I have a detached single car garage. I will soon be turning it into a
small woodshop / workshop.

Right now there is a 20 amp line run out to the garage. I would like
to install a Sub-Panel. Would there be any problems installing a 100
amp breaker into a existing 100amp service panel to supply the
sub-panel?

My biggest draw at the moment is a 13" Thickness planer. Other than
that is small bench power tools. And none of those would be run at the
same time.

Thanks

Bill

None.

Just remember to use #1 (?) cable to take the amperage and voltage.

I think the number is right. The cable is about 1" thick. Both your main and your sub will have 100 amp breakers giving you a bit of insurance should anything go wrong and you will get a bonus in that you can back feed power from a generator by merely shutting off the main breaker. The bonus isn't quite what OSHA would want, but it works.
--
PDQ

--
"Bill Davis Jr" wrote in message ...
| I have a detached single car garage. I will soon be turning it into a
| small woodshop / workshop.
|
| Right now there is a 20 amp line run out to the garage. I would like
| to install a Sub-Panel. Would there be any problems installing a 100
| amp breaker into a existing 100amp service panel to supply the
| sub-panel?
|
| My biggest draw at the moment is a 13" Thickness planer. Other than
| that is small bench power tools. And none of those would be run at the
| same time.
|
| Thanks
|
| Bill

Bill Davis Jr wrote in
:

I have a detached single car garage. I will soon be turning it into a
small woodshop / workshop.

Right now there is a 20 amp line run out to the garage. I would like
to install a Sub-Panel. Would there be any problems installing a 100
amp breaker into a existing 100amp service panel to supply the
sub-panel?

Some panels have a limit to how much power they can deliver over a single
bus connection. That should be documented on the sticker in the panel.
That and space in the panel for wires that big would probably be your main
technical issues.

Practically I'm not sure why you want to do this. 100a breakers are
typically several times more expensive than 60a and under. If you actually
were drawing 100a in the garage then you couldn't have anything else on in
the house at the same time. It also sounds like your simultaneous loads
wouldn't come close to using that much anytime soon.

It may be smart to install 100a capable wiring if possible, especially if
you're going underground. That way you could get there more easily in the
future if you need it and do a service upgrade.

Doug

"Bill Davis Jr" wrote in message

Right now there is a 20 amp line run out to the garage. I would like
to install a Sub-Panel. Would there be any problems installing a 100
amp breaker into a existing 100amp service panel to supply the
sub-panel?

I think so, but I'm not an electrician. Sounds too big unless you have 200A
service to the house.

Ask on rec.woodworking. A lot of guys there have shops and subpanels and can
give you accurate information. Be sure to allow for the 3hp saw down the
road that needs 220V. Ideal would be 220 lines for the tablesaw, dust
collector, maybe the jointer if you get a big one.

great point!
"Doug" wrote in message
. ..
Bill Davis Jr wrote in
:

I have a detached single car garage. I will soon be turning it into a
small woodshop / workshop.

Right now there is a 20 amp line run out to the garage. I would like
to install a Sub-Panel. Would there be any problems installing a 100
amp breaker into a existing 100amp service panel to supply the
sub-panel?

Some panels have a limit to how much power they can deliver over a single
bus connection. That should be documented on the sticker in the panel.
That and space in the panel for wires that big would probably be your main
technical issues.

Practically I'm not sure why you want to do this. 100a breakers are
typically several times more expensive than 60a and under. If you
actually
were drawing 100a in the garage then you couldn't have anything else on in
the house at the same time. It also sounds like your simultaneous loads
wouldn't come close to using that much anytime soon.

It may be smart to install 100a capable wiring if possible, especially if
you're going underground. That way you could get there more easily in the
future if you need it and do a service upgrade.

Doug

#1 is more than NEC calls for. If you have a 200amp panel in the house
and want to run a 100amp sub panel, you will need to run #2AL or #4
Copper. You will find that the Aluminum is much cheaper. I am doing
the same thing. All I really needed was 60amp service to the garage,
but it turns out cheaper to run a 100amp service based on wiring
costs/availability. #6 copper is way more expensive than #2 AL. You
will also need a grounding rod most likely. You should contact the
inspector to see if there is anything specific required in your area.

