Home » Public Forums » GMCnet » Onan house wiring question
| Onan house wiring question [message #268673] |
Thu, 01 January 2015 23:56  |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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When I pulled the 50A plug out of the cord compartment, I THOUGHT all 4 wires were the same size...#10. Do I mis-remember what I saw?
Reason I ask is that should not the neutral be large enough to carry 50Amps while each hot leg can be #10 for 25Amps?
It would be OK if the two hot legs were out of phase but I didn't think they were???
Can someone school me on this. I may need to run a larger neutral from my automatic transfer switch.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: Onan house wiring question [message #268679 is a reply to message #268673] |
Fri, 02 January 2015 02:29  |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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If they are #10, they are undersized Kerry. Fifty amp really needs #6 in a SO cable and the neutral needs to carry the whole load in a 120 volt system. If you had any 240 volt loads there wouldn't be any added load on the neutral as it will balance out. Your 50 amp service is really 50 amps per leg, actually 100 amps, 120 volt total. Most of our rigs can't use the full 100 amps( 50 amp 2 pole) and a smaller cable will probably work but the over current devise (breaker) at the power pole is higher than the wires capacity.
Clear as mud, right?
Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: Onan house wiring question [message #268688 is a reply to message #268673] |
Fri, 02 January 2015 08:38 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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Hal, the 50A plug in my cord box was wired with solid wire. #10 solid can carry 30A so that part is fine. BUT the Onan puts TWO 25A outputs, one on each hot leg to neutral. The neutral is my concern. If the Onan legs are in phase, then max load would be 50A on that neutral. If they are out of phase then there isn't a problem because only one leg at a time is 'on'. Right? I'm pretty sure they are in phase because there is no reading between the hot legs like there is in a 220 V system.
As I think I understand it, what the RV world uses for 50A is two 25A hots
Dealing with a 120V system with two hot legs in the RV world has my head twisted a bit.
To be safe, I can just replace the neutral with a #8 and be done with it. I can also pull the box out and check the size of the original wiring but I thought I'd ask the brain trust.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: Onan house wiring question [message #268697 is a reply to message #268673] |
Fri, 02 January 2015 10:28 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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kerry pinkerton wrote on Thu, 01 January 2015 23:56When I pulled the 50A plug out of the cord compartment, I THOUGHT all 4 wires were the same size...#10. Do I mis-remember what I saw?
Reason I ask is that should not the neutral be large enough to carry 50Amps while each hot leg can be #10 for 25Amps?
It would be OK if the two hot legs were out of phase but I didn't think they were???
Can someone school me on this. I may need to run a larger neutral from my automatic transfer switch. The Onan legs are in phase and can put out 25A on each leg and the neutral would then be carrying 50A.
On shore power the hots are out of phase and the neutral will never carry more than the difference between the two hot legs. If one hot lead is not carrying any current and the other is at 50A, the neutral will be carrying 50A. If one hot is carrying 10A and the other is carrying 40A, the neutral will be carrying 30A. Simple, right?
[Updated on: Fri, 02 January 2015 10:31] Report message to a moderator |
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| Re: Onan house wiring question [message #268700 is a reply to message #268688] |
Fri, 02 January 2015 11:05 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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kerry pinkerton wrote on Fri, 02 January 2015 09:38Hal, the 50A plug in my cord box was wired with solid wire. #10 solid can carry 30A so that part is fine. BUT the Onan puts TWO 25A outputs, one on each hot leg to neutral. The neutral is my concern. If the Onan legs are in phase, then max load would be 50A on that neutral. If they are out of phase then there isn't a problem because only one leg at a time is 'on'. Right? I'm pretty sure they are in phase because there is no reading between the hot legs like there is in a 220 V system.
As I think I understand it, what the RV world uses for 50A is two 25A hots
Dealing with a 120V system with two hot legs in the RV world has my head twisted a bit.
To be safe, I can just replace the neutral with a #8 and be done with it. I can also pull the box out and check the size of the original wiring but I thought I'd ask the brain trust.
Kerry,
Your confusion is very understandable.
Upsizing the neutral might be a good idea as you are going to electric heat.
#10 in an SJO (90°C) cable is good for about 40 amps, other wire not in a bundle can be good for more.
I am sure that part of GMs reasoning was that they didn't put enough in the coach to draw more.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Onan house wiring question [message #268703 is a reply to message #268697] |
Fri, 02 January 2015 11:20 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
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The Onan 6500 is technically capable of delivering 120-125 Volts AC at 50 Amps (total). Its output is delivered equally to both "hot" terminals of the 240V socket. I believe each "side" of that plug feeds a 20 Amp breaker in the AC distribution panel. Since ALL current passes in the neutral line, that conductor must be capable of handling at least 40 Amps.
