# Electrical 240V 10 or 12 gauge?



## Ed3443 (Jul 7, 2013)

My Grizzly jointer came this week and I need to install a NEMA 6-20 outlet in my garage which is attached to my house. The fuse box is located near the garage. On the Grizzly specs they indicate a minimum circuit size of 20 amps. This would indicate that I need to run a 12/3 line to the garage. However I have seen comments suggesting to use 10/3 instead. Is there any advantage in this situation to jump to 10 gauge? Thanks.


----------



## Cherryville Chuck (Sep 28, 2010)

Wiring code here says that if the run is 75 feet or more you should go one larger size. Otherwise it should be fine with the 12 gauge. Unless it has digital display or some other electrical accessory it should only need 12/2. Ground wires aren't included in the nomenclature (I guess they are assumed) so that means 2 insulated conductors plus a bare ground wire.


----------



## kp91 (Sep 10, 2004)

Recommended Circuit size should always higher than the load on the motor. Your jointer is probably going to run a lot lower than 20 amps except on starting, so the 12 ga is appropriate . The 10 ga wire adds a little safety margin, but not a lot. The big issue is the duty cycle you are going to be asking if the jointer. If you are using it intermittently, no big deal with the 12 ga. If you are going to be pushing the machine for hours at a time the cord will get hotter and internal resistance increases. Having a larger Gage wire might then make sense.

I tend to be more conservative, so I would run 10 ga if the price wasn't significantly higher. The key is what you can fit into the service connection on the tool and what you're willing to spend


----------



## Stick486 (Jan 4, 2013)

I agree w/ Charles but believe 10GA is the better way to go and Doug makes valid sense....

xx/2-w/G wire will have a white conductor as well as a black one and a ground...
any exposed white conductor will need a color change to either red or black using shrink tube and not w/ colored tape when used in a 220V circuit...

xx/3-w/G wire will have a red conductor in addition to the black and white as well as a ground and is the wire most often used for 220V circuits...


----------



## RainMan 2.0 (May 6, 2014)

12/3 to your garage . I’d step that up , as there’s in rush current and distance to consider , *plus you may want to run a dust collector at the same time .*
I don’t know how far you have to go but I’d go with 8 gauge minimum. I had 10/3 going to my garage and couldn’t run a 5hp compressor unfortunately


----------



## Stick486 (Jan 4, 2013)

you need separate circuits for each machine Rick...


----------



## Cherryville Chuck (Sep 28, 2010)

Stick's right Rick. You aren't allowed to run two 240 volt machines from the same breaker. You should have run a larger gauge wire to a sub panel instead where you could have multiple machines coming off that panel.

The larger wire for continuously running machines is I think part of the commercial wiring code and not residential code. In a commercial setting it's assumed that a machine could run continuously through a shift (and also be pushed hard) and the load should be calculated at only 80% of circuit capacity in that case. If you had a 15 amp load in that situation you would have to up to 12 gauge and 20 amp breaker and if it was 20 you'd have to go up to 10 gauge and 30 amp breaker, etc. It would be pretty hard to run a jointer that hard in a home work shop. You'd literally need 3 people running it to work it that hard. One guy loading onto the infeed table, the operator, and one guy taking the boards off.


----------



## Ed3443 (Jul 7, 2013)

If I decided to go with a 100 amp sub box what size SER wire should I go with? Is aluminum safe to use? 3-3-3-5 copper is outrageously expensive. #1 or 2 in aluminum? Thanks.


----------



## Herb Stoops (Aug 28, 2012)

Ed3443 said:


> If I decided to go with a 100 amp sub box what size SER wire should I go with? Is aluminum safe to use? 3-3-3-5 copper is outrageously expensive. #1 or 2 in aluminum? Thanks.


I don't recommend Aluminum electrical wire for any thing including service to the shop.
Herb


----------



## RainMan 2.0 (May 6, 2014)

Herb Stoops said:


> I don't recommend Aluminum electrical wire for any thing including service to the shop.
> Herb


I hate aluminum,but my electrician said it’s fine for the mains , just don’t use it for branches .
Your house has an aluminum main feed


----------



## RainMan 2.0 (May 6, 2014)

Stick486 said:


> you need separate circuits for each machine Rick...


I was thinking he was going to a panel . But ya there’s no question .

The idiot that had my house ran 10/3 to a 30 amp panel . Pretty much useless for my scenario


----------



## Stick486 (Jan 4, 2013)

these conductors are installed in conduit...

for COPPER...
#3 rated at 75 or 95°C (THHN/THWN)...

for ALUMINUM
#1.....
#1AL is marginal so #1/0 is the better size...

for SEU or SER cables (service entrance)
#2 in copper @75/95°C and #1 in aluminum...


----------



## sreilly (May 22, 2018)

Ed this went from a simple circuit to a sub-panel which is most certainly the way to go if you are a good distance from the main panel. It will probably save you money in the long run if you find you need more circuits later. Make sure the panel has room for any desired additional circuits you may later want to add. Also be sure the amp load is sufficient to handle the highest running load you can imagine in you shop at one time. That's key, what is the total load at one time.

