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Opinions please #4: Electrical outlets

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Blog entry by curliejones posted 224 days ago 742 reads 0 times favorited 15 comments Add to Favorites Watch
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Ah the winter doldrums in Louisiana. Too wet to dig footings so I’m trying to nail down some electrical details. I’d treasure some advice on the following – I plan to run a couple of 220V circuits for future growth while I’m wiring the shop even though I have no tools or utilities requiring that now. The new shop will be designed such that part or all can be insulated and heated/cooled other than naturally. One bit of advice I came across was to place four-plex boxes as you wire the place and put 220V alongside 120V circuits. This raises the question for me – how can you fool-proof the receptacles? I plan to use NEMA 5-20R connected to 12/2 wg for the 20 amp 115V circuits. I’m sure the same receptacles would be fine for 220V wiring where the Amps are cut in half at higher voltages. Do you all recommend a different NEMA config for the other duplex when using 4-gang locations? I might consider the same NEMA 5-20R in a separate box that has a hinged cover and appropriately marked for 220V, but even that seems unwise if a future owner, stranger, etc comes along.
Thanks for helping with this. My only 220V circuits at home are dedicated and hard-wired with no plug-ins.

-- Like Guy Clark sez - "Sometimes I use my head, Sometimes I get a bigger hammer"



15 comments so far

View dbray45's profile

dbray45

2482 posts in 1373 days


#1 posted 224 days ago

220 receptacles have a plug that looks like this (|—) so you cannot plug in a device that is 120.

Myself, I would run separate circuits for the 220 – either way, call your local code enforcement folks, they have the answers you seek. I do know that in most places, you cannot run low voltage (12-24 volts) with 110-120 volts, they have to have separate boxes.

-- David in Damascus, MD

View Bogeyguy's profile

Bogeyguy

457 posts in 664 days


#2 posted 224 days ago

What dbray said.

-- Art, Pittsburgh.

View HerbC's profile

HerbC

1152 posts in 1455 days


#3 posted 224 days ago

Do NOT use the same type receptacles for both voltages, even with signs, covers, etc, you are still inviting a user to make a mistake.

You should use a NEMA 6-20 receptacle. It is similar to the NEMA 5-20 but the blade configuration is the opposite orientation, making it impossible to mistakenly plug the 125 V plug into the 250 V receptacle or vice versa. It would be good practice to also make at least the 250 V receptacles with the voltage.

Good Luck!

Be Careful!

Herb

-- Herb, Florida - Here's why I close most messages with "Be Careful!" http://lumberjocks.com/HerbC/blog/17090

View mantwi's profile

mantwi

296 posts in 492 days


#4 posted 223 days ago

I ran a separate circuit for each 220 receptacle and used the 6-20’s. The 4-plex receptacle would be as impractical as it is unsafe. What are the chances that all of your machines are going to be clustered together around it’s location? Plan the location of your machines and any machine you may upgrade to 220, table saw, dust collector, planer etc run a line to it’s location. I have 20 amp 110 receptacles every 6 feet along the perimeter of my shop, they are cheap and the convenience is worth the extra effort to wire them. One thing most of us can count on is the inevitable upgrade in equipment that’s down the road and it’s easier to wire for the future than to add to a system that may be restricted by the capacity of your service panel. Bigger is better and not that much more expensive.

View Picklehead's profile

Picklehead

548 posts in 525 days


#5 posted 223 days ago

Not a direct answer to your question, but in regards to the four outlet boxes my electrician put the left two on one breaker, and the right two on another breaker, so I can plug in two high-amp tools in one box and be on two different breakers. Real handy.

-- You've got to be smarter than the tree.

View dbray45's profile

dbray45

2482 posts in 1373 days


#6 posted 223 days ago

For safety sake – I would never have multiple breakers going to a single box – if you have a problem in the future, you can throw a breaker and still have electric in that box – never a good idea and it is probably not to code – just my two cents.

A word to the wise when dealing with electricity – where it comes to inductive loads (motors), if you are running something that draws more than 10 Locked Rotor AMPs (LRA), put it on its own circuit and use 10 gauge wire to the panel – may be required if going over 50 feet. Costs more but is a whole lot safer.

-- David in Damascus, MD

View curliejones's profile

curliejones

78 posts in 862 days


#7 posted 223 days ago

Good advice and HerbC thanks for the precision of a NEMA configuration – exactly what I needed. seconded by mantwi too! Also – I agree with the lot of you – put it in a separate box. Hey Picklehead, Greetings! I think that I will perhaps use two separate single boxes together so that I may plug in two tools with higher than avg amp draw. It will just cost a few bucks more to use another single space box at around 10 locations. Have the left box on one circuit and the right box on another. Same number of receptacles, same am’t of wire, but like dbray45 says, you won’t get fooled into thinking the box is dead. Great stuff guys!

