# 60AMP Subpanel Wire Size/Type Question



## Gigs (Oct 26, 2008)

> stripping the cover off the underground/conduit section (HD suggestion)


No need to do this.


> QO120M100C


That load center comes with a 100 amp main breaker installed. You don't need a main breaker in your sub panel. You can use a cheaper main lug panel since it's protected upstream.

You need to keep the neutral and ground separate in the subpanel too. This panel just has one neutral bus.


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## jbfan (Jul 1, 2004)

You can not use nm-b for the underground part. You must use 6/3 uf , or transition to conduit underground.


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## xv144 (Nov 26, 2008)

jbfan said:


> You can not use nm-b for the underground part. You must use 6/3 uf , or transition to conduit underground.


I plan to use conduit underground.


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## jbfan (Jul 1, 2004)

xv144 said:


> I plan to use conduit underground.


You still can not use nm-b outside. You must use uf(then you do not need conduit), or use thwn and use conduit all the way from panel to panel.


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## xv144 (Nov 26, 2008)

Gigs said:


> No need to do this.
> That load center comes with a 100 amp main breaker installed. You don't need a main breaker in your sub panel. You can use a cheaper main lug panel since it's protected upstream.
> 
> You need to keep the neutral and ground separate in the subpanel too. This panel just has one neutral bus.


Any idea what QO load panel will give me at least 12 slots that will be cheaper? I'll probably putting in 2-240 lines (4 slots), 2-120 (2 slots) for just the heaters, some separate lines for some machinery, and a room for expansion?


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## SD515 (Aug 17, 2008)

Just a couple comments...

Gigs suggestion of a main load center without a main disconnect in the garage may not fly...first check with your AHJ as to whether your garage is still consider 'detached'...the breezeway may not make it 'attached'. If it's considered 'detached', it will need a main disconnect and a ground rod or two. If it's 'attached' it won't need either of those.

To add to jbfan's comment of transitioning to underground conduit...the underground wires have to be rated THWN. Most THHN type wire is multi-rated (THHN/THWN/MTW, etc.) but check it first. You can run NM up to a junction box and then transition to a conduit run which would have the THWN wires in it.


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## jbfan (Jul 1, 2004)

Using that panel will be fine. The wire will be protected by the breaker in the main panel, and the 100 amp breaker just becomes a disconnect for the garage.


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## xv144 (Nov 26, 2008)

jbfan said:


> You still can not use nm-b outside. You must use uf(then you do not need conduit), or use thwn and use conduit all the way from panel to panel.


Thanks. Would appreciate more comments from others on this. I'll be using conduit for the 10 feet outside whatever I go with.


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## HouseHelper (Mar 20, 2007)

xv144 said:


> I plan to use conduit underground.


Doesn't matter... you cannot use type NM cable in a wet location, which underground in conduit is. And it is never acceptable to "strip the cover off" of NM to make it acceptable for use in conduit. Another "HD suggestion" that is totally wrong.

If this garage is detached, you need a panel with a main breaker, a four wire feeder, and a ground rod. If it is attached, you may substitute a main lug panel, you still need a four wire feeder, but no additional ground rod is required.

I would use 6/3 NM for the portion inside, transition to THWN for the conduit portion (3-#6, 1-#10), and continue in conduit to the subpanel; OR run 6/3 UF the whole way, with no conduit underground.

You guys type too fast!


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## xv144 (Nov 26, 2008)

SD515 said:


> ...first check with your AHJ as to whether your garage is still consider 'detached'....


I don't believe they have codes in my area. I am out in the country. Don't plan on having inspectors.


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## xv144 (Nov 26, 2008)

HouseHelper said:


> OR run 6/3 UF the whole way, with no conduit underground.
> quote]
> If I go with UF, can I put the UF in conduit for appearances sake. It will be running on the outside of my building for 2 feet before it hits the ground.


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## xv144 (Nov 26, 2008)

jbfan said:


> Using that panel will be fine. The wire will be protected by the breaker in the main panel, and the 100 amp breaker just becomes a disconnect for the garage.