For most of us that's a power tool and at least lights, and a dust collection system. Leave room for your wildest hope of an upgrade or you'll possibly be looking to do this again. Be sure you check local codes for your location and national codes also play in. SER/SEU is almost always aluminum but some places do carry a copper SE cable. Key there is very tight connections on the lug and using the electrical paste. You'll have two choices, main lug and main breaker. The main breaker is the safest way in that you can kill power to all the circuits by shutting off the main breaker. 

Otherwise if there is a fair distance, or dictated by electrical code, you may need/want to install a disconnect to feed the panel otherwise you'd need to kill the breaker feeding the sub panel from the main panel. In as many jobs as I have worked I've never seen copper going to the sub-panel.

_But_ with all this said, unless you really know what you're doing, know electrical code/have reliable (not here) knowledge I strongly suggest at least consulting an electrician and do check with your city/county building division for the need of permits and inspections. If it is required and you don't go this route you leave yourself wide open to negated insurance claims should they arise as well as possible action by your locality.


----------



## Knothead47 (Feb 10, 2010)

10 ga. minimum, depending on the run. 12 ga. is more for 120 volts as interior wiring for outlets and lights. "Little bit is good, more is a whole lot better."


----------



## sreilly (May 22, 2018)

Knothead47 said:


> 10 ga. minimum, depending on the run. 12 ga. is more for 120 volts as interior wiring for outlets and lights. "Little bit is good, more is a whole lot better."


You size your wire base on amp load and distance of run. Properly installed outlets are designed by amp load as well dictating the plug style. Again, this really isn't where anyone should be getting definitive answers. General fine but the responsibility lies with the doer. Some things are best left to those that know.


----------



## biotec (Nov 17, 2019)

good ay all:

there a a lot of good web sites with wire size and distance voltage drop and more.
note some low cost panels do not come with ground bars.

also make list of all your equipment. voltage amperage. most equipment will have minimum breaker size. order the list in which unit run the most of the time. like the large dust collector with a 5 hp 240 volt motor at 28 amps running more for start up. this would be a 40 amp breaker
then next 2 hp table saw at 12 amps. and so forth.

please note when sizing a new sub panel that standard is 80% max. so a 100 amp panel max is 80 amps. also make sure the sub panel is rated for aluminum and type. as there many different kinds.
panel are sold by the number of spaces available. not max current of all the beakers together.

all wiring expands and contracts. When current is going through the wire it heats up and expands. When there is no current, it contracts. After so many of these cycles, the connections at the devices and in the electrical panels will loosen over time, which can cause fires. wire maintenance is recommended. tighten the connections.

Aluminum also oxides or corrodes. The National Electric Code requires that aluminum wire be connected together using special UL listed device, with an anti-oxidant compound.

It should be noted that most insurance agencies will not cover homes with aluminum wiring in Florida. the ones that do charge a premium for it. the first cost savings is gone in less than a year. note some companies will not tell you this up front.

verify your local codes. some have more leeway than others. and check with your insurance agencies. ask a lot of questions.


Single-Phase Motors - HP and Full-Load Currents

Power	Full Load Current (amp)
(hp)	(kW)	115 V	208 V	230 V
1/6	0.13	4.4 2.4	2.2
1/4	0.19	5.8 3.2	2.9
1/3	0.25	7.2 4.0	3.6
1/2	0.38	9.8 5.4	4.9
3/4	0.56	13.8 7.6	6.9
1	0.75	16 8.8	8
1.5	1.1	20 11	10
2	1.5	24 13.2	12
3	2.3	34 18.7	17
5	3.8	56 30.8	28


----------



## Cherryville Chuck (Sep 28, 2010)

Up here we are not allowed to run aluminum into a building or use it for branch circuits or to supply a sub panel. The wire can't be run inside a conduit so we have to connect to copper from an aluminum overhead wire (triplex) before running it into the main service. For 100 amp our code requires #3 gauge. We are allowed to use a smaller ground wire for a main service (#6) but that may not be true for you or for a branch panel. For something as major as a sub panld be permitted so when you get the permit you can ask what the requirements are for where you live. You don't want to put it in without a permit because if your house burned and the insurance company found out there was unpermitted panel they might not want to pay.


----------



## Stick486 (Jan 4, 2013)

IIRC one size down in copper for the ground...


----------



## Knothead47 (Feb 10, 2010)

sreilly said:


> You size your wire base on amp load and distance of run. Properly installed outlets are designed by amp load as well dictating the plug style. Again, this really isn't where anyone should be getting definitive answers. General fine but the responsibility lies with the doer. Some things are best left to those that know.


Steve, should have been clearer. I agree with your first two sentences. I ran wiring for a couple of houses and went even heavier for water heaters, range, etc. If I was running 240V for equipment, I would only have one line, #10, and breaker for each one. My house is wired so that over half of the outlets and lights are on one breaker! Found this when I moved in and traced all the outlets and lights...one at a time. Drew a sketch so I can keep track.


----------



## Cherryville Chuck (Sep 28, 2010)

That's pretty serious overkill John but better than the other way around. Up here we are allowed up to 12 outlets (plugs or light fixtures) per 15 amp branch but the electrical code strongly recommends that the plugs and lights be mixed in different circuits. That's in case you pop a breaker in one room the lights don't go out at the same time.


----------

