Electrician questions

I have a service panel on the side of the house that feeds a sub panel
inside. Over the years a few breakers got added to supply an air
conditioner and electric clothes dryer (in the outdoor panel directly
under the meter).

I was planning on running some power out to the garage - about 80 feet
of cable. I figured to just tap into the outside box (the inside
panel is ancient and has plug fuses);.

Run 240 out to the garage via a regular 12 AWG "2 wires plus ground"
and put a 20 amp 240 volt GFI breaker in the outside panel on the
house to a small sub panel in the garage for lights and a workbench.

The cable will run in a trench buried in the ground and only be
protected with conduit where it goes into the ground and comes out.
There should be no cause to dig in the area and the GFI should protect
against shock should someone dig.

Intent is to bury plain old vinyl insulated cable. I don't see any
that is rated for direct ground burial in the hardware stores - is
this important and why?

Any reasons this won't work and be safe?

I do see "outdoor cable" in the store, but from reading the specs it
appears that it's only claim to fame is the UV inhibitors in the vinyl
- other than the label, it is indistinguishable from the indoor stuff
- cuts and strips just like the indoor cable no tougher outside
covering. The package says it can be buried... and it costs roughly
double.

 

[Rich Grise]

default wrote:
....

The cable will run in a trench buried in the ground and only be
protected with conduit where it goes into the ground and comes out.
There should be no cause to dig in the area and the GFI should protect
against shock should someone dig.

Intent is to bury plain old vinyl insulated cable. I don't see any
that is rated for direct ground burial in the hardware stores - is
this important and why?

Yes, because if it isn't, the vinyl will rot and critters will eat
through it.

Any reasons this won't work and be safe?

See above.

I do see "outdoor cable" in the store, but from reading the specs it
appears that it's only claim to fame is the UV inhibitors in the vinyl
- other than the label, it is indistinguishable from the indoor stuff
- cuts and strips just like the indoor cable no tougher outside
covering. The package says it can be buried... and it costs roughly
double.

If it says it can be buried, it can be buried. If it doesn't, it can't.

Which costs you more - 80 feet of buriable conduit, or the difference
in price between the buriable and non-buriable cable?

Good Luck!
Rich

 

[John G]

After serious thinking default wrote :

I have a service panel on the side of the house that feeds a sub panel
inside. Over the years a few breakers got added to supply an air
conditioner and electric clothes dryer (in the outdoor panel directly
under the meter).

I was planning on running some power out to the garage - about 80 feet
of cable. I figured to just tap into the outside box (the inside
panel is ancient and has plug fuses);.

Run 240 out to the garage via a regular 12 AWG "2 wires plus ground"
and put a 20 amp 240 volt GFI breaker in the outside panel on the
house to a small sub panel in the garage for lights and a workbench.

The cable will run in a trench buried in the ground and only be
protected with conduit where it goes into the ground and comes out.
There should be no cause to dig in the area and the GFI should protect
against shock should someone dig.

Intent is to bury plain old vinyl insulated cable. I don't see any
that is rated for direct ground burial in the hardware stores - is
this important and why?

Any reasons this won't work and be safe?

I do see "outdoor cable" in the store, but from reading the specs it
appears that it's only claim to fame is the UV inhibitors in the vinyl
- other than the label, it is indistinguishable from the indoor stuff
- cuts and strips just like the indoor cable no tougher outside
covering. The package says it can be buried... and it costs roughly
double.

You need three (3) wires AND Ground to get 240 and 120 at the garage
and you will surely need 120. Assuming you are in the USA of course.

--
John G

 

[Ecnerwal]

In article <qmjvo6hkp0dkud6hagbvr1ukgt4fn23kna@4ax.com>, default wrote:

Run 240 out to the garage via a regular 12 AWG "2 wires plus ground"
and put a 20 amp 240 volt GFI breaker in the outside panel on the
house to a small sub panel in the garage for lights and a workbench.

The cable will run in a trench buried in the ground and only be
protected with conduit where it goes into the ground and comes out.
There should be no cause to dig in the area and the GFI should protect
against shock should someone dig.

GFIs can and do fail to trip. That's why they have the test buttons on
them.

Intent is to bury plain old vinyl insulated cable. I don't see any
that is rated for direct ground burial in the hardware stores - is
this important and why?

Any reasons this won't work and be safe?

Well, you're probably just a troll, but: Plenty. Also quite a few
reasons that it's penny pinching and pound foolish....Right off the bat,
you're short one wire, so "you doing the work yourself" is not looking
like a good plan, and anyone qualified to do the work won't be doing it
"your way." Likewise, anyone willing to do it "your way" is not
qualified to do the work.

I do see "outdoor cable" in the store, but from reading the specs it
appears that it's only claim to fame is the UV inhibitors in the vinyl
- other than the label, it is indistinguishable from the indoor stuff
- cuts and strips just like the indoor cable no tougher outside
covering. The package says it can be buried... and it costs roughly
double.

