Electrical Questions... Lots of them!

[grandpa_e]

I am almost ready to start running power to my shop and I have quite a few questions. I can wire things up but I don't know how to size everything. I have a meter pole about 40 feet away from the shop with 200 amp service that also feeds a mobile home. This pole has the meter base and a breaker box with about 4 or 5 free slots. I want to run 100 amp 220V service to the shop. So that said, here are the questions.

I know I want a 100 amp breaker in the box at the meter pole, but what type?

What size conductors will I need for 100 amps and about a 40' run? Is #2 copper good enough? I've found a lot of conflicting information on the net about this.

Will I need a new ground rod at the shop or do I run 4 wire to the shop and use the existing ground at the pole? The mobile home has 4 wires run to it, using the ground at the pole. Don't know what current code is.

Once The power is to the shop, I plan on three 20 amp circuits for lights. Probably 6 two bulb fluorescent fixtures on each circuit. Is this adequate and what gauge wire would be good here.

I will also have two 20 amp circuits for outlets and one 30 amp 220v circuit for a future welder.

So, where am I going wrong or what just won't work? Any thoughts are appreciated!

 

[grsthegreat]

errr. lots of possible answers. first, look in the panel at the meter and see if you can even put a 100 amp breaker in there. most of those boxes only allow a 50 amp maximum breaker to be added. as for the wire, you'll find out quickly that copper is way too expensive to use. a #2 copper will handle 100 amp, but you wont believe the cost. i am an electrical contractor (in idaho). we generally can use a #2 xhhw aluminum wire fed underground. we run it as a #2/#2/#4 combination along with a #6 for the ground. the current Nat. Electrical code requires a ground to run WITH the sub-feeds to outbuildings. you will also be required to supply 1 or 2 ground rods at the outbuilding depending on local codes. overhead feeds would require a different kind of wire to be used . are you going overhead or underground. i strongly advise against overhead for rural.... as I've done lots of repairs to these due to errant farm equipment and trees over the years. Also, always kick in the extra for conduit..dont go direct burial. ive also had to locate and repair a LOT of these wires over the years. ive never had to repair one in conduit. been at this for 30+ years too.

as for the lights, it depends on the amperage of the light fixtures. if you use newer T-8 light strips, you may be able to run up to 8 fixtures on one 20 amp circuit. look at the amperage rating on the lights and multiply by number of light fixtures. a 20 amp lighting circuit can handle (legally) 16 amps continuous load. so if each light = 1.8 amps say, then 8-9 lights per circuit is ok to use.

 

[LD1]

I am almost ready to start running power to my shop and I have quite a few questions. I can wire things up but I don't know how to size everything. I have a meter pole about 40 feet away from the shop with 200 amp service that also feeds a mobile home. This pole has the meter base and a breaker box with about 4 or 5 free slots. I want to run 100 amp 220V service to the shop. So that said, here are the questions.

I know I want a 100 amp breaker in the box at the meter pole, but what type?

What size conductors will I need for 100 amps and about a 40' run? Is #2 copper good enough? I've found a lot of conflicting information on the net about this.

Will I need a new ground rod at the shop or do I run 4 wire to the shop and use the existing ground at the pole? The mobile home has 4 wires run to it, using the ground at the pole. Don't know what current code is.

Once The power is to the shop, I plan on three 20 amp circuits for lights. Probably 6 two bulb fluorescent fixtures on each circuit. Is this adequate and what gauge wire would be good here.

I will also have two 20 amp circuits for outlets and one 30 amp 220v circuit for a future welder.

So, where am I going wrong or what just won't work? Any thoughts are appreciated!

As far as the MAIN service is required, yo might be best to hire or at least consult an electricial in your area. He will be familiar with the local codes and requirements as well as what is acceptable to your power company.

Also, do you plan on running underground or overhead to the building from the meter?? And Aluminum is probabally going to be cheaper than copper.

Once you have the main power figured out, the inside stuff is easier. Personally, for just the lights, I would run 15A circuits. Especiall if you are only putting 6 2-bulb fixtures on each circuit. 6 flourescent fixtures will probabally be under 500watts. That is less than 5A, so why the need for 20A circuit. Not to mention that 20Aswitches and outlets are more $$$ than 15A.

But either way, 12ga wire with 20A breaker and 14ga with 15A breakers

 

[grandpa_e]

Sorry, I forgot to mention I do plan to go underground. Probably 2-1/2" conduit.

grsthegreat, you are saying I would need to run the ground from the box at the meter pole to the new box in the shop, but also have new ground rods at the shop? I'm all over DC wiring, but this AC grounding stuff confuses me. Would the ground wire into the shop and the new ground rods be tied into the neutral bus in the shop?

