Questions tagged [120-240v]

For question dealing with 120/240V single split phase electrical circuits.

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32
votes
8answers
420k views

Why Do 240V Circuits Not Require Neutral?

Someone told me that a 240V circuit does not require a neutral wire in the cable. Can anyone explain this phenomenon from the electricity perspective and generally explain why circuits do and do not ...
28
votes
2answers
18k views

What is a tandem breaker (aka duplex, cheater, twin, double-stuff, etc.)?

I keep hearing about tandem breakers, and how they won't work with 240V loads and how they should never be used for a multi-wire branch circuit. Aside from those issues... What is a tandem breaker? ...
17
votes
4answers
12k views

240 V outlet is not delivering 240 V

I recently moved into an apartment with a 3-prong, NEMA 10-30 outlet. It looks like this: I bought an old dryer that I confirmed was working before purchasing it and hooked it up and unfortunately ...
16
votes
5answers
3k views

Should I run 240v for any supported appliances?

I am having my main circuit breaker panel replaced (by a licensed electrician) and he told me I can run new circuits for him to hook up to the new panel. Is there any benefit to running 240v circuits ...
15
votes
3answers
8k views

Can I use 220 V outlets on a 15 ampere breaker and wire it up as 110 V?

I purchased a 220 V outlet and didn't realize it. My circuit is 15 amperes. I wanted to hook up a series of normal 15 ampere 110 V outlets. When I look at the outlet it looks exactly like a regular 15 ...
10
votes
5answers
5k views

Why would replacing this 240 V outlet with a 120 V outlet trip my breaker?

I recently replaced a 20 A 250 V single outlet with a 20 A 125 V single outlet so that I could use it for my microwave in the kitchen. The original outlet had two gold screws and a grounding screw. ...
10
votes
8answers
2k views

Do travel voltage transformers really not have grounding?

Example 220v-to-110v converter here. It seems like it accepts a 110V plug with grounding, and yet the converter itself only has a two-pronged plug (to a 240v outlet). Does this mean that plugging a ...
9
votes
6answers
4k views

Can I safely plug a 15A 100V appliance into a 20A 250V wall outlet?

I have a convection microwave oven that has a normal 15A 100V plug. I can only conveniently access a 20A 250V outlet, which looks like this: (I am located in Taiwan). Are there any safety issues ...
9
votes
3answers
1k views

Can you use a 2 pole 2-slot wide breaker to provide 240V?

Forgive my ignorance in terminology, I am a computer engineer but not an electrician. The concepts make sense to me, but I don't know all the industry standards and jargon. I recently had a 240V ...
8
votes
1answer
451 views

Proper way to modernize 1940's cabin sub-panels

This cabin is located in the United States, and was built in the 1940's. However, it has obviously had various electrical panels added to it after its original construction. I'm starting this new ...
7
votes
4answers
4k views

Why does my electric oven present the option of 40A and 50A breakers?

The oven in question states 40A with 120/240 volts. In the installation manual: This range is manufactured with the neutral terminal connected to the cabinet. Use a 3-wire, UL Listed. 40- or 50-...
7
votes
2answers
1k views

Electrical service sizing mix up in Mexico

Facts: The national electrical supply company of Mexico called "Comisión Federal de Electricidad" (CFE) oficially instructs users to install: A two pole one trip main interrupt behind the ...
6
votes
4answers
6k views

What is the explicit difference between the ground and neutral wire in 110V systems?

So, I've put in or replaced several outlets following wiring instructions online and in the box. Nothing big. I know that if I fail to turn off the breaker then I shouldn't directly touch the black ...
5
votes
2answers
33k views

Replacing 240V outlet with 120V

I just moved into a new home, and we have an outlet in the bathroom that was set up for a washer/dryer in case we wanted to go that route. The outlet is a NEMA 10-30R. We are happy with the dryer ...
5
votes
3answers
2k views

How wasteful is a voltage transformer?

If an appliance that is rated for 220V is used with a 110v-to-220v transformer in a 110v country, or an appliance that is rated for 110V is used with a 220v-to-110v transformer in a 220v country, how ...
5
votes
5answers
4k views

Does running a dryer on 120 V drive up electricity costs?

So I have a ventless dryer, and it's a relatively new LG model (LG DLEC855W 4.2 cu. ft. Compact Electric Dryer) that I have hooked up to a 120 V outlet. I know it's not supposed to run on a 120&...
5
votes
3answers
10k views

What is wrong with this panel wiring?