Indoor cable insulation is not waterproof. Any exterior cable (including
those in conduit, which is assumed to be wet, because it usually is)
must be waterproof (there will be a W in the "type") Within a relatively
short time (might be a few years, but a proper installation lasts many
decades) the insulation will fail.

Because you are a penny pincher, you'll then have to dig the whole
trench up again. If you use conduit correctly, you only have to dig
once. Conduit is CHEAP. Trenches are EXPENSIVE. If you were planning to
dig the trench yourself, it's quite expensive in terms of labor - a
shallow trench is unsafe, and violates electrical code. 18-24" minimum
to the top of the line or conduit. A good job goes below frost line to
keep the line from being stressed each year with ground movements, but
that is not required by code, just by economics (long-term version).
Warm up the pick and shovel muscles, you've got a lot of dirt to move.

The correct (waterproof) wire to run in conduit and conduit are usually
LESS expensive (together) than correct direct burial wire - and the
conduit solution is also much less subject to rodent or rock damage.
Direct burial cable is a failure waiting, none too patiently, to happen.
Any sensible person will oversize the conduit and add extra conduit when
digging a trench, as both are trivial compared to having to dig it up
again when you decide to run something else (ie, network) out there, or
larger service, or some utility you don't even have yet.

--
Cats, coffee, chocolate...vices to live by

 

[Jamie]

default wrote:

I have a service panel on the side of the house that feeds a sub panel
inside. Over the years a few breakers got added to supply an air
conditioner and electric clothes dryer (in the outdoor panel directly
under the meter).

I was planning on running some power out to the garage - about 80 feet
of cable. I figured to just tap into the outside box (the inside
panel is ancient and has plug fuses);.

Run 240 out to the garage via a regular 12 AWG "2 wires plus ground"
and put a 20 amp 240 volt GFI breaker in the outside panel on the
house to a small sub panel in the garage for lights and a workbench.

The cable will run in a trench buried in the ground and only be
protected with conduit where it goes into the ground and comes out.
There should be no cause to dig in the area and the GFI should protect
against shock should someone dig.

Intent is to bury plain old vinyl insulated cable. I don't see any
that is rated for direct ground burial in the hardware stores - is
this important and why?

Any reasons this won't work and be safe?

I do see "outdoor cable" in the store, but from reading the specs it
appears that it's only claim to fame is the UV inhibitors in the vinyl
- other than the label, it is indistinguishable from the indoor stuff
- cuts and strips just like the indoor cable no tougher outside
covering. The package says it can be buried... and it costs roughly
double.


Do yourself a favor, do it right!

First off, you should rent a trench digger and check with your local
gov for the depth you need it at. Some places require a min of 36"
others 42. etc..

Get 4 of #8 cable Black,white, red and grean/bare wire for ground.
You can get DUR how ever, its not needed because you should be using
ABS pipe coupled together as you pull the cable through it. Use what
size you need that fits.. 1 1/4 sounds about rite. Get some plumbers
pipe glue, plastic couplings and 1 1/4" rigid elbows, straights that
will come up out of the ground into your boxes on both ends. You don't
want just cable coming out of the ground or plastic pipe. It has to be
protected with a strong wall of something. This is to keep pets, kids,
wild animals from chewing on it, and maybe the weed whacker!
The plumber shops have the proper couplings to join plastic and metal
hardware.

P.S.
The ABS keeps water out, bugs out and allows you to pull new wire
through if you ever have a mother nature strike!
Jamie

 

[John G]

default used his keyboard to write :

On Mon, 28 Mar 2011 11:10:37 +1100, John G <greentest@ozemail.com.au
wrote:

You need three (3) wires AND Ground to get 240 and 120 at the garage
and you will surely need 120. Assuming you are in the USA of course.

Why? my electric range, AC, clothes dryer are all three wire devices.
In the case of the electric range the neutral is carrying current when
the 120 volt outlet on the stove is used, likewise the oven and range
top lights.

If you big devices only have 3 wires then they do not confirm with
today's practice which requires that the ground wire does not carry any
current except fault current and the neutral has wire of its own.

--
John G

 

[John G]

default brought next idea :

On Sun, 27 Mar 2011 21:29:21 -0400, Ecnerwal
MyNameForward@ReplaceWithMyVices.Com.invalid> wrote:

In article <qmjvo6hkp0dkud6hagbvr1ukgt4fn23kna@4ax.com>, default wrote:
Run 240 out to the garage via a regular 12 AWG "2 wires plus ground"
and put a 20 amp 240 volt GFI breaker in the outside panel on the
house to a small sub panel in the garage for lights and a workbench.

The cable will run in a trench buried in the ground and only be
protected with conduit where it goes into the ground and comes out.
There should be no cause to dig in the area and the GFI should protect
against shock should someone dig.

GFIs can and do fail to trip. That's why they have the test buttons on
them.

Intent is to bury plain old vinyl insulated cable. I don't see any
that is rated for direct ground burial in the hardware stores - is
this important and why?

