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120/240 Dual Voltage Outlet and GFCI Protection

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Forum topic by ras61 posted 03-31-2014 06:24 PM 789 views 0 times favorited 19 replies Add to Favorites Watch
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ras61

92 posts in 211 days


03-31-2014 06:24 PM

I’m planning to run a 240 volt outlet from my garage sub-panel, and want GFCI protection just to be on the safe side. Since they don’t make 240 volt GFCI outlets, the only option seems to be a 2 pole GFCI circuit breaker. When looking at outlets I noticed a 120/240 dual volt receptacle with one outlet for each voltage, you just need to run 3 wire romex and use the black and red for the 240 outlet, and black and white for the 120 outlet. This would provided extra flexibility and convenience at that location, but I have a question concerning GFCI protection: while the 240 volt outlet should be adequately covered, will the 120 volt outlet also have GFCI protection from the 2 pole GFCI circuit breaker? Thanks for the help.

Russ

-- "South Carolina is too small for a republic and too large for an insane asylum" - James L. Petigru, 1860


19 replies so far

View Fred Hargis's profile

Fred Hargis

1891 posts in 1184 days


#1 posted 03-31-2014 07:49 PM

I believe you need a 240V CB that has a neutral lug… it’s my understanding they make them without the neutral for straight 240V applications, and with the neutral for those appliances that need both 120V and 240V service. I think (but do not know) that your dual voltage outlet is the same as that appliance, and will require the special breaker with the neutral lug. If you need the one with the neutral, be prepared to pay through the nose for it.

-- Our village hasn't lost it's idiot, he was elected to congress.

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ras61

92 posts in 211 days


#2 posted 03-31-2014 08:29 PM

Hi Fred – I’m not sure I understand, maybe because I’ve never heard of a circuit breaker with a neutral lug (?). I’ve always been under the impression that all neutral wires go to the neutral bus in the service panel, but I’m obviously no expert when it comes to electricity. Just to clarify if there’s a misconception, I’m not talking about a 240 line similar to what’s used for an electric range that has both 240 for heating elements and 120 for electronic controls, this is a duplex receptacle with one outlet for straight 240, and the other outlet for standard 120. Hopefully this pic will better explain things:

-- "South Carolina is too small for a republic and too large for an insane asylum" - James L. Petigru, 1860

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Fred Hargis

1891 posts in 1184 days


#3 posted 03-31-2014 09:00 PM

A normal 120V GFCI breaker will have a neutral lug along with a hot. That neutral lug accepts the wire from the circuit, and then in turn goes to the neutral bus. Now, to have GFCI protection, the trick is to measure the load in a way that any leakage will be detected…with 120V it has to “see” the voltage between the hot and the neutral, that’s the purpose fulfilled with what i just described. I understood what you wanted to install, but the 120V side will have a hot and a neutral…somehow the CB will have to “see” what’s on the neutral to do the balance required to identify the any leakage. If you didn’t include the neutral in the balance, you would have an imbalance in the circuit that would trick the breaker. You said you wanted to run one of the hots to both outlets, somehow the GFCI needs to know it hasn’t got out of the circuit; since some part of that is going to the neutral leg, it needs to include that. I’m sure I didn’t word that as clear (if at all) as I wanted, but it’s a little tough to explain…..maybe one of the sparky’s will show up and clear it up. If you think a pic of a 120V GFCI hooked up will help, I have one in my panel I can photo showing that neutral lug.

Edit in: look at this 240V GFCI breaker. You see the wire coiled wire? That connects to te neutral bus. This breaker will have a lug will the neutral from the circuit is connected, so the 2 hots and the neutral will connect to the breaker, and the breaker, in turn, connects to the 2 hots and the neutral buses in the panel. That allows it to see the balance between the 2 hots and/or the 2 hots and the neutral.
linky

Now, back to the question: I think with a CB like this, hooked up properly, you can have both the 120V and the 240V circuits protected.

-- Our village hasn't lost it's idiot, he was elected to congress.

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ras61

92 posts in 211 days


#4 posted 03-31-2014 09:43 PM

Thanks for help Fred, I think I understand better now. I’ve never installed a GFI breaker before, so I have some learning to do on the process and terminology.

-- "South Carolina is too small for a republic and too large for an insane asylum" - James L. Petigru, 1860

View Shawn Masterson's profile

Shawn Masterson

1262 posts in 639 days


#5 posted 03-31-2014 10:58 PM

Just for morbid curiosity why do you want gfci for you 220?? Are you standing in water while you are sawing??

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ras61

92 posts in 211 days


#6 posted 03-31-2014 11:34 PM

Shaun – the saw will be in the garage, which can be a damp environment, and since the garage is also for vehicle, bike and general storage, I plan to roll it outside when I can to help control dust. Maybe I’m wrong, and I admit I don’t have a great grasp of electricity, but I figured if 120 volts were bad for you in the wrong conditions, 240 volts would be a really bad day, and that the extra $50 for GFI protection wasn’t worth risking getting electrocuted over.

