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  #1   Report Post  
Peter De Smidt
 
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Default Electrical Wiring Question

I'm trying to turn my 1-car, 70 year old garage into a workshop. At
the moment, it has two 15 amp lines run through 1/2 metal conduit.
The wire is 14 ga, and there are two hots, one neutral and a ground.
I'd like to increase this a bit. I was thinking of putting in a
sub-panel. I'd like to be able to run the new wires in the same
conduit, as it's a little too frozen here at the moment for me to dig
a new trench. My idea was to replace the 14 ga wires with 10 ga.
According to my sources, a 1/2 metal conduit will take 5 - 10 ga
wires, and so 4 should be no problem. My understanding was that if
the run was under 35 ft, that each of the 10 ga. hot wires would
support 30 amps, and hence that I should hook each hot wire to a 30
amp breaker in the main box. The salesman in the Menards electrical
section told me that this wasn't right. The four wire system would
only support 30 amps. Any comments?

-Peter De Smidt
  #2   Report Post  
Doug Miller
 
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In article , Peter De Smidt wrote:
I'm trying to turn my 1-car, 70 year old garage into a workshop. At
the moment, it has two 15 amp lines run through 1/2 metal conduit.
The wire is 14 ga, and there are two hots, one neutral and a ground.


Hopefully, these are fed from one duplex circuit breaker. If not, it's a Code
violation and a fire hazard.

I'd like to increase this a bit. I was thinking of putting in a
sub-panel. I'd like to be able to run the new wires in the same
conduit, as it's a little too frozen here at the moment for me to dig
a new trench. My idea was to replace the 14 ga wires with 10 ga.
According to my sources, a 1/2 metal conduit will take 5 - 10 ga
wires, and so 4 should be no problem. My understanding was that if
the run was under 35 ft, that each of the 10 ga. hot wires would
support 30 amps, and hence that I should hook each hot wire to a 30
amp breaker in the main box. The salesman in the Menards electrical
section told me that this wasn't right. The four wire system would
only support 30 amps. Any comments?

How many wires the Code allows in the conduit depends on the type of
insulation on the wires, but for the types of wire that you'd buy as single
wires (not cables) at Menard's, yes, the Code allows 5 or even 6 #10 wires in
a 1/2" conduit.

Please note, however, that there is a *large* difference between the number of
wires the Code permits in a conduit, and the number of wires that can be
easily pulled through the same conduit. Even though the Code permits five #10
wires in a 1/2" conduit, you will encounter substantial difficulty in trying
to pull them through it.

If you succeed in pulling four #10 wires through this conduit, you're still
limited to a 30A version of what you have now: two 30A 120V circuits with a
shared neutral. What will you do with a 30A 120V circuit? Not too many 120V
tools require 30A.

It would help a lot if you provided more information about what your objective
is. What tools do you want to run in your garage/shop, and how much current do
they require?

--
Doug Miller (alphageek at milmac dot com)

How come we choose from just two people to run for president and 50 for Miss America?
  #3   Report Post  
A Dubya
 
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What about hanging a sub/pony panel in your garage and feeding it with 220v
and 3/8 in your conduit.

Cheers,

Andy


  #4   Report Post  
Peter De Smidt
 
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Default Electrical Wiring Question

On Mon, 26 Jan 2004 15:29:58 GMT, (Doug Miller)
wrote:

In article , Peter De Smidt wrote:
I'm trying to turn my 1-car, 70 year old garage into a workshop. At
the moment, it has two 15 amp lines run through 1/2 metal conduit.
The wire is 14 ga, and there are two hots, one neutral and a ground.


Hopefully, these are fed from one duplex circuit breaker. If not, it's a Code
violation and a fire hazard.


Yes, these are on one duplex circuit breaker.


If you succeed in pulling four #10 wires through this conduit, you're still
limited to a 30A version of what you have now: two 30A 120V circuits with a
shared neutral. What will you do with a 30A 120V circuit? Not too many 120V
tools require 30A.

It would help a lot if you provided more information about what your objective
is. What tools do you want to run in your garage/shop, and how much current do
they require?