Any reasons this won't work and be safe?

Well, you're probably just a troll, but: Plenty. Also quite a few
reasons that it's penny pinching and pound foolish....Right off the bat,
you're short one wire, so "you doing the work yourself" is not looking
like a good plan, and anyone qualified to do the work won't be doing it
"your way." Likewise, anyone willing to do it "your way" is not
qualified to do the work.

I do see "outdoor cable" in the store, but from reading the specs it
appears that it's only claim to fame is the UV inhibitors in the vinyl
- other than the label, it is indistinguishable from the indoor stuff
- cuts and strips just like the indoor cable no tougher outside
covering. The package says it can be buried... and it costs roughly
double.

Indoor cable insulation is not waterproof. Any exterior cable (including
those in conduit, which is assumed to be wet, because it usually is)
must be waterproof (there will be a W in the "type") Within a relatively
short time (might be a few years, but a proper installation lasts many
decades) the insulation will fail.

Because you are a penny pincher, you'll then have to dig the whole
trench up again. If you use conduit correctly, you only have to dig
once. Conduit is CHEAP. Trenches are EXPENSIVE. If you were planning to
dig the trench yourself, it's quite expensive in terms of labor - a
shallow trench is unsafe, and violates electrical code. 18-24" minimum
to the top of the line or conduit. A good job goes below frost line to
keep the line from being stressed each year with ground movements, but
that is not required by code, just by economics (long-term version).
Warm up the pick and shovel muscles, you've got a lot of dirt to move.

The correct (waterproof) wire to run in conduit and conduit are usually
LESS expensive (together) than correct direct burial wire - and the
conduit solution is also much less subject to rodent or rock damage.
Direct burial cable is a failure waiting, none too patiently, to happen.
Any sensible person will oversize the conduit and add extra conduit when
digging a trench, as both are trivial compared to having to dig it up
again when you decide to run something else (ie, network) out there, or
larger service, or some utility you don't even have yet.

'Thanks. That makes sense. Downside of conduit is that unless it is
flexible it won't fit the trench a gas powered wire laying trencher
makes, and if it is flexible it won't offer much protection. Ideally
I need flexible to curve around some tree roots.

It was my plan to drop some coax, cat 5, etc. in the trench too.

There is a space required between power and data wiring but I do not
know the details for the USA.

I lived in one house where someone buried a three wire extension cord
out to an outbuilding and had a 240 volt welder running from it (not
me).

I just dug a line for water 12" (below the frost line - to building
codes) took me three days with a mattock, shovel and axe to hack
through tree roots. This time I figured to rent a trencher and do it
in a few minutes. (they claim 5 feet a minute worst case)

--
John G

 

[Beryl]

John G wrote:

default used his keyboard to write :
On Mon, 28 Mar 2011 11:10:37 +1100, John G <greentest@ozemail.com.au
wrote:

You need three (3) wires AND Ground to get 240 and 120 at the garage
and you will surely need 120. Assuming you are in the USA of course.

Why? my electric range, AC, clothes dryer are all three wire devices.
In the case of the electric range the neutral is carrying current when
the 120 volt outlet on the stove is used, likewise the oven and range
top lights.

If you big devices only have 3 wires then they do not confirm with
today's practice which requires that the ground wire does not carry any
current except fault current and the neutral has wire of its own.

Also the stove and dryer, probably AC too, are on separate circuits for
each of them. There are no other appliances downstream sharing 120V
"ground" wires.

 

On Mon, 28 Mar 2011 11:10:37 +1100, John G <greentest@ozemail.com.au>
wrote:

You need three (3) wires AND Ground to get 240 and 120 at the garage
and you will surely need 120. Assuming you are in the USA of course.

Why? my electric range, AC, clothes dryer are all three wire devices.
In the case of the electric range the neutral is carrying current when
the 120 volt outlet on the stove is used, likewise the oven and range
top lights.

 

On Sun, 27 Mar 2011 21:29:21 -0400, Ecnerwal
<MyNameForward@ReplaceWithMyVices.Com.invalid> wrote:

In article <qmjvo6hkp0dkud6hagbvr1ukgt4fn23kna@4ax.com>, default wrote:
Run 240 out to the garage via a regular 12 AWG "2 wires plus ground"
and put a 20 amp 240 volt GFI breaker in the outside panel on the
house to a small sub panel in the garage for lights and a workbench.

The cable will run in a trench buried in the ground and only be
protected with conduit where it goes into the ground and comes out.
There should be no cause to dig in the area and the GFI should protect
against shock should someone dig.

GFIs can and do fail to trip. That's why they have the test buttons on
them.

Intent is to bury plain old vinyl insulated cable. I don't see any
that is rated for direct ground burial in the hardware stores - is
this important and why?

Any reasons this won't work and be safe?