The original 50 Amp power cable uses three #6 AWG conductors and one #8 AWG conductor (for safety ground). One of our resident electricians can advise if that is sufficient to handle 40 or 50 Amps.
In the original 50A wiring, the return (common) side wiring MUST be able to handle the FULL amperage delivered by either the genset or the "shore" power connection.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~ ~ ~ ~ TZE166V101966 ~ ~ ~ ~
~ ~ ~ '76 ex-Palm Beach ~ ~ ~
~~ k2gkk + hotmail dot com ~~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
(Politically Incorrect and defiantly proud of that.)
______________
*[ ]~~~[][ ][|\
*--OO--[]---O-*
> Date: Fri, 2 Jan 2015 09:28:14 -0700
> To: gmclist@temp.gmcnet.org
> From: markbb1@netzero.com
> Subject: Re: [GMCnet] Onan house wiring question
>
> kerry pinkerton wrote on Thu, 01 January 2015 23:56
>> When I pulled the 50A plug out of the cord compartment, I THOUGHT all 4 wires were the same size...#10. Do I mis-remember what I saw?
>>
>> Reason I ask is that should not the neutral be large enough to carry 50Amps while each hot leg can be #10 for 25Amps?
>>
>> It would be OK if the two hot legs were out of phase but I didn't think they were???
>>
>> Can someone school me on this. I may need to run a larger neutral from my automatic transfer switch.
> The Onan can put out 25A on each leg and the neutral would then be carrying 50A.
>
> On shore power the neutral will never carry more than the difference between the two hot legs. If one hot lead is not carrying any current and the
> other is at 50A, the neutral will be carrying 50A. If one hot is carrying 10A and the other is carrying 40A, the neutral will be carrying 30A. Simple,
> right?
>
> --
> '73 23' Sequoia For Sale
> '73 23' CanyonLands For Sale
> Upper Alabama
> Perpetually annoyed that "political correctness" and Secular Humanism control every aspect of American life
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| Re: Onan house wiring question [message #268705 is a reply to message #268673] |
Fri, 02 January 2015 12:17 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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Senior Member |
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I think I understand what everyone is saying and agree with you. HOWEVER, I'm confused by the reality of what is in my coach which APPEARS to be original.
The 50A female plug on the front side of the cable storage box is wired with 10-3 with ground that comes out of a steel conduit from below. This is the plug that the power cable plugs into when we want to use the ONAN. The NEUTRAL in the plug is/was wired with a SINGLE #10 white wire.
According to the shop manual (X-7725)in section 24B, there is a 120 V living area schematic. It shows that the wires that come from the ONAN are "#6-2 wire cord in metal conduit. This goes to an outlet box (#10 in the drawing) on the rear side of the cable storage box. Item #2 in the drawing is another cable box containing "#8 wire cord type '50' with plug". That is #8 wire going to the female 50A plug in the cable box.
So I pull the back of my closet and sure enough there is the 1" steel flexible conduit. As luck would have it, the spiral conduit has opened up and I can see there are indeed TWO #6 black wires inside it. NOTHING ELSE! So I look toward the cable storage box and EXPECT to see a junction box where these 2 #6 wires are split into the 10-3 with ground. No box, and no sign there ever was a box attached to the black plastic cable storage box. The steel conduit runs directly on top of the wheel well and turns up into the outlet box that contains the 50A female plug.
There ain't no other boxes between where I can see the two #6 wires and where the four #10 wires come out and go into the female 50A plug.
So I am left with these conclusions:
1- SOMEWHERE in the conduit between where I can see the two #6 wires and the female 40A plug, there are some cable splices.
2- The conduit itself is used for ground. This is OK.
3- One of the #6 wires is split into TWO #10 wires that feed into the 50A female. That's OK but I would have expected it to be at least two #8 wires (the insulation is marked 10 and it measures .10 which is #10.
4- The OTHER #6 wire is the neutral and is connected to a #10 white wire neutral. This is not large enough for a 50A neutral and should have been at least a #8 as shown in the diagram in the shop manual X-7725
Now, my coach has the buzz box replaced by a PD unit so sometime or another someone has been into the electricals and for some reason replaced the junction box that had the two #6 wires going to four #8s with four #10s.
I want to fix this so it is correct and safe. The fact that I won't pull over 30 amps means I won't overheat the #10 wires TODAY but down the road if I add more stuff or turn on too much stuff today, I could have a problem.
Remember, I have just installed an automatic transfer switch. So here are the questions:
1- HOW was this thing wired originally?
2- In the rear outlet box did the ONE of the #6 wires get broken out to a #8 neutral (white), the other #6 became TWO #8 hot (black) wires), and the conduit become a #8 ground?