My plan was to install a subpanel, and then run the necessary 120 and
220 circuits off of this. At the moment, my only big piece of
equipment is a 2hp table saw. I'd like to rewire it for 220. At the
moment, I'm going to use my shop vac with a HEPA filter for dust
control, although down the road I'll probably want a 220 DC system.
For lights, I plan on using a 400 watt HMI light, and maybe a few
small task lights. Eventually, I hope to add a planer, jointer... but
these will only be run one at a time. For heat, I'm hoping to install
a used high efficiency furnace, but at the moment all I have is a 1450
watt space heater.

Peter
  #5   Report Post  
gabriel
 
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Default Electrical Wiring Question

You might need more juice than that. Do this calculation:

Add the most power-hungry stuff you will be using at the same time:

The 2HP Table saw - 220V @ 8-9 Amps (See your motor for this exact
amperage)

Dust Collector - 220V @ ??? Amps

Lights - 110V @ 4 Amps + other lights

It seems to me that you will be close to maxed out from the start.

If you are willing to forgo the bigger DC and TS, then you are fine, but it
would sure be frustrating to not be able to get a bigger machine because
you only have 30A coming into your shop.

--
gabriel


  #6   Report Post  
Peter De Smidt
 
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Default Electrical Wiring Question

On Mon, 26 Jan 2004 10:42:18 -0500, "A Dubya"
wrote:

What about hanging a sub/pony panel in your garage and feeding it with 220v
and 3/8 in your conduit.

Cheers,

Andy


I'd like to be able to do that, but according to my Black and Decker
_Advanced Home Wiring_ only two 8 ga wires will fit in the conduit. I
wish that I could install bigger conduit, but I wouldn't be able to do
so until spring. It'd be nice to do a little woodworking now

-Peter
  #7   Report Post  
Toller
 
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Default Electrical Wiring Question



My plan was to install a subpanel, and then run the necessary 120 and
220 circuits off of this. At the moment, my only big piece of
equipment is a 2hp table saw. I'd like to rewire it for 220. At the
moment, I'm going to use my shop vac with a HEPA filter for dust
control, although down the road I'll probably want a 220 DC system.
For lights, I plan on using a 400 watt HMI light, and maybe a few
small task lights. Eventually, I hope to add a planer, jointer... but
these will only be run one at a time. For heat, I'm hoping to install
a used high efficiency furnace, but at the moment all I have is a 1450
watt space heater.

That might be adequate, but just barely. You can make a single 240v circuit
and two 20a 120v circuits, but you can't fully utilize the the 240v and 120v
at the same time.

You have to figure out exactly what you need, and see if you have enough
juice.
But, bear in mind that saw and planers only draw their rated current when
they are being heavily used; which probably isn't for more than a minute at
a time. So, you can fudge a bit, because your 10a wires/breakers will allow
35a for a minute or two.


  #8   Report Post  
Gretch
 
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Default Electrical Wiring Question

On Mon, 26 Jan 2004 09:04:52 -0600, Peter De Smidt wrote:

I'm trying to turn my 1-car, 70 year old garage into a workshop. At the
moment, it has two 15 amp lines run through 1/2 metal conduit. The wire is
14 ga, and there are two hots, one neutral and a ground. I'd like to
increase this a bit. I was thinking of putting in a sub-panel. I'd like
to be able to run the new wires in the same conduit, as it's a little too
frozen here at the moment for me to dig a new trench. My idea was to
replace the 14 ga wires with 10 ga. According to my sources, a 1/2 metal
conduit will take 5 - 10 ga wires, and so 4 should be no problem. My
understanding was that if the run was under 35 ft, that each of the 10 ga.
hot wires would support 30 amps, and hence that I should hook each hot
wire to a 30 amp breaker in the main box. The salesman in the Menards
electrical section told me that this wasn't right. The four wire system
would only support 30 amps. Any comments?

-Peter De Smidt


The fact you are posting here would seem to indicate that you are unsure
of wiring and buiding codes. Your best and safest bet is to contact your
local building or electrical inspector to ask for their recommendations.
Other than having to pull a permit, the advice should cost you nothing.
In our community, a homeowner can do his/her own wiring as long as it is
done up to code.