Well, you're probably just a troll, but: Plenty. Also quite a few
reasons that it's penny pinching and pound foolish....Right off the bat,
you're short one wire, so "you doing the work yourself" is not looking
like a good plan, and anyone qualified to do the work won't be doing it
"your way." Likewise, anyone willing to do it "your way" is not
qualified to do the work.

I do see "outdoor cable" in the store, but from reading the specs it
appears that it's only claim to fame is the UV inhibitors in the vinyl
- other than the label, it is indistinguishable from the indoor stuff
- cuts and strips just like the indoor cable no tougher outside
covering. The package says it can be buried... and it costs roughly
double.

Indoor cable insulation is not waterproof. Any exterior cable (including
those in conduit, which is assumed to be wet, because it usually is)
must be waterproof (there will be a W in the "type") Within a relatively
short time (might be a few years, but a proper installation lasts many
decades) the insulation will fail.

Because you are a penny pincher, you'll then have to dig the whole
trench up again. If you use conduit correctly, you only have to dig
once. Conduit is CHEAP. Trenches are EXPENSIVE. If you were planning to
dig the trench yourself, it's quite expensive in terms of labor - a
shallow trench is unsafe, and violates electrical code. 18-24" minimum
to the top of the line or conduit. A good job goes below frost line to
keep the line from being stressed each year with ground movements, but
that is not required by code, just by economics (long-term version).
Warm up the pick and shovel muscles, you've got a lot of dirt to move.

The correct (waterproof) wire to run in conduit and conduit are usually
LESS expensive (together) than correct direct burial wire - and the
conduit solution is also much less subject to rodent or rock damage.
Direct burial cable is a failure waiting, none too patiently, to happen.
Any sensible person will oversize the conduit and add extra conduit when
digging a trench, as both are trivial compared to having to dig it up
again when you decide to run something else (ie, network) out there, or
larger service, or some utility you don't even have yet.

'Thanks. That makes sense. Downside of conduit is that unless it is
flexible it won't fit the trench a gas powered wire laying trencher
makes, and if it is flexible it won't offer much protection. Ideally
I need flexible to curve around some tree roots.

It was my plan to drop some coax, cat 5, etc. in the trench too.

I lived in one house where someone buried a three wire extension cord
out to an outbuilding and had a 240 volt welder running from it (not
me).

I just dug a line for water 12" (below the frost line - to building
codes) took me three days with a mattock, shovel and axe to hack
through tree roots. This time I figured to rent a trencher and do it
in a few minutes. (they claim 5 feet a minute worst case)

 

[Ecnerwal]

In article <-96dnQvcGJ_VnQ3QnZ2dnUVZ_rqdnZ2d@westnet.com.au>,
John G <greentest@ozemail.com.au> wrote:

default brought next idea :

'Thanks. That makes sense. Downside of conduit is that unless it is
flexible it won't fit the trench a gas powered wire laying trencher
makes, and if it is flexible it won't offer much protection. Ideally
I need flexible to curve around some tree roots.

PVC "rigid" conduit makes large bends with no effort at all when you put
a few sticks of it together. What seems "stiff" with one stick becomes
floppy when you get to three or so (30 feet.) You can also get actual
sweeps if you need to take serious corners, but don't use too many
without also using a pull box or you won't be able to pull cable. Either
drive the trencher fairly straight (stretch a string and paint a line to
follow), or come back and clean up the trench a bit with your mattock
after it. If you are "bending" around tree roots in a larger circle (as
to avoid damaging the all the roots of a tree you like) rather than in
small jinks (as to bend rather than cutting one root) it should be fine,
if you use your conduit, dry-fitted, to mark out the line to dig, and
then follow it. If your trencher won't dig through tree roots, it's not
worth renting, or you should rent a different tool (or tool and operator
- have somebody come dig the trench with an excavator and you fill it
back in by hand.)

Also - use PVC conduit (gray), not plumbing pipe. Since you're barely
willing to consider conduit, you probably won't consider schedule 80
(heavywall, not generally seen in chain stores, much stronger) but you
really should. You have to find someplace (generally an electrical
supply house) that sells it, and it costs a little bit more than
schedule 40 (what the chain stores sell.)

It was my plan to drop some coax, cat 5, etc. in the trench too.

There is a space required between power and data wiring but I do not
know the details for the USA.

12" minimum, face to face (ie, if you have a 2" conduit for power and
another 2" conduit for network, cable, etc the nearest two faces need to
be at least 12" apart, not the two conduits running 12" on center (only
10" face to face.) Some local codes may require more separation.

If you have the digging done, vertical separation with the power below
the communications gives one more warning (besides the "Buried Electric
Line Below" warning tape you WILL put in the trench as you are filling
it back in, so it gets dug up first) before the next person to dig gets
into the electric line. Otherwise you can go side to side in a shallower
trench. Given the typical roll size on that tape, might as well put in a
couple of them at various depths - the top one should be no more than
6-8" under the surface of the ground, so it's easy to find well before
the wire is in danger.