I have a main breaker panel downstairs, and a subpanel upstairs. After I hired an electrician to rerun the service entry cables, nothing upstairs is right, and all the upstairs lights blew as soon as ...
5
votes
2answers
650 views

In a multiwire branch circuit, can the two hots be connected to the same phase?

This may be an obvious question, but I haven't been able to find a direct answer. I believe I have a MWBC - I have two hot wires connected to two separate circuit breakers, sharing a neutral and ...
5
votes
3answers
2k views

Why is it said that a typical 120V household circuit "reverses" polarity?

Responders have been very helpful with a recent post of mine. But I'm sorry to say this part still perplexes me: In a 120VAC circuit, current flows from Line 1 through the load, and returns via ...
5
votes
1answer
7k views

Why would a 120v circuit work without a neutral?

My home has a relatively typical (in America) 100 amp 240v feed accomplished via three conductors - two 120v "hot" wires and one neutral. This gives me my 240v circuits (the two hots) and my 120v ...
5
votes
1answer
384 views

Very unsafe-looking receptacle

While I was searching for duplex receptacles where one was NEMA 5 (120V) and the other was NEMA 6 (240V), I found a few normal ones that were what I was looking for (Leviton 5031, 5842, 5844, Hubbell ...
4
votes
6answers
115k views

Using a 30-amp tandem circuit breaker for a 120/240v circuit?

I inherited a main panel box from a homeowner that wasn't always fond of meeting the required NEC codes. As such, there are some oddities in the panel. One such oddity is the fact that he installed ...
4
votes
3answers
550 views

Electrical Wiring - New Circuits (Added pics)

I have run two 12/2 Romex “Home Runs” to a junction box, each for 120V to Circuits A and B. T-off at the junction box, two 12/2 Romex lines split to one 2-gang box, and two more 12/2 Romex lines split ...
4
votes
2answers
2k views

Can I add 240v 40A circuit to my breaker box to power an electric range?

This is my breaker box; I'm concerned about not having enough space to accommodate an electric range which requires 240v 40A. My box has tandem circuits, although I'm not sure if consolidating ...
4
votes
2answers
8k views

Can a sub-panel have a larger main breaker than the feeder breaker in the main panel?

I have a weird setup that I'm trying to configure, but I'm only 90% certain of my logic (and with electrical items I want to be 100%). I have a new 400A meter/main combo unit with 1 built-in (...
3
votes
3answers
14k views

Explain voltage readings on NEMA 10-30 socket

The clothes dryer in the garage is plugged into what appears to be a NEMA 10-30 socket (receptacle). Reading the voltages on the socket with a multimeter, the voltage between the two diagonal blades ...
3
votes
2answers
524 views

Multi wire circuit or 2 separate 120V 20A dedicated circuits?

I'm planning to purchase a portable indoor infrared sauna and locate it outdoors under my deck. The sauna will require a dedicated 120V 20A outlet. I'm wondering if it makes sense to install a multi-...
3
votes
2answers
36k views

Why can't I (or: shouldn't I) run a power cord through a wall?

I would like to wall-mount my TV and have the wall be as clean as possible. I found this box and my idea was to mount this on the back side of that same wall , then run the power cable (and other ...
3
votes
2answers
3k views

Can I add a 120v branch for a washer to a 240v dryer circuit?

I’m running 10-3 Romex for a 240v electric dryer in our garage. It would be very convenient to tap into one hot leg and add a 120v outlet for the washer (they will be stacked). Is this allowed per NEC ...
3
votes
1answer
66 views

Can I draw 240v out of this configuration?

This is how my subpanel looks like. I am looking to install a breaker for an AC unit. 20A. The only caveat is that this has to be 240V. This is a subpanel coming from the main one. There is a breaker ...
2
votes
2answers
7k views

Do 240V receptacle use the same connectors as 120V receptacles for the same amperage?

I feel like I'm missing something obvious. I know different plug styles are used based on a circuit's amperage (in the US) but is the same style of plug used for both 110V and 220V outlets of the same ...
2
votes
3answers
866 views

Can I use four-wire cable from the panel to create a two-circuit duplex outlet?

I am planning on adding a server to one of the closets in my house. In order to do that I need to run electrical to the location of the server. For severs they recommend having 2 independent lines of ...
2
votes
1answer
174 views

Is it possible to wire a 240v outlet so that after I don't need 240v anymore I will have two 120v circuits?

I'm in the US. I will be installing a 240v outdoor outlet for an EVSE (electric car charger). However, in a few years I will have a garage built (elsewhere) and will move the EVSE to the garage, so ...
2
votes
2answers
163 views

Dryer 240 to 120 question

I have a 240 volt dryer currently, and I want to change it out for a gas dryer that will utilize 120 volt. Since the circuit is 240 volt 30 amp, I'd like to use the existing 6-8 gauge wire and ...
2
votes
3answers
2k views

Is a 240v solar panel setup better than 120v?

