| Plugging in to shore power [message #351375] |
Mon, 13 January 2020 07:18  |
6cuda6
Messages: 975
Registered: June 2019
Karma: -6
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Whats better....plugging into a 50amp outlet with an adaptor to 30amps or plugging into the 30amp outlet directly with a 30amp coach.
Curious to see what people hsve found if the 50amp with 30 adapter is better or 30amp direct puts out better power at sites.
Rich Mondor,
Brockville, ON
77 Hughes 2600
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| Re: Plugging in to shore power [message #351377 is a reply to message #351375] |
Mon, 13 January 2020 09:15  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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Same same. The pedestal will supply up to 30 amps at 120 volts maximum no matter what you plug into it.
I prefer 240 volt at 50 amp because most places have this service these days and the cable will have 1/2 of the total current draw across any of the conductors for the same load. If I am forced to use a 30 amp pedestal then I simply add an adapter to the cable.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Plugging in to shore power [message #351379 is a reply to message #351378] |
Mon, 13 January 2020 11:36 |
mghamms
Messages: 466
Registered: March 2016
Location: Ware, Massachusetts
Karma: 2
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the 30 amp plug gives 30 amps at 120 volts.
The 50 amp plug gives 50 amps on each leg so 100 amps at 120 volts.
1977 Kingsley 455 as stock as it gets except lots of Ragusa parts
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| Re: Plugging in to shore power [message #351381 is a reply to message #351375] |
Tue, 14 January 2020 08:28 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
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Technically the 50 to 30A adaptor is not code. (14-50 to TT-30)
The post breaker is over sized for protecting the 30A cord set.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Plugging in to shore power [message #351385 is a reply to message #351379] |
Tue, 14 January 2020 19:30 |
Bullitthead
Messages: 1411
Registered: November 2013
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No 100 amps from the 50 amp circuit...25 amps on each power leg to neutral at 120 volts and 50 amps between both power legs at 240 volts.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: Plugging in to shore power [message #351386 is a reply to message #351385] |
Tue, 14 January 2020 20:45 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
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It's 50 amps per leg, a 2 pole 50 amp over currant devise. You can call it 100 amps but it's really 50 amps @ 240 volts. If you tried to pull 100 amps @ 120 volts you'd put twice the amps on the grounded conductor (neutral) that it is rated for. If you had a 2 pole 25 amp breaker, I'd give you the 50 amp total but again the same conditions applying to the neutral.
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: Plugging in to shore power [message #351388 is a reply to message #351386] |
Wed, 15 January 2020 06:38 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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Hal, I will enter the fray here.
The current on the neutral conductor will be the difference of the two hot conductors, not the sum. So if you had 25 amps on each of the hot conductors, the current on the neutral would be ZERO amps. If you had 25 on one and 20 on the other, then the current on the neutral would be 5 amps.
Respectively,
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Plugging in to shore power [message #351389 is a reply to message #351375] |
Wed, 15 January 2020 08:14 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
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Very true Ken B. But to be even pickier, GMC upfit coaches usually have a 40A dual pole main breaker at the coach box. When on Onan, the full combined L1 and L2 is carried by the neutral, but the 50A Onan breaker protects the cord set which was not designed for 80A on the neutral. So they thought it through
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Plugging in to shore power [message #351390 is a reply to message #351389] |
Wed, 15 January 2020 09:40 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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You are correct. I thought were were talking feeding the coach with 240 volt shore power vs. 30 amp 120 volt shore power.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Plugging in to shore power [message #351391 is a reply to message #351375] |
Wed, 15 January 2020 09:50 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
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We were. But to truly understand the reasons "why" , you really need a full understanding of the system. I assume he has a TT-30 non GMC upfit system. So-- if you have an 14-50P to TT-30R adapter at the shore post, you have the potential of overheating the TT-30 cord set, should a fault occur.
John Lebetski
Woodstock, IL
77 Eleganza II
[Updated on: Wed, 15 January 2020 09:51] Report message to a moderator |
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| Re: Plugging in to shore power [message #351392 is a reply to message #351391] |
Wed, 15 January 2020 10:59 |
Bill Van Vlack
Messages: 419
Registered: September 2015
Location: Guemes Island, Washington
Karma: 14
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Here is Blue Sea's explanation and diagram of neutral current on a 220/110v electrical system... As Ken Burton points out above, the load on the neutral is the imbalance of the load on each leg, so, for L1 at 15A load and L2 at 20A load the neutral load is 20-25=5 Amps.
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid November 2015.
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| Re: Plugging in to shore power [message #351393 is a reply to message #351388] |
Wed, 15 January 2020 18:33 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
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Ken Burton wrote on Wed, 15 January 2020 05:38Hal, I will enter the fray here.
