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Subpanel wiring

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diiulio

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Nov 14, 2008
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136
Location
Saratoga Springs, NY
I have a detached garage that is 115' from the panel in the house (house is 65' away, but panel is on opposite side).

House has a 150amp panel.
Garage will have a loft above when I build it next year, but for now I need some power to the existing garage. I will remove panel, pull wiring, build garage then reuse panel and wiring for new garage.

I plan to run 2" PVC conduit 18" below grade from house to garage.
Install 2 ground rods at subpanel.
100a subpanel
add 100a break to existing house panel.

Things that will be run in the garage (eventually)
5hp 220v air compressor
Older Millermatic 200 mig welder - it is 220v and recommended 8AWG/60a breaker
Hobart Handler 120 - 110v mig welder
Eventually a 2 post car lift
Potentially a Bridgeport vertical mill with phase converter
The loft above is planned to have a gas water heater and furnace.

So, what type/size wire do I need to run from main to sub?
I have read a bunch of threads that recommend aluminum over copper due to pricing, I saw 2-2-2-4 mhf was recommended and to purchase at wireandcableyourway.com for prices better than local suppliers.
I saw recommendations for running direct burial cable over conduit, but I have a hard time mentally thinking that it is as safe as wire in a conduit. Is it that much cheaper? If I went this route, what wire would I need to run here?


Of course, the garage I am building will be 4-5 closer to the house (because I am building bigger) so I will need to pull wire, cut conduit shorter, install new conduit, then repull wire.
Thanks
 
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kd7gab

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You may want to go bigger than 2" conduit if you run aluminum wire. The aluminum will not flex as easily as equivilent copper conductors.

For the wire size, the breaker in your main panel and the voltage drop calculations will dictate the size for you. Use your max simultaneous current draw + at least a small buffer to get your minimum breaker size. Then you can look at the commonly available sizes for your main panel and pick something appropriate. The alternative is to simply error on the side of bigger is better and run a 90 or 100 AMP breaker.

Regardless of any advice, find out which version of code your locality follows. You can access the NEC/NFPA 70 online for free. Knowing the applicable code will help a bunch, assuming you have to get a permit and inspection done.

Sent from my SM-N920T using Tapatalk
 
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pattenp

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Virginia - USA
The 2-2-2-4 MHF is a good common choice. For your distance you can feed it with up to a 90A breaker in the main service panel and use a 100A main breaker panel in the garage. 2" PVC conduit will do nicely. The MHF will need to be in conduit inside the structures and where above ground but is a direct bury cable so conduit is not needed where buried but I recommend conduit even where buried.
 
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matt_i

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Also there is the 500' spool of #2 awg THHN/THWN that you "phase tape" to identify, plus a bare #6 ground wire. I don't think Cu is as economical as AL wire.

The roll of wire is quite heavy and cutting off 3 individual conductors to pull at once deserves some careful measurement.
 
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klassenl

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Southern Alberta
Call an electrician. You may think that they are expensive but your time is not free and doing things twice is very expensive.
 
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wyliesdiesels

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Modesto, CA
matt_i said:
Also there is the 500' spool of #2 awg THHN/THWN that you "phase tape" to identify, plus a bare #6 ground wire. I don't think Cu is as economical as AL wire.

The roll of wire is quite heavy and cutting off 3 individual conductors to pull at once deserves some careful measurement.
Click to expand...

I would NOT run bare wire underground.
 
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Falcon67

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Merkel, TX
I'd stick with the 2-2-2-4 and 2" pipe. That's what I used for a 120' run. Also, I have more stuff than you do and it's all running off a 70A breaker at the meter with no trips, so 2-2-2-4 should be plenty for what you listed and more.
 
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-Brent-

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Utah
pattenp said:
The 2-2-2-4 MHF is a good common choice. For your distance you can feed it with up to a 90A breaker in the main service panel and use a 100A main breaker panel in the garage. 2" PVC conduit will do nicely. The MHF will need to be in conduit inside the structures and where above ground but is a direct bury cable so conduit is not needed where buried but I recommend conduit even where buried.
Click to expand...

This is 100% good advice. Take it from someone that didn't take the advice and ended up with a bunch of extra labor. Doing it over I would go MHF and a 90A breaker.
 
