Help with Subpanel feed

ccm399 · Oct 5, 2012

Hi all,

I really hate to do this but I am having a hard time finding the answers to my questions. I have searched "panel" and read through all info but I have some questions that don't seem to be answered.

1. I am planning on installing a 100amp sub panel in my barn this one:
100 Amp Panel the run from the house to the barn is about 180 -190 feet It seems I should be using 1-1-1-3 wire. Is that correct?

2. Can I get 1-1-1-3 MHF? I see southwire lists they have it to carry 100 amp but is seems they could this as 2-2-2-4 which from my research is only good for 90 amps. What size conduit would be used for either of these? The only thing I can find in 1-1-1-3 is SER but it doesn't appear I can run this under ground even if it is in a conduit.

3. I was also wondering if it would be better to install a disconnect on the outside of the house so I did not have to go through the block wall into the house panel. Is there any benefit to going this route? Good idea or bad?

The house is 200 amp service. There is already a sub panel in the house but there should be room to add the 100 amp breaker for the barn no problem.

Thanks for your time.

Chris

pattenp · Oct 5, 2012

For a 100A load at 190' you'd need to use #1/0 Al to keep the voltage drop close to 3%. The MHF doesn't come in 1/0, you'd need to use 2/0. 2" conduit will work, but 2 1/2" would be better for pulling 2/0 that distance . Also 100A breakers will handle up to #2/0.

You can get #1/0 in a URD, but this cable cannot be run inside. The Southwire product is Quadruplex and is listed as a secondary UD cable. You'd have to transition to SER where it enters the structure.

ccm399 · Oct 5, 2012

Thanks for that.

Am I getting out of Home Depot territory for a source on the wire? I can't seem to find anything on their site. I am thinking it would be 2/0 2/0 2/0 1 correct? Or would the 2/0 2/0 1 4 be the one I need?

Thanks!

CNGsaves · Oct 5, 2012

I've got similar situation but shorter distance, and has existing conduit.

House needs upgrade from 60A to 200A, and then will upgrade garage that is about 40 linear feet away from it's minimal electric through 3/4" conduit. Currently garage has single wires to accomodate lighting and outlets (no subpanel) and unique 3-way feature where garage lights can be shut-off from house.

Possible to get 100A to garage through existing small conduit using single wire approach? Will the 3-way light feature be able to be saved? If not 100A, then would 50A or 60A be possible through old conduit & save 3-way light feature? What size single wires through conduit to get 50A or 60A?

If new underground plastic conduit needs ran, what recommended for wiresize and conduit to reach 100A? Had one electrician say I can only have one conduit entrance to the garage, so would lose 3-way light feature?? Or could I just old conduit for stuff like CATV, phone, and internet?

Finally, what size subpanel makes sense for garage (maybe a 12 slot / 24 circuit, or simple 20 slot)? Any benefit to all copper bus with GE panels?

Charles (in GA) · Oct 5, 2012

It sounds as if you are wanting a 100 amp circuit simply because you are going to use a 100 amp panel. If you do not need 100 amp capability, I would go with the 2-2-2-4 MHF and breaker it at 90 amps and forget about it. It is OK to have a properly rated, properly protected circuit supplying a panel of a larger size, even if it has a main breaker in it, The circuit will be protected by the 90 amp breaker in the panel supplying this circuit.

Charles

Charles (in GA) · Oct 5, 2012

CNGsaves said:
I've got similar situation but shorter distance, and has existing conduit.

House needs upgrade from 60A to 200A, and then will upgrade garage that is about 40 linear feet away from it's minimal electric through 3/4" conduit. Currently garage has single wires to accomodate lighting and outlets (no subpanel) and unique 3-way feature where garage lights can be shut-off from house.

Possible to get 100A to garage through existing small conduit using single wire approach? Will the 3-way light feature be able to be saved? If not 100A, then would 50A or 60A be possible through old conduit & save 3-way light feature?