In article .com, wrote:
#1 is more than NEC calls for. If you have a 200amp panel in the house
and want to run a 100amp sub panel, you will need to run #2AL or #4
Copper.

Ummmm.... this depends a LOT on the specifics of the installation. 100 amps on
#4 copper single insulated conductors in free air is OK, but NOT in raceway or
cable or earth. Ditto #2 aluminum, with the additional caveat that it *also*
depends on the temperature rating of the conductor insulation, e.g. #2
aluminum UF cable is limited to 75A, but #2 aluminum THHN is OK at 100A.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

wrote in message
oups.com...
#1 is more than NEC calls for. If you have a 200amp panel in the
house
and want to run a 100amp sub panel, you will need to run #2AL or #4
Copper. You will find that the Aluminum is much cheaper. I am
doing
the same thing. All I really needed was 60amp service to the
garage,
but it turns out cheaper to run a 100amp service based on wiring
costs/availability. #6 copper is way more expensive than #2 AL.
You
will also need a grounding rod most likely. You should contact the
inspector to see if there is anything specific required in your
area.


Normally the wire size you specify applies to service entrance
conductors...

Doug Miller wrote:
In article .com, wrote:

#1 is more than NEC calls for. If you have a 200amp panel in the house
and want to run a 100amp sub panel, you will need to run #2AL or #4
Copper.


Ummmm.... this depends a LOT on the specifics of the installation. 100 amps on
#4 copper single insulated conductors in free air is OK, but NOT in raceway or
cable or earth. Ditto #2 aluminum, with the additional caveat that it *also*
depends on the temperature rating of the conductor insulation, e.g. #2
aluminum UF cable is limited to 75A, but #2 aluminum THHN is OK at 100A.



Doug
I'm not trying to quibble when I say that the 90 degree column is useful
only when derating the wire do to the number of conductors in a cable or
raceway or the ambient temperature. Very few terminals are actually
rated at 90 degrees centigrade so your final ampacity is limited to the
ampacity of the conductor at the temperature rating of the terminals to
which it is connected. Since the ampacity of the #2 Al is ninety
amperes at 75 degree centigrade rating of most terminals and that is a
standard breaker and fuse size a larger wire is required.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
for general use." Thomas Alva Edison

On Wed, 09 Nov 2005 17:37:05 GMT, HorneTD
wrote:

Doug Miller wrote:
In article .com, wrote:

#1 is more than NEC calls for. If you have a 200amp panel in the house
and want to run a 100amp sub panel, you will need to run #2AL or #4
Copper.


Ummmm.... this depends a LOT on the specifics of the installation. 100 amps on
#4 copper single insulated conductors in free air is OK, but NOT in raceway or
cable or earth. Ditto #2 aluminum, with the additional caveat that it *also*
depends on the temperature rating of the conductor insulation, e.g. #2
aluminum UF cable is limited to 75A, but #2 aluminum THHN is OK at 100A.



Doug
I'm not trying to quibble when I say that the 90 degree column is useful
only when derating the wire do to the number of conductors in a cable or
raceway or the ambient temperature. Very few terminals are actually
rated at 90 degrees centigrade so your final ampacity is limited to the
ampacity of the conductor at the temperature rating of the terminals to
which it is connected. Since the ampacity of the #2 Al is ninety
amperes at 75 degree centigrade rating of most terminals and that is a
standard breaker and fuse size a larger wire is required.



WOW!

I brought this up to a fellow electrician. Why are we allowed to use
#2 AL for 100amp subpanel, and he said he's used #2 for servers and
feeders for dwellings for years, per Table 310.15(B)(6). I agreed,
and said I wasn't feeding a dewlling, just a sub panel in the same
dwelling, so per 110.14(c)(1) and table 310.16 and limited by 75C
terminals on the sub panel and feeder breaker aren't I limited to 90
amps?

The concensious is #2 AL is good for 100 amps because of Table
310.15(B)(6) reguardless if it's feeding a dewelling or a portion of a
dewelling, it's still a dewelling (loads).

Can anyone confirm this?

later,

tom

"The Real Tom" Tom @ www.Love-Calculators.com wrote in message
...
On Wed, 09 Nov 2005 17:37:05 GMT, HorneTD
wrote:

Doug Miller wrote:
In article
.com,
wrote:

#1 is more than NEC calls for. If you have a 200amp panel in the
house
and want to run a 100amp sub panel, you will need to run #2AL or
#4
Copper.


