125a sub panel ?s

[jgorm]

I'm adding a 125a sub panel off of a 200a main panel that is ~100' away. Most of the run is under my house, and the rest (~15') is in 2" conduit underground. Under the house I was going to tie the wires into the rest of the electrical wires that run under the house. I was planning on using #2 copper for the 2 hots and the common, but I'm unsure about what size ground, or if I even need to run a ground. I have a Ufer ground (20' rebar in the slab) at the subpanel location.

Can anyone let me know what size ground I need, or if I even need to run one?

Is it typical to use single #2 wires, or a bundled set?

 

[slow]

can your main panel support a 125 breaker?

Is this the same or different building as the main?

 

[jgorm]

This is a detached workshop. I can physically add a 125A breaker, they have them the same size as the other 220v breakers. I really can't see myself pulling more than 80A ever, but I wanted to oversize it just in case. I removed a 40A breaker for a electric stove that I converted to gas, and a 30A breaker for a dryer outlet that is not used.

 

[pattenp]

If you are using individual wires they also need to be in conduit under the house. The ground needs to be #8 Cu. #2 Cu isn't enough for 125A, you need at least #1.

 

[Charles (in GA)]

You probably need to rethink your desire to have 125 amp to the garage. You can come out much cheaper if you drop down to 90 amps, by using 2-2-2-4 aluminum in conduit.

Charles

 

[Aceman]

The VERY first thing you need to do is read the label on your main panel about allowable breaker sizes. Just because you can fit a 125 amp breaker doesn't mean your panel is designed to take one. Some Siemens panels I've seen only allow up to 110 amps per buss stab.

 

[jgorm]

You probably need to rethink your desire to have 125 amp to the garage. You can come out much cheaper if you drop down to 90 amps, by using 2-2-2-4 aluminum in conduit.

Charles

Thanks Charles! I think I might do that, or maybe 100a. My big welder will pull 80A at full tilt, but I doubt that I will even need to turn it up that high. I ran it fine on a 40A breaker at my last house for years. It will weld 1"+ at full tilt and I hardly ever use more than 1/4"

 

[Notgrownup]

I am running a 125 main lug panel in my shop, I am using 2-2-2-4 URD in 2" conduit... I am powering it off of a 100A breaker from my main panel. The odds of me using the whole 100a is slim to none... I just got a good deal from Eaton because my wife works for them... 24 space mail lug Cutler Hammer style breaker... 8 20A/120, 2 20a/220 1 30a/220 and 1 50a/220 all for $75.00 delivered.
My electrician told me to go to a 125 main lug and use the breaker on my main panel which is on my meter base outside... only 50" away from the shop.

 

[wyliesdiesels]

I'm adding a 125a sub panel off of a 200a main panel that is ~100' away. Most of the run is under my house, and the rest (~15') is in 2" conduit underground. Under the house I was going to tie the wires into the rest of the electrical wires that run under the house. I was planning on using #2 copper for the 2 hots and the common, but I'm unsure about what size ground, or if I even need to run a ground. I have a Ufer ground (20' rebar in the slab) at the subpanel location.

Can anyone let me know what size ground I need, or if I even need to run one?

Is it typical to use single #2 wires, or a bundled set?

Yes u need a ground wire. A picture is worth a thousand words so see below...BTW a grounding electrode and an EGC are 2 different animals and one shouldnt be confused for the other...

And underground u need to use wire rated for underground locations.

Bundled set? Do u mean jacketed? Romex SER AND SEU are jacketed and are NOT allowed in wet locations...

I would go with #2 AL MHF @ 90a...what all do u plan on running? AC electric heat, eletric water heater, etc etc?

I am running a 125 main lug panel in my shop, I am using 2-2-2-4 URD in 2" conduit... I am powering it off of a 100A breaker from my main panel. The odds of me using the whole 100a is slim to none... I just got a good deal from Eaton because my wife works for them... 24 space mail lug Cutler Hammer style breaker... 8 20A/120, 2 20a/220 1 30a/220 and 1 50a/220 all for $75.00 delivered.
My electrician told me to go to a 125 main lug and use the breaker on my main panel which is on my meter base outside... only 50" away from the shop.

#2 AL is only good upto 90a in a feeder application and URD if not multirated is NOT allowed inside structures...

 

[Notgrownup]

Yes u need a ground wire. A picture is worth a thousand words so see below...BTW a grounding electrode and an EGC are 2 different animals and one shouldnt be confused for the other...

And underground u need to use wire rated for wet locations.

Bundled set? Do u mean jacketed? Romex SER AND SEU are jacketed and are NOT allowed in wet locations...

I would go with #2 AL MHF @ 90a...what all do u plan on running? AC electric heat, eletric water heater, etc etc?



#2 AL is only good upto 90a in a feeder application and URD if not multirated is NOT allowed inside structures...

Actually what I got was MHF 2-2-2-4...getting what my electrician is telling to get or picking it up from the electrical vendor...