With conduit you might get away with interior Cat5 up to the point you
want to replace it with the next thing, or a fresh piece of cat5. If you
direct-bury interior cat5 (and/or coax) it will fail, and you won't be
able to replace it, nor will you have a hole available to pull (say)
fiber through if fiber around the home becomes normal at some later
date.

--
Cats, coffee, chocolate...vices to live by

 

[amdx]

Because you are a penny pincher, you'll then have to dig the whole
trench up again. If you use conduit correctly, you only have to dig
once. Conduit is CHEAP. Trenches are EXPENSIVE. If you were planning to
dig the trench yourself, it's quite expensive in terms of labor - a
shallow trench is unsafe, and violates electrical code. 18-24" minimum
to the top of the line or conduit.

Yes, deeper is better, The house I'm in has a 60 ft run of PVC conduit
about
12" below ground to a shed.. I have dug two times to put a tower in and a
post. I hit the
darn conduit both times! Recently I put in several fence posts, I hit the
cable
tv line going to the house. But my bad luck is sometimes good luck, I was
beginning
a dig to install a cleanout on a sewer pipe and hit --- a cleanout!---
Saved me a weekend of hard labor.

Mikek

 

On Mon, 28 Mar 2011 14:25:56 +1100, John G <greentest@ozemail.com.au>
wrote:

default used his keyboard to write :
On Mon, 28 Mar 2011 11:10:37 +1100, John G <greentest@ozemail.com.au
wrote:

You need three (3) wires AND Ground to get 240 and 120 at the garage
and you will surely need 120. Assuming you are in the USA of course.

Why? my electric range, AC, clothes dryer are all three wire devices.
In the case of the electric range the neutral is carrying current when
the 120 volt outlet on the stove is used, likewise the oven and range
top lights.

If you big devices only have 3 wires then they do not confirm with
today's practice which requires that the ground wire does not carry any
current except fault current and the neutral has wire of its own.

I thought that might be the case. I checked out some new ranges and
they do have four wires.

 

[ehsjr]

default wrote:

I have a service panel on the side of the house that feeds a sub panel
inside. Over the years a few breakers got added to supply an air
conditioner and electric clothes dryer (in the outdoor panel directly
under the meter).

I was planning on running some power out to the garage - about 80 feet
of cable. I figured to just tap into the outside box (the inside
panel is ancient and has plug fuses);.

Run 240 out to the garage via a regular 12 AWG "2 wires plus ground"
and put a 20 amp 240 volt GFI breaker in the outside panel on the
house to a small sub panel in the garage for lights and a workbench.

The cable will run in a trench buried in the ground and only be
protected with conduit where it goes into the ground and comes out.
There should be no cause to dig in the area and the GFI should protect
against shock should someone dig.

Intent is to bury plain old vinyl insulated cable. I don't see any
that is rated for direct ground burial in the hardware stores - is
this important and why?

Any reasons this won't work and be safe?

I do see "outdoor cable" in the store, but from reading the specs it
appears that it's only claim to fame is the UV inhibitors in the vinyl
- other than the label, it is indistinguishable from the indoor stuff
- cuts and strips just like the indoor cable no tougher outside
covering. The package says it can be buried... and it costs roughly
double.

You've already heard the right way to do it: electrical (not plumbing)
plastic conduit, 4 wires, buried at LEAST 18", etc.

I think it best to plan the entire installation on paper, before
lifting tool 1 or spending penny 1 on it.

Consider the design: almost all the work is in the trenching. Saving
money on parts is just plain not worth it. #12 wire feeding a workbench
+ lights over an 80' distance is a not a good choice. At _least_ one
size bigger is better.
Consider what you are burying in the trench: one feeder circuit to
the garage subpanel. Suppose you want to be able to turn on a light,
mounted on the outside of the garage, from the house?
Why not build that capability in while the trench is there? Add a 3
wire + ground of #12 to enable switching of a garage light from the
house or garage.

Do you have plans for adding a generator in the future, to power the
house during power outages? If so, you might want to house the
generator in the garage, and you might want to consider burying
cable for that at this time.

As to GFI: if your intention is to split the 240 into 2 120V
branches in the garage, don't use a 240 GFI breaker. Instead,
use 2 GFCI receptacles, each installed as the first receptacle
on the branch and wired to protect all of the "downstream"
outlets on the branch. It is _much_ cheaper that way. If
you later decide to use a 240 volt branch from the subpanel,
you can add the 240V GFI breaker at that time.

_Grounding_

You are feeding a separate building on your premises. You need to
ground the sub-panel properly, per the electrical code.
The neutral bus MUST NOT be connected to the ground bus in the
sub panel. The ground wire in the feeder cable from the house
MUST BE connected to the ground bus in the sub panel. The only
place where neutral and ground are allowed and required to be
connected together in your service is at the main service panel.
You need to understand what (and where in your subpanel) the
"bonding jumper" is. It MUST be removed.