Ummmm.... this depends a LOT on the specifics of the
installation. 100 amps on
#4 copper single insulated conductors in free air is OK, but NOT
in raceway or
cable or earth. Ditto #2 aluminum, with the additional caveat
that it *also*
depends on the temperature rating of the conductor insulation,
e.g. #2
aluminum UF cable is limited to 75A, but #2 aluminum THHN is OK
at 100A.



Doug
I'm not trying to quibble when I say that the 90 degree column is
useful
only when derating the wire do to the number of conductors in a
cable or
raceway or the ambient temperature. Very few terminals are
actually
rated at 90 degrees centigrade so your final ampacity is limited to
the
ampacity of the conductor at the temperature rating of the
terminals to
which it is connected. Since the ampacity of the #2 Al is ninety
amperes at 75 degree centigrade rating of most terminals and that
is a
standard breaker and fuse size a larger wire is required.



WOW!

I brought this up to a fellow electrician. Why are we allowed to
use
#2 AL for 100amp subpanel, and he said he's used #2 for servers and
feeders for dwellings for years, per Table 310.15(B)(6). I agreed,
and said I wasn't feeding a dewlling, just a sub panel in the same
dwelling, so per 110.14(c)(1) and table 310.16 and limited by 75C
terminals on the sub panel and feeder breaker aren't I limited to 90
amps?

The concensious is #2 AL is good for 100 amps because of Table
310.15(B)(6) reguardless if it's feeding a dewelling or a portion of
a
dewelling, it's still a dewelling (loads).

Can anyone confirm this?

later,

tom


310-15(b)(6)

120/240 volt, 3 wire, single phase dwelling service and feeders

For dwelling units, conductors as listed in Table 310-15(b)(6) shall
be permitted as 120/240 volt 3 wire single phase service entrance
conductors, service lateral conductors, and feeder conductors that
serve as the main power feeder to a dwelling unit and are installed
in raceway or cable with or without an equipment grounding conductor.
For application of this section, the main power feeder shall be the
feeder(s) between the main disconnect and the lighting and appliance
branch circuit panelboards...


The last line is kind of vague, does a subpanel qualify? I've always
considered Table 310-15(b)(6) as just for service drops...

"Rick" wrote in message
ink.net...

"The Real Tom" Tom @ www.Love-Calculators.com wrote in message
...
On Wed, 09 Nov 2005 17:37:05 GMT, HorneTD
wrote:

Doug Miller wrote:
In article
.com,
wrote:

#1 is more than NEC calls for. If you have a 200amp panel in
the
house
and want to run a 100amp sub panel, you will need to run #2AL
or
#4
Copper.


Ummmm.... this depends a LOT on the specifics of the
installation. 100 amps on
#4 copper single insulated conductors in free air is OK, but
NOT
in raceway or
cable or earth. Ditto #2 aluminum, with the additional caveat
that it *also*
depends on the temperature rating of the conductor insulation,
e.g. #2
aluminum UF cable is limited to 75A, but #2 aluminum THHN is OK
at 100A.



Doug
I'm not trying to quibble when I say that the 90 degree column is
useful
only when derating the wire do to the number of conductors in a
cable or
raceway or the ambient temperature. Very few terminals are
actually
rated at 90 degrees centigrade so your final ampacity is limited
to
the
ampacity of the conductor at the temperature rating of the
terminals to
which it is connected. Since the ampacity of the #2 Al is ninety
amperes at 75 degree centigrade rating of most terminals and that
is a
standard breaker and fuse size a larger wire is required.



WOW!

I brought this up to a fellow electrician. Why are we allowed to
use
#2 AL for 100amp subpanel, and he said he's used #2 for servers
and
feeders for dwellings for years, per Table 310.15(B)(6). I
agreed,
and said I wasn't feeding a dewlling, just a sub panel in the same
dwelling, so per 110.14(c)(1) and table 310.16 and limited by 75C
terminals on the sub panel and feeder breaker aren't I limited to
90
amps?

The concensious is #2 AL is good for 100 amps because of Table
310.15(B)(6) reguardless if it's feeding a dewelling or a portion
of
a
dewelling, it's still a dewelling (loads).

