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Old 12-27-2011, 02:57 PM   #1
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Help! what is causing this?


hello.

I purchased an older greenville county portable class room which was probably made in the 80s. has a 200 amp main panel, single phase, neutral and ground on same bar. this will be used a shed and there is no grid power whatsoever where it was delivered. I also bought a good old 3 phase generator (4 wires) (correction:5 wires) running on LP mounted on a traiker which will be the sole way to power the shed/classroom. long story short in an effort to save $$$ and re use most of the existing hardware i buy a 3 prong box and plug rated at 50 amp and make a quick connect/disconnect where the shed plugs in the generator (using only two phases). so everything powers up fine, have 2 hot. (115v) coming in the shed's main panel UNTIL I flip a 20 amp breaker on. then one bus reads 60v and one 170V. breakers are good, panel checks up good, everything seems wired soundly.
generator is an older industrial generac model sg15 model powered by 1.3l mazda engine no other information is visible. what is going on?


Last edited by nsxtasy; 12-27-2011 at 06:13 PM.
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Old 12-27-2011, 02:59 PM   #2
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Help! what is causing this?


loose/missing neutral from generator

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Old 12-27-2011, 03:18 PM   #3
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Help! what is causing this?


Thank you for your quick reply. How can I check it is indeed loose/missing and later that I fixed it?
My setup currently is as follows: The neutral (white cable) on the generator is tied in at a different location than the ground (green cable). The plug receptacle on the generator uses the ground which is tied in with the old utility's bare cable.
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Old 12-27-2011, 03:22 PM   #4
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Help! what is causing this?


Quote:
Originally Posted by nsxtasy View Post
Thank you for your quick reply. How can I check ..... that I fixed it?
Flip the 20 amp breaker and get 120 volts on both inputs.
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Old 12-27-2011, 03:24 PM   #5
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Help! what is causing this?


Can you give us some specifics about the three phase generator? Specifically, what are the phase to phase voltages this generator puts out, and is it wired delta or Wye?
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Old 12-27-2011, 03:37 PM   #6
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Quote:
Originally Posted by joed View Post
Flip the 20 amp breaker and get 120 volts on both inputs.
If you you saying to connect the generator to the shed, fire it up, flip any 20 amp breaker on and check both inputs (big black wires to the shed's panel) then this is what i did and got 60 on one and 170 on the other. When I turn all breakers off, I get 115 v on each. If I misunserstood, please forgive me and spell it out for me

If i keep the shed's main off and feed 115v directly to the shed's outlet thru a male-male extension cord, i have 115v ok on the bus which has that breaker...

Last edited by nsxtasy; 12-27-2011 at 03:46 PM.
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Old 12-27-2011, 03:43 PM   #7
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Help! what is causing this?


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Originally Posted by Daniel Holzman View Post
Can you give us some specifics about the three phase generator? Specifically, what are the phase to phase voltages this generator puts out, and is it wired delta or Wye?
Unfortunately I dont know much about this genset. It s made by generac, its an industrial version thats mounted on a trailer. It came wIth no manuals. all I know it is a 3 phase generator with 4 (correction:5) wires coming out of the winds. 1 of the wires goes to the ground (correction: 1 goes to neutral) and 3 goto a breaker of 60 amps. If a measure voltage between any of the black wires and ground I get 115 and if I measure voltage between any of the black wires I get 230. If you can teach me and walk me thru how to test I wIll gladly try It out...

Last edited by nsxtasy; 12-27-2011 at 06:12 PM.
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Old 12-27-2011, 05:06 PM   #8
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Help! what is causing this?


If the panel is single phase,
Then you DO NOT need two hots,
unless you intend to have only 230v.

If you want 115v,
then you need ONLY ONE HOT,
and a neutral.

You said you have two hots.
WHY TWO HOTS !
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Old 12-27-2011, 05:16 PM   #9
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Originally Posted by dmxtothemax View Post
If the panel is single phase,
Then you DO NOT need two hots,
unless you intend to have only 230v.

If you want 115v,
then you need ONLY ONE HOT,
and a neutral.