If new underground plastic conduit needs ran, what recommended for wiresize and conduit to reach 100A? Had one electrician say I can only have one conduit entrance to the garage, so would lose 3-way light feature?? Or could I just old conduit for stuff like CATV, phone, and internet?

Finally, what size subpanel makes sense for garage (maybe a 12 slot / 24 circuit, or simple 20 slot)? Any benefit to all copper bus with GE panels?

Panel size is largely dependent on the size of the garage and intended uses. I'm one to go way overboard on the size of a panel. Get one with the intention of using full size breakers and not the half thickness breakers. Thats a lot of heat concentrated in a tight space, and not a lot of room to run wires inside the panel.

Always go with the copper bus. Do not get a plated aluminum bus.

Charles

pattenp · Oct 5, 2012

One thing you need to consider is voltage drop. 190' is not a short run and if you use #2 MHF at 90A you'll get a 11 volt drop. Effectively you will be limited to a 60A load to keep from having over a 3% voltage drop. A 3% drop is what's recommended as a max.

pattenp · Oct 5, 2012

CNGsaves, the 3/4" conduit isn't going to cut it. For 100A you need #3 Cu and to have a switch loop for the 3way a 1 1/2" conduit would be needed to hold it all. The current 3way switch loop will need to changed and be powered from the new garage sub-panel for it to be legal. You can't have 2 sources of power going to the garage.

mrobins297aaa · Oct 5, 2012

pattenp said:
CNGsaves, the 3/4" conduit isn't going to cut it. For 100A you need #3 Cu and to have a switch loop for the 3way a 1 1/2" conduit would be needed to hold it all. The current 3way switch loop will need to changed and be powered from the new garage sub-panel for it to be legal. You can't have 2 sources of power going to the garage.

You learn something everyday, didn't know that. I ran a separate 14-3 for my 3 way switch and was thinking of powering it up on the house side. I haven't hooked up the wire yet so I guess I'll power it on the barn side.
thanks

mrobins297aaa · Oct 5, 2012

I was 220' from my 200amp panel and the inspector told me no more than 70 amps with 2-2-2-4............he wanted 2/0-2/0-2/0-1 for 100 amps so thats what I did.

Aceman · Oct 6, 2012

pattenp said:
The current 3way switch loop will need to changed and be powered from the new garage sub-panel for it to be legal. You can't have 2 sources of power going to the garage.

Have you read 225.30(D)?

CNGsaves · Oct 6, 2012

Thanks Pattenb for the info/education. I had it explained to me that when subpanel in garage, need only one power entrance so single throw can turn down power to whole building structure .... right for safety of emergency workers/homeowner/etc? One guy claims there now are wireless 3-way switches that would reach the 30 feet from garage to house so could have some sort of remote control ... ever seen one of these/brands/do they work?

If I end up just maximizing space of existing conduit (like 50A or 60A), what wiring would it be (#4 copper single strands 4 wires or what)?

Can the garage subpanel have one slot serve as Main with a respective 50A, 60A or 100A breaker? Or does it need breaker panel where the main breaker at top is single-throw that kills the whole panel? Any benefit of matching brands of panels in garage and house for interchangeability of breakers? Aren't GE panels more restrictive on types of breakers they will take? Any you would recommend over others?

Any short answer to explain the 1 ott, and 2 ott regarding wiring needed for longer runs like 190 ft in this pole barn example? Those made of copper or aluminum? Can you explain what 1-1-1-3 MHF 1-1-1-3 is SER and 2-2-2-4 MHF all mean?

pattenp · Oct 6, 2012

Aceman said:
Have you read 225.30(D)?

Do you have the 2011 NEC. My understanding of 225.30 is that only one branch circuit is allowed to provide power back to the original structure unless permitted by 225.30 (A) through (E). (A) through (E) allows more than one circuit back to the original structure, the power needs to originate in the outbuilding.

