Converting a 120v outlet to 240v

[Ruahrc]

So I have a question:

I am planning to have a central vacuum system installed in my house. When the house was built, vacuum conduit was installed in the walls and routed to the garage, but a system was never installed. In the garage near the place where the vacuum conduit terminates, there is a 120V 20A circuit to be used to power the vacuum. At the breaker box there is a breaker labeled "VAC" which makes me think this is a dedicated circuit installed specifically for a vacuum system. (Aside: does anyone know how to test this? I turned off the breaker on the VAC circuit and no other outlet in the garage turned off, but guess it would behoove me to check all the other outlets in the house too).

One of the vacuum unit options I am looking at requires 240V AC and not 120V like I already have. If I chose this particular vacuum, I would need to upgrade, install, or convert my 120V 20A plug into a 240V plug. What exactly is involved to do this?

The contractor from the vacuum place who came and wrote up my estimate told me that if I already had a dedicated 120V 20A circuit for the vacuum, it could be converted to a 240V by just changing the connection at the breaker box and changing the outlet plug to the 240V fitting. i.e. the wiring used is the same, which means I would not have to rip anything out or run new wire. This would significantly lower the cost to have this done, and potentially I could also do it myself?

Is this true? Is the wire used for 240V vs 120V circuits the same? Would I need to worry about delivered power and the gauge of the wire? (I'm guessing no? Since doubling the voltage means halving the current for the same power, and since wire gauge limits the current capacity not the voltage).

Is this the kind of thing a licensed electrician has to do or inspect, or is this something that a homeowner can do by themselves? This is a little beyond what I have done before but I have replaced outlets and light switches in my house, and if I am understanding what needs to be done correctly, it does not sound that hard that I couldn't do it without a little research.

Thanks
Ruahrc

 

[mjbasford]

most of the central vac units that I install that require 240 use a 6-15R/6-30R (depending on model) connector, so there is no neutral required. If it is in fact a dedicated circuit, then you should be able to switch it our without issue.

Check local codes re: whether you can do this or need to contract it, and keep in mind you will be working inside the breaker box, adding and possibly relocating breakers, comfort level decision is up to you.

 

[pattenp]

Yes you can switch the 120V/20A circuit to a 240V/20A. If romex wire was used it's a matter of using the white wire as the second hot wire and replacing the single pole 20A breaker with a 2 pole 20A breaker and putting in a 240V 20A outlet. This is all provided that the vacuum only needs a 20A circuit and not more. You can do it if you feel comfortable removing a breaker and moving the white wire from the neutral bar to a new 2 pole breaker which may require the movement of other breakers so the new breaker will fit.


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[wyliesdiesels]

Yes you can switch the 120V/20A circuit to a 240V/20A. If romex wire was used it's a matter of using the white wire as the second hot wire and replacing the single pole 20A breaker with a 2 pole 20A breaker and putting in a 240V 20A outlet. This is all provided that the vacuum only needs a 20A circuit and not more. You can do it if you feel comfortable removing a breaker and moving the white wire from the neutral bar to a new 2 pole breaker which may require the movement of other breakers so the new breaker will fit.


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OP is the wire in conduit or is it NM-b aka Romex?

 

[Dick in Wisconsin]

If you do this, I think you need to put black or red tape around both ends of the white wire I signify and alert future tinkerers that the white wire "hot" and not a neutral anymore.

 

[nadogail]

The most difficult part of the job might be identifying the neutral conductor of the 120 volt receptacle.

So many of the panels I have opened had unidentified neutrals. You might have to "ring out" the conductor.

 

[Dick in Wisconsin]

The most difficult part of the job might be identifying the neutral conductor of the 120 volt receptacle.

So many of the panels I have opened had unidentified neutrals. You might have to "ring out" the conductor.

Good question. Wouldn't one of those little gizmos with all the lights for checking for proper wiring tell you that?

http://www.kleintools.com/catalog/electrical-testers/gfci-receptacle-tester

 

[Norcal]

If the cable is NM, and a home run, it is a simple matter find the breaker supplying it then find the neutral coming from the same cable as the hot wire, & remove it from the neutral bus, the white conductor has to be re-identified to black, red, blue, or any color, other then white, gray, or green, after installing a 2-pole breaker and a appropriate 250V rated receptacle then should be good to go.

If the wiring method is conduit, you cannot re-identify a white to another color.

 

[Richard Cranium]

It all depends on how comfortable you are with working with electric. If you are not sure, just pay some one to do it. Make sure that the vacuum is the only thing on that circuit.

 

[wyliesdiesels]

If you do this, I think you need to put black or red tape around both ends of the white wire I signify and alert future tinkerers that the white wire "hot" and not a neutral anymore.