Ed

 

[Tom Biasi]

"default" wrote in message
news:gh52p6p6nivs44kluq440upl6l0cvkmo0n@4ax.com...

On Mon, 28 Mar 2011 12:25:40 -0400, ehsjr <ehsjr@nospamverizon.net>
wrote:


Which raises another question. The GFI breakers I looked at have a
white wire coming out of the breaker (prepped - coiled and stripped
white "pigtail" sold already in place) where would that go on the sub
panel in the garage ground or neutral?

It would go on the neutral. On the main panel the neutral and ground are
usually the same but on your sub-panel they are (should be) isolated.
Tom

 

On Mon, 28 Mar 2011 12:25:40 -0400, ehsjr <ehsjr@nospamverizon.net>
wrote:

default wrote:
I have a service panel on the side of the house that feeds a sub panel
inside. Over the years a few breakers got added to supply an air
conditioner and electric clothes dryer (in the outdoor panel directly
under the meter).

I was planning on running some power out to the garage - about 80 feet
of cable. I figured to just tap into the outside box (the inside
panel is ancient and has plug fuses);.

Run 240 out to the garage via a regular 12 AWG "2 wires plus ground"
and put a 20 amp 240 volt GFI breaker in the outside panel on the
house to a small sub panel in the garage for lights and a workbench.

The cable will run in a trench buried in the ground and only be
protected with conduit where it goes into the ground and comes out.
There should be no cause to dig in the area and the GFI should protect
against shock should someone dig.

Intent is to bury plain old vinyl insulated cable. I don't see any
that is rated for direct ground burial in the hardware stores - is
this important and why?

Any reasons this won't work and be safe?

I do see "outdoor cable" in the store, but from reading the specs it
appears that it's only claim to fame is the UV inhibitors in the vinyl
- other than the label, it is indistinguishable from the indoor stuff
- cuts and strips just like the indoor cable no tougher outside
covering. The package says it can be buried... and it costs roughly
double.



You've already heard the right way to do it: electrical (not plumbing)
plastic conduit, 4 wires, buried at LEAST 18", etc.

I think it best to plan the entire installation on paper, before
lifting tool 1 or spending penny 1 on it.

Consider the design: almost all the work is in the trenching. Saving
money on parts is just plain not worth it. #12 wire feeding a workbench
+ lights over an 80' distance is a not a good choice. At _least_ one
size bigger is better.
Consider what you are burying in the trench: one feeder circuit to
the garage subpanel. Suppose you want to be able to turn on a light,
mounted on the outside of the garage, from the house?
Why not build that capability in while the trench is there? Add a 3
wire + ground of #12 to enable switching of a garage light from the
house or garage.

She will be able to switch the garage light on and off from the house
- via a relay and communication cable to be buried with the feeder.
That is already in Plan A. Because I can already see it - she will
want lights inside the garage then want to know they are off or on and
be able to control them from the house too.

This, I feel, is likely, but I don't want to put ideas in her head.

Do you have plans for adding a generator in the future, to power the
house during power outages? If so, you might want to house the
generator in the garage, and you might want to consider burying
cable for that at this time.

That is called "mission creep" by the military (and it is one of my
faults too). Keep it simple. This is for my wife's house and she's
footing the bill. A generator isn't in the future, and her use of a
workbench would be limited.

The rule of thumb is 3% voltage drop. With 14 AWG that would be about
17 amps, so 12 AWG is already one size larger.

As to GFI: if your intention is to split the 240 into 2 120V
branches in the garage, don't use a 240 GFI breaker. Instead,
use 2 GFCI receptacles, each installed as the first receptacle
on the branch and wired to protect all of the "downstream"
outlets on the branch. It is _much_ cheaper that way. If
you later decide to use a 240 volt branch from the subpanel,
you can add the 240V GFI breaker at that time.

I was thinking the wire underground needs GFI as much as any circuit
outdoors. No?

I'll probably just put in 120 to keep the cost down after reading the

responses here.... The 240 would be if she wants to insulate the
garage or a part of it and add air conditioning or heating. The
building really isn't worth putting that into it in my opinion, but my
opinion doesn't count.

_Grounding_

You are feeding a separate building on your premises. You need to
ground the sub-panel properly, per the electrical code.
The neutral bus MUST NOT be connected to the ground bus in the
sub panel. The ground wire in the feeder cable from the house
MUST BE connected to the ground bus in the sub panel. The only
place where neutral and ground are allowed and required to be
connected together in your service is at the main service panel.
You need to understand what (and where in your subpanel) the
"bonding jumper" is. It MUST be removed.

Ed

That is interesting. This is the deep south and electricians don't
necessarily have opposed thumbs... There was no ground rod at the
meter, I installed one some years ago trying to get the hum out of her
stereo - that problem turned out to be no ground on the power
transformer at the pole. I called up the power company and they added
a ground and the buzzing went away.

BUT to get back to what you are saying, so I understand it. (assume
a plain old vanilla 120 circuit - cost will determine if it is 240)
The neutral will run from the panel on the house to the sub panel in
the garage, but must be isolated from the ground at the sub panel -
while the default is to have them connected as they come from the
store?