Edit: Ace, Looks like I have to eat my words. I read 225.30 again and it does appear to allow multiple feeds both ways via (A) through (E). In the overall section it states the exceptions (A)-(E) twice, once from the service load side and from the additional building side.

That's something else I have to change that's been ingrained in my brain.

Edit: Coming back to this... In the end I think a switch loop to control lights at the detached garage from the house should be powered from the sub-panel in the garage. That just seems better to me regardless of what code allows.

wyliesdiesels · Oct 6, 2012

@OP- pattenp led you in the right direction! I would not go with #2MHF due to voltage drop over that distance. If you run any high load machines, the voltage drop could be worse during startup!

pattenp · Oct 6, 2012

CNGsaves said:
Thanks Pattenb for the info/education. I had it explained to me that when subpanel in garage, need only one power entrance so single throw can turn down power to whole building structure .... right for safety of emergency workers/homeowner/etc? One guy claims there now are wireless 3-way switches that would reach the 30 feet from garage to house so could have some sort of remote control ... ever seen one of these/brands/do they work?

If I end up just maximizing space of existing conduit (like 50A or 60A), what wiring would it be (#4 copper single strands 4 wires or what)?

Can the garage subpanel have one slot serve as Main with a respective 50A, 60A or 100A breaker? Or does it need breaker panel where the main breaker at top is single-throw that kills the whole panel? Any benefit of matching brands of panels in garage and house for interchangeability of breakers? Aren't GE panels more restrictive on types of breakers they will take? Any you would recommend over others?

Any short answer to explain the 1 ott, and 2 ott regarding wiring needed for longer runs like 190 ft in this pole barn example? Those made of copper or aluminum? Can you explain what 1-1-1-3 MHF 1-1-1-3 is SER and 2-2-2-4 MHF all mean?

¾” conduit can’t handle the wire needed to get 50A or 60A plus the wires for the switch loop. ¾” conduit at best can handle #6 Cu THHN to supply 70A. #8 Cu will be 50A, but still no space for the switch loop wires. #4 Cu will take a minimum of 1” conduit and give you 90A.

The panel for the garage can be either a main lug or main service. The main lug you can use a double pole breaker back fed as the main disconnect. The main service has the main breaker already installed in the panel. The only benefit of matching panels is if you are moving circuits from the main to the sub and can reuse those breakers. I don’t know where you are as to what’s available, but I used Square-D panels.

1-1-1-3 is the conductor sizes. #1 Hot, #1 Hot, #1 Neutral, #3 Ground. #1 wire has a larger diameter than #2. #2/0 is larger than #2. The larger the wire the less the voltage drop will be over long distances.

MHF (Mobile Home Feeder) is a direct burial in earth cable that can also be run inside in conduit. SER (Service Entrance Type R) is service entrance cable with a bare ground conductor and may be used in wet or dry above ground locations.

CNGsaves · Oct 6, 2012

Thanks so much Pattenb for sharing your expertise.

Sorry but I double checked and what I have now is 1 inch plastic conduit (outside diameter). That change possibility of saving the 3-way light feature if I settle for 50A or 60A over to garage using single wire technique? Would #4 or #6 copper handle that?

Or just bite bullet and retrench with 3 inch plastic conduit for 100A over to the garage? Would code allow me to keep old 1" plastic conduit for pulling CATV, internet, and phone over to garage if I had the 3" for electricity about 8 inches over where it comes up out of ground? Any interference if pipes too close together?

Regarding panels, I was just trying to save bucks by catching bargain on Ebay or CL at least for the garage panel. Surely a cheap plain jane panel would be good enough for garage? Is copper bus by GE a real big deal as SquareD, CutlerHammer, Murray, etc all have aluminum main bus from what I've learned so far? Breakers interchangeable between brands?

brewchief · Oct 6, 2012

CNGsaves said:
Sorry but I double checked and what I have now is 1 inch plastic conduit (outside diameter).