The current on the neutral conductor will be the difference of the two hot conductors, not the sum. So if you had 25 amps on each of the hot conductors, the current on the neutral would be ZERO amps. If you had 25 on one and 20 on the other, then the current on the neutral would be 5 amps.
Respectively,
Ken B.
True only if they are on different phases. When people start using 50/30 adapters loads imposed on the neutral can get out of wack depending on how the rest of the system is wired.
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: Plugging in to shore power [message #351394 is a reply to message #351375] |
Wed, 15 January 2020 19:37 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Sir, I prefer to plug our 30 amp Crestmont in a 30 amp outlet while I prefer to plug our 50 amp Eleganza II in a 50 amp outlet.
6cuda6 wrote on Mon, 13 January 2020 08:18Whats better....plugging into a 50amp outlet with an adaptor to 30amps or plugging into the 30amp outlet directly with a 30amp coach.
Curious to see what people hsve found if the 50amp with 30 adapter is better or 30amp direct puts out better power at sites.
C. Boyd
76 Crestmont
East Tennessee
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| Re: Plugging in to shore power [message #351404 is a reply to message #351394] |
Fri, 17 January 2020 09:17 |
Melbo
Messages: 144
Registered: August 2018
Location: Albuquerque NM
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Isn't electricity fun?
If properly wired it should be as Ken says.
If not done properly you could end up with what Hal says.
Most of the "newer" pedestals seem to be wired correctly and I personally have not had issues. In older parks or Mexico I never trust them and typically check with a meter before connecting. If I get zero volts across the two hots on a 50 amp receptacle and 120 volts on each leg to ground I severely limit my electrical use just to be safe.
Just My Way.
HTH
Melbo
Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
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| Re: Plugging in to shore power [message #351405 is a reply to message #351375] |
Fri, 17 January 2020 09:33 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
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Besides all the other reasons listed, the more adaptors you add, the more Voltage drop you get, if the connectors are warm, you are losing Voltage. At some point it's like Clark Griswold in Christmas Vacation
John Lebetski
Woodstock, IL
77 Eleganza II
[Updated on: Fri, 17 January 2020 09:35] Report message to a moderator |
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| Re: Plugging in to shore power [message #351406 is a reply to message #351393] |
Fri, 17 January 2020 10:10 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
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Ken Burton wrote on Wed, 15 January 2020 05:38Hal, I will enter the fray here.
The current on the neutral conductor will be the difference of the two hot conductors, not the sum. So if you had 25 amps on each of the hot conductors, the current on the neutral would be ZERO amps. If you had 25 on one and 20 on the other, then the current on the neutral would be 5 amps.
Respectively,
Ken B.
Hal StClair wrote on Wed, 15 January 2020 19:33True only if they are on different phases. When people start using 50/30 adapters loads imposed on the neutral can get out of wack depending on how the rest of the system is wired.
Hal
Hal,
There is a severe nomenclature problem here.
For a 14-50 receptacle to be approved, the two hot (L1,L2) have to be the opposite ends of the same phase. This makes those two 180° out of phase. This is colloquially described in the trade (was mine once) as the "other side of the phase". Then we get to Y vs Delta vs Star (Multi-phase not seen shore-side).
If they were one leg on another phase, it would not be 240-120/120 because the legs would not not be 180° out, but leading or lagging by 120°. That is when you see numbers like 208, 168 & 86 Volts and now the guy that had to fix it has to try to find out what got done where and get the power back where the Chief wants it.
If someone were to connect a 14-50 as you suggest, yes, the neutral would be at risk. But, I do believe that in the USA and Canada most of that stuff is inspected. If a GMC owner does not carry a meter, he should get one at Hazard Fright for cheap. Most other 50 amp coaches that I have seen have safety systems or power protection devices that would warn the owners of this case.
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: Plugging in to shore power [message #351407 is a reply to message #351404] |
Fri, 17 January 2020 10:12 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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One of the things I always do is check the connector(s) with my hand to see if any are getting warm. I do this after 5 or 10 minutes of running the coach and again a hour or two later.
Where there is heat there is a poor connection or an undersized wire. I also keep a 3 light tester inside. I just leave it plugged in all the time. Usually in the kitchen plug.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Plugging in to shore power [message #351408 is a reply to message #351375] |
Fri, 17 January 2020 11:59 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Since Matt got into the nuts and bolts of 14-50, there is one more "odd" condition to be aware of. If the neutral has a poor connection, your Voltage on the lighter loaded leg can swing ABOVE the 125V mark. This is because the lack of neutral connections allows the one phase to reference the other approaching the 240V present.
John Lebetski
Woodstock, IL
77 Eleganza II
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