I have a lot of experience with typical home wiring and main panel installation. However, I am in the process of installing a subpanel; I have never done this before and want to make sure my information is correct. The main panel in my house is 200 amp. I am adding a 100 amp subpanel to my woodworking shop that is in my basement (not a detached building). The subpanel is a standard panel, which I believe can be used as a main load center or subpanel (it does not have the typical main load breaker - just a 100 amp removable circuit breaker that attaches directly to the hot bus bars). I typically work alone, so other than having the lights for the shop on (lights will be from the subpanel), I am only running one piece of equipment at a time and a dust collector - the load should be pretty light most of the time). I was told that I should run #2 3 wire (100 amp entrance wire) from my main panel to my subpanel connecting the two hots to the 100 amp breaker and the neutral to the neutral bus bar. I was told that I would need to ground the subpanel just like I would a regular main panel - continuous loop ground wire to 2 ground rods set 8' apart. I was told to keep the ground and neutral bus bars bonded. Is all of this the correct? I have a couple of additional questions. 1) If I go with this configuration, other research indicates that I should also run a ground to the main panel. Is this correct? 2)Other research indicates that since this panel is in my house and not in a separate building that I should instead run a #2 4 wire (entrance wire?). The two hot wires to the breaker, neutral to neutral bus bar, ground to ground bus bar, break the bond between neutral and ground bus bars, with no separate ground rods. Is #2 wire the appropriate size for this use? By going this route, will my sub panel be adequately grounded through the main panel. I would appreciate any thoughts on this. Thanks. Craig
Sorry to say that you have received some bad info. Subpanels are required by the 08 NEC to be fed by 4 wire feeds. There used to be an exemption for a 3 wire feed to a detached structure. It has been removed.
Instead of back-feeding a breaker and installing the required hold down clip just install a main breaker if you desire a way to shut the panel down. You can install a main lug panel, but will not be able to shut the panel down except at the main panel.
Ground rods are only required in a sub in a detached building
I ran #3 for my 100a sub in my attached great room
2 hots, 1 neutral & a #6 green ground
Neutral not bonded to the case at the sub
Grounds & neutrals on seperate buss - not bonded together
Also your subpanel may have come with only a neutral bar.
And there is a "neutral bonding screw" which would come with a panel.
There would need to be a separate ground bar and the 4th "ground wire" would connect to this. And this ground bar would be bonded to the metal case of the subpanel.
The neutral bar would NOT be bonded to the metal case of the subpanel (the neutral bonding screw not installed).
You can buy separate ground bars to add on to panels. Some panels come with the holes predrilled. Otherwise drill your own holes.
I knew i'd get some flak for posting that Ok this obscure code section was pointed out to me by an Instructor, and he spent an hour proving it to an unbeliving me.
What this says is that unless we can prove that our ALL of our equipment is listed for 75deg or higher(which is hard to prove), we will be forced to use the 60deg collum in table 310.16.
Which by the time we get down to a wire that says >100 is #1copper @110A or 1/0Al @ an ampicity of 100A.
I know that this is not as complete leason as given to me, butmy figers hurt But it wil get you started with a rebuttle.
What this says is that unless we can prove that our ALL of our equipment is listed for 75deg or higher(which is hard to prove), we will be forced to use the 60deg collum in table 310.16.
You posted that #1 MUST be used
The section you qouted does not require you to use #1
There are 4 parts to the section, each has a different requirement
You can't pull one part out & state that is what must be met
If we are talking about breaker panelboards it isn't just the breaker that terminal ratings must meet the wire insulation but the entire panelboard. That information is listed on the specifications sheet. If you want to put to rest and learn a bit this should square you away. Read it carefully and take some time doing so.
In particular line 36 about temperature ratings for the equipment as to what wire can be connected this will lead to the correct ampacity. In residential I don't know of any breakers that would not be slash rated 60/75 C in the last 25 years at least. But the panel board rating for wire terminations is what counts. I'll post it for reference the last of this reply.
I have an old challenger panel 1970's vintage I just took a look at in my junk pile and it states
Equipment for use with conductors
#14-#2 at 60 C
#1 - 60/75C
1/0 or larger 75C
so not as simple as one might think on older panels.
Also you might find 20 A & B interesting about the 6 disconnect rule and what it takes for the panel to qualify... in particular "the panelboard must have at least one combintion of breakers where only 6 single throws will fill all the spaces of the panel...that was new to me at least...
I have been having some idle time after getting the laundry finished and the painting inside done and the cooking and the.... god my wife is lucky.. She says she loves me but I can't hardly blame her for that. To freakin cold to fish so just looking at my new drive to park the boat and truck.
Hope all the guys here are doing well after turkey day.... Been making a few replies to the forum over the last couple days.
Just wanted to say there isn't much issue today as all residential panelboards/load centers are listed for 75C wire connections. You want to be careful of the big lugs though cause they will be listed at 90C lots of times but you cannot use 90c ampacity on those lugs because the panel is not listed that way.
Thanks for the response guys. This confirms some of my research and I am grateful for the advice. this will help save some time, some money, and some bad wiring.
And I went ahead & installed #3, inspected by the Inspector & was done with it
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