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120v & 240v outlets on the same circuit

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Forum topic by rbrjr1 posted 11-22-2017 04:42 PM 727 views 0 times favorited 47 replies Add to Favorites Watch
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rbrjr1

91 posts in 38 days


11-22-2017 04:42 PM

Topic tags/keywords: rbrjr1 shop electrical small shop 120v 240v table saw router insert table saw station

Here is what I’m thinking about as I re-wire my shop (lets brainstorm and see if we can’t make this work). SHOP DATA POINTS:
-Shop is 25’ wire run from the panel
-Lighting is 3ea 8’ fluorescent double tube fixtures (T12 VHOs)
-Shop is very small 11’X22’ and used for all kinds of DIY tasks, not just woodworking
-No dedicated dust collection in place (shop vacs) but I’d like to one day
eventual dust collection would be something like SHOP FOX W1826 Fox W1826 (3.5A @240v) and would be wired into the same circuit as the 240v/120v saw station
-Table saw station contains both Table Saw (240v?) and Router Table insert (120v)
-Table saw is 2hp (9.3A @240v)
-Router is 3.25hp (15A@120v)

I have 2ea 1” breaker “spaces” in my panel (approximately 25’ wire length from my shop). Right now, each of the two spaces have been filled with 1/2” breakers giving me 4 (20A)circuits to the shop.
-1 for lights,
-1 for a bank of outlets at my bench (includes small air compressor, battery chargers, etc).
-1 I’ve used to power a tankless water heater and chest freezer (yes, I know the WH should really be on a dedicated circuit).
-1 spare.

SO:
I’m thinking about wiring my table saw station to use a 240v, 4 wire extension cord which will provide power to both the router and the table saw (I’d never use them both simultaneously, of course).
I’d wire the outlet at the table saw station like THIS:

which does essentially THIS at the panel (bottom 10/3 illustration):

I’d use a 240v/20A double pole 1” breaker in the box similar to THIS:

If possible, I’d like to work within the confines of a single circuit for 120v outlets, a single circuit for the tankless/freezer, and this double pole/two circuit configuration described above for the table saw / router station..
(I could move the lights over to the “garage lights” circuit as they replaced the existing lighting.)
I know the total current on the 20A breaker cannot be more than 20A (using any combo of 120v or 240v tools) at any given time.

so..
Tell me what I’m not thinking about..
What am I missing?
Why wouldn’t this work ?
Has anyone else done something similar?

-- measure twice, cut once.


47 replies so far

View bonesbr549's profile

bonesbr549

1445 posts in 2900 days


#1 posted 11-22-2017 06:00 PM

If I read you properly, you want to leverage a 10/3 to have both 120 & 240 in same line. As long as not using both at same time would work. Depending on municipality, that would be frowned upon as they want singles.

I have a 10/3 for my TS as it needs 120 & 240, and I wanted a 20A outlet for my hand tools that draw a lot. Unfortunately my basement shop (prebuilt) only has 15A outlets. Your problem is going to be you won’t be able to find 30A outlet for 120. At least I could not.

I’m assuming you comfortable wiring your panel. Be careful you can get you killed if not.

It comes down to load. Do the math, should work.

-- Sooner or later Liberals run out of other people's money.

View Roy Turbett's profile

Roy Turbett

137 posts in 3412 days


#2 posted 11-23-2017 02:05 AM

I used the configuration in your diagram for essentially the same machines without a problem. But I’d consider using the two pole breaker slot to add a sub-panel so you’re not limited for future expansion and you can kill the power to all your machines if you have kids around. Depending on the sub-panel, you may also need to purchase a bus bar because it shouldn’t be bonded.

View TheFridge's profile

TheFridge

8287 posts in 1319 days


#3 posted 11-23-2017 02:16 AM

Will it work. Yes.

Is it proper. No.

Strictly for general purpose recepts. Yes.

For a 250v load and general purpose recepts. No.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View rbrjr1's profile

rbrjr1

91 posts in 38 days


#4 posted 11-23-2017 01:25 PM


Your problem is going to be you won t be able to find 30A outlet for 120. At least I could not.
- bonesbr549

I wont need a 30a outlet for the 120, if you look closely, the receptacle in the picture is 240v on the upper and 120v on the lower.