I am considering a small 1kW solar system (4x 250-watt panels). The seller offers them in both 120v and 240v configurations with "micro-inverters". Given a 25-year panel warranty, could the amperage ...
2
votes
1answer
977 views

120/240 Multi wire branch circuit - failed inspection because of uneven loads?

From a double pole 20-amp breaker, I ran 12/3 w/g to a quad box with a 120 receptacle and a 240 receptacle. Red wire from one pole of the breaker to the 240, ground to the grounds, white to neutral ...
2
votes
1answer
107 views

Outlets (top only) and lights wired together with trail wire not working

I have a room in my house where the top of each outlet is controlled by a switch, and all of the ceiling lights by another switch. I thought I could just bypass the switch for the outlets and have ...
2
votes
1answer
3k views

Can I have a 120 volt branch off a 120/240 volt circuit?

So I'm wiring up my woodshop and I've got a question about branching a 120 volt circuit off a 240 circuit. I'm running 12/3 for this circuit coming of a 20 amp 2 pole breaker. The thought for this ...
2
votes
2answers
2k views

120 v to 12 v puck light conversion

I have 7 hardwired under cabinet puck lights which are 10 year old halogen type . All 7 or powered as 120 from one wall switch . Limited access to each light other than removing old puck and pulling ...
1
vote
2answers
115 views

Wiring for 120 now with 240 option later?

I want to wire a dedicated plugin to the front of my garage for a new EV, which at the moment needs to be 120. But later, I may upgrade to a 240 based charger. Is there a suggested way I could wire ...
1
vote
3answers
3k views

Powering a 240V 15A air compressor with a 6-20 plug

I have an air compressor with a 240V 15A power requirement and a 6-20 plug (looks like normal US plug but with one of the flat ends turned at a 90 degree angle). Instruction manual can be found [here][...
1
vote
2answers
1k views

Future proofing for 240V outlet

I currently have a 12A EVSE that takes either 120V or 240V and uses a normal three-prong (NEMA 5-15) plug. I am looking to install a 240V outlet on a 50A circuit breaker to use with this EVSE, but I'm ...
1
vote
1answer
148 views

Can I run conduit containing 120V wires inside larger conduit for 240V wires?

I was wondering if I could run 120v wires inside in a larger conduit that has higher voltage wires 240v, in a smaller piece of conduit? The reason I ask is that I have a manufactured home and when ...
1
vote
3answers
570 views

Can I safely create another 120V outlet using the fourth neutral wire from a 4 wire 240V line?

I recently just ran a 4 conductor 240 volt line out to my shed. I chose to run the extra conductor just in case, but I do not currently need it for my application. My question is, can I add a 120V ...
1
vote
6answers
18k views

Can I handle-tie two 120V CH breakers for a 240V load?

Due to an ordering error a long time ago, I have too many 30A 1-pole "CH" brand breakers. (these are single breakers, not tandem/double-stuff). As you probably realize, there isn't much call for ...
1
vote
1answer
117 views

How to connect 5-15P plug into 6-20R receptacle?

I have a computer power supply (PSU), input voltage is 120-240V, I assume I can safely plug it into a 240V outlet. I have one those outlets in my garage, problem is that it is 6-20R type receptable ...
1
vote
2answers
3k views

Getting 120v single phase & 240v three phase out of 240v single phase receptical

Will the following wiring diagram work? This 240v single phase NEMA L14-30R receptacle is right off the main panel with a 30amp breaker. I want to obtain both 120v single phase and 240v three phase ...
1
vote
1answer
1k views

Control 12V LED circuit and 120V power supply from one switch

I want to have two switches (preferably in the same box) that control two separate runs of LED lights, both powered by a single Allanson power supply: I plan to switch the lights by breaking the 12V ...
1
vote
2answers
2k views

Is it possible to adapt a NEMA 14-50R to a NEMA 6-20P or NEMA 6-30P appliance?

In a Canadian residential kitchen, in a house built in the late 1970's, there is a NEMA 14-50R, on a 30 Amp breaker. Currently a standard oven/range combo is plugged into this receptacle. I would ...
1
vote
1answer
5k views

Converting appliances from 120v -> 240v

I've been getting U.S. appliances sent to E.U. where the voltage is doubled. I'm using autotransformers so they can work, but this isn't ideal. I do this to save money. EU retailers add their ...