Which raises another question. The GFI breakers I looked at have a
white wire coming out of the breaker (prepped - coiled and stripped
white "pigtail" sold already in place) where would that go on the sub
panel in the garage ground or neutral?

 

[ehsjr]

default wrote:

On Mon, 28 Mar 2011 12:25:40 -0400, ehsjr <ehsjr@nospamverizon.net
wrote:


default wrote:

I have a service panel on the side of the house that feeds a sub panel
inside. Over the years a few breakers got added to supply an air
conditioner and electric clothes dryer (in the outdoor panel directly
under the meter).

I was planning on running some power out to the garage - about 80 feet
of cable. I figured to just tap into the outside box (the inside
panel is ancient and has plug fuses);.

Run 240 out to the garage via a regular 12 AWG "2 wires plus ground"
and put a 20 amp 240 volt GFI breaker in the outside panel on the
house to a small sub panel in the garage for lights and a workbench.

The cable will run in a trench buried in the ground and only be
protected with conduit where it goes into the ground and comes out.
There should be no cause to dig in the area and the GFI should protect
against shock should someone dig.

Intent is to bury plain old vinyl insulated cable. I don't see any
that is rated for direct ground burial in the hardware stores - is
this important and why?

Any reasons this won't work and be safe?

I do see "outdoor cable" in the store, but from reading the specs it
appears that it's only claim to fame is the UV inhibitors in the vinyl
- other than the label, it is indistinguishable from the indoor stuff
- cuts and strips just like the indoor cable no tougher outside
covering. The package says it can be buried... and it costs roughly
double.



You've already heard the right way to do it: electrical (not plumbing)
plastic conduit, 4 wires, buried at LEAST 18", etc.

I think it best to plan the entire installation on paper, before
lifting tool 1 or spending penny 1 on it.

Consider the design: almost all the work is in the trenching. Saving
money on parts is just plain not worth it. #12 wire feeding a workbench
+ lights over an 80' distance is a not a good choice. At _least_ one
size bigger is better.
Consider what you are burying in the trench: one feeder circuit to
the garage subpanel. Suppose you want to be able to turn on a light,
mounted on the outside of the garage, from the house?
Why not build that capability in while the trench is there? Add a 3
wire + ground of #12 to enable switching of a garage light from the
house or garage.


She will be able to switch the garage light on and off from the house
- via a relay and communication cable to be buried with the feeder.
That is already in Plan A. Because I can already see it - she will
want lights inside the garage then want to know they are off or on and
be able to control them from the house too.

This, I feel, is likely, but I don't want to put ideas in her head.



Do you have plans for adding a generator in the future, to power the
house during power outages? If so, you might want to house the
generator in the garage, and you might want to consider burying
cable for that at this time.


That is called "mission creep" by the military (and it is one of my
faults too). Keep it simple. This is for my wife's house and she's
footing the bill. A generator isn't in the future, and her use of a
workbench would be limited.

The rule of thumb is 3% voltage drop. With 14 AWG that would be about
17 amps, so 12 AWG is already one size larger.

Not quite. #14 wire is 3.14 ohms per 1000 feet. The computation:
17 * 3.14/1000 * 160 = 8.5408 volts; 8.5408/120 = .0711 or a bit
over 7%

Using #12 wire at 1.98 ohms per 1000 feet:
17* 1.98/1000 * 160 = 5.3856 volts; 5.3856/120 = .0448 or
4.48%.

My guess is that you used 80 feet in the calculation instead
of 160. You have to use 160 because there are two wires in
the 80 foot run.

As to GFI: if your intention is to split the 240 into 2 120V
branches in the garage, don't use a 240 GFI breaker. Instead,
use 2 GFCI receptacles, each installed as the first receptacle
on the branch and wired to protect all of the "downstream"
outlets on the branch. It is _much_ cheaper that way. If
you later decide to use a 240 volt branch from the subpanel,
you can add the 240V GFI breaker at that time.


I was thinking the wire underground needs GFI as much as any circuit
outdoors. No?

No - you can't come into contact with the buried wires. GFI is
not to protect wiring - it is to protect personnel from conducting
current to ground.

I'll probably just put in 120 to keep the cost down after reading the
responses here.... The 240 would be if she wants to insulate the
garage or a part of it and add air conditioning or heating. The
building really isn't worth putting that into it in my opinion, but my
opinion doesn't count.


_Grounding_

You are feeding a separate building on your premises. You need to
ground the sub-panel properly, per the electrical code.
The neutral bus MUST NOT be connected to the ground bus in the
sub panel. The ground wire in the feeder cable from the house
MUST BE connected to the ground bus in the sub panel. The only
place where neutral and ground are allowed and required to be
connected together in your service is at the main service panel.
You need to understand what (and where in your subpanel) the
"bonding jumper" is. It MUST be removed.