Another choice is to pay an electrician as a consultant with the
understanding you will do the grunt work.

Trusting the advice given in newsgroups is always iffy. There is much
good advice here but how do you know which is good and which is not?

Bad wiring can cause fire as well as physical harm. Unless you are
absolutely sure and comfortable with wiring and electricity, seek the
right advice. 'Tis but a very small price to pay for contentment.

  #9   Report Post  
Doug Miller
 
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Default Electrical Wiring Question

In article , Peter De Smidt wrote:
On Mon, 26 Jan 2004 10:42:18 -0500, "A Dubya"
wrote:

What about hanging a sub/pony panel in your garage and feeding it with 220v
and 3/8 in your conduit.

I'd like to be able to do that, but according to my Black and Decker
_Advanced Home Wiring_ only two 8 ga wires will fit in the conduit. I
wish that I could install bigger conduit, but I wouldn't be able to do
so until spring. It'd be nice to do a little woodworking now

The National Electrical Code (NEC) permits three 8ga wires in 1/2" conduit if
the insulation is type THHN or THWN. As I noted in another post, however, what
the NEC permits in a conduit, and what is physically practical to try to pull
through it, are two different things.

--
Doug Miller (alphageek at milmac dot com)

How come we choose from just two people to run for president and 50 for Miss America?
  #10   Report Post  
Clarke Echols
 
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Default Electrical Wiring Question

First of all, be sure the person giving you advice is qualified to do so.
You're missing a lot of better input, so I'll give it a shot.

First of all, the NEC (National Electrical Code) specifies that circuit
breakers must be sized such that they do not exceed 80% of their trip
capacity under normal circumstances. If you are running motors that pull
high currents for a short time (saws, planers, jointers come to mind)
either at start-up or during operation, you work from maximum normal
operating current, not peak-load current. A #10 wire can carry 30 amps.
A 30 amp breaker is allowed to carry a steady-state load of 24 amps. Thus
you can use a 40-amp breaker on 30-ga. wire for motor loads (actually you
can use a 50-amp breaker if you're running an arc welder). Local codes
might vary, but I got this from a retired industrial electrician of
substantial experience. You have to go to the NEC and look in the area
that talks about motor and welding loads.

Since it's cold, I suggest pulling the 14-gauge wire and replacing it with
10-gauge with a 30-amp breaker. Run 4 wires, black, red, white, and green
into a subpanel in the garage. Put a 40-amp breaker in the main panel,
then connect the white to the neutral bus in the main panel and sub-panel,
connect green to the safety ground bus (where all the bare wires are)
in the main panel, and to the safety ground bus in the sub-panel. DO NOT
INSTALL THE BONDING SCREW IN THE SUB-PANEL! This is necessary in order
to keep neutral currents from flowing through the safety-ground wire
(required by code).

Connect the red and black wires to the L1 and L1 lugs on the sub-panel
and to the 40-amp 2-pole breaker in the main panel. Install a 20-amp
2-pole breaker for your table saw's 240-volt (not 220 -- that's a European
voltage) receptacle and wiring, then put in a pair of single-pole breakers
for two 120-volt, 20-amp circuits, using the normal wiring methods.

Then, when the frost is gone and spring/summer arrives, put in a bigger
conduit (1" would be nice, but it's a 70-year-old garage, so no sense
in overdoing things) and run #8 copper with a 50-amp breaker to the same
sub-panel. You can then put in a second 240-volt circuit, or just run
the TS and DC from a single 30-amp, 240-volt circuit with multiple
receptacles like I do in my 26 x 30-foot garage/shop.

I built my own home (7500 square feet plus garage) in the 1970s, and the
state electrical inspector took great pains to catch me on a code
violation. He came up with nothing. :-) I got my license as a
registered professional engineer in 1980, and have been wiring homes
from time to time since the 1950s. I also was responsible for
specifying wiring and grounding for industrial electricians in a
semiconductor manufacturing plant in the 1970s.

