best upgrade for me personally.
I also found that the 1' adaptors going from 50 amp to 30 amp to 15 amp cord ends, did not burn as easily or get as hot as quickly as just the little adaptor plug.
so this:
http://www.amazon.com/Camco-55165-PowerGrip-Dogbone-Electrical/dp/B000BUU5YA/ref=sr_1_2?ie=UTF8&qid=1439323645&sr=8-2&keywords=30+amp+to+1 5+amp+adapter
did not get nearly as hot as quick as:
http://www.amazon.com/Camco-55223-15M-PowerGrip-Adapter/dp/B00192JGA8/ref=sr_1_1?ie=UTF8&qid=1439323645&sr=8-1&keywords=30+amp+to+15+amp+a dapter
BTW, if you want a 25' extension cord with one of those last adapters permanently melted to the end, let me know.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Minimal extension cord [message #284591 is a reply to message #284580] |
Tue, 11 August 2015 16:37 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Hopefully the wall outlet is a 20A with 12GA wire and fairly close to the panel. If 25' you might get away with 12/3 SO with some Hubble or Leviton ends. 10/3 is better but it is just possible to get all the strands into the connector holes. Be sure you put the correct sex on the correct end of the cable so you don't have to cross the conductors over each other to wire it, be neat and tighten to the max. The big DuoTherm draws around 17A running and the shorter rear one about 14A IIRC. At my old house I installed a 14-50 (Same 4 pin as GMC) weatherproof on the side of the building. I ran 10 ga THHN and used 20A breakers just as a temporary deal. I was going to go 30A for the 10ga not wanting to pull 6 ga for the 50A. They never tripped so I left them at 20A (40 total) showing wire gauge and good connections are most important. My roof airs are one on each leg so it balances pretty well not exceeding 20A per leg and the breakers held at startup though that spikes higher, the time constant in the breaker allowed it.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Minimal extension cord [message #284592 is a reply to message #284580] |
Tue, 11 August 2015 16:48 |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
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Senior Member |
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30A is #10 wire. Not gonna find a cheap cord in #10. Most of the problem is in the plugs on BOTH ends, and the adapters (you usually have to use two to go from 50-30-20). This is where you have your high resistance. The more it runs, the worse it gets. The higher resistance at the plug adapter glob also cause the load to draw more current, which will usually get the other end of the cord hot where it is plugged into the wall. Most outlets at home also are only 15A, and the outlets are too. Another weak link.
I run a hardwired TT30 outlet mounted in a metal four square box (2 gang) on a 20A circuit with #12 and it works fine for my 15K Carrier LP. Nothing gets hot. The only plug is at the RV.
That cord is 30' long and wired to an outlet box at the back of my garage that has probably 150' ft of #12THHN back to my main panel. (It used to be for the swimming pool we no longer have)
Now, I only have a 30A TT plug on my RV, but you can do the same with a 50A outlet and outlet box. Same as a Dryer outlet. You just tie both hots to the same connector so both sides of the bus in the GMC see 120V. Just run the AC unit (and the charger) by itself. Don't try to run the water heater as well, you will trip the breaker in the house. Don't try to plug a household clothes dryer into it either. Won't power it.
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
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