Home » Public Forums » GMCnet » [GMCnet] basic shore power question
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| Re: [GMCnet] basic shore power question [message #80613 is a reply to message #80611] |
Thu, 15 April 2010 11:22   |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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| Richard Lister wrote on Thu, 15 April 2010 08:53 |
... Can we plug into a 50 amp power source? I see the plug on the shore power line will fit a 50 amp connection, but the warning label says 40amps...
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Short answer, Yes. You can plug into the 50 amp plugs at RV parks.
Little longer...
There are other 50 amp plugs found elsewhere that may not work, these are normally "keyed" differently.
GMC upfitted coaches, like your Kingsley, came from the factory with 50 amp plugs feeding a pair of 20amp circuit breakers. (One on each leg) That is where the 40 amp limitation comes from.
True 50 amp systems are 240v between the legs. (120v to N on each leg, 180* out of phase, making 240v difference between the legs.) Power feeding one leg is returned down the other leg... very little power runs on the neutral, just the imbalance.
You may find RV "50amp" systems that are not 240v but are 120v from each leg to neutral. (Same phase on each leg) The stock Onan provides this type of power. This works in the stock system but ALL the power is returned on the neutral line. This is more important if you are replacing cables or installing something that expects 240v power. (Not likely.)
I am sure you can get someone to provide an even longer answer.... 
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] basic shore power question [message #80614 is a reply to message #80611] |
Thu, 15 April 2010 11:25 |
Dave Wilson
Messages: 94
Registered: September 2009
Location: Livonia, MI
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| Richard Lister wrote on Thu, 15 April 2010 10:53 |
Hi all.
We are taking our "new" GMC on its maiden voyage this weekend. Can we plug into a 50 amp power source? I see the plug on the shore power line will fit a 50 amp connection, but the warning label says 40amps...
Thanks!
Richard, DC
78 Kingsley
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Hi Richard,
From personal experience we have plugged all of our family's GMCs into 50 Amp service when available. I've run 2 roof A/C's, fridge and lights when plugged in. I probably would turn off 1 A/C if I ran the microwave though (just to play safe).
I wish you and your family well on your trip!
Dave Wilson
'77 Eleganza II
Photos @ http://www.gmcmhphotos.com/photos/member.php?uid=2183&protype=1
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| Re: [GMCnet] basic shore power question [message #80617 is a reply to message #80611] |
Thu, 15 April 2010 11:32 |
Rick Denney
Messages: 430
Registered: January 2004
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| Richard Lister wrote on Thu, 15 April 2010 11:53 |
Hi all.
We are taking our "new" GMC on its maiden voyage this weekend. Can we plug into a 50 amp power source? I see the plug on the shore power line will fit a 50 amp connection, but the warning label says 40amps...
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Richard, the source can, and should, be as big or bigger than the load. Your coach's 40-amp breakers keep the load from exceeding 40 amps, which means you won't be overloading that 50-amp supply. If you use an adapter and plug it into a 30-amp supply, then you have to make sure your loads do not exceed 30 amps, though the worst that might happen is you pop the breaker on the campsite pedestal. (I have a 50-amp cable but have never exceeded 30 amps in use, with one roof AC, a water heater, a microwave, and a converter, all in intermittent use. If I let the Redhead dry her hair, though, I need to turn something else off. Those hair dryers pull about 10 amps--up to 50% more than the water heater. The roof air requires about 20 briefly on startup, but maybe 12 after that. The water heater is 7 or 8 amps, the converter 4 or 5 when loaded fully, and the microwave as much as 8 amps.)
Rick "who plugs into 50-amp supplies and doesn't worry about anything" Denney
'73 Glacier 230 "Jaws"
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| Re: [GMCnet] basic shore power question [message #80631 is a reply to message #80611] |
Thu, 15 April 2010 13:39 |
bill schurman
Messages: 97
Registered: February 2004
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Rick,
I've run two overhead a/c's on a 50 amp plug. Wasn't that the purpose of the 50 amp plug ?
Bill Schurman
1978 Palm Beach TZE168V100258
Steamboat Springs, CO
at the base of "Rabbit Ears Pass"
With a 7% grade
--- rick@rickdenney.com wrote:
From: Rick Denney <rick@rickdenney.com>
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] basic shore power question
Date: Thu, 15 Apr 2010 11:32:33 -0500
Richard Lister wrote on Thu, 15 April 2010 11:53
> Hi all.
>
> We are taking our "new" GMC on its maiden voyage this weekend. Can we plug into a 50 amp power source? I see the plug on the shore power line will fit a 50 amp connection, but the warning label says 40amps...
Richard, the source can, and should, be as big or bigger than the load. Your coach's 40-amp breakers keep the load from exceeding 40 amps, which means you won't be overloading that 50-amp supply. If you use an adapter and plug it into a 30-amp supply, then you have to make sure your loads do not exceed 30 amps, though the worst that might happen is you pop the breaker on the campsite pedestal. (I have a 50-amp cable but have never exceeded 30 amps in use, with one roof AC, a water heater, a microwave, and a converter, all in intermittent use. If I let the Redhead dry her hair, though, I need to turn something else off. Those hair dryers pull about 10 amps--up to 50% more than the water heater. The roof air requires about 20 briefly on startup, but maybe 12 after that. The water heater is 7 or 8 amps, the converter 4 or 5 when loaded fully, and the microwave as much as 8 amps.)
Rick "who plugs into 50-amp supplies and doesn't worry about anything" Denney
--
'73 Glacier 230 "Jaws"
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| Re: [GMCnet] basic shore power question [message #80633 is a reply to message #80613] |
Thu, 15 April 2010 13:54 |
Kosier
Messages: 834
Registered: February 2008
Karma: 1
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Senior Member |
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Mike,
The basic question is answered in other posts, but I want to
correct the error in your answer.
The GMC comes equipped with two 120 volt circuits, each rated at
40 amps. We have two
'77 coaches that have always been that and the above statement is
a direct quotation from my
1977 owner's manual. I'm not hammering you, but I've seen this
misstatement several times
on the net and have to speak up.
Gary Kosier
77EII & 77PB
Newark, Ohio
----- Original Message -----
From: "Mike Miller" <m000035@gmail.com>
To: <gmclist@temp.gmcnet.org>
Sent: Thursday, April 15, 2010 12:22 PM
Subject: Re: [GMCnet] basic shore power question
>
> Short answer, Yes. You can plug into the 50 amp plugs at RV
> parks.
>
> Little longer...
> There are other 50 amp plugs found elsewhere that may not work,
> these are normally "keyed" differently.
>
> GMC upfitted coaches, like your Kingsley, came from the factory
> with 50 amp plugs feeding a pair of 20amp circuit breakers.
> (One on each leg) That is where the 40 amp limitation comes
> from.
>
> True 50 amp systems are 240v between the legs. (120v to N on
> each leg, 180* out of phase, making 240v difference between the
> legs.) Power feeding one leg is returned down the other leg...
> very little power runs on the neutral, just the imbalance.
>
> You may find RV "50amp" systems that are not 240v but are 120v
> from each leg to neutral. (Same phase on each leg) The stock
> Onan provides this type of power. This works in the stock
> system but ALL the power is returned on the neutral line. This
> is more important if you are replacing cables or installing
> something that expects 240v power. (Not likely.)
>
> I am sure you can get someone to provide an even longer
> answer.... :twisted:
> --
> Mike Miller
> `73 26' X Painted D.
> `78 23' Birchaven
> Hillsboro, OR
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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GMCnet mailing list
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