You said you have two hots.
WHY TWO HOTS !
Thank you for your reply. The panel on the shed (the generator also has a panel) is what understand to be a single phase but wired for 230V b/c there is an a/c unit and 4 electric heaters. The shed's main panel has 2 black wires and one bare cable.
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Old 12-27-2011, 05:31 PM   #10
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Help! what is causing this?


Quote:
Originally Posted by nsxtasy View Post
If you you saying to connect the generator to the shed, fire it up, flip any 20 amp breaker on and check both inputs (big black wires to the shed's panel) then this is what i did and got 60 on one and 170 on the other. When I turn all breakers off, I get 115 v on each. If I misunserstood, please forgive me and spell it out for me

If i keep the shed's main off and feed 115v directly to the shed's outlet thru a male-male extension cord, i have 115v ok on the bus which has that breaker...
No. I am saying after you think you have the problem resolved then do the same test you just did to verify it is cured.

You need to find out more about your genny. You don't mention a neutral only a ground. You need to determine if it is delta or wye and if there is a neutral and where it is connected. It seems it is not connected to the ground. It is possible there was never a neutral used on this unit if it was not required for the attached loads.
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Last edited by joed; 12-27-2011 at 05:34 PM.
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Old 12-27-2011, 05:32 PM   #11
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Help! what is causing this?


If the panel to be fed is two hots,
You can tell for sure by looking at the main switch/breaker,
How many connections are on the feed in side ???

the other most likely problem is your neutral bad.
Make sure the main neutral in the panel
is solidly connected to the main neutral of the genny.

Correct connection details can be found online,
just find the model number and do a google search.

Also find out if it is DELTA OR WYE ?
Cause if you are trying to use a delta genny in a wye configuration it wont work !

If you can find the model number,
put it online, and we can interperate further.
This part is important !

Last edited by dmxtothemax; 12-27-2011 at 05:38 PM.
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Old 12-27-2011, 05:50 PM   #12
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Help! what is causing this?


Quote:
Originally Posted by joed View Post
You need to find out more about your genny. You don't mention a neutral only a ground.
This is correct. When looking at the genset's electrical panel, there are only 4 (correction:5) wires coming in. One goes to the side where the grounds are, (correction: one goes to neutral) and the 3 others to that 60 amp breaker I already mentioned. I do not see any neutral coming from generator (correction: on closer inspection there is a neutral wire coming from generator) The outlets that are on the generator do use neutral.

Quote:
Originally Posted by joed View Post
You need to determine if it is delta or wye and if there is a neutral and where it is connected. It seems it is not connected to the ground. It is possible there was never a neutral used on this unit if it was not required for the attached loads.
This is an older model. Internet info are very limited. I already contacted the manufacturer and they sent me info on the mazda engine but nothing on the generator side. It is a SG15 unit. Is there a way to test/tell if it's a wye or delta config?

Last edited by nsxtasy; 12-27-2011 at 06:09 PM.
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Old 12-27-2011, 06:11 PM   #13
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Help! what is causing this?


Folks, I messed up. There is a fifth wire coming from the generator that goes to the neutral bar which is independent of the ground and is not connected to the chassis like the ground is. I am correcting my posts to reflect this new information. I apologize if I misguided you.
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Old 12-27-2011, 06:52 PM   #14
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Help! what is causing this?


Here are some pictures to help you help me





Last edited by nsxtasy; 12-27-2011 at 07:01 PM.
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Old 12-27-2011, 07:37 PM   #15
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Help! what is causing this?


thanks for your reply,
[quote=dmxtothemax;801548]
You can tell for sure by looking at the main itch/breaker,
How many connections are on the feed in side ???
[\quote]
two

[quote=dmxtothemax;801548]
the other most likely problem is your neutral bad.
Make sure the main neutral in the panel
is solidly connected to the main neutral of the genny.
[\quote]
there is no neutral in the panel, just ground

Quote:
Correct connection details can be found online,
just find the model number and do a google search.

Also find out if it is DELTA OR WYE ?
Cause if you are trying to use a delta genny in a wye configuration it wont work !

If you can find the model number,
put it online, and we can interperate further.
This part is important !
are you saying what I have in the shed is a wye configuration?


Last edited by nsxtasy; 12-27-2011 at 07:57 PM.
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