3/4" pvc conduit is very close to 1" od

What are your power needs? If your not using a lot of power hungry tools 50-60 amps may be more then enough, if your running a welder, compressor, plasma cutter, etc with several people working at once it will likely not be enough.

pattenp · Oct 6, 2012

Conduit size is its ID. Sch 40 3/4" PVC is a shade over 1" OD.

ccm399 · Oct 6, 2012

Charles (in GA) said:
It sounds as if you are wanting a 100 amp circuit simply because you are going to use a 100 amp panel. If you do not need 100 amp capability, I would go with the 2-2-2-4 MHF and breaker it at 90 amps and forget about it. It is OK to have a properly rated, properly protected circuit supplying a panel of a larger size, even if it has a main breaker in it, The circuit will be protected by the 90 amp breaker in the panel supplying this circuit.

Charles

Hey Charles,

I was thinking to myself as I was lying in bed last night that I had not told you guys the equipment that is going in there.

1. 3ph Bridgeport (this on is only a 1.5hp motor) I have this machine now
2. 3ph Lathe (possibly up to 3hp) Coming when I have the funds
3. Miller 175 MIG welder (willl be upgraded to 216 Lincoln)
4. Miller Diversion 165 TIG (will be upgraded to at least a Dynasty 200 or hopefully a 350)
5. Bendpak lift
6. 7hp single phase Compressor
7. AC (hopefully someday)

I will normally be the only one working but if the compressor kicks on when I am welding we are looking at a good amount of current (plus lights and other always on kind of items)

I would really like to make sure I am at a fill 100 amps with minimal voltage loss at the barn panel.

Thanks,
Chris

wyliesdiesels · Oct 6, 2012

ccm399 said:
Hey Charles,

I was thinking to myself as I was lying in bed last night that I had not told you guys the equipment that is going in there.

1. 3ph Bridgeport (this on is only a 1.5hp motor) I have this machine now
2. 3ph Lathe (possibly up to 3hp) Coming when I have the funds
3. Miller 175 MIG welder (willl be upgraded to 216 Lincoln)
4. Miller Diversion 165 TIG (will be upgraded to at least a Dynasty 200 or hopefully a 350)
5. Bendpak lift
6. 7hp single phase Compressor
7. AC (hopefully someday)

I will normally be the only one working but if the compressor kicks on when I am welding we are looking at a good amount of current (plus lights and other always on kind of items)

I would really like to make sure I am at a fill 100 amps with minimal voltage loss at the barn panel.

Thanks,
Chris

Wait a minute! Are u saying those 1st 2 machines are 3Ø? If so, you will need a rotary phase converter! Also, in order to figure out what size service u need, we will need more details. What are the electrical requirements for each piece of equipment?

Norcal · Oct 7, 2012

CNGsaves said:
Thanks so much Pattenb for sharing your expertise.

Sorry but I double checked and what I have now is 1 inch plastic conduit (outside diameter). That change possibility of saving the 3-way light feature if I settle for 50A or 60A over to garage using single wire technique? Would #4 or #6 copper handle that?

Or just bite bullet and retrench with 3 inch plastic conduit for 100A over to the garage? Would code allow me to keep old 1" plastic conduit for pulling CATV, internet, and phone over to garage if I had the 3" for electricity about 8 inches over where it comes up out of ground? Any interference if pipes too close together?

Regarding panels, I was just trying to save bucks by catching bargain on Ebay or CL at least for the garage panel. Surely a cheap plain jane panel would be good enough for garage? Is copper bus by GE a real big deal as SquareD, CutlerHammer, Murray, etc all have aluminum main bus from what I've learned so far? Breakers interchangeable between brands?

