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11-08-2015, 07:01 AM
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#29
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Registered User
Join Date: Mar 2010
Posts: 8,777
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Quote:
Originally Posted by zman7458
what I meant to say is you can adapt a 50 amp cord to run from a 30 amp breaker, but not a 30 amp cord to run from a 50 amp breaker. once again my apologies.
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zman7458
You're getting closer.
The reality is:
You can adapt a 50 amp cord to run from a 30 amp breaker...AND you can safely and successfully use a 30A cord plugged into a receptacle protected by a 50A breaker.... IF you:
1.) Use the proper power cord adapter.
2.) Do not try to draw more than 30A through the 30A cord.
Mel
'96 Safari
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11-08-2015, 07:17 AM
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#30
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Community Moderator
Join Date: Aug 2011
Posts: 6,186
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Quote:
Originally Posted by mel s
You're getting closer.
You can safely and successfully use a 30A cord from a receptacle protected by a 50A breaker if you do not try to draw more than 30A through that cord.
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I think the point the electricians are trying to make is this: breakers are meant to protect the wiring. If the wire in your house can safely carry 15 amps, then a 15 amp breaker is installed. If a dead short develops in the wiring, the breaker pops before any other damage develops in other areas of the wire.
Unlikely - but suppose your power cord is damaged so a short or bad connection develops, the 50 amp pedestal breaker will allow enough excess current to flow that the wire could melt.
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11-08-2015, 08:06 AM
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#31
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Senior Member
Nor'easters Club Freightliner Owners Club
Join Date: Feb 2014
Location: on the road
Posts: 215
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lol, lol. I just like reading about this when it comes up. I know now why the test to get my elec. lic. was so hard!
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11-08-2015, 08:27 AM
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#32
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Registered User
Join Date: Mar 2010
Posts: 8,777
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Quote:
Originally Posted by pasdad1
I think the point the electricians are trying to make is this: breakers are meant to protect the wiring. If the wire in your house can safely carry 15 amps, then a 15 amp breaker is installed. If a dead short develops in the wiring, the breaker pops before any other damage develops in other areas of the wire.
Unlikely - but suppose your power cord is damaged so a short or bad connection develops, the 50 amp pedestal breaker will allow enough excess current to flow that the wire could melt.
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pasdad1
It is perfectly safe to use a 30A cord plugged into to a 50A pedestal receptacle if you do not try to use more than 30A in the RV. (aka: use common sense electric management in your RV) .
Using a 30A cord from a 50A receptacle to power a RV is no more hazardous than plugging the cord of a lamp with a 100 watt, (.83A), light bulb in it into a receptacle protected by a 15A circuit breaker in your house.
Mel
'96 Safari
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11-08-2015, 10:30 AM
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#33
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Senior Member
Join Date: Oct 2015
Location: Saint John, Mo.
Posts: 158
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Quote:
Originally Posted by double t
I said nuthin about overloading or bypassing a breaker or adding a heavier one your only going to pull the amperage the lowest rated breaker is being in the camper or on the pedestal
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lol, but you ARE exceeding the amperage rating of the supply cable, which according to the NFPA and NECA is illegal and could leave you open to prosecution and/or claim denial by your insurance company should something happen involving that supply cable. granted the odds are slim, but why risk it. do it right and be done with it.
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11-08-2015, 10:40 AM
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#34
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Senior Member
Join Date: Oct 2015
Location: Saint John, Mo.
Posts: 158
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as a side note, that is the reason the plugs are different in the first place. so you cant plug a 30 amp cable into a 50 amp pedestal.
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11-08-2015, 11:05 AM
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#35
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Senior Member
Join Date: Sep 2012
Posts: 8,055
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FWIW You will be hard pressed to melt a wire with 100% overload or 2x the rated current. There will be a bit more line drop but no melting with the values specified by the NEC code. That said, fuse things properly.
All the discussion about 50 vs 100 A service is silly. The correct answer is that the supply is a 50 A (or 200 A in a S&B) center tapped transformer that will supply the rated current from one hot to the other hot, ie 50 A @ 240 VAC. Since the center tap is grounded as a common return 120 VAC loads on either side of the supply transformer can draw up to 50 A or whatever the rated supply is. That current sums in the neutral buss at the panel so no more than 50 A can flow back to the transformer via the neutral. There is no place in the circuit where one can draw 100 Amps. One can use either 120 VAC or 240 VAC to get the rated supply current. The wattage is additive not the current because the voltage is additive in a series circuit.
The T panels some folks talk about are only there to keep the user from getting 240 VAC. You still get the same 50 A divided either side of the AC neutral. The supply is supplying 50 A @ 240 VAC and the loads are sharing it on either side of the neutral when using 120 VAC instead of the 240 VAC supplied.
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11-08-2015, 05:26 PM
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#37
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Senior Member
Join Date: Oct 2015
Location: Saint John, Mo.
Posts: 158
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Quote:
Originally Posted by DonavonP
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hmmm, I think that only applies in like Colorado or Warshington
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11-08-2015, 06:20 PM
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#38
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Senior Member
Join Date: Jan 2012
Posts: 996
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Quote:
Originally Posted by DonavonP
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That's primarily an issue on the other side of the pond.... We know to use + for the side that electrocutes you, and the - side as ground..
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