I am probably going to use a 20A breaker instead of a 30A but I will run 10/3 conductor to the shop wall and build a 10/3 “extension cord” for the table saw station that will plug into the wall with a twist lock plug

yes sir, I’m comfortably cautious around electricity, residential loads, anyway.


Strictly for general purpose recepts. Yes.
For a 250v load and general purpose recepts. No.
- TheFridge

im confused, how is my setup different than for what the outlet was intended?
it’s an outlet that has 240v and 110v sockets, how could it NOT be used for both 240v and general purpose at the same time?

the diagram is from an air conditioning website for AC units that pull both standard voltage and high voltage at the same machine, so I’m confused as to your reply.

-- measure twice, cut once.

View sawdustdad's profile

sawdustdad

333 posts in 718 days


#5 posted 11-23-2017 01:34 PM

I would put a 2 pole 30A breaker in the panel, run 10/3 w/ground to a sub panel in the shop. Then run the necessary circuits from there. Or, better yet, step it up to 8/3 and a 40A breaker. If you are going to the effort, might as well think ahead for future needs.

-- Murphy's Carpentry Corollary #3: Half of all boards cut to a specific length will be too short.

View rwe2156's profile

rwe2156

2707 posts in 1313 days


#6 posted 11-23-2017 01:51 PM

AFAIK, in order to use that type outlet, you need a 3 conductor wire that can carry 2 or more circuits (not sure of terminology what I mean is 3 hots, a neutral and ground). In this case, it would be 2 circuits supplied by one double pole (240V) and single pole (120V) breaker.

If you don’t have enough room, why not install a small subpanel or see if you can free up some slots using split 120 v breakers?

BTW 10 gauge wire is rated for 30A up to 5HP motors why would you use that on a 20A circuit?

As always, my advice is : CHECK WITH AN ELECTRICIAN, not LJ’s.

-- Everything is a prototype thats why its one of a kind!!

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Tennessee

2587 posts in 2347 days


#7 posted 11-23-2017 02:06 PM

I agree with sawdustdad but go big or go home in my book. I have found you almost never have enough power over time.
To me, running all this convoluted wiring to enable the use of one 240 VAC item is workable, but shaky and limits your future.

If you have four slots in your main breaker box, and that box is a standard 200 amp residential box, I would simply put in a 60 amp 240 VAC breaker, (two slots), run a single wire, 240VAC 6/3, (or 6/4 if you don’t have a separate ground spike in the garage) to a sub panel, and that will give you about 60 amps of whatever power you want at the sub panel inside the shop.

You can run 120 VAC circuits and 240 VAC circuits safely from that sub depending on how many slots are in the sub. And it probably would pass code. Most of the usual ones I have seen are 8 slots. That is twice what you are trying to work with now. You’ll spend the money now, or spend the money later.

I’d run the heavier wire, especially if it is more difficult run, since you don’t want to run out of power at a later date and have to run that wire all over again.

-- Tsunami Guitars and Custom Woodworking, Cleveland, TN

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jonah

1441 posts in 3131 days


#8 posted 11-23-2017 02:09 PM

While it will function as you diagrammed, it’s not safe (nor code compliant) to have 120V and 240V loads on the same circuit. If you’re out of space in your panel, use one of the slots to install a subpanel for the shop. Use 8AWG wire and a 40A breaker so you’ll have plenty of capacity in the shop area. 8AWG is a huge pain to work with, but it’s not impossible.

View WhyMe's profile

WhyMe

909 posts in 1393 days


#9 posted 11-23-2017 02:44 PM



While it will function as you diagrammed, it s not safe (nor code compliant) to have 120V and 240V loads on the same circuit. If you re out of space in your panel, use one of the slots to install a subpanel for the shop. Use 8AWG wire and a 40A breaker so you ll have plenty of capacity in the shop area. 8AWG is a huge pain to work with, but it s not impossible.