3" for 100A? That is normal for PoCo's that require compliance w/ EUSERC* requirements like PG&E,which does not apply here, but a 2" should be fine, and there a number of circuit breakers that "will fit" but unless a user has the paperwork stating that a competing make is UL "classified" (Only OEM is "listed") to fit another make of loadcenter, it should not be done.

My #1 choice for a loadcenter is Cutler-Hammer CH "Classic", but SQ D QO, or Siemens are the other two IMO, I DESPISE the C-H BR loadcenters (have hated them for 30 years when they were still Bryant), SQ D Homeline (HOM) I call em "Homoline", :evil:

is a AL bussed panel & GE " Good Enough" or "Government Electric" is not on my list at all.

*EUSERC = Electric Utility Service Entrance Requirement Committee, made up of West Coast utilities.

ccm399 · Oct 7, 2012

wyliesdiesels said:
Wait a minute! Are u saying those 1st 2 machines are 3Ø? If so, you will need a rotary phase converter! Also, in order to figure out what size service u need, we will need more details. What are the electrical requirements for each piece of equipment?

Yes correct. I have a 3hp rotary phase converter for the bridgeport. I plan to run the bridgeport and lathe off the same converter (one at a time of course).

The lathe I don't have yet but the size I am looking for would be 3hp max.

The welders are spec'd for 30 amp circuits each (I intend to run both of the same circuit again, one at a time). The big boy Dynasty will require a 50 amp circuit. I would guess the Lincoln will fall between those at 40 amps.

The lift shouldn't need more than a 20 amp circuit.

The Compressor is a 40amp circuit.

The AC in our house is off a 20 amp (maybe 30) circuit.

Hope this helps.

Chris

ccm399 · Oct 9, 2012

pattenp said:
For a 100A load at 190' you'd need to use #1/0 Al to keep the voltage drop close to 3%. The MHF doesn't come in 1/0, you'd need to use 2/0. 2" conduit will work, but 2 1/2" would be better for pulling 2/0 that distance . Also 100A breakers will handle up to #2/0.

You can get #1/0 in a URD, but this cable cannot be run inside. The Southwire product is Quadruplex and is listed as a secondary UD cable. You'd have to transition to SER where it enters the structure.

Hi there,

Thanks for that. If the cable is run in a conduit from panel to panel would URD be OK? I had an electrician over this evening and he tells me that as long as the wire is in a conduit then it can be run end to end without ant need to transition to SER. Does that sound right?

I plan to run conduit the whole way panel to panel.

Thanks,

Chris

wyliesdiesels · Oct 9, 2012

ccm399 said:
Hi there,

Thanks for that. If the cable is run in a conduit from panel to panel would URD be OK? I had an electrician over this evening and he tells me that as long as the wire is in a conduit then it can be run end to end without a need to transition to SER. Does that sound right?

I plan to run conduit the whole way panel to panel.

Thanks,

Chris

URD does NOT need to be run in conduit underground- it is a direct bury cable! It DOES need to be run in conduit where exposed above ground. And regardless if its in conduit, it CANNOT be run inside because it is not fire resistant! Now when you say panel to panel, are both panels on the outside of the building?

ccm399 · Oct 9, 2012

Howdy,

Actually both panels are inside so URD is out as I have no room on the house for an additional box. So what should I get wire wise for this install? I am thinking maybe 1/0 wire and pull 3 separate conductors and a ground? Would that be my best approach?

Thanks,

Chris

ccm399 · Oct 9, 2012

Maybe something like this:

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet3

Chris

pattenp · Oct 9, 2012

ccm399 said:
Maybe something like this:

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet3

Chris

Yes, XHHW can be run from panel to panel but needs to be in conduit the whole way.

Another option is wire that has a THWN rating. THWN needs to be in conduit from end to end.

Or wire that is USE that also has the RHW rating.

*

ccm399 · Oct 9, 2012

pattenp said:
Yes, XHHW can be run from panel to panel but needs to be in conduit the whole way.

Another option is wire that has a THWN rating. THWN needs to be in conduit from end to end.