 

[pattenp]

Bundled set? Do u mean jacketed? Romex SER AND SEU are jacketed and are NOT allowed in wet locations...

SE cable can be used in wet above ground locations.

 

[jgorm]

I'm trying to fully understand the codes. From what I can tell I need to run SER wire under the house if I don't want to do conduit (and i dont because it would had hours to the work). If I run SER 2-2-2-4 Cu (I know it's overkill) to a junction box on the last wall, then run URD 2-2-2-4 through the conduit underground, and in couduit straight up the the circuit box, it should be up to code. I know the circuit box has to have the common bus bar isolated from the box for subpanels. Then I would tie in the bare #4 ground from the URD to the ground bus bar, and then another #4 bare wire from the bus bar, to the Ufer rebar ground. Does this seem legit? The electrical contractors want between $2800 and $3800 to do this work. I estimate roughly $900-1000 in materials. The underground 2" Sh80 conduit is already done.

 

[pattenp]

You don't need to use copper SER, just stick with aluminum. Also most URD is not rated for use inside of the structure. Typically URD needs to be terminated outside. You are better off using 2-2-2-4 MHF (Mobile Home Feeder). Using #2 Al the max feeding breaker needs to be 90 amps.

Edit: Make sure the URD cable if used from inside the structure to outside underground has a rating of USE-2/RHH/RHW-2.

 

[wyliesdiesels]

SE cable can be used in wet above ground locations.

Yeah my mistake. I was typing faster than my brain could process...

I'm trying to fully understand the codes. From what I can tell I need to run SER wire under the house if I don't want to do conduit (and i dont because it would had hours to the work). If I run SER 2-2-2-4 Cu (I know it's overkill) to a junction box on the last wall, then run URD 2-2-2-4 through the conduit underground, and in couduit straight up the the circuit box, it should be up to code. I know the circuit box has to have the common bus bar isolated from the box for subpanels. Then I would tie in the bare #4 ground from the URD to the ground bus bar, and then another #4 bare wire from the bus bar, to the Ufer rebar ground. Does this seem legit? The electrical contractors want between $2800 and $3800 to do this work. I estimate roughly $900-1000 in materials. The underground 2" Sh80 conduit is already done.

I would use #2 AL SER in the house(no conduit needed) then transition to #2 AL MHF in a box on the outside...

 

[jgorm]

I'm set on #2 copper wire, overkill is good. I can't seem to find anything bigger that #6 that is rated for underground use. I read that I can use #2 THWN in the underground conduit. I'll run 2-2-2-4 SER Cu under the house, then splice to the THWN wires to go through the conduit, and up to the panel. Does anyone see any problem with this?

 

[Charles (in GA)]

If you use copper, stick with it all the way thru. You are inviting nothing but trouble down the road, if you splice copper and aluminum. Don't care what anyone says, eventually you or someone after you will have problems, most likely sooner than later.

Charles

 

[Aceman]

You are inviting nothing but trouble down the road, if you splice copper and aluminum.

I can't agree with that.

If you use Polaris connectors how do you think it would make a difference?

 

[jgorm]

If you use copper, stick with it all the way thru. You are inviting nothing but trouble down the road, if you splice copper and aluminum. Don't care what anyone says, eventually you or someone after you will have problems, most likely sooner than later.

Charles

I am. I much prefer copper over aluminum. My question is about using THWN individual wires in underground conduit because I can't fine USE wire anywhere.

 

[pattenp]

THHN/THWN is fine in conduit under ground. If that's what you want to use go for it.

 

[jgorm]

Nobody seems to have SER in copper, but they have romex NH-b. From what I can tell that is fine under the house without conduit. Is that true?

 

[Charles (in GA)]

I can't agree with that.

If you use Polaris connectors how do you think it would make a difference?

In that case, it would not matter, as the two wires would not be touching each other. Other types of splicing such as split bolts would be a corrosion disaster.

Charles

 

[Norcal]

In that case, it would not matter, as the two wires would not be touching each other. Other types of splicing such as split bolts would be a corrosion disaster.

Charles

AL/CU rated split bolts have a "spacer" between conductors, so no copper or aluminum conductors in contact with each other, but I would rather not use them, Polaris connectors are much less hassle.

 

[jgorm]

There is no aluminum being used. I mentioned that earlier. I'm a firm believer in using the best materials.

 

[jgorm]

Does this look legit?
#2 THWN for hots and common through sc 80 underground.
#4 THWN ground
Common isolated from ground
Ground tied into ufer ground.

I plan to connect to romex NM-B 2-3 with ground inside the conduit box pictured. I have copper split bolts, covered with rubber tape, then electrical tape.

 

[wyliesdiesels]

Does this look legit?
#2 THWN for hots and common through sc 80 underground.
#4 THWN ground
Common isolated from ground
Ground tied into ufer ground.