As far as the lighting circuit size, I may go with 15, but I haven't picked out the actual fixtures I will use yet. When I do, I can see what they draw and go from there. Lights will probably be T8's.

 

[Luremaker]

You may be able to purchase a code book with the local codes for your state. Here in Ontario we can purchase the "Electrical Code Simplified Ontario Edition".

It is a great book, it explains all of the requirements for additions, garages, shops and household wiring in simple to understand language.

 

[ustmd]

I would echo LD1's recommendation.

I would hire an electrician to do the run from the main to the sub panel in the shop.

That is what I did. I dug the trench and he took care of the rest. I then pulled the circuits once the sub panel was installed. It eliminated a lot of sleepless nights over whether I had done it correctly.

 

[grsthegreat]

Sorry, I forgot to mention I do plan to go underground. Probably 2-1/2" conduit.

grsthegreat, you are saying I would need to run the ground from the box at the meter pole to the new box in the shop, but also have new ground rods at the shop? I'm all over DC wiring, but this AC grounding stuff confuses me. Would the ground wire into the shop and the new ground rods be tied into the neutral bus in the shop?

As far as the lighting circuit size, I may go with 15, but I haven't picked out the actual fixtures I will use yet. When I do, I can see what they draw and go from there. Lights will probably be T8's.

yes, the national electrical codes (US) require both a wire run from the main panel to the shop sub-panel, and a separate ground rod. the grounds cannot be attached to the new shops neutral bus, but rather you need to use a shop panel with a main breaker AND a separate ground bus and isolated neutral bus. the white wires go to the isolated neutral bus, the grounds all go to the grounding bus. also, be sure to look at the existing electrical meter/panel . there should be a label on the panel that states the largest breaker you can use in addition to the 200 for the mobile home. i can tell you from experience it usually says..max subfeed breaker 50 amps.mind you, if all you have plans for is 6-8 lights and a few 110 circuits plus occasional use of a 30 amp -240 volt welder, 50 amps is plenty. i have a 30x40 shop that ran on 50 amps for 5 years....i even used an occasional 50amp stick welder. had 8 high output florescent lights and lots of 110 equipment. remember, usually someone uses only one of the 110v pieces of equipment at a time. when i added the cnc plasma table i finally had to upgrade to 200 amps. for most applications 50 amps may be plenty.

 

[LBrown59]

1*I have a meter pole about 40 feet away from the shop with 200 amp service that also feeds a mobile home. 2*This pole has the meter base and a breaker box with about 4 or 5 free slots.
3*I want to run 100 amp 220V service to the shop.

1*I had the same sort of set up for years but always hated the meter being on the pole.
2*later when I built my shop /garage I switched my meter base and breaker box from the pole to the
shop /garage and cut down the post.
3*I Then reconnected the wires that were on the pole to the new breaker box at the shop /garage .

 

[LD1]

yes, the national electrical codes (US) require both a wire run from the main panel to the shop sub-panel, and a separate ground rod. the grounds cannot be attached to the new shops neutral bus, but rather you need to use a shop panel with a main breaker AND a separate ground bus and isolated neutral bus. the white wires go to the isolated neutral bus, the grounds all go to the grounding bus. also, be sure to look at the existing electrical meter/panel . there should be a label on the panel that states the largest breaker you can use in addition to the 200 for the mobile home. i can tell you from experience it usually says..max subfeed breaker 50 amps.mind you, if all you have plans for is 6-8 lights and a few 110 circuits plus occasional use of a 30 amp -240 volt welder, 50 amps is plenty. i have a 30x40 shop that ran on 50 amps for 5 years....i even used an occasional 50amp stick welder. had 8 high output florescent lights and lots of 110 equipment. remember, usually someone uses only one of the 110v pieces of equipment at a time. when i added the cnc plasma table i finally had to upgrade to 200 amps. for most applications 50 amps may be plenty.

I woul still reccomend going with 100A service. Or at least burry wire large enough to support 100amp. It will not be that much more expensive to do it now. But in the future, if you decide you want to upgrade, you'll have to dig the trench up again and start all over. Plan ahead. go with 100A wire to the garage at a minimum.

 

[LarryD]

a #2 copper will handle 100 amp, but you wont believe the cost. i am an electrical contractor (in idaho). we generally can use a #2 xhhw aluminum wire fed underground. we run it as a #2/#2/#4 combination along with a #6 for the ground.

I don't think copper and aluminum have the same current carrying characteristics. Usually have to upsize for aluminum.