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Shore Power [message #302231]

Fri, 17 June 2016 16:31

jor

Messages: 43
Registered: June 2016
Location: Tucson

Karma: 0

Member

Another Newbie Question:

In that my new rig has only one air conditioner I intended to install a standard 30 amp RV outlet on the side of my house. However, the GMC's shore power electric setup is a little different than what I am accustomed to. On my previous 50 amp rigs the standard plug consisted of two 120 vac hots, a neutral and a ground. Each hot could supply 50 amps for a total of 100 amps available. A voltmeter across those hots would show 240 volts. Could someone give me a quick brief on the GMC's shore power setup?

Actually, I don't need any more than a 30 amp supply but if I were to add a second air conditioner, for example, would the existing stock wiring support that? Thanks.
jor

John O'Reilly 76 Eleganza II (quad bags, disc brakes w/ reaction arm. 3.70 gears, manny trans, headers, Patterson dist.) Tucson, AZ

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Re: Shore Power [message #302233 is a reply to message #302231]

Fri, 17 June 2016 17:54

tphipps

Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL

Karma: 9

Senior Member

Depending upon who actually finished the coach, there should be a 110 pair in the ceiling near the rear vent. Removing the vent and dropping in a second A/C is not a big deal. Otherwise, you may need to drop a pair of wires.
If you remove the interior trim on the rear vent, you may find the preinstalled pair.
Tom, MS II

2012 Phoenix Cruiser model 2552 KA4CSG

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Re: Shore Power [message #302235 is a reply to message #302231]

Fri, 17 June 2016 18:40

A Hamilto

Messages: 4508
Registered: April 2011

Karma: 39

Senior Member

jor wrote on Fri, 17 June 2016 16:31

Another Newbie Question:
In that my new rig has only one air conditioner I intended to install a standard 30 amp RV outlet on the side of my house. However, the GMC's shore power electric setup is a little different than what I am accustomed to. On my previous 50 amp rigs the standard plug consisted of two 120 vac hots, a neutral and a ground. Each hot could supply 50 amps for a total of 100 amps available. A voltmeter across those hots would show 240 volts. Could someone give me a quick brief on the GMC's shore power setup?

Actually, I don't need any more than a 30 amp supply but if I were to add a second air conditioner, for example, would the existing stock wiring support that? Thanks.
jor

If your Eleganza is wired like my 73s, the shore power plug is a NEMA 50A and the wiring mostly works like you are used to. The only difference is the Onan only puts out 120V, which powers both hot legs. The voltage between the hot leads from the Onan is zero, and between the hot leads from 50A shore power is 240V. Nothing on the stock GMC was wired for 240, so it wasn't needed.

If you add a second roof AC, 30A won't be enough. One OEM roof AC pulls about 16A running and more than 20A to get the compressor spinning every time it kicks on. Even if you had two newer ones with less running current, if both compressors kick on at the same time, the 30A breaker would trip.

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Re: Shore Power [message #302236 is a reply to message #302231]

Fri, 17 June 2016 18:41

Dennis S

Messages: 3046
Registered: November 2005

Karma: 2

Senior Member

Jor

You might go to the GMC east site

http://gmceast.com

And under the tech section read this

http://www.gmceast.com/technical/Denney_GMC_Electrical_Sys.pdf

Dennis

jor wrote on Fri, 17 June 2016 16:31

Another Newbie Question:

In that my new rig has only one air conditioner I intended to install a standard 30 amp RV outlet on the side of my house. However, the GMC's shore power electric setup is a little different than what I am accustomed to. On my previous 50 amp rigs the standard plug consisted of two 120 vac hots, a neutral and a ground. Each hot could supply 50 amps for a total of 100 amps available. A voltmeter across those hots would show 240 volts. Could someone give me a quick brief on the GMC's shore power setup?