I plan to connect to romex NM-B 2-3 with ground inside the conduit box pictured. I have copper split bolts, covered with rubber tape, then electrical tape.

What size breaker? If 125a then NO. #2 NM-b is good upto 95a(100a breaker because 95a isnt standard size) and #2 THHN is 115a...

 

[Norcal]

Where is the terminal adapter & locknut/bushing for the PVC, & a connector on the grounding electrode conductor? Any open knockout is a invite for rodents.


Edit: That LB will not have the cubic inches necessary to splice those conductors, a 12X12X4 NEMA type 3R can will give plenty of room, and if metal will need to be bonded.

 

[Charles (in GA)]

Where is your disconnect? You have to have one at the panel or where the circuit enters. I don't see one or a way to install one. You could add a main breaker to that panel easy enough. Norcal is correct, the conduit needs an end fitting and locknut. Cannot just stick it thru the hole. Inspector will shoot that down in an instant. It will also clue him in to start looking closer at everthing else.

 

[Norcal]

It's a main breaker loadcenter.

 

[wyliesdiesels]

Yup i see it. Gotta zoom in...

 

[jgorm]

Thanks guys! I'll source out some adapter for the 2" conduit. Is there a code that says I can't make the splice in the conduit adapter? I think I can can it in there if I stagger the splices. Is that crazy?
Norcal, what do you mean by a connector on the grounding electrode conductor?

 

[wyliesdiesels]

What size breaker are u using? Did u read comment #25 above?

 

[jgorm]

90A max in my main panel, but I'll keep the 100 on the sub panel as the shutoff.

 

[Charles (in GA)]

It's a main breaker loadcenter.

Missed that. Didn't zoom it. Looked like lugs.

Bite the bullet. Disconnect the wires, remove the panel, cut the conduit down, glue on the threaded adapter, remount the panel, add the bushing, reconnect the wires.

 

[jgorm]

I bought the male adapter and the lock ring for the conduit. I had to fight the wires in the main panel for a long time! It's packed full with 32 breakers. I pulled all the breakers and tidied it up a bit. I had to cut a hole in my daughter's closet to gain access and drill through the floor.

What about trying to tie the NM-B to the THWN in the 2" lb? Is that totally crazy? Against code? If not I could install a box on the backside of the lb under my house. Check out my pictures and let me know if you see anything that might flag an inspector. I really appreciate all of you help! I'm way over budget and this wire run saves around 1500 -2500 by doing it myself.

 

[zmaxmotorsports]

If you are using individual wires they also need to be in conduit under the house. The ground needs to be #8 Cu. #2 Cu isn't enough for 125A, you need at least #1.

#8 ground for a 125a sub panel? I use #6 for 100a panels #4 for 200a panels,Id go with the 6 atleast.

 

[zmaxmotorsports]

Does this look legit?
#2 THWN for hots and common through sc 80 underground.
#4 THWN ground
Common isolated from ground
Ground tied into ufer ground.

I plan to connect to romex NM-B 2-3 with ground inside the conduit box pictured. I have copper split bolts, covered with rubber tape, then electrical tape.

I wouldn't splice wire inside of an Lb like that.

 

[zmaxmotorsports]

Where is the terminal adapter & locknut/bushing for the PVC, & a connector on the grounding electrode conductor? Any open knockout is a invite for rodents.


Edit: That LB will not have the cubic inches necessary to splice those conductors, a 12X12X4 NEMA type 3R can will give plenty of room, and if metal will need to be bonded.

Yeah,Why run conduit all that way then blow it all there at the panel?Whats up with that big loop in the ground wire?
Put a separate lug in for the ground to the rebar,and straighten/clamp the wires.

 

[jgorm]

I wouldn't splice wire inside of an Lb like that.

Why not? I'm just trying to learn as much as I can.

Yeah,Why run conduit all that way then blow it all there at the panel?Whats up with that big loop in the ground wire?
Put a separate lug in for the ground to the rebar,and straighten/clamp the wires.

I'm going to fix the conduit attachment to the box. Good idea in the extra lug. I'm trying to make it look as legit as possible so the inspector doesn't start getting picky. As far as I can tell, everything is up to code, but this is my first time hooking up a subpanel with this many amps.

 

[Norcal]

Why not splice in a LB? Because it's trying to stuff 15 pounds of **** in a 5 pound bag, I like to be generous with junction boxes as it makes the job easier and bending conductors too tight is not allowed by code.

 

[zmaxmotorsports]

Why not? I'm just trying to learn as much as I can.

I'm going to fix the conduit attachment to the box. Good idea in the extra lug. I'm trying to make it look as legit as possible so the inspector doesn't start getting picky. As far as I can tell, everything is up to code, but this is my first time hooking up a subpanel with this many amps.

Theres not enough room in the Lb,Its meant to be a pull box not a junction box.
Once you try splicing/stuffing some split bolts in there it will be overfilled fast.