Or wire that is USE that also has the RHW rating.

*

Awesome Thank you for listing out those options for me! I am sure I can find what I need now.

Chris

ccm399 · Oct 21, 2012

Started the Sub-Panel wiring today. Removed the bonding screw from the Neutral bus and added the larger lug to the ground bus for the #2 ground wire.

Wires are 1/0 1/0 1/0 #2 xhhw.

Chris

wyliesdiesels · Oct 21, 2012

Looks great! Good job on the wire bends. Just keep it up with the clean wire routing so u don't end up with spaghetti!

ccm399 · Oct 21, 2012

wyliesdiesels said:
Looks great! Good job on the wire bends. Just keep it up with the clean wire routing so u don't end up with spaghetti!

Thanks! Will do.

Aceman · Oct 21, 2012

I agree!! Looks great, you're off to a good start!

pattenp · Oct 21, 2012

Now that wylie and Ace have blown your head up I'll let you know that technically you didn't need to mark the one hot feed leg as red.

ccm399 · Oct 23, 2012

pattenp said:
Now that wylie and Ace have blown your head up I'll let you know that technically you didn't need to mark the one hot feed leg as red.

I know... It just made pulling the wire easier. :thumbup:

Question though... The panel on my house has no room for the #2 ground wire and it is an older GE box so I cannot seem to find an add-on lug for this. My question is:

Can I put an add-on ground lug to the box by removing the paint and using a self tapping screw to attach it to the case. My other thought is to add an additional ground bar then add the lug to that. The ground buss is bonded to the case on the house panel.

Would I need to run a #6 or some other size copper wire from the new lug or bus to the current one where the ground rod is attached?

Thanks for your help!

Chris

pattenp · Oct 23, 2012

It may be overkill, but I'd go the route of adding an additional ground bar and putting a larger lug on it. And just for grounding assurances I'd jumper the new bar to the existing bar with a piece of #6 Cu.

I'm surprised you can't find a universal lug to fit the GE ground bar. Did you try Lowes or HD?

*

Charles (in GA) · Oct 23, 2012

ccm399 said:
Question though... The panel on my house has no room for the #2 ground wire and it is an older GE box so I cannot seem to find an add-on lug for this. My question is:

Can I put an add-on ground lug to the box by removing the paint and using a self tapping screw to attach it to the case. My other thought is to add an additional ground bar then add the lug to that. The ground buss is bonded to the case on the house panel.

You could use a self tapping machine screw, the kind with a slightly tapered end and the funny angled cut in it to make threads. It cannot be a sheet metal screw. Other option is a add on lug that has two ears to plug into two adjacent holes in the ground bar, somewhat universal, but dependent on the hole spacing in the ground bar.

wyliesdiesels · Oct 23, 2012

2x what Charles and pattenp suggested. I use add-on lugs all the time on older retrofit jobs!

ccm399 · Oct 23, 2012

Charles you are the MAN (thank to the everyone else too). I have one of the pictured items, the one with a small forked end but I was not trying to install it as you suggested... Stupid me. :lol_hitti

Pattenp I have tried HD as I have no Lowes close by they do not have the same type of lug you have pictured I think the one I have (that Charles posted) will work as described by Charles.

Thanks a TON guys!

Chris

ccm399 · Oct 23, 2012

House side all done!

Please note... the only wiring I did in this box is the feed for the sub panel! The mess was there when I started...

Overall pic:

Add-on ground lug (thanks again guys!):

I have to adjust my kudos a little.... It turns out the lug pattenp posted was the correct one for my panel. I ended up finding it at HD it was in the same section I was looking in but the peg was kind of hidden from plain view.

Either way thank you to ALL people that have taken the time to help me.

Chris

madosta · Oct 23, 2012

Nice work, and I love your build!

Now, do you need a ground rod or two at the building? I'm not sure...

Help with Subpanel feed

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