Receptical Outlet Idea (Bad or Good)

[600SL]

In a shop like mine you never know where you want a plug and what voltage should be available at that plug. So I have devised a way of running 2 20 amp 230V circuits and 2 20 amp 120v circuits around my shop in a neat orderly and very reconfigurable fashion.

The concept is to place a 4-11/16 box every 10' near the ceiling of my shop. Why every 10' because a piece of EMT is 10' long, maybe make this 8' but unimportant for the moment.

Each box would have a 1/2" EMT drop to a 4" outlet box.

Each 4-11/16" box would be connected to each other by 2 parallel 3/4" EMT runs. Top run carrying 2 3 wire 240V circuits. The bottom run carrying 2 120V circuits. This is a total of 11 12 ga conductors including ground. Cannot go with a single 1" EMT due to derating issues. Plus it also helps with confusion of conductors.

Using this configuration from any box I have the capability of dropping a single 120V line to the 4" box below or a 120V and 240V combination. Worst case which I don't anticipate would be 2 240V drops. The twin 240V drops would put the 1/2" EMT fill at max with a ground over about a 5 ft length and would bring the conductor count in the 4-11/16" boxes up to 23 requiring a box extension to cover 52 cu in.

Question #1 If I have to derate for conductors in an EMT conduit do the same rules apply for conductors in a box.

Question #2 I recently had to remove a grey neutral wire from a 2 circuit 240V EMT run and replacing it with a white wire. The inspector said different color neutrals were only permissible in multi voltage conduit. In this case I will have single voltage conduits and multi voltage boxes. I can find anywhere in the code where this is discussed. Alternatively I could put a 120V and 240V in each conduit and use grey for the 240V circuits.

Question #3 Dose anyone see any issues with this setup?

 

[Charles (in GA)]

How big is your shop? What do you do in your shop? Do you have a variety of power equipment that is a mix of 120v and 240v power, and do you have a need to frequently move this equipment around?

If you are trying to prepare for the future, and that is an unknown, you are wasting your time as far as the 240v goes. 120v you can reasonably expect to use almost anywhere and you want lots of receptacles and circuits to make things convenient but with 240v its different. Some grinders and table saws will be 240v at 20 amp or less, but beyond that, you probably playing a guessing game and the best thing you can do is run a conduit and box where you need it, when you need it. Otherwise, you would be wasting a lot of wire for nothing.

I prefer to keep 120v and 240v in separate conduits (and boxes). Just makes it easier to figure out later on down the road.

Also its a receptacle.

Charles

 

[600SL]

Thanks Charles. I see the spell checker does not work in the title box.

The shop is 30 x 48. It is a automotive shop on one end and a machine shop at the other.

I keep all my 2HP and larger motors on dedicated circuits. Most of my smaller motors can be run either 120V or 240V but I prefer to run 240V. My milling machine has to be 240V but as I have found I often want a neutral so I can take off 120V for an accessory or task lighting so I would like to opt for 3 wire 240V.

As far as planning for the future yes that's part of it but there is also the near term when I am in the state of confusion and not sure where I'm going to put stuff. I do have a tentative layout that you can find on my lighting thread but I know how that will more than likely change.

In any case the wires need to be run the same direction and using a common box really avoids the EMT clutter and bending around other EMT and cuts down the drops by large factor.

I have never had a reason to use a double 12V duplex although I could see it possibly arise and could be configure as such, but I have had many times where I needed a duplex and 240V.

The initial configuration of this shop will be mostly 120V duplexes and 4 240V receptacles. Additional 240V recitals will only be pulled down as required.

I don't see the need for me ever having an combination of 240V 120V or double 240V receptacles at any one box as long as I am running neutrals to the 240V boxes but the capability will be there if required and only then would I need a box extender as the conductor count would be below 17 and will fit in a 42 cu box.

As far as confusion I'm not too concerned especially with it with the duel conduit arrangement although I am considering eliminating black and red conductors from the 240V circuits and would love to go with grey neutrals.

Also had the CB box been located on the machine shop side machine shop side of the garage this issue may not have come up. So for the most part the 240V circuits will all be pass through conductors as they go through the automotive shop.

 

[PRH44]

Question #1 If I have to derate for conductors in an EMT conduit do the same rules apply for conductors in a box.

Derating of conductor ampacity is not required in a pull or J-box.

Sharing boxes and or conduits with 120 and 240 volt circuits is not a problem at all.

 

[PRH44]

Question #2 I recently had to remove a grey neutral wire from a 2 circuit 240V EMT run and replacing it with a white wire. The inspector said different color neutrals were only permissible in multi voltage conduit. In this case I will have single voltage conduits and multi voltage boxes. I can find anywhere in the code where this is discussed. Alternatively I could put a 120V and 240V in each conduit and use grey for the 240V circuits.

What you have is a single system 240/120 derived from a single source.
Your inspector is correct interpreting to the letter of 200.6 below. You are permitted to use ONE method of ID.

200.6 Means of Identifying Grounded Conductors.
(A) Sizes 6 AWG or Smaller. An insulated grounded conductor of 6 AWG or smaller shall be identified by one of
the following means:
(1) A continuous white outer finish.
(2) A continuous gray outer finish.
ETC.
Should you have 2 or more system voltages on a premises, each system is required to be distinguished from the other. For example in a commercial installation it would be very common to have the following color code for two different systems.
480/277 Grey neutrals
208/120 White neutrals

Hope that helps

 

[600SL]

What you have is a single system 240/120 derived from a single source.
Your inspector is correct interpreting to the letter of 200.6 below. You are permitted to use ONE method of ID.

200.6 Means of Identifying Grounded Conductors.
(A) Sizes 6 AWG or Smaller. An insulated grounded conductor of 6 AWG or smaller shall be identified by one of
the following means:
(1) A continuous white outer finish.
(2) A continuous gray outer finish.
ETC.
Should you have 2 or more system voltages on a premises, each system is required to be distinguished from the other. For example in a commercial installation it would be very common to have the following color code for two different systems.
480/277 Grey neutrals
208/120 White neutrals

Hope that helps

Many Thanks

You know I think I read this and confused the words "grounded conductors" with the ground wires. I couldn't understand why I could find white and grey listed under ground but no reference to neutrals.

I also understand Charles concern for separating the boxes to keep thing simple but with the twin conduits I like this idea.

I will be running this buy the inspector next time I see him.

 

[Charles (in GA)]

They do make duplex receptacles that are both 120v and 240v

http://fruitridgetools.com/storefrontprofiles/DeluxeSFItemDetail.aspx?sfid=136763&i=249916678&c=0

http://fruitridgetools.com/storefrontprofiles/DeluxeSFItemDetail.aspx?sfid=136763&i=251373747&c=0

Power this from a Multi Wire Branch Circuit. If you ever do MWBC make sure the neutrals are spliced using wirenuts and pigtails or similar, do not use the terminals on the receptacle to make the splices for the neutral. Neutral must remain continuous and intact even if a receptacle is physically removed from the circuit.

 

[600SL]

Thats interesting. Never seen those. It would still require me to bring down a 240V or 115V lines and necessitate a box extension up top, unless I split the neutral from the 3 wire 240V.