You really should get an electrical permit and have the work inspected
by local officials to protect yourself anytime you do this kind of work
if you are not absolutely dead-certain you know what you are doing. If
you don't, get someone who does to help you. Do-it-yourself books might
be useful, but they're no substitute for first-hand, first-rate knowledge
and experience, and wiring screw-ups can and have killed lots of people.

I saw a situation years ago of a homemaker who could have been killed.
She complained of sparks between washer and dryer. If she had touched
them both at the same time, she's have possibly been dead. Some idiot
"wired" 240V into the trailer for a dryer and got the wires on the wrong
terminals in the receptacle so there was 120 volts AC between the dryer
cabinet and the washer.

For more about overload protection for electrical motors as well as
grounding and other info, see

http://cnets.net/~eclectic/woodworki...arkeMotors.htm

Since you are considering dust collection, invest some time getting
educated on dust collection at

http://cnets.net/~eclectic/woodworki...lone/index.cfm

and when you're ready for a really exceptional cyclone dust collection
system in kit form so you can save some bucks and get the satisfaction
of building it yourself while getting first-class results, check out

http://cnets.net/~eclectic/woodworki...larkesKits.cfm

Clarke

Peter De Smidt wrote:

I'm trying to turn my 1-car, 70 year old garage into a workshop. At
the moment, it has two 15 amp lines run through 1/2 metal conduit.
The wire is 14 ga, and there are two hots, one neutral and a ground.
I'd like to increase this a bit. I was thinking of putting in a
sub-panel. I'd like to be able to run the new wires in the same
conduit, as it's a little too frozen here at the moment for me to dig
a new trench. My idea was to replace the 14 ga wires with 10 ga.
According to my sources, a 1/2 metal conduit will take 5 - 10 ga
wires, and so 4 should be no problem. My understanding was that if
the run was under 35 ft, that each of the 10 ga. hot wires would
support 30 amps, and hence that I should hook each hot wire to a 30
amp breaker in the main box. The salesman in the Menards electrical
section told me that this wasn't right. The four wire system would
only support 30 amps. Any comments?

-Peter De Smidt



  #11   Report Post  
Doug Miller
 
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Default Electrical Wiring Question

In article , Peter De Smidt wrote:
My plan was to install a subpanel, and then run the necessary 120 and
220 circuits off of this. At the moment, my only big piece of
equipment is a 2hp table saw. I'd like to rewire it for 220. At the
moment, I'm going to use my shop vac with a HEPA filter for dust
control, although down the road I'll probably want a 220 DC system.
For lights, I plan on using a 400 watt HMI light, and maybe a few
small task lights. Eventually, I hope to add a planer, jointer... but
these will only be run one at a time. For heat, I'm hoping to install
a used high efficiency furnace, but at the moment all I have is a 1450
watt space heater.


The circuit ampacity must be based on the heaviest loads that can be placed on
it *simultaneously*. In your case, that looks like table saw + dust collector
+ lights + heater.

A 2hp table saw doesn't draw the full 2hp most of the time. Likely continuous
load is in the neighborhood of 6A to 8A at 240V (1440 to 1920VA). A decent
240V dust collector is probably going to draw somewhere around 10A as well
(2400VA).

Figure about 2000W total for your heater and lights. (2000VA)

The dust collector, lights, and heater are "continuous loads" as defined in
the NEC and the ampacity of the circuit(s) supplying them is required to be
derated by 20%. Thus to supply the total of 4400VA for these loads, you need a
circuit rated at a minimum of 5500VA. Add 1440 to 1920VA for the table saw,
and you're at 6940 to 7420 VA -- which is 29 to 31A at 240V.

So a 30A 240V circuit is _just_barely_ adequate, and leaves you _no_ room at
all for adding additional loads.

And that's assuming that you're going to be able to pull three #8 wires
through a 1/2" conduit in the first place. :-)

--
Doug Miller (alphageek at milmac dot com)

How come we choose from just two people to run for president and 50 for Miss America?
  #12   Report Post  
gabriel
 
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Default Electrical Wiring Question

the same sub-panel. You can then put in a second 240-volt circuit, or
just run the TS and DC from a single 30-amp, 240-volt circuit with
multiple receptacles like I do in my 26 x 30-foot garage/shop.