- jonah

There is no code restriction of having 120V and 240V loads on the same circuit. The main thing is the 240V and 120V outlets be the same amp rating which in this case is 20A max. The breaker must be a double pole common trip breaker if serving both line-to-line and line-to-neutral loads. The problem is if this is a garage or shop with the floor at or below grade the 120V outlets need to be GFCI protected and that is a problem with a multiwire branch circuit. GFCI cannot share a neutral.

View richardchaos's profile

richardchaos

517 posts in 212 days


#10 posted 11-23-2017 03:29 PM

I will suggest this. Have a dedicated circuit for the following,,,,, Table saw, compressor, well heck every large standalone!

-- β€œIn a time of universal deceit, telling the truth is a revolutionary act.” ― George Orwell

View alittleoff's profile

alittleoff

444 posts in 1109 days


#11 posted 11-23-2017 04:02 PM

When you put a 2 pole breaker on a single 110 volt circuit, you run the risk of the breaker not triping. The breakers are tied together with a tie bar and an internal connection.Each recptical should be controlled by an individual breaker to be right. If you cut the tie bar on the 2 pole breaker the 220 circuit might not trip. All being said It will work but its not ithe right way to do it. Personally I’d wire the 220 on a circuit by itself and clear up another space by using more half or thin breakers for the 110 circuit and everything would be right.
Gerald

View Roy Turbett's profile

Roy Turbett

137 posts in 3412 days


#12 posted 11-23-2017 05:21 PM


When you put a 2 pole breaker on a single 110 volt circuit, you run the risk of the breaker not triping. The breakers are tied together with a tie bar and an internal connection.Each recptical should be controlled by an individual breaker to be right. If you cut the tie bar on the 2 pole breaker the 220 circuit might not trip. All being said It will work but its not ithe right way to do it. Personally I d wire the 220 on a circuit by itself and clear up another space by using more half or thin breakers for the 110 circuit and everything would be right.
Gerald

- alittleoff

I believe you are mistaken about there being “an internal connection” because 2 pole breakers are designed so that if one leg trips both will trip. Another common example is when 12/3 wire is run to wire separate circuits for a dishwasher and garbage disposal from the same duplex outlet where the bond is broken on the hot side and the neutral is shared. This is to make the entire box cold if one appliance trips. If separate single pole breakers are used, they are required to have a bar that ties them together which is the same thing a double pole breaker does.

View TheFridge's profile

TheFridge

8287 posts in 1319 days


#13 posted 11-23-2017 05:28 PM


As always, my advice is : CHECK WITH AN ELECTRICIAN, not LJ s.

- rwe2156

17 years. Just saying.

I’ll dig up the article. Might take a bit.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View Roy Turbett's profile

Roy Turbett

137 posts in 3412 days


#14 posted 11-23-2017 05:41 PM



If I read you properly, you want to leverage a 10/3 to have both 120 & 240 in same line. As long as not using both at same time would work. Depending on municipality, that would be frowned upon as they want singles.

I have a 10/3 for my TS as it needs 120 & 240, and I wanted a 20A outlet for my hand tools that draw a lot. Unfortunately my basement shop (prebuilt) only has 15A outlets. Your problem is going to be you won t be able to find 30A outlet for 120. At least I could not.

- bonesbr549

You are correct in assuming that 30 amp breakers require 30 amp outlets. However, in a previous LJ forum it was pointed out that some (perhaps most?) jurisdictions also interpret the code to be that you can only have one 30 amp outlet per 30 amp breaker. But you may still want to run 10/3 wire with a 20 amp breaker if you need both 120 and 240 going to the same machine to keep the loads balanced. I use this configuration for my lathe where 240 supplies the VFD and each 120 leg supplies a duplex outlet for lights and a hand sander. The lights pull juice from one leg and the sander pulls juice from the other. The neutral is shared.

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TheFridge

8287 posts in 1319 days


#15 posted 11-23-2017 05:42 PM

Here’s one. Branch circuits- 210.4© a multi wire branch circuit shall supply only to neutral loads.

The exceptions don’t apply. This is the first one I found that said no.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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