Ed


That is interesting. This is the deep south and electricians don't
necessarily have opposed thumbs... There was no ground rod at the
meter, I installed one some years ago trying to get the hum out of her
stereo - that problem turned out to be no ground on the power
transformer at the pole. I called up the power company and they added
a ground and the buzzing went away.

BUT to get back to what you are saying, so I understand it. (assume
a plain old vanilla 120 circuit - cost will determine if it is 240)
The neutral will run from the panel on the house to the sub panel in
the garage, but must be isolated from the ground at the sub panel -

Yes.

while the default is to have them connected as they come from the
store?

Likely.

Which raises another question. The GFI breakers I looked at have a
white wire coming out of the breaker (prepped - coiled and stripped
white "pigtail" sold already in place) where would that go on the sub
panel in the garage ground or neutral?

The white wire always goes to the neutral bus, regardless of
whether the GFI is installed in the main panel or a sub panel.
GFI never needs to be connected to the ground bus, nor does
a GFI in the panel or GFCI receptacle need a connection to ground
to function properly. At a GFCI receptacle installed in a grounded
system, the ground wire must be connected to the ground screw
on the receptacle. That serves the same function as the ground wire
connection to a regular receptacle - to ground the 3rd prong of
a plug (and therefore ground whatever device is plugged in). It has
nothing to do with the ground fault operation.

Ed

 

On Mon, 28 Mar 2011 22:29:35 -0400, ehsjr <ehsjr@nospamverizon.net>
wrote:

The rule of thumb is 3% voltage drop. With 14 AWG that would be about
17 amps, so 12 AWG is already one size larger.

Not quite. #14 wire is 3.14 ohms per 1000 feet. The computation:
17 * 3.14/1000 * 160 = 8.5408 volts; 8.5408/120 = .0711 or a bit
over 7%

Using #12 wire at 1.98 ohms per 1000 feet:
17* 1.98/1000 * 160 = 5.3856 volts; 5.3856/120 = .0448 or
4.48%.

My guess is that you used 80 feet in the calculation instead
of 160. You have to use 160 because there are two wires in
the 80 foot run.

That is exactly what I did. Thanks for pointing out the error.

My ARRL handbook puts 14 AWG at 2.575 ohms per thousand

and 12 at 1.619 ohms/1000.

8.7 amps with 14
14 amps with 12
for 3%

 

[ehsjr]

default wrote:

On Mon, 28 Mar 2011 22:29:35 -0400, ehsjr <ehsjr@nospamverizon.net
wrote:


The rule of thumb is 3% voltage drop. With 14 AWG that would be about
17 amps, so 12 AWG is already one size larger.

Not quite. #14 wire is 3.14 ohms per 1000 feet. The computation:
17 * 3.14/1000 * 160 = 8.5408 volts; 8.5408/120 = .0711 or a bit
over 7%

Using #12 wire at 1.98 ohms per 1000 feet:
17* 1.98/1000 * 160 = 5.3856 volts; 5.3856/120 = .0448 or
4.48%.

My guess is that you used 80 feet in the calculation instead
of 160. You have to use 160 because there are two wires in
the 80 foot run.


That is exactly what I did. Thanks for pointing out the error.

Guess why I am familiar with that particular error. :-(

My ARRL handbook puts 14 AWG at 2.575 ohms per thousand

and 12 at 1.619 ohms/1000.

There are several different wire tables floating around, so
it's not unusual to find different values for the same wire.
For house wiring, I figure it's best to use the table in the
NEC (National Electrical Code). The table in the ARRL book
may be more accurate - I don't know.

Ed

8.7 amps with 14
14 amps with 12
for 3%

 

[Michael A. Terrell]

ehsjr wrote:

default wrote:
On Mon, 28 Mar 2011 22:29:35 -0400, ehsjr <ehsjr@nospamverizon.net
wrote:


The rule of thumb is 3% voltage drop. With 14 AWG that would be about
17 amps, so 12 AWG is already one size larger.

Not quite. #14 wire is 3.14 ohms per 1000 feet. The computation:
17 * 3.14/1000 * 160 = 8.5408 volts; 8.5408/120 = .0711 or a bit
over 7%

Using #12 wire at 1.98 ohms per 1000 feet:
17* 1.98/1000 * 160 = 5.3856 volts; 5.3856/120 = .0448 or
4.48%.

My guess is that you used 80 feet in the calculation instead
of 160. You have to use 160 because there are two wires in
the 80 foot run.


That is exactly what I did. Thanks for pointing out the error.

Guess why I am familiar with that particular error. :-(


My ARRL handbook puts 14 AWG at 2.575 ohms per thousand

and 12 at 1.619 ohms/1000.

There are several different wire tables floating around, so
it's not unusual to find different values for the same wire.
For house wiring, I figure it's best to use the table in the
NEC (National Electrical Code). The table in the ARRL book
may be more accurate - I don't know.

The ARRL table is for winding transformers.


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.