Actually, I don't need any more than a 30 amp supply but if I were to add a second air conditioner, for example, would the existing stock wiring support that? Thanks.
jor

Dennis S
73 Painted Desert 230
Memphis TN Metro

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Re: Shore Power [message #302238 is a reply to message #302236]

Fri, 17 June 2016 18:57

jor

Messages: 43
Registered: June 2016
Location: Tucson

Karma: 0

Member

Quote:

The voltage between the hot leads from the Onan is zero, and between the hot leads from 50A shore power is 240V.

That is exactly what I wanted to know. Thanks.

Dennis, good document. I've bookmarked the site. Also, I got a lot of documentation with my rig so I'm going through it now and we just joined GMCMI so I'm getting the USB drive with lots of gigs of reference material. Having a pretty good time!

I'm running the A/C and converter now on a 20a circuit. It's about 102 out and it's holding its own. It will likely pop the breaker on one of its starts but so far so good. Now I just need to decide whether to put a 50 or 30 on the house.
jor

John O'Reilly 76 Eleganza II (quad bags, disc brakes w/ reaction arm. 3.70 gears, manny trans, headers, Patterson dist.) Tucson, AZ

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Re: [GMCnet] Shore Power [message #302240 is a reply to message #302238]

Fri, 17 June 2016 19:14

Ken Henderson

Messages: 8726
Registered: March 2004
Location: Americus, GA

Karma: 9

Senior Member

John,

Install the 50A or, preferably, both. It's much easier to downsize than
upsize.

Ken H.

On Fri, Jun 17, 2016 at 7:57 PM, John O'Reilly
wrote:

> Quote:
>> The voltage between the hot leads from the Onan is zero, and between the
> hot leads from 50A shore power is 240V.
>
> That is exactly what I wanted to know. Thanks.
>
> Dennis, good document. I've bookmarked the site. Also, I got a lot of
> documentation with my rig so I'm going through it now and we just joined
> GMCMI
> so I'm getting the USB drive with lots of gigs of reference material.
> Having a pretty good time!
>
> I'm running the A/C and converter now on a 20a circuit. It's about 102 out
> and it's holding its own. It will likely pop the breaker on one of its
> starts but so far so good. Now I just need to decide whether to put a 50
> or 30 on the house.
> jor
> --
> 76 Eleganza II
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach

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Re: Shore Power [message #302241 is a reply to message #302231]

Fri, 17 June 2016 19:28

JohnL455

Messages: 4447
Registered: October 2006
Location: Woodstock, IL

Karma: 12

Senior Member

Your original paragraph is correct NEMA 14-50R is what you want. 2 hots on different phases, neutral and ground. Though you meter 240V hot to hot, all GMC circuits are referenced to neutral so only 120V is used in the coach.

John Lebetski
Woodstock, IL
77 Eleganza II

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Re: Shore Power [message #302254 is a reply to message #302241]

Fri, 17 June 2016 21:41

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

Put the a 240 volt 50amp out there. It only requires one additional wire, when compared to a 30 service, and a double breaker instead of a single 30. If you have a future need for a 30 device to plug into that receiptical, use an adapter cable that is available almost everywhere including Walmart.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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Re: Shore Power [message #302255 is a reply to message #302254]

Fri, 17 June 2016 21:50

jor

Messages: 43
Registered: June 2016
Location: Tucson

Karma: 0

Member

Quote:

Put the a 240 volt 50amp out there.

Yea, that's what I'll do. What the heck. Might put one in my garage too since I already have 220 there.
jor

John O'Reilly 76 Eleganza II (quad bags, disc brakes w/ reaction arm. 3.70 gears, manny trans, headers, Patterson dist.) Tucson, AZ

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Re: Shore Power [message #302257 is a reply to message #302255]

Sat, 18 June 2016 06:31

tphipps

Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL

Karma: 9

Senior Member

And when you at Wal-Mart purchasing a 50 amp to 30 amp adapter, get the one that is a pigtail with handle. It is easier to work with. Consider also getting a 30amp to 15amp pigtail. No telling which combination you might need. Last trip out, I left the pigtails at home. Guess what I needed. Some one actually had a spare.
Tom, MS II

2012 Phoenix Cruiser model 2552 KA4CSG

[Updated on: Sat, 18 June 2016 06:31]

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