I do want a cutoff in the garage. Good to keep the equipment safe from minors (if my daughter ever has kids).


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## jbfan (Jul 1, 2004)

xv144 said:


> HouseHelper said:
> 
> 
> > OR run 6/3 UF the whole way, with no conduit underground.
> ...


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## xv144 (Nov 26, 2008)

HouseHelper said:


> I would use 6/3 NM for the portion inside, transition to THWN for the conduit portion (3-#6, 1-#10), and continue in conduit to the subpanel; OR run 6/3 UF the whole way, with no conduit underground.
> 
> 
> > This sounds reasonable. If I go this way I'll have to price the THWN and UF and see how things work out.
> ...


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## xv144 (Nov 26, 2008)

The THHN I priced is called "WCU THHN 6 STR 5000". Is the W in this for waterproof (THWN)?


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## Stubbie (Jan 7, 2007)

This is the spool information we need the specifications off the outer sheath of the wire.
If this came off the outersheath then it would not be imo thwn rated.


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## xv144 (Nov 26, 2008)

xv144 said:


> The THHN I priced is called "WCU THHN 6 STR 5000". Is the W in this for waterproof (THWN)?


I called the local elec store who said I can run this in underground conduit.

The 6-6-6-10 option above appears to be the cheapest at 2.07/ft.


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## Stubbie (Jan 7, 2007)

Ok... but before I walk out of the place with it I'd check the insulation outer sheath for THWN somewhere or when you get home contact the manufacturer of the wire for clarification. That is not a UL approved marking for wet locations as you posted it.

For those wanting to learn about wire types and insulation this would be a good bookmark/favorite....

http://www-group.slac.stanford.edu/essg/pdf/mgwire.pdf


How hard would it be for you to run PVC panel to panel? This would eliminate the splice from nm-b to thwn. It's not a big deal I just hate splicing feeders..

Things you need to know

Burial depth for pvc conduit is 18 inches ...direct burial is 24 inches

If you use #6 nm-b transitioning to thwn in conduit your allowed ampacity is 55 amps you can use a 60 amp breaker or smaller in this situation.

UF-b is 55 amps for #6 also 60 amp breaker or smaller

Panel to panel with pvc conduit and thwn allows 65 amps and you may use a 70 amp breaker or smaller. I would use 1 inch conduit but 3/4 will work.

As mentioned 4 wire feeder with neutral and ground separated (not bonded) in the sub panel inside the garage. SEE attached diagram. Reason I say this is that 4 wires are required in the feeder if you run phone/data lines out there or metal water pipes.

Since you say you are not under any jurisdiction for electrical inspections (better to be sure of that) it would be my understanding that a breezeway would make the garage attached and no ground rod would be required at the sub-panel. But that is not a certainty.


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## xv144 (Nov 26, 2008)

Stubbie said:


> Ok... but before I walk out of the place with it I'd check the insulation outer sheath for THWN somewhere or when you get home contact the manufacturer of the wire for clarification.


Good drawing. It is fairly accurate. The one side of my breezeway has a wall to block the wind, and there is already two circuits running into the garage (through the breezeway roof) so I consider it 'attached'.

I did not buy the wire yet, but will verify the THWN. I will add a ground bar to the subpanel. Thanks for your time on this.


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## kbsparky (Sep 11, 2008)

xv144 said:


> The THHN I priced is called "WCU THHN 6 STR 5000". Is the W in this for waterproof (THWN)?


Here is this item decoded:

*W* = Wire
*CU* = Copper
*THHN* = type THHN
*6* = #6 AWG
*STR* = Stranded
*5000* = cut from a master reel which originally contained 5000 feet

FWIW, most THHN out there today is also rated THWN as well as MTW.

You may even find that it is rated THHN/THWN-2


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## kbsparky (Sep 11, 2008)

Stubbie said:


> ....Since you say you are not under any jurisdiction for electrical inspections (better to be sure of that) it would be my understanding that a breezeway would make the garage attached and no ground rod would be required at the sub-panel. But that is not a certainty.