Can anyone confirm this?

later,

tom


310-15(b)(6)

120/240 volt, 3 wire, single phase dwelling service and feeders

For dwelling units, conductors as listed in Table 310-15(b)(6) shall
be permitted as 120/240 volt 3 wire single phase service entrance
conductors, service lateral conductors, and feeder conductors that
serve as the main power feeder to a dwelling unit and are installed
in raceway or cable with or without an equipment grounding
conductor.
For application of this section, the main power feeder shall be the
feeder(s) between the main disconnect and the lighting and appliance
branch circuit panelboards...


The last line is kind of vague, does a subpanel qualify? I've always
considered Table 310-15(b)(6) as just for service drops...


OK, I looked at an older (1990) version of an NEC handbook. A footnote
in the handbook states in part "If there are panelboards on the load
side of the main service-entrance equipment supplied by feeders, Note
3 also permits a reduction in the conductor size of these feeders as a
result of a revision for the 1990 NEC".

Can't say if that's still in effect for 2005...

"Rick" wrote in message
ink.net...

"Rick" wrote in message
ink.net...

"The Real Tom" Tom @ www.Love-Calculators.com wrote in message
...
WOW!

I brought this up to a fellow electrician. Why are we allowed
to
use
#2 AL for 100amp subpanel, and he said he's used #2 for servers
and
feeders for dwellings for years, per Table 310.15(B)(6). I
agreed,
and said I wasn't feeding a dewlling, just a sub panel in the
same
dwelling, so per 110.14(c)(1) and table 310.16 and limited by
75C
terminals on the sub panel and feeder breaker aren't I limited
to
90
amps?

The concensious is #2 AL is good for 100 amps because of Table
310.15(B)(6) reguardless if it's feeding a dewelling or a
portion
of
a
dewelling, it's still a dewelling (loads).

Can anyone confirm this?

later,

tom


310-15(b)(6)

120/240 volt, 3 wire, single phase dwelling service and feeders

For dwelling units, conductors as listed in Table 310-15(b)(6)
shall
be permitted as 120/240 volt 3 wire single phase service entrance
conductors, service lateral conductors, and feeder conductors that
serve as the main power feeder to a dwelling unit and are
installed
in raceway or cable with or without an equipment grounding
conductor.
For application of this section, the main power feeder shall be
the
feeder(s) between the main disconnect and the lighting and
appliance
branch circuit panelboards...


The last line is kind of vague, does a subpanel qualify? I've
always
considered Table 310-15(b)(6) as just for service drops...


OK, I looked at an older (1990) version of an NEC handbook. A
footnote
in the handbook states in part "If there are panelboards on the load
side of the main service-entrance equipment supplied by feeders,
Note
3 also permits a reduction in the conductor size of these feeders as
a
result of a revision for the 1990 NEC".

Can't say if that's still in effect for 2005...


The two illustrations of an allowed reduction in conductor size in the
1990 Handbook has are of a common service for three apartments.

1 Each connected to a meter and a service disconnecting means at the
panelboards-still considered a service drop from the meters to the
panelboard

2 Each having a service disconnect at the meter instead of the
panelboard-considered a feeder between the disconnect and the
panelboard.

The Real Tom wrote:
On Wed, 09 Nov 2005 17:37:05 GMT, HorneTD
wrote:


Doug Miller wrote:

In article .com, wrote:


#1 is more than NEC calls for. If you have a 200amp panel in the house
and want to run a 100amp sub panel, you will need to run #2AL or #4
Copper.


Ummmm.... this depends a LOT on the specifics of the installation. 100 amps on
#4 copper single insulated conductors in free air is OK, but NOT in raceway or
cable or earth. Ditto #2 aluminum, with the additional caveat that it *also*
depends on the temperature rating of the conductor insulation, e.g. #2
aluminum UF cable is limited to 75A, but #2 aluminum THHN is OK at 100A.



Doug
I'm not trying to quibble when I say that the 90 degree column is useful
only when derating the wire do to the number of conductors in a cable or
raceway or the ambient temperature. Very few terminals are actually
rated at 90 degrees centigrade so your final ampacity is limited to the
ampacity of the conductor at the temperature rating of the terminals to
which it is connected. Since the ampacity of the #2 Al is ninety
amperes at 75 degree centigrade rating of most terminals and that is a
standard breaker and fuse size a larger wire is required.