-- "South Carolina is too small for a republic and too large for an insane asylum" - James L. Petigru, 1860

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ras61

92 posts in 211 days


#7 posted 03-31-2014 11:46 PM

GFCI may be overkill, but it’s a small price for peace of mind. Heaven forbid someone spills a bucket of water and one of my kids is standing near the cord or outlet.

-- "South Carolina is too small for a republic and too large for an insane asylum" - James L. Petigru, 1860

View Grandpa's profile

Grandpa

3190 posts in 1366 days


#8 posted 04-01-2014 01:16 AM

I am not sure the 120V will trip a 2 pole 240V breaker. If I wanted to use the GFCI on the 120V line I would use a GFCI receptacle in a separate box.

Edit: BTW I use GFCI receptacle for all the 110V in my shop. At least all that is reachable from the shop floor. They are required on all circuits in the garage, outdoors, within 15 ft. of pools and spas, on the kitchen counters in unfinished basements and in bathrooms unless it is a dedicated receptacle for an appliance such as a sump pump, refrig, freezer or washing machine. I chose to use them since my shop is not any different than a garage.

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ras61

92 posts in 211 days


#9 posted 04-01-2014 01:31 AM

Thanks Grandpa, if the 120 isn’t protected by the GFCI breaker I’ll just drop it and only go with 240. It just seemed convenient to able to have one line and location where you could run any tool in the shop.

-- "South Carolina is too small for a republic and too large for an insane asylum" - James L. Petigru, 1860

View oldnovice's profile

oldnovice

3798 posts in 2058 days


#10 posted 04-01-2014 04:40 AM

I have a 220VAC 40A GFCI breaker available. I had originally requested 40A but code here states if I only need 30A I cannot have a 40A GFCI and so it was never used and no sits on a shelf.

Current code requires GFCI for any outlets outside of the house and it appears that the code will include garage outlets in the very near future.

So I have a Square D 230V, 40A GFCI, normally over $140 that I will sell for $100!
Let me know with a PM if you are interested.

-- "I never met a board I didn't like!"

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ras61

92 posts in 211 days


#11 posted 04-01-2014 01:24 PM

After doing more research, there doesn’t seem to be a definitive answer on whether this will work or not, and despite the flexibility of having both voltages at one receptacle, the trouble and uncertainty doesn’t seem to make it worth while.

A bigger question I’ve run across is whether the initial start-up of a table saw motor on a 240 volt GFCI line will cause a current imbalance and trip the GFCI? Is anyone using their TS with a 240 GFCI breaker? This is an interesting question since it appears the electrical code may soon require these lines to be GFI protected.

-- "South Carolina is too small for a republic and too large for an insane asylum" - James L. Petigru, 1860

View Fred Hargis's profile

Fred Hargis

1891 posts in 1184 days


#12 posted 04-01-2014 02:37 PM

A strictly 240V GFCI looks for balance between the amp draw on both hot legs, there is some small difference that if you exceed it the ground fault trips. It’s quite possible the amperage difference on a large motor start up may have a greater difference on the legs than the GFCI will allow. Speculation on my part, but still seems to be a possibility.

-- Our village hasn't lost it's idiot, he was elected to congress.

View FellingStudio's profile

FellingStudio

50 posts in 373 days


#13 posted 04-01-2014 02:56 PM

I will strongly caution you to not install a duplex receptacle with 120V on one half of the receptacle and 240V on the other half.

You are just asking for a mix up in voltages … plugging a 120V machine, battery charger, or appliance into the 240V half of the receptacle seems like a not if, but when it will happen scenario. And, while a toaster might be able to handle the 240V, your DeWalt or IPhone charger certainly won’t, and it seems like a recipe for easy burnt motors to me.

A dedicated 240V receptacle will be no more difficult to install than the duplex receptacle, and there will be no possibility for a 120V cord end to be mistakenly plugged in.

-- Jesse Felling - http://www.fellingstudio.com

View Fred Hargis's profile

Fred Hargis

1891 posts in 1184 days


#14 posted 04-01-2014 04:04 PM

>>>>You are just asking for a mix up in voltages … plugging a 120V machine, battery charger, or appliance into the 240V half of the receptacle seems like a not if, but when it will happen scenario.

That can’t happen if the tools have proper plugs, they will not interchange.

-- Our village hasn't lost it's idiot, he was elected to congress.

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Grandpa

3190 posts in 1366 days


#15 posted 04-01-2014 04:20 PM

GFCI checks for amperage out and amperage back. The deviation is what trips the breaker. That is the way the 110V works. It is amperage that kills. Voltage pushes it through you. If a car battery had enough voltage to drive it, it would be lethal. I operate motors on GFCI all the time and have had no issues. That is my personal experience. According to the code check book that I have GFCI is required in garages and has been for over 10 years.

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