Yes this is required by code.

The most difficult part of the job might be identifying the neutral conductor of the 120 volt receptacle.

So many of the panels I have opened had unidentified neutrals. You might have to "ring out" the conductor.

Code didnt use to require the reidentification of the neutral wire when it is used as an ungrounded conductor. So thats why u will still find unlabeled white neutral conductors.

 

[tfi racing]

The most difficult part of the job might be identifying the neutral conductor of the 120 volt receptacle.

So many of the panels I have opened had unidentified neutrals. You might have to "ring out" the conductor.

Please explain.I'm not sure why this would be a big mystery or be difficult for any qualified individual.

 

[Ruahrc]

I am pretty sure the wire is NM(?) Romex. It is run inside the walls not EMT conduit and presumably was added when the house was built. There is actually a small cubby of unfinished dead space above my garage that I have access to (via the master bathroom, no less ) and I see Romex wire running along the joists there. I am pretty certain one of those wires is the one for the central vac circuit.

Thanks for the info I will try to verify my circuit is a dedicated line (just the one outlet) and also see if the vacuum unit requiring 240V can be done on a 20A circuit or if the needed amperage is higher. I do have space in the breaker box to add/convert the existing 120V 20A breaker to a 240V model, although to do it neatly I would probably have to move all the breakers below it down by 1 to make the extra room. Or just move it to a different location altogether.

 

[nadogail]

Please explain.I'm not sure why this would be a big mystery or be difficult for any qualified individual.

The catch is that the OP does not seem to be a "qualified individual".

Ringing out a circuit refers back to the "old days" before sophisticated test equipment when continuity checks and wire sorting were done with a battery and a door bell.

 

[Dick in Wisconsin]

If the wiring method is conduit, you cannot re-identify a white to another color.

Does this mean that if the wire (presuming 12 gauge) is in conduit is currently a 120volt circuit and you need to upgrade it to a 240volt circuit, you have to remove the existing black/white/ground and replace it with black/red/ground wire in the conduit?

 

[pattenp]

Does this mean that if the wire (presuming 12 gauge) is in conduit is currently a 120volt circuit and you need to upgrade it to a 240volt circuit, you have to remove the existing black/white/ground and replace it with black/red/ground wire in the conduit?

If in conduit and it's single wires and not a cable, you only remove the one white wire (if you can) and replace it with the correct color wire for now being an ungrounded conductor.


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[wyliesdiesels]

Does this mean that if the wire (presuming 12 gauge) is in conduit is currently a 120volt circuit and you need to upgrade it to a 240volt circuit, you have to remove the existing black/white/ground and replace it with black/red/ground wire in the conduit?

Yes but the only wire that would need to be changed is the white wire. Code allows the reidentification of wires ONLY in assembled cables such as MC or NM-b.

 

[theoldwizard1]

Please explain.I'm not sure why this would be a big mystery or be difficult for any qualified individual.

In a large "load center" (breaker box) with a large number of breakers (and therefore hot and neutral wires) It may be difficult to trace back the hot (black) to the cable (NM/Romex) where it enters the box, You really do NOT want to accidentally connect the wrong neutral to a hot !

To double check yourself, you need a continuity test (usually built into most DMM) :

• Shut off the main
• Disconnect the neutral wire you THINK you want to convert to a second hot from the neutral buss bar.
• Go to the outlet you want to change, remove the cover and remove the old receptacle. Verify that the circuit does NOT continue to another receptacle.
• SHORT hot and neutral (see step #1)
• At the load center, connect your DMM set on continuity and test/verify across hot and the disconnected neutral

 

[Ruahrc]

Old thread I wanted to post an update

I decided to go ahead with this and convert my socket. The motivation behind doing all this is that as mentioned above I plan on installing a central vacuum system. But I planned on getting a hide-a-hose system which requires a larger power unit which runs on 240. My existing vacuum circuit is 20A but only 120V.

Today I had the day off so I went to city hall and got an electrical permit which was just over $70

Then went to Home Depot and picked up a 6-20R socket. Went to get a breaker only to find out that you have to get the same breaker as your breaker box. So I had to go home and discover that my box is a Siemens. So back to Home Depot and get a 2-pole 20A breaker. Because this is going in the garage and apparently code now requires all garage outlets to have a GFCI I got a breaker with GFCI attached (there were no 6-20R sockets with GFCIs available) boy is that sucker pricey! It was $77, a standard 2-pole 20A breaker without GFCI was like $10.

Got home and shut off the mains. Carefully checked/tested everything to make sure it was all dead