In the rest of your post you preached about following code, but is this not
a code violation, at least in many places? I've heard everywhere that a
240V circuit should go to a single device/plug only...

--
gabriel
  #13   Report Post  
Al Reid
 
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Default Electrical Wiring Question

Clarke,

I highly doubt that you will find an electrical inspector willing to pass a residential installation that protects a #10 conductor
that is protected by either a 40 or 50 A breaker. Even though the current carrying capacity of a #10 THHN is 40 A, the NEC limits
it to 30A. Can you get away with it? Probably. Will meet code and pass an inspection? I sincerely doubt it.

--
Al Reid

"It ain't what you don't know that gets you into trouble. It's what you know
for sure that just ain't so." --- Mark Twain

"Clarke Echols" wrote in message ...
First of all, be sure the person giving you advice is qualified to do so.
You're missing a lot of better input, so I'll give it a shot.

First of all, the NEC (National Electrical Code) specifies that circuit
breakers must be sized such that they do not exceed 80% of their trip
capacity under normal circumstances. If you are running motors that pull
high currents for a short time (saws, planers, jointers come to mind)
either at start-up or during operation, you work from maximum normal
operating current, not peak-load current. A #10 wire can carry 30 amps.
A 30 amp breaker is allowed to carry a steady-state load of 24 amps. Thus
you can use a 40-amp breaker on 30-ga. wire for motor loads (actually you
can use a 50-amp breaker if you're running an arc welder). Local codes
might vary, but I got this from a retired industrial electrician of
substantial experience. You have to go to the NEC and look in the area
that talks about motor and welding loads.

Since it's cold, I suggest pulling the 14-gauge wire and replacing it with
10-gauge with a 30-amp breaker. Run 4 wires, black, red, white, and green
into a subpanel in the garage. Put a 40-amp breaker in the main panel,
then connect the white to the neutral bus in the main panel and sub-panel,
connect green to the safety ground bus (where all the bare wires are)
in the main panel, and to the safety ground bus in the sub-panel. DO NOT
INSTALL THE BONDING SCREW IN THE SUB-PANEL! This is necessary in order
to keep neutral currents from flowing through the safety-ground wire
(required by code).

Connect the red and black wires to the L1 and L1 lugs on the sub-panel
and to the 40-amp 2-pole breaker in the main panel. Install a 20-amp
2-pole breaker for your table saw's 240-volt (not 220 -- that's a European
voltage) receptacle and wiring, then put in a pair of single-pole breakers
for two 120-volt, 20-amp circuits, using the normal wiring methods.

Then, when the frost is gone and spring/summer arrives, put in a bigger
conduit (1" would be nice, but it's a 70-year-old garage, so no sense
in overdoing things) and run #8 copper with a 50-amp breaker to the same
sub-panel. You can then put in a second 240-volt circuit, or just run
the TS and DC from a single 30-amp, 240-volt circuit with multiple
receptacles like I do in my 26 x 30-foot garage/shop.

I built my own home (7500 square feet plus garage) in the 1970s, and the
state electrical inspector took great pains to catch me on a code
violation. He came up with nothing. :-) I got my license as a
registered professional engineer in 1980, and have been wiring homes
from time to time since the 1950s. I also was responsible for
specifying wiring and grounding for industrial electricians in a
semiconductor manufacturing plant in the 1970s.

You really should get an electrical permit and have the work inspected
by local officials to protect yourself anytime you do this kind of work
if you are not absolutely dead-certain you know what you are doing. If
you don't, get someone who does to help you. Do-it-yourself books might
be useful, but they're no substitute for first-hand, first-rate knowledge
and experience, and wiring screw-ups can and have killed lots of people.

I saw a situation years ago of a homemaker who could have been killed.
She complained of sparks between washer and dryer. If she had touched
them both at the same time, she's have possibly been dead. Some idiot
"wired" 240V into the trailer for a dryer and got the wires on the wrong
terminals in the receptacle so there was 120 volts AC between the dryer
cabinet and the washer.