WOW!

I brought this up to a fellow electrician. Why are we allowed to use
#2 AL for 100amp subpanel, and he said he's used #2 for servers and
feeders for dwellings for years, per Table 310.15(B)(6). I agreed,
and said I wasn't feeding a dewlling, just a sub panel in the same
dwelling, so per 110.14(c)(1) and table 310.16 and limited by 75C
terminals on the sub panel and feeder breaker aren't I limited to 90
amps?

The concensious is #2 AL is good for 100 amps because of Table
310.15(B)(6) reguardless if it's feeding a dewelling or a portion of a
dewelling, it's still a dewelling (loads).

Can anyone confirm this?

later,

tom

Once you are supplying a part of the dwellings load you are no longer
sizing the "the main power feeder to a dwelling unit." The is a
singular pronoun. Subpanel supply feeders simply cannot be the main
power feeder to the dwelling unit.

(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders.
For dwelling units, conductors, as listed in Table 310.15(B)(6), shall
be permitted as 120/240-volt, 3-wire, single-phase service-entrance
conductors, service lateral conductors, and feeder conductors that serve
as the main power feeder to a dwelling unit and are installed in raceway
or cable with or without an equipment grounding conductor. For
application of this section, the main power feeder shall be the
feeder(s) between the main disconnect and the lighting and appliance
branch-circuit panelboard(s).
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
for general use." Thomas Alva Edison

In article et, HorneTD wrote:
Doug Miller wrote:
In article .com,
wrote:

#1 is more than NEC calls for. If you have a 200amp panel in the house
and want to run a 100amp sub panel, you will need to run #2AL or #4
Copper.


Ummmm.... this depends a LOT on the specifics of the installation. 100 amps
on
#4 copper single insulated conductors in free air is OK, but NOT in raceway
or
cable or earth. Ditto #2 aluminum, with the additional caveat that it *also*
depends on the temperature rating of the conductor insulation, e.g. #2
aluminum UF cable is limited to 75A, but #2 aluminum THHN is OK at 100A.



Doug
I'm not trying to quibble when I say that the 90 degree column is useful
only when derating the wire do to the number of conductors in a cable or
raceway or the ambient temperature. Very few terminals are actually
rated at 90 degrees centigrade so your final ampacity is limited to the
ampacity of the conductor at the temperature rating of the terminals to
which it is connected. Since the ampacity of the #2 Al is ninety
amperes at 75 degree centigrade rating of most terminals and that is a
standard breaker and fuse size a larger wire is required.

OK, fine -- doesn't change the fact that the previous poster was undersizing
the job.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

Doug Miller wrote:
In article et, HorneTD wrote:

Doug Miller wrote:

In article .com,

wrote:

#1 is more than NEC calls for. If you have a 200amp panel in the house
and want to run a 100amp sub panel, you will need to run #2AL or #4
Copper.


Ummmm.... this depends a LOT on the specifics of the installation. 100 amps

on

#4 copper single insulated conductors in free air is OK, but NOT in raceway

or

cable or earth. Ditto #2 aluminum, with the additional caveat that it *also*
depends on the temperature rating of the conductor insulation, e.g. #2
aluminum UF cable is limited to 75A, but #2 aluminum THHN is OK at 100A.



Doug
I'm not trying to quibble when I say that the 90 degree column is useful
only when derating the wire do to the number of conductors in a cable or
raceway or the ambient temperature. Very few terminals are actually
rated at 90 degrees centigrade so your final ampacity is limited to the
ampacity of the conductor at the temperature rating of the terminals to
which it is connected. Since the ampacity of the #2 Al is ninety
amperes at 75 degree centigrade rating of most terminals and that is a
standard breaker and fuse size a larger wire is required.


OK, fine -- doesn't change the fact that the previous poster was undersizing
the job.


I agree. I just didn't want to leave anyone with the impression that a
ninety degree column ampacity would ever be the ending point for an
ampacity question.
--
Tom Horne

Well we aren't no thin blue heroes and yet we aren't no blackguards to.
We're just working men and woman most remarkable like you.