looking to install a sub panel to my attached garage. planning on 100 amps. Will be adding circuits for welder, lighting, misc power tools. 100 amps may be a little more than needed right now but room for expanding later would be smart. I am planning to run from the main breaker box up the outside garage wall, in the soffit vent, across the attic and down the inside garage wall opposite the main panel to the sub panel. I am thinking PVC conduit sch80. Were I am a bit lost is what type and gauge of wire to use. I was wanting to go with cable so I didnt need to run conduit through the attic, as opposed to individual wires. Does my plan so far sound like the correct way to go? any help or suggestions will be appreciated
Any electricians here? need advice
- Thread starter Doc1976
- Start date
- Tags advice electricians
I would think you might best call a local electrician or just the code enforcer because you probrobly need a permit for that anyway. might as well get one now and make sure its in accordance with the local codes or you will need to deal with it when you sell the house. Atlest thats what happens here
Simple , If your house is on a 200 amp main breaker you should be fine , for 100 amp service you can run 2/3 romex ( NM - nonmetallic sheathed cable ) available by the foot at all box stores and supply houses . Where it is ran exposed do sleeve it in Sch80 gray elec. PVC , I would use 1-1/4 " and no worries with voltage drop unless the run will be longer than 200 ft . Good Luck , let me know if you have any more questions . BTW , the 2/3 cable will have a bare copper ground in it as well so it is actually a 4 conductor cable , Black-Red-White-_bare !!
First thing you need to know is how big of a service you have now on the house and how many amps the house is pulling. If you only have a 100 amp service and your house draws 80 amps it's not gonna do any good no matter what gauge of wire you run trying to add a 100 amp sub panel without addressing the house service first. Personal experience people building a house very rarely pony up the money to put in a panel bigger than they have to. House builders are all about cheap, cheaper, cheapest, and sell big.
Over all I agree with calling in a local sparky. I can tell you all kinds of things that are legal to my local codes but might get you red flagged where you are at. I'm only licensed to work in my state and 2 surrounding states right now and there are a surprising number of things I can get away with here or there and not in the others. For some reason I remember being told in chicago anything over the 2nd story has to be ran in a conduit even in a house. In the 3 states I can work conduit in a house is rather unheard of after you leave the panel.
Over all I agree with calling in a local sparky. I can tell you all kinds of things that are legal to my local codes but might get you red flagged where you are at. I'm only licensed to work in my state and 2 surrounding states right now and there are a surprising number of things I can get away with here or there and not in the others. For some reason I remember being told in chicago anything over the 2nd story has to be ran in a conduit even in a house. In the 3 states I can work conduit in a house is rather unheard of after you leave the panel.
Last edited:
Your sub panel needs its own 8 foot ground rod and maybe two at least 6 feet apart. Top of rods 1-2 feet below ground level.
Sub panel box must have a separate ground bar for all the bare ground wires to attach to. Ground bar must be connected to the ground rod/rods via a #6 bare ground wire. If two rods are used #6 wire has to be continuous. It can not be spliced. #6 wire outside building should be in conduit.
White wires must be connected to the sub panel neutral bar. No interconnection between white wires and bare ground wires.
Do not connect the bare wire from your house panel to the sub panel.
Make certain there is no GREEN BONDING SCREW between the sub panel box and neutral bar.
Sub panel box must have a separate ground bar for all the bare ground wires to attach to. Ground bar must be connected to the ground rod/rods via a #6 bare ground wire. If two rods are used #6 wire has to be continuous. It can not be spliced. #6 wire outside building should be in conduit.
White wires must be connected to the sub panel neutral bar. No interconnection between white wires and bare ground wires.
Do not connect the bare wire from your house panel to the sub panel.
Make certain there is no GREEN BONDING SCREW between the sub panel box and neutral bar.
I think your pointing out some local code jurisdiction requirements for your area. That 6 foot rule is minimum, depending on the dirt you are putting them in they might have to be further apart (mainly wet locations). I wired a house where we had to have the rods no closer than 10 feet because it was near a lake and the earth was so saturated any closer created a loop right back to the panel. Here that 6awg is the minimum for ground conductor. If you want to run it in 350mcm for some reason you can. I've never seen/had a properly labeled stranded grounding conductor of the minimum or bigger size failed. I've never had to drive a vertical ground rod 1-2 feet under the top of the earth. Now laying them horizontal in a trench yes they have to be 2 feet deep.
I've actually ran 1000mcm grounding for lighting protection in commercial buildings before. Cad welding, ground plates, having everything tested, and all kinds of fun stuff. Nothing is a continuous length when you have to bond to all the building steel.
I've actually ran 1000mcm grounding for lighting protection in commercial buildings before. Cad welding, ground plates, having everything tested, and all kinds of fun stuff. Nothing is a continuous length when you have to bond to all the building steel.
Useng1 is correct on grounds and nuetrals being separated as this is a sub panel , all grounds bonded to panel can and grounded conductors ( neutral ) are to be isolated from the panel can . One ground rod or 10 are not needed for a sub panel in an attached structure , only an equipment ground is required and that is the bare conductor in the cable , and as I said before if you have a 200 amp service you will be fine to run the 100amp sub-feed !
Last edited:
