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Old 11-27-2007, 11:36 PM   #16
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100 amp sub panel hook up?


Ponch

You are good to go with 1 1/2 pvc if you choose to run the ser. You are allowed a 53% fill of 1.052 inch squared for a cable in 1 1/2 pvc. Ser 2-2-2-4 is 955 mils.... converted it is .7159 inch squared so it is well below the max. 53% fill.

Yes.... 6 guage copper gec to the ground rods.

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Last edited by Stubbie; 11-27-2007 at 11:51 PM.
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Old 11-27-2007, 11:54 PM   #17
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100 amp sub panel hook up?


Thanks for all the info and advice stubbie. I will see what i can come up with for the wire but whatever i get i will know it is done right thanks to you. Why not run cable in conduit? What would be my other options? mobile home wire? THHN in conduit?
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Old 11-28-2007, 12:16 AM   #18
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100 amp sub panel hook up?


Yes... those are good options I posted a link to mobile home feeder in a post just before this. IMO the biggest draw back to cable in conduit is it is really hard to pull through and it is not quite as good at getting rid of heat in conduits as it would be with individual conductors like thwn.....thhn is not wet rated but most thhn is now dual rated for wet location and will show thhn/thwn on the outer insulation.. (w) = wet rated. Underground runs of conduit are considered wet locations as the conduit over time will get water in it.

If we had the input amperage of the welder and the amperage of the air compressor and voltage requirements we might be able to get a little more accurate with the amperage you need out at the garage. If you can give me that or the names of the manufacturers and model numbers I might be able to figure that up and get a better handle on the power requirements for the garage. At any rate 90 amps will certainly take care of now and future needs. So look at it in terms of cost benefit. If you can get by on 60 or 70 amp feed we can get the wire size down and conduit size down etc...Direct bury saves a little in labor and conduit costs.

Also if you use conduit you can always install larger conductors someday if needed. You just have to try to be realistic about the demands of your equipment in the future and not overkill for no good reason it's too costly with no benefit.

Hope this is helping and not confusing you.
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Old 11-28-2007, 12:40 AM   #19
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100 amp sub panel hook up?


It is making sense and really helpful. According to the manual for the welder the input is 53 amps at 230 volts. I'm not sure about the compressor but it is 230 volts, probably 30 amps or so, i will have to check later. Then i will have the misc. lighting and receps, nothing major here, just a 2.5 car garage. So does that 53 input amps meen that if i 60 amps feeding the sub panel and use the welder that is about all i can use? If this is so i think the 2-2-2-4 ser cable is my best bet for the price and a 90 amp breaker? I don't think i am going to find any cable cheaper than 1.76/ft. The mobile home wire would have to be in conduit from the main panel to the outside of the house, about 30 ft or so in the basement? Thanks

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Old 11-28-2007, 01:48 AM   #20
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100 amp sub panel hook up?


Well 53 amps is the maximum required input amperage to produce the rated output amperage for the arc of the welder. You would probably not use the welder at that setting often. If you don't consider duty cycle that is pretty hefty. Most of the time your probably going to be welding at around 30 to 40 amps or less input. It is likely that the compressor will cycle while you are welding and that will usually work out as long as you are not welding at maximum output setting. But you have to design for the correct operation of the equipment.... so 60 amps is cutting it too close.
I would say that you might as well use the Ser which will not have to be in conduit till you get outside with it. Put it on a 90 amp breaker or an 80....can you return the 100 amp? Hope so.
Yes the mobile home feeder would have to be in conduit till you leave the house and go underground and back into conduit at the garage. So from what you posted as distance from your main panel to the outside it doesn't look like your going to save anything.
Normally you should assemble the conduit with a pull string and pull the cable thru. If you elect to not do that be very careful of the glue and don't let a bunch of it get on the cable. It will eat up the cable jacket. At the sub I like bottom entry with the panel lugs to the top. Just use the side gutter to go up and over to your main lugs and neutral lug. Some panels are designed to be rotated 180 degrees....top down so to speak....to facilitate bottom entry...I hate this but it is acceptable so just a heads up. You likely will need a ground bar kit for the sub. It will install in prepunched swaged hole sets in the panel back. Like this...do not install the bonding means in the neutral bar. Remove it if it has been factory installed. Every panel is a little different and some have two neutral bars that can be arranged so that one can be configured into a ground only..... isolated electrically from the neutral. Just remember the neutral bar is the one on the insulated stand offs with no bond to the metal of the panel or the ground bar unless you want it that way.


The image below is a bonding jumper it can be used in some cases to convert a neutral bar to a grounding bar. But mostly this is to bond the neutral to ground in a main panel situation. You see these a lot in panels with two neutral bars that have a metal strap between them. The jumper bonds the neutral to the metal of the panel for a service equipment application. You don't want this in your sub-panel. You will not install this jumper and add the ground bar like the image before this. Remove this jumper if it has been installed by the factory, Then install your ground bar kit. Just want you to see that not all panels are the same. Some use a green bonding screw.


Last edited by Stubbie; 11-28-2007 at 12:18 PM.
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Old 11-28-2007, 03:15 AM   #21
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100 amp sub panel hook up?


Let me point out, It's one thing to understand how, another thing to understand why. 2-2-2-4 is OK for a 100a residential service, even though #2 isn't quite rated for 100 amps, because the instances when a residence with a 100a service actually approach a 100a load on either of the 2 120v service legs is rare, and any such load would surely be intermittant.
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Old 11-28-2007, 04:29 AM   #22
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100 amp sub panel hook up?


Hey Stubbie, 225.31 is the applicable code.

Andy
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Old 11-28-2007, 12:15 PM   #23
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100 amp sub panel hook up?


Thanks Andy

I read househelper to mean a main breaker is required in the sub-panel as the only form of disconnect allowed. I have actually heard this before but have not been able to find that to be clear in the NEC. Maybe I just read too much into hh's post.
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Old 11-30-2007, 08:57 PM   #24
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100 amp sub panel hook up?


Maybe this is a good place for a related question. I have a detached garage. I messed up and only got 3 wire 222 Type SEU to run from the house panel. But I believe I can use it if I ground the garage panel to the rebar in the foundation and a 8' ground rod. Then the neutral bar and grounding bar will be connected. I will run the SEU through the attic and wall to a junction box on the outside wall of the house. Then I will splice to XHHW and pull through buried PVC conduit to the garage. The neutral is bare stranded wire. Should the neutral be spliced to a jacketed XHHW to pull through the conduit? In other words, 2 jacketed hots and a bare neutral spliced to 3 jacketed wires for the conduit.
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Old 12-01-2007, 12:47 AM   #25
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100 amp sub panel hook up?


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