Bevis
Well-known member
After a bust on another grow house. My neighbor works for the power company and he gave me 3 rolls of #2 copper (100' - 150' rolls). Could I use this in my 2" buried conduit. It's 55' from the house to the shop sub panel.
Wiring for sub panel
- Thread starter Bevis
- Start date
wow nice neighbor! that stuffs not cheap. first thing, is what is the wire type. Is it THHN/THWN? You need 4 lines to the sub panel, 2 hots, a neutral, and a ground. You need to check the charts and do any derating for distance, but you should be good for 90-100amps. Use the #2 for hots, and neutral. Then get some #6 for the ground (check to make sure #6 is the right size) Your 2" conduit is plenty large.
redsky49
Well-known member
Just curious
If the normal current carrying wires (neutral and hot) are properly sized at #2, why is it that the ground conductor should be a smaller size?
In the event of a ground fault, say at an appliance with a poor ground, this conductor should theoretically carry the fault current safely to ground. In the case of a serious short circuit, this grounding conductor could have the full circuit current flowing it. Doesn't this present a danger to occupants, and isn't this even more important when dealing with higher amperage (240V, 208-460V) circuits?
What are your thoughts mrb?
If the normal current carrying wires (neutral and hot) are properly sized at #2, why is it that the ground conductor should be a smaller size?
In the event of a ground fault, say at an appliance with a poor ground, this conductor should theoretically carry the fault current safely to ground. In the case of a serious short circuit, this grounding conductor could have the full circuit current flowing it. Doesn't this present a danger to occupants, and isn't this even more important when dealing with higher amperage (240V, 208-460V) circuits?
What are your thoughts mrb?
tfi racing
Well-known member
No,code only requires #8 ground for up to 100A,however it must be mechanically protected so most just use #6 to save time and material. Theoretically the ground conductor will only see the fault current instaneously,that is one of the reasons it is considerably smaller.
Voltage has no bearing on the size of a conductor, amperage, length and the conditions the conductor is placed in determine the size.
Voltage has no bearing on the size of a conductor, amperage, length and the conditions the conductor is placed in determine the size.
Charles (in GA)
Well-known member
Code allows a undersized ground, as it will not be carrying the current for long.
Be sure and identify the neutral with white/grey tape around the ends.
Charles
Be sure and identify the neutral with white/grey tape around the ends.
Charles
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GSSFC
Well-known member
Aceman
Well-known member
Bevis, make sure that wire is dual rated as THWN also. If it's straight rated THHN(which I've never seen) you can't use it in a wet location(i.e. underground in conduit).
If the insulation checks out, I'd try to get 2 runs out of one of the rolls and use the #2 for a ground wire also. It'll save you from buying anymore wire.
You'll need a collar strap most likely to fit the #2 wire on your ground bar. Siemens part #ECCS1. I only remember that because I bought one this morning....
If the insulation checks out, I'd try to get 2 runs out of one of the rolls and use the #2 for a ground wire also. It'll save you from buying anymore wire.
You'll need a collar strap most likely to fit the #2 wire on your ground bar. Siemens part #ECCS1. I only remember that because I bought one this morning....
Bevis, make sure that wire is dual rated as THWN also. If it's straight rated THHN(which I've never seen) you can't use it in a wet location(i.e. underground in conduit).
If the insulation checks out, I'd try to get 2 runs out of one of the rolls and use the #2 for a ground wire also. It'll save you from buying anymore wire.
You'll need a collar strap most likely to fit the #2 wire on your ground bar. Siemens part #ECCS1. I only remember that because I bought one this morning....
I would save the longest piece of #2, buy the #8 needed for the ground, and sell the #2
PGBioD
Member
You don't need to run the safety ground all the way back to the 'main'.
But you do need to drive a ground rod right near the sub-panel and attach your wire.
Just get the regular bare ground wire.
Much easier, safer, and cheaper.
Goodluck
But you do need to drive a ground rod right near the sub-panel and attach your wire.
Just get the regular bare ground wire.
Much easier, safer, and cheaper.
Goodluck
you do need to run the ground back to the main, as well as drive a ground rod at the detached structure.
make sure you keep your neutral and ground seperate at the sub panel
tfi racing
Well-known member
You may want to double check on that piece of advice.Feel free to give us examples where that would be permissable by code.
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Torque1st
MEMBER EMERITUS
EDIT- OOPS I read it wrong. A ground wire IS required with a single 110 circuit but a ground rod is not required. That is by the ancient pre-millenium code.
The site below is excellent but they must be making some site changes. The 2002 code article is not available anymore so the following is the newest they have at the moment.
http://www.selfhelpandmore.com/1999...o-dwellings/wiring-a-detached-garage-1999.php
With 220 a ground wire and a ground rod is required.
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Its Now Code In Nj To Put 2 Grounding Rods 6 Ft Apart,fyi. Also Why Not Put It Through Conduit? Its Cheap And Protects The Buried Wire, Just Make Sure To Tape Your Grounds With White Tape On Both Ends Before Pulling Through The Pipe, Good Luck,mike.
Charles (in GA)
Well-known member
Neutral gets the white or grey tape markings on the end (if the wire is not already properly color coded), not the ground, which must be green, green/yellow striped, etc as specified in the code.
Charles
Torque1st
MEMBER EMERITUS
Soil conditions (moisture content) and conductivity in some areas determine how many ground rods are required. The local authority just amends the code as necessary.
Got the conduit in the ground this morning before the rain started...Pulled out wire to pull thru conduit and found that the #2 cable had been cut right in the middle of two runs. Can this THNN/THWN copper be spliced undergound?? If not guess I;ll be buying 120' run of #2 (60' x 2).
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sberry
Banned
Code calls for 1 rod if you can meet 23 ohms or less resistance, if not you use 2. Its simple and easier to just use 2 and as Torque eluded to some places just require 2 due to the local soil conditions. There are even places where 3 wire panels fed from existing service may be acceptable but for this crowd they should be 4 wire period. There are just too many possibilities to mess up the grounding system and provide for alternate current pathways that a 4 wire system just plain eliminates a lot of confusion.
Thats for a service, does it hold true for a sub panel?
nate379
Banned
I didn't know that a sub panel needed it's own rod though.
What's the reason for that?? Running a ground from the subpanel to the main would tie it to the main panel's rods.
What's the reason for that?? Running a ground from the subpanel to the main would tie it to the main panel's rods.
If its detached, it does. Lightning protection would be my guess
sberry
Banned
Step potentials another, makes the surface you are standing on similar to the building you are in.
Charles (in GA)
Well-known member
That would be expensive. Luckily things are cheaper right now than last year. Not positive, but I seem to recall that you cannot splice inside a conduit. I certainly would not do it. It would have to be a waterproof underground splice in any case, as this is a wet location.
Charles