Electrical question for new workshop

Posted by rlz on February 3, 2009, 10:09 am

Hopefully, this is a simple question that someone can answer. I'm
looking for the type/size cable to run (inside conduit) from my house
underground to my new shop.

I am building an unattached workshop in my backyard. I am planning on
running my electrical off of my house's panel. I am going to install
an auxuillary panel in the workshop (100 Amp). I'm planning on two 15
Amp circuits for outlets, One 220V circuit, and 1 circuit for
lighting. The distance between the house and the shop will be about a
40' run.

I know I'll have to have an electrician come out and finish the work,
but I want to purchase the correct size wire when I purchase my
building materials.

Posted by Steve Barker TB on February 3, 2009, 10:26 am

rlz wrote:

> Hopefully, this is a simple question that someone can answer. I'm
> looking for the type/size cable to run (inside conduit) from my house
> underground to my new shop.
>
> I am building an unattached workshop in my backyard. I am planning on
> running my electrical off of my house's panel. I am going to install
> an auxuillary panel in the workshop (100 Amp). I'm planning on two 15
> Amp circuits for outlets, One 220V circuit, and 1 circuit for
> lighting. The distance between the house and the shop will be about a
> 40' run.
>
> I know I'll have to have an electrician come out and finish the work,
> but I want to purchase the correct size wire when I purchase my
> building materials.
>

You'll get as many opinions as responses. Just suffice to say, that we
ran a detached garage for over 30 years , 300 feet from the house, on
an underground direct burial 10/3 . Yes, we had lights, fans, forced
air heat, welder, grinders, air compressor, stereo, the whole gammut of
equipment you'd find in the average home fabricators shop. Never once
in 30 years, did we trip the 30A breaker in the house. YMMV.

steve

Posted by Steve Barker TB on February 3, 2009, 10:31 am

Steve Barker TB wrote:

> rlz wrote:

>> Hopefully, this is a simple question that someone can answer. I'm
>> looking for the type/size cable to run (inside conduit) from my house
>> underground to my new shop.
>> I am building an unattached workshop in my backyard. I am planning on
>> running my electrical off of my house's panel. I am going to install
>> an auxuillary panel in the workshop (100 Amp). I'm planning on two 15
>> Amp circuits for outlets, One 220V circuit, and 1 circuit for
>> lighting. The distance between the house and the shop will be about a
>> 40' run.
>> I know I'll have to have an electrician come out and finish the work,
>> but I want to purchase the correct size wire when I purchase my
>> building materials.

>
> You'll get as many opinions as responses. Just suffice to say, that we
> ran a detached garage for over 30 years , 300 feet from the house, on
> an underground direct burial 10/3 . Yes, we had lights, fans, forced
> air heat, welder, grinders, air compressor, stereo, the whole gammut of
> equipment you'd find in the average home fabricators shop. Never once
> in 30 years, did we trip the 30A breaker in the house. YMMV.
>
> steve
>

Let me go on to say, if _I_ were doing what you're doing today, I'd
probably run a 6/3 with ground and hook it to a 50A breaker. That's
going to be more than plenty for a home shop. That's what I plan to do
for the feed to my current 30x40 that is about 400' away. The size of
the sub panel can be dictated by how many breakers you want to break it
down into. A 100A sub is a bit of an overkill in my opinion. An eight
breaker panel would probably be enough, unless you plan to have more
than one 220V outlet, or device.

steve

Posted by Wayne Whitney on February 3, 2009, 1:04 pm

> Let me go on to say, if _I_ were doing what you're doing today, I'd
> probably run a 6/3 with ground and hook it to a 50A breaker. That's
> going to be more than plenty for a home shop. That's what I plan to do
> for the feed to my current 30x40 that is about 400' away.

At 400' away, you had best perform a voltage drop calculation, which
will probably lead to increasing the wire size above #6 Cu for a 50
amp circuit.

Cheers, Wayne

Posted by Steve Barker TB on February 3, 2009, 6:35 pm

Wayne Whitney wrote:

>> Let me go on to say, if _I_ were doing what you're doing today, I'd
>> probably run a 6/3 with ground and hook it to a 50A breaker. That's
>> going to be more than plenty for a home shop. That's what I plan to do
>> for the feed to my current 30x40 that is about 400' away.

>
> At 400' away, you had best perform a voltage drop calculation, which
> will probably lead to increasing the wire size above #6 Cu for a 50
> amp circuit.
>
> Cheers, Wayne

I hear ya, but as i stated before, we ran a shop 300 feet away for 30
years on a 10ga. The barn i have now, will probably never see a welder,
and if it does, it'll be seldom used. Right now, it's been run on a 12
ga. NM-b laying on top the ground for two years. Lights and door
openers are all that i have in regular use.

steve

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