3- Does it make any difference WHICH black wire is used for hot or neutral?
Given that I won't be using the 50A female plug any longer, I can put an outlet box behind the closet and break it out as described in #2 (or whatever is the correct way...HELP) and just run that to the transfer switch.
OR I could run a whole new 4 wire #8 (or #6) back to the ONAN output and tie it all together there.
I'm still a bit confused because this doesn't make much sense to me. I have verified that there are two #6 wires coming out of the ONAN. I don't understand why GMC would have run #6 forward and then gone to #8. Why not run #8 all the way?
Advice please.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] Onan house wiring question [message #268706 is a reply to message #268705] |
Fri, 02 January 2015 12:29 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
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Senior Member |
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Hi, Kerry!
What you have described below seems to me to be what is commonly known as a "Cluster Foxtrot." I can only surmise that some P.O. (or maybe more than one) has really gone whacko on your wiring.
I know that you are quite a few hundred miles from Jim Bounds' COOP, but I really suggest that you give him a call and see what he suggests. I know that he and his troops have rewired MANY coaches to get them safe and efficient.
He may be able to suggest at least a temporary solution to improve safety in your wiring.
I would THINK that any power input to the coach (Onan or shore power) should first go to the distribution box's main circuit breakers.
You MAY wish to schedule a trip down to Orlando to get things brought up to best possible condition.
Good luck, no matter which way you proceed.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~ ~ ~ ~ TZE166V101966 ~ ~ ~ ~
~ ~ ~ '76 ex-Palm Beach ~ ~ ~
~~ k2gkk + hotmail dot com ~~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
______________
*[ ]~~~[][ ][|\
*--OO--[]---O-*
> Date: Fri, 2 Jan 2015 11:17:06 -0700
> To: gmclist@temp.gmcnet.org
> From: Pinkertonk@MCHSI.com
> Subject: Re: [GMCnet] Onan house wiring question
>
> I think I understand what everyone is saying and agree with you. HOWEVER, I'm confused by the reality of what is in my coach which APPEARS to be
> original.
>
> The 50A female plug on the front side of the cable storage box is wired with 10-3 with ground that comes out of a steel conduit from below. This is
> the plug that the power cable plugs into when we want to use the ONAN. The NEUTRAL in the plug is/was wired with a SINGLE #10 white wire.
>
> According to the shop manual (X-7725)in section 24B, there is a 120 V living area schematic. It shows that the wires that come from the ONAN are
> "#6-2 wire cord in metal conduit. This goes to an outlet box (#10 in the drawing) on the rear side of the cable storage box. Item #2 in the drawing
> is another cable box containing "#8 wire cord type '50' with plug". That is #8 wire going to the female 50A plug in the cable box.
>
> So I pull the back of my closet and sure enough there is the 1" steel flexible conduit. As luck would have it, the spiral conduit has opened up and I
> can see there are indeed TWO #6 black wires inside it. NOTHING ELSE! So I look toward the cable storage box and EXPECT to see a junction box where
> these 2 #6 wires are split into the 10-3 with ground. No box, and no sign there ever was a box attached to the black plastic cable storage box. The
> steel conduit runs directly on top of the wheel well and turns up into the outlet box that contains the 50A female plug.
>
> There ain't no other boxes between where I can see the two #6 wires and where the four #10 wires come out and go into the female 50A plug.
>
> So I am left with these conclusions:
>
> 1- SOMEWHERE in the conduit between where I can see the two #6 wires and the female 40A plug, there are some cable splices.
>
> 2- The conduit itself is used for ground. This is OK.
>
> 3- One of the #6 wires is split into TWO #10 wires that feed into the 50A female. That's OK but I would have expected it to be at least two #8 wires
> (the insulation is marked 10 and it measures .10 which is #10.
>
> 4- The OTHER #6 wire is the neutral and is connected to a #10 white wire neutral. This is not large enough for a 50A neutral and should have been at
> least a #8 as shown in the diagram in the shop manual X-7725
>
> Now, my coach has the buzz box replaced by a PD unit so sometime or another someone has been into the electricals and for some reason replaced the
> junction box that had the two #6 wires going to four #8s with four #10s.
>
> I want to fix this so it is correct and safe. The fact that I won't pull over 30 amps means I won't overheat the #10 wires TODAY but down the road if
> I add more stuff or turn on too much stuff today, I could have a problem.
>
> Remember, I have just installed an automatic transfer switch. So here are the questions:
>
> 1- HOW was this thing wired originally?
>
> 2- In the rear outlet box did the ONE of the #6 wires get broken out to a #8 neutral (white), the other #6 became TWO #8 hot (black) wires), and the
> conduit become a #8 ground?
>
> 3- Does it make any difference WHICH black wire is used for hot or neutral?