-- Like Guy Clark sez - "Sometimes I use my head, Sometimes I get a bigger hammer"

View MT_Stringer's profile

MT_Stringer

1797 posts in 1827 days


#8 posted 223 days ago

Planning stage, huh?

220v for:
  • Table saw
  • Dust Collector
  • 8 inch jointer
  • spare

Note: My Grizzly 1023 has a Nema 6-15 plug on it so I matched it.

-- Handcrafted by Mike Henderson - Channelview, Texas

View Eddie_T's profile

Eddie_T

104 posts in 667 days


#9 posted 223 days ago

I don’t know about today’s codes but I recall a spllt circuit design where the straps on 120v receptacles are broken off to isolate upper and lower circuits to be fed from opposite legs of 240v with a common neutral. That would be using 3 conductor plus ground romex. Using this approach 240v reeceptacles could also be placed in the circuit where needed.

View dbray45's profile

dbray45

2482 posts in 1373 days


#10 posted 223 days ago

Eddie – the split circuit design in the receptacle was to isolate the individual receptacles to put one of them on a switch. My father did this in the house he built so every receptacle was on the lighting switch as well as a constant on.

Uses a lot of electrical wire to do this. I don’t remember seeing a receptacle that had both a 220 and 120 outlet in the same receptacle – not saying there isn’t but it would be stupid. Both 120 breakers that make up the 220 are joined to blow as one, separating them would burn up the 220 device plugged into the receptacle if one of the two breakers tripped.

-- David in Damascus, MD

View Eddie_T's profile

Eddie_T

104 posts in 667 days


#11 posted 222 days ago

I did not say that 120v and 240v recepticals were in the same wall box or that two breakers were used. The design was that each wall box could be set up as desired, 120v or 240v. For any box set up for 240v recepticals the neutral wire is not used so if a 120v device happens to pop the breaker any 240v device just sees an open circuit.

View EEngineer's profile

EEngineer

885 posts in 2209 days


#12 posted 221 days ago

For any box set up for 240v recepticals the neutral wire is not used so if a 120v device happens to pop the breaker any 240v device just sees an open circuit.

Still better gang them. It’s a safety thang! Flipping the breaker must kill all the live voltages in the branch. NEC is pretty unforgiving on this. It is the reason that 220V breakers are ganged together even though either breaker opening will kill the circuit. Allowing only side to trip still leaves 120V to neutral (which is effectively ground) in the box if you go to work on it.

-- "Find out what you cannot do and then go do it!"

View Eddie_T's profile

Eddie_T

104 posts in 667 days


#13 posted 221 days ago

I did not mean to imply a feed with unganged 120v breakers, I would use a 240v (ganged) breaker so any fault would take down all, plus provide a means of total disconnect. I made my comment only to address David’s misconception that a single breaker pop could burn out a 240v device. I should point out that I did mispeak with respect to breaking tabs on the 120v receptacles, the neutral tab should be left connected. If one chose to use this approach remember that the neutral is shared by upper and lower receptacles. Not really a problem in that if loads are near balanced there will be little neutral current. Also how many machines do we have running simultaneously, I have only one machine, a radio and maybe a heater in operation at any given time (wire size in my shop is to minimize voltage drop).

View dbray45's profile

dbray45

2482 posts in 1373 days


#14 posted 219 days ago

Eddie – its all good, what I was saying was for all those folks that want to do their own electrical work and have not done the research required.

-- David in Damascus, MD

View curliejones's profile

curliejones

78 posts in 862 days


#15 posted 210 days ago

Thanks to all and Happy Holidays!
I’ve been digging ‘round and am surprised at how little info there is regarding running MC cable. So far I’ve learned the following: Red Heads are recommended – this was wasted on me – I married one. Pigtails are necessary – well they worked for my redhead when she was a bit younger, but I have not seen them in a couple decades.
Then there’s the serious stuff – metal wall and switch boxes are used that have the right clamps for MC cable. For 115V runs, the ground wire (green) needs to be tied (pigtailed) to the switch and or receptacle ground, and to the box which is tied thru metal connectors to both incoming and outgoing cables (line and load). Don’t think I’d trust snap-in connectors to carry the continuous ground required for the cladding.
What I’m not sure of yet – seems like 4” square boxes are the norm whether you want to wire one duplex receptacle or two. Mud rings then give you the option of one or two duplex receptacles. So this question arises – are handy boxes (much cheaper) acceptable if combined with an MC cable connector? Paying for both instead of having them incorporated into the box evens the cost out, but takes less space. This is especially true for my intentions of running two circuits to each plug-in location and in separate boxes. Thought I’d use gray receptacles in one box and ivory in the other, remaining consistent to the circuit. I did not see any boxes made with MC clamps for receptacles that would accept only one duplex.
Does anyone know of a good publication that clearly explains the hardware options and procedures for installing those varying options???

-- Like Guy Clark sez - "Sometimes I use my head, Sometimes I get a bigger hammer"

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