Pennsylvania does not have any license requirements. Some of the local cities, towns, or counties (townships?) may have their own quirky rules, however. :whistling2:


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## xv144 (Nov 26, 2008)

*60amp Gfi*

Another Question:
Can I put a 60AMP GFI circuit breaker in the main panel going to this subpanel so I don't have to put all GFI circuits in the subpanel?


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## kbsparky (Sep 11, 2008)

Putting a GFCI breaker on the feeder will provide protection if you can find one that is rated at 60 Amps. Most manufacturers only make suitable breakers up to 50 Amps that include the grounded circuit conductor.

HOWEVER, it can be most inconvenient when you trip it out, as it will cut off everything, including any lighting you may have connected to the subpanel.

I would not recommend doing this, but instead install individual GFCI devices on each circuit where required. This will enable you to more quickly determine which is the offending circuit/device when it trips out.:whistling2:


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## xv144 (Nov 26, 2008)

kbsparky said:


> ... it can be most inconvenient when you trip it out.
> 
> I would not recommend doing this, but instead install individual GFCI devices on each circuit where required. :whistling2:


Makes sense. You guys are great (and fast). Thanks again.


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## frenchelectrican (Apr 12, 2006)

I will agree with KBsparky it far much cheaper to buy indivual GFCI receptales than get two pole GFCI breaker { those don't come cheap }

However speaking about the GFCI receptales if you are on 2008 code cycle *ALL* the 120 volt 15 and 20 amp circuits in the garage have to be GFCI'ed that do included the GDO { Garage door opener }

Merci,Marc


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## joey b (Oct 18, 2008)

only readily accessible outlets need to be gfci. This excludes the door opener and lights. The wall outlets, however, do need to be gfci.


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## chris75 (Aug 25, 2007)

joey b said:


> only readily accessible outlets need to be gfci. This excludes the door opener and lights. The wall outlets, however, do need to be gfci.


Depends on what code cycle your on, 2008 did away with those exceptions. just FYI.


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## jbfan (Jul 1, 2004)

chris75 said:


> Depends on what code cycle your on, 2008 did away with those exceptions. just FYI.


My area adopted the 08 code, but left the 05 code in for gfci's and arcfaults.:whistling2:


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## xv144 (Nov 26, 2008)

I plan on doing all GFI's in the garage.


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## xv144 (Nov 26, 2008)

*QO120L125GC as subpanel?*

Would a Square-D QO120L125GC work as my subpanel? Says it is a "main lug", is a main lug a sub panel---seems to be designed this way? It has a grounding bar installed and is only $58 at Lowes. I have an extra 60AMP circuit breaker I could use as a main switch in this (back fed).


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## frenchelectrican (Apr 12, 2006)

xv144 said:


> Would a Square-D QO120L125GC work as my subpanel? Says it is a "main lug", is a main lug a sub panel---seems to be designed this way? It has a grounding bar installed and is only $58 at Lowes. I have an extra 60AMP circuit breaker I could use as a main switch in this (back fed).


 
Yep it is legit and keep the netural and ground seperated on that location also make sure you get the main breaker tiedown kit { this is the only way to be legit on this set up }

Merci,Marc


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## ACB Electric (Nov 29, 2008)

xv144 said:


> I don't believe they have codes in my area. I am out in the country. Don't plan on having inspectors.


 
get an inspection, the codes are everywhere thats why its called the "national electrical code" the inspection is not to anoy you but to make sure you did not make either a major or minor error that could either burn your house down, electricute someone, damage electrically whatever you plug in or hook up, or at the least fail to work due to a problem a few years later.

I have lots of people coment "its my house I can do as I please" or some kind of comment along those lines, but when something happens or someone gets hurt or killed, guess who becomes 100% liable. when you insurance company denies your claim after your house burns down as a result, then what? if you are confident that your doing the job right then it will pass inspection and there will be no problem.


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## chris75 (Aug 25, 2007)

jbfan said:


> My area adopted the 08 code, but left the 05 code in for gfci's and arcfaults.:whistling2:


 
Connecticut skipped the 2008 altogether. YEE-HAW!!! :laughing:


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