OP
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diiulio

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Saratoga Springs, NY
Ok, next hurdle. I was going to put a 100a breaker in my main panel in the house and it had a space on each side that looked like blanks, but when I pulled the cover, it is a full 150a panel.
What is the best option to get an open space for a 100a breaker to feed the subpanel in the garage?
IMG_0530.jpg
 
OP
D

diiulio

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That is what I was thinking. Is there any issue of phasing when putting two together? Does it matter where on the panel I do this? Is it to code if I add two tandems?
 
A

Aceman

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Eastern Oregon
theoldwizard1 said:
Remove 4 breakers. Install 2 tandem breakers.
Click to expand...

He needs to verify that his panel can accept twins first.

Whether it be by reading the sticker on the inside of the door or removing the breakers at the bottom of the panel to see if the buss bar is notched to accept a twin breaker.

Even though his panel already has a twin, people have been known to force them into a panel where they don't belong.
 
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wyliesdiesels

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diiulio said:
Ok, next hurdle. I was going to put a 100a breaker in my main panel in the house and it had a space on each side that looked like blanks, but when I pulled the cover, it is a full 150a panel.
What is the best option to get an open space for a 100a breaker to feed the subpanel in the garage?
IMG_0530.jpg
Click to expand...

If youre gonna use #2 al MHF, the max breaker u can use is 90a.
 
C

CNGsaves

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KS and OK
OP . . . . so tell us . . . .
. . . . . .What was the INCREMENTAL 1-1-1-4 Al wire cost MORE than $1.50/ft that the MHF 2-2-2-4 Al would have cost ??

Do you think it was worth that for extra 10A from 90A to 100A ???

Is buried depth of conduit at only 24 inches code in your area ??
I'd want 30" to 36" if it were me.
 
OP
D

diiulio

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Saratoga Springs, NY
The cost was around $100 more to go from 90a to 100a. Is it worth it, not sure. I don't remember the $/ft cost, but you are in the ball park. I was contemplating having a separate run directly from my meter with another box directly to the garage without touching my main box. So, it the $100 is a lot less than the alternative to get 150a to the garage.
Do I need it? I don't know, but $100 sure doesn't seem like a lot in the grand scheme of things. Now going to copper would cost about $400 more. Is that worth it? I don't see the value in it since what I have read is that the aluminum doesn't seem to have the same issues as it use to when using nox and proper torque during installation.
 
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wyliesdiesels

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Modesto, CA
diiulio said:
The cost was around $100 more to go from 90a to 100a. Is it worth it, not sure. I don't remember the $/ft cost, but you are in the ball park. I was contemplating having a separate run directly from my meter with another box directly to the garage without touching my main box. So, it the $100 is a lot less than the alternative to get 150a to the garage.
Do I need it? I don't know, but $100 sure doesn't seem like a lot in the grand scheme of things. Now going to copper would cost about $400 more. Is that worth it? I don't see the value in it since what I have read is that the aluminum doesn't seem to have the same issues as it use to when using nox and proper torque during installation.
Click to expand...

Unless your meter has dual lugs, u wont be able to hookup additional wire to it.

#1 is not large enough for 150a.
 
T

theoldwizard1

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SE MI
diiulio said:
I was contemplating having a separate run directly from my meter with another box directly to the garage without touching my main box.
Click to expand...
Many PoCos or local building authorities do NOT allow double tapping the meter, or require a meter base that has double taps. You need to verify that this is acceptable.

If not, you can come off the meter and into box with double breakers, one for the house and one for the garage.



You are IGNORING sound advice from multiple experts just to get a few more amps that you have no proof that you really need !
 
1

1Garageman

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Columbus, Ohio
theoldwizard1 said:
Many PoCos or local building authorities do NOT allow double tapping the meter, or require a meter base that has double taps. You need to verify that this is acceptable.

If not, you can come off the meter and into box with double breakers, one for the house and one for the garage.



You are IGNORING sound advice from multiple experts just to get a few more amps that you have no proof that you really need !
Click to expand...

Come on now. What could possibly go wrong with not following what professionals say to do in their field???:eyecrazy::lol:
Panel_Fire_jpg_360x540_autocrop-True_q85.jpg
 
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