>
> Given that I won't be using the 50A female plug any longer, I can put an outlet box behind the closet and break it out as described in #2 (or whatever
> is the correct way...HELP) and just run that to the transfer switch.
>
> OR I could run a whole new 4 wire #8 (or #6) back to the ONAN output and tie it all together there.
>
> I'm still a bit confused because this doesn't make much sense to me. I have verified that there are two #6 wires coming out of the ONAN. I don't
> understand why GMC would have run #6 forward and then gone to #8. Why not run #8 all the way?
>
> Advice please.
> --
> Kerry Pinkerton
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, Manny Brakes, 1 ton, tranny also a 76 Eleganza to be re-bodied as an Art Deco car hauler
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| Re: Onan house wiring question [message #268708 is a reply to message #268673] |
Fri, 02 January 2015 12:47 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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Senior Member |
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Upon further inspection, what appears to be TWO #6 wires in the conduit apparently is two pair of wires in a single sheath. One sheath has two black wires that measure 0.10 (which is #10 AWG) and the other pair is two white wires. I can't get to the box in the back of the ONAN compartment to verify unless I pull the ONAN which I don't really want to do.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: Onan house wiring question [message #268710 is a reply to message #268673] |
Fri, 02 January 2015 14:08 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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Senior Member |
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More info and a question.
The two white wires in a sheath and two black wires in a sheath will be OK for 50 A IF, the two white wires are bonded to one of the ONAN outputs and the two black wires bonded to the other AND the metal conduit is used for ground.
IF that is the way GMC did it, then what I had was a PO that moved a neutral to ground on the 50A plug. All I would need to do is put both the #10 whites to neutral AND connect the ground to the metal conduit which runs back to ONAN ground.
Does anyone know?
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] Onan house wiring question [message #268729 is a reply to message #268724] |
Fri, 02 January 2015 18:24 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Senior Member |
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Things are a bit confusing Kerry but I think you are correct in using the two black #10 wires as hot conductors and the parallel whites as the neutral. I'd be a little concerned using the conduit for the safety ground and would pull a # 10 ground wire into the flex for a better installation. Codes have changed over the years and a ground wire would be used today in your application. If you don't wish to pull another green conductor in at least install some set screw connectors on either end of the flex.
BTW, a 50 amp service does have a two pole 50 amp over currant devise, 50 amps on both legs. Some early RV parks did have two pole 25 amp service that they 'called' 50 amps, but I doubt you'll find any today.
Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: [GMCnet] Onan house wiring question [message #268738 is a reply to message #268690] |
Fri, 02 January 2015 20:24 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Steve,
Most Birchavens and Royales were equipped with 30A cords. That's what I've
had for 15+ years and would return to it immediately if I got saddled with
a 50A. No sense manhandling that monster when the coach doesn't need it.
Even if I had two A/C's, I'd serve the second one with a separate circuit.
Ken H.
On Fri, Jan 2, 2015 at 10:23 AM, Steve Weinstock
wrote:
> Well...
>
> My 50 amp cord is somewhat difficult to manage. Mostly for coiling it up
> into the storage compartment.
>
> Folks have recommended replacement with a smaller and more flexible 30 amp
> cord - and then using a plug adapter to plug it into the 50 amp generator
> plug.
>
> It's a 23' coach with only one rooftop air conditioner.
>
> Thoughts ?? Advice ??
>
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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: [GMCnet] Onan house wiring question [message #268739 is a reply to message #268738] |
Fri, 02 January 2015 20:36 |
Emery Stora
Messages: 959
Registered: January 2011
Karma: 4
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Senior Member |
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Lets not overlook the fact that the "50 amp" in the GMC was actually 40 amp. If one looks closely at the cable it is stamped 40 amps all along the cable.
Emery Stora
77 Kingsley
Frederick, CO
> On Jan 2, 2015, at 7:24 PM, Ken Henderson wrote:
>
> Steve,
>
> Most Birchavens and Royales were equipped with 30A cords. That's what I've
> had for 15+ years and would return to it immediately if I got saddled with
> a 50A. No sense manhandling that monster when the coach doesn't need it.
> Even if I had two A/C's, I'd serve the second one with a separate circuit.
>
> Ken H.
>
>
> On Fri, Jan 2, 2015 at 10:23 AM, Steve Weinstock
> wrote:
>
>> Well...
>>
>> My 50 amp cord is somewhat difficult to manage. Mostly for coiling it up
>> into the storage compartment.
>>
>> Folks have recommended replacement with a smaller and more flexible 30 amp
>> cord - and then using a plug adapter to plug it into the 50 amp generator
>> plug.
>>
>> It's a 23' coach with only one rooftop air conditioner.
>>
>> Thoughts ?? Advice ??
>>
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