Generator install at house

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  #1  
Old 02-16-15, 05:04 AM
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Generator install at house

I am installing a 25kw Generac Guardian - older one 0913-2 -
It has 125 Amp breakers on the box on the gen set. I am running about 50 feet to a 200 Amp service, manual throw, GE Transfer Switch that was installed by the electricians when my house was built a few months ago.

Questions:
-I am intending to use Aluminum, 1-0, stranded, USE-2, single wire cable (three runs phase, phase, neutral) is this too heavy, can I get by with # 1 gauge?

-Trench depth. Is there a national code or is it a state/local code for trench depth and width? If local does anyone happen to know or can look up the code for Douglas County Colorado?

-Is it necessary to have a riser pipe on both ends, house and gen? Is there a mounting brace/bracket requirement?
Thanks
 
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Old 02-16-15, 06:17 AM
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The #1/0 aluminum is the minimum size you can use for 125A. It needs to be buried 24" deep if directly buried cable or 18" deep if pulled through PVC conduit. Riser pipes from the trench bottom are required in either case. They do not need to be fastened underground, but need to be secured with clamps every 3' above grade.
 
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Old 02-16-15, 06:46 AM
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Will I have to run a 4th wire for ground to the transfer switch?. Another #1-0 or something smaller. Or just earth the generator at the generator?
 
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Old 02-16-15, 07:00 AM
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Could you tell us about the wiring at the transfer switch relative to the meter and main panel? How about the grounding at the service entrance? How many wires at each and where are the breakers located? It would be really helpful if you could post pictures of the interiors of the transfer cabinet and the main panel cabinet.

In any case it is wrong to ground the generator directly to the earth.
 
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Old 02-16-15, 07:16 AM
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The transfer switch is wired as a normal manual switch. Meter comes in with 2 phases and a neutral to on side of switch, main panel is wired to the center of the switch to the 200 amp main breaker in the box.
I am not at home. Working offshore in Africa right now so can't post pics. But I believe there is a grounding rod outside at the entrance with a #10 or 12 copper bare wire to it from the main panel. Can't recall seeing anything else in the Transfer switch box but the 3 big aluminum wires from the meter.
The transfer switch is mounted inside the garage right next to the main panel. All put in by an electrician when the house was built a few months ago.
 
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Old 02-16-15, 07:25 AM
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Ok, that would be tough to get pics. My biggest concern is where the neutral-ground bond is in your service entrance. In a configuration like this it would sometimes be in the transfer switch and sometimes be in the main panel. That has some effect on where and how the service and generator is grounded.
 
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Old 02-16-15, 07:43 AM
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Ok that's good to know. Will have to sort that out as I wire it.
Will that be an issue of running a separate ground to the generator and connecting in the panel or the transfer switch or moving a ground from the panel to transfer switch or vice versa?
 
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Old 02-16-15, 08:17 AM
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Terminology note:
Meter comes in with 2 phases
No such critter since the early 1900s and even then not residential. You have single phase. Each hot is a leg.
 
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Old 02-16-15, 09:16 AM
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OK. Thanks for the terminology correction, "legs" is right . Yes, I do understand I have single phase.
 
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Old 02-17-15, 12:41 AM
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I am not at home so can't actually check but assume I could take an ohmmeter and check for a neutral/ground bond in the generator. I looked at the schematics for the generator and can't see one there. Here is a link to the drawing http://www.zabatt.com/generators/pro...als/0c1000.pdf .
If there is no bonding point in the generator and the bond is on the middle post of the transfer switch I am thinking it will be ok. Or if it is in the main service panel can it be moved to the transfer switch so it serves the utility service entrance and the generator depending on which is the in-use power source?
 
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Old 03-06-15, 09:31 AM
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Generator Install at house

I am back at home and able to look at my panel and Transfer switch. I have attached some pictures of both.
Looks like the Neutral-Ground bond is in the Transfer switch (see pic) which I would assume is correct as it is the closest to the meter entrance and will be the closest to the generator.

My question now is to earth the generator (I assume that is necessary) do I run a wire/cable from the generator to the tie point in the Transfer switch (at the bonding block at the bottom) and if so what gauge wire do I need to use. I intend to use 1-0 for the 2 legs and neutral from the generator as it has a 125 amp breaker at the output.
Is it normal to have a transfer switch only on the two 120volt legs and not switch the neutral in the transfer switch?
Having trouble inserting pictures. Upload keeps failing
 
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Old 03-06-15, 09:49 AM
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Generator Install at house

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Old 03-07-15, 03:21 PM
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Wire size/type

Looking at 1-0 aluminum cable for the generator to indoor transfer switch.
Length is about 60' per leg and neutral. Breaker on generator is 125 amp.
Question is type of direct burial cable. If I put in a USE-2 cable it can carry 130 amps per tables. But does it need a dual rating as in" Type USE-2/RHH/RHW-2" so it can be run underground as well as continuing into the building and into the transfer switch as in pictures below? i.e same cable underground as well as inside conduit inside the building?
 
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Old 03-09-15, 06:57 AM
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The #1/0 aluminum should be ok for the hots and neutral, #4 aluminum for the ground. The USE needs to have the RHW rating for it to be legal entering the house. If it is only USE/URD it cannot enter the home. Make sure to use noalox paste on the aluminum wire terminations.
 
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Old 03-09-15, 07:40 AM
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Generator Install at house

Thanks for that Ben
Reading the code here and since the generator is 50 feet away from the house.... it is a little unclear as to the earth connection wire to the generator as far as the type and insulation. Reading it I am getting that I can use a bare copper wire (#6) or if I go with the #4 aluminum it cannot be bare, i.e. needs a USE insulation as the aluminum can't be exposed to the earth. If that is the case would an aluminum earth wire also have to have the USE and RHW rating?
 
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Old 03-09-15, 02:15 PM
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Yes, but that's probably all you would find anyway. Aluminum wire is almost exclusively made with cross-linked polyethylene insulation and listed as either URD or USE/RHH/RHW/XHHW. Really the only difference between those is the insulation thickness and how much flame retardants and UV inhibitor additives are in the mix.

Honestly I don't know the specifics that well of doing a generator 50 feet from the house. We almost exclusively install them right next to a building. I can see the inspector wanting a separate earthing means (ground rods) installed at the generator, or I can also see them being okay with just using the house earthing. The code doesn't explicitly define what an "outbuilding" is in this case -- the generator pad could qualify so it's an issue of interpretation.

I don't think you would go wrong installing a rod at the generator and bonding it to the ground wire and to the generator frame lug.
 
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