For more about overload protection for electrical motors as well as
grounding and other info, see

http://cnets.net/~eclectic/woodworki...arkeMotors.htm

Since you are considering dust collection, invest some time getting
educated on dust collection at

http://cnets.net/~eclectic/woodworki...lone/index.cfm

and when you're ready for a really exceptional cyclone dust collection
system in kit form so you can save some bucks and get the satisfaction
of building it yourself while getting first-class results, check out

http://cnets.net/~eclectic/woodworki...larkesKits.cfm

Clarke

Peter De Smidt wrote:

I'm trying to turn my 1-car, 70 year old garage into a workshop. At
the moment, it has two 15 amp lines run through 1/2 metal conduit.
The wire is 14 ga, and there are two hots, one neutral and a ground.
I'd like to increase this a bit. I was thinking of putting in a
sub-panel. I'd like to be able to run the new wires in the same
conduit, as it's a little too frozen here at the moment for me to dig
a new trench. My idea was to replace the 14 ga wires with 10 ga.
According to my sources, a 1/2 metal conduit will take 5 - 10 ga
wires, and so 4 should be no problem. My understanding was that if
the run was under 35 ft, that each of the 10 ga. hot wires would
support 30 amps, and hence that I should hook each hot wire to a 30
amp breaker in the main box. The salesman in the Menards electrical
section told me that this wasn't right. The four wire system would
only support 30 amps. Any comments?

-Peter De Smidt



  #14   Report Post  
Greg
 
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Default Electrical Wiring Question

One thing he might do to make this easier to pull is to install conduit bodies
at both ends of the underground part of the run to get short pull points. If
you do run 3 wires you are depending on the conduit as the grounding path or
you are setting up a 3 wire feeder and regrounding the neutral in the garage.
Both require driving a ground rod at the garage. (actually every scenario of a
sub panel does).

See this from the 2002 NEC handbook

http://members.aol.com/gfretwell/sub...g2subpanel.htm
  #15   Report Post  
Robert Bonomi
 
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In article ,
Peter De Smidt wrote:
I'm trying to turn my 1-car, 70 year old garage into a workshop. At
the moment, it has two 15 amp lines run through 1/2 metal conduit.
The wire is 14 ga, and there are two hots, one neutral and a ground.
I'd like to increase this a bit. I was thinking of putting in a
sub-panel. I'd like to be able to run the new wires in the same
conduit, as it's a little too frozen here at the moment for me to dig
a new trench. My idea was to replace the 14 ga wires with 10 ga.
According to my sources, a 1/2 metal conduit will take 5 - 10 ga
wires, and so 4 should be no problem. My understanding was that if
the run was under 35 ft, that each of the 10 ga. hot wires would
support 30 amps, and hence that I should hook each hot wire to a 30
amp breaker in the main box. The salesman in the Menards electrical
section told me that this wasn't right. The four wire system would
only support 30 amps. Any comments?

-Peter De Smidt


Yes, 10 ga wire is good for 30A.

Depending on the number of bends in the conduit, it may be a difficult 'pull'.

For a sub-panel, you need 240V "to the panel". So, the 4 wires gives
you *one* 240V circuit, which will have 2 hot wires, each connected to
one pole of a 'double pole' breaker. This will be a 30A 240V breaker.




  #16   Report Post  
Toller
 
Posts: n/a
Default Electrical Wiring Question


The dust collector, lights, and heater are "continuous loads" as defined

in
the NEC and the ampacity of the circuit(s) supplying them is required to

be
derated by 20%. Thus to supply the total of 4400VA for these loads, you

need a
circuit rated at a minimum of 5500VA. Add 1440 to 1920VA for the table

saw,
and you're at 6940 to 7420 VA -- which is 29 to 31A at 240V.

So a 30A 240V circuit is _just_barely_ adequate, and leaves you _no_ room

at
all for adding additional loads.

Since the heater is a quarter of the load and is only temporary, it probably
wouldn't be a big hardship to turn it to low (or off) when he needs to use
the saw.


  #17   Report Post  
Toller
 
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Default Electrical Wiring Question


"Gretch" wrote in message
news
On Mon, 26 Jan 2004 09:04:52 -0600, Peter De Smidt wrote:

I'm trying to turn my 1-car, 70 year old garage into a workshop. At the
moment, it has two 15 amp lines run through 1/2 metal conduit. The wire

is
14 ga, and there are two hots, one neutral and a ground. I'd like to
increase this a bit. I was thinking of putting in a sub-panel. I'd like
to be able to run the new wires in the same conduit, as it's a little

too
frozen here at the moment for me to dig a new trench. My idea was to
replace the 14 ga wires with 10 ga. According to my sources, a 1/2 metal
conduit will take 5 - 10 ga wires, and so 4 should be no problem. My
understanding was that if the run was under 35 ft, that each of the 10

ga.
hot wires would support 30 amps, and hence that I should hook each hot
wire to a 30 amp breaker in the main box. The salesman in the Menards
electrical section told me that this wasn't right. The four wire system
would only support 30 amps. Any comments?

-Peter De Smidt


The fact you are posting here would seem to indicate that you are unsure
of wiring and buiding codes. Your best and safest bet is to contact your
local building or electrical inspector to ask for their recommendations.
Other than having to pull a permit, the advice should cost you nothing.
In our community, a homeowner can do his/her own wiring as long as it is
done up to code.

Around here that would obligate you to an inspection for $50.


  #18   Report Post  
Toller
 
Posts: n/a
Default Electrical Wiring Question


"gabriel" wrote in message
rvers.com...
the same sub-panel. You can then put in a second 240-volt circuit, or
just run the TS and DC from a single 30-amp, 240-volt circuit with
multiple receptacles like I do in my 26 x 30-foot garage/shop.


In the rest of your post you preached about following code, but is this

not
a code violation, at least in many places? I've heard everywhere that a
240V circuit should go to a single device/plug only...

I've heard that also, but never with a code reference.
It is certainly common enough to have an oven and a cooktop on the same
circuit.


  #19   Report Post  
ATP
 
Posts: n/a
Default Electrical Wiring Question

Clarke Echols wrote:
First of all, be sure the person giving you advice is qualified to do
so. You're missing a lot of better input, so I'll give it a shot.

First of all, the NEC (National Electrical Code) specifies that
circuit breakers must be sized such that they do not exceed 80% of
their trip capacity under normal circumstances. If you are running
motors that pull high currents for a short time (saws, planers,
jointers come to mind) either at start-up or during operation, you
work from maximum normal operating current, not peak-load current. A
#10 wire can carry 30 amps. A 30 amp breaker is allowed to carry a
steady-state load of 24 amps. Thus you can use a 40-amp breaker on
30-ga. wire for motor loads (actually you can use a 50-amp breaker if
you're running an arc welder). Local codes might vary, but I got
this from a retired industrial electrician of substantial experience.
You have to go to the NEC and look in the area that talks about motor
and welding loads.

You can't oversize the breaker to a subpanel because it has some motor loads
on it. That exception is meant to allow motors to start without tripping the
breaker.


  #20   Report Post  
Sleeping Bear
 
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Default Electrical Wiring Question

Fat chance of pulling 5- #10 wires in a 1/2 inch conduit. Ain'T gonna
happen. Besides it is against the electrical code.


On Mon, 26 Jan 2004 09:04:52 -0600, Peter De Smidt
wrote:

I'm trying to turn my 1-car, 70 year old garage into a workshop. At
the moment, it has two 15 amp lines run through 1/2 metal conduit.
The wire is 14 ga, and there are two hots, one neutral and a ground.
I'd like to increase this a bit. I was thinking of putting in a
sub-panel. I'd like to be able to run the new wires in the same
conduit, as it's a little too frozen here at the moment for me to dig
a new trench. My idea was to replace the 14 ga wires with 10 ga.
According to my sources, a 1/2 metal conduit will take 5 - 10 ga
wires, and so 4 should be no problem. My understanding was that if
the run was under 35 ft, that each of the 10 ga. hot wires would
support 30 amps, and hence that I should hook each hot wire to a 30
amp breaker in the main box. The salesman in the Menards electrical
section told me that this wasn't right. The four wire system would
only support 30 amps. Any comments?

-Peter De Smidt




  #21   Report Post  
Doug Miller
 
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Default Electrical Wiring Question

In article , Sleeping Bear wrote:
Fat chance of pulling 5- #10 wires in a 1/2 inch conduit. Ain'T gonna
happen. Besides it is against the electrical code.

Actually, it is permitted by the NEC (depending on the insulation type). But
you're right about being able to pull the wires.

--
Doug Miller (alphageek at milmac dot com)

How come we choose from just two people to run for president and 50 for Miss America?
  #22   Report Post  
Robert Bonomi
 
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Default Electrical Wiring Question

In article ,
Sleeping Bear wrote:
Fat chance of pulling 5- #10 wires in a 1/2 inch conduit. Ain'T gonna
happen. Besides it is against the electrical code.


You know not that of which you speak.

U.S. National Electrical Code allows *SIX* #10 wires in 1/2" conduit, with
appropriate insulation -- e.g. THHN.

And it _can_ be done, over short distances, with a limited number of bends .
I _know_, because I've _got_ a circa 8' section, that is so loaded.
It was a *real* b*tch to pull the wiring, particularly past the 3rd bend.

Done under 'permit' from the city, and the City electrical inspector _has_
signed off on it.

On Mon, 26 Jan 2004 09:04:52 -0600, Peter De Smidt
wrote:

I'm trying to turn my 1-car, 70 year old garage into a workshop. At
the moment, it has two 15 amp lines run through 1/2 metal conduit.
The wire is 14 ga, and there are two hots, one neutral and a ground.
I'd like to increase this a bit. I was thinking of putting in a
sub-panel. I'd like to be able to run the new wires in the same
conduit, as it's a little too frozen here at the moment for me to dig
a new trench. My idea was to replace the 14 ga wires with 10 ga.
According to my sources, a 1/2 metal conduit will take 5 - 10 ga
wires, and so 4 should be no problem. My understanding was that if
the run was under 35 ft, that each of the 10 ga. hot wires would
support 30 amps, and hence that I should hook each hot wire to a 30
amp breaker in the main box. The salesman in the Menards electrical
section told me that this wasn't right. The four wire system would
only support 30 amps. Any comments?

-Peter De Smidt




  #23   Report Post  
Jim Wilson
 
Posts: n/a
Default Electrical Wiring Question

Robert Bonomi wrote...

You know not that of which you speak.


Yep, he was mistaken in that...


U.S. National Electrical Code allows *SIX* #10 wires in 1/2" conduit, with
appropriate insulation -- e.g. THHN.

And it _can_ be done, over short distances, with a limited number of bends .
I _know_, because I've _got_ a circa 8' section, that is so loaded.
It was a *real* b*tch to pull the wiring, particularly past the 3rd bend.


What was the derating factor?

Jim
  #24   Report Post  
Greg
 
Posts: n/a
Default Electrical Wiring Question

U.S. National Electrical Code allows *SIX* #10 wires in 1/2" conduit, with
appropriate insulation -- e.g. THHN.


What was the derating factor?



Derating in this application is not important. You would derate to 80% but THHN
#10 cu is good for 40a and 240.4(D) limits you to 30a so you still have a
safety factor, even with the derate.
You only have to derate based on current carrying conductors and you don't need
to derate the conductors that only carry the unbalanced current of a multiwire
circuit so it usually takes a lot of wire in a pipe before a THHN run is
affected.
  #25   Report Post  
Robert Bonomi
 
Posts: n/a
Default Electrical Wiring Question

In article t,
Jim Wilson wrote:
Robert Bonomi wrote...

You know not that of which you speak.


Yep, he was mistaken in that...


U.S. National Electrical Code allows *SIX* #10 wires in 1/2" conduit, with
appropriate insulation -- e.g. THHN.

And it _can_ be done, over short distances, with a limited number of bends .
I _know_, because I've _got_ a circa 8' section, that is so loaded.
It was a *real* b*tch to pull the wiring, particularly past the 3rd bend.


What was the derating factor?


Didn't come into play. Only 4 hot leads. (two pairs of 3-wire 'Edison'
circuits)

However, outlets were 20Rs, so I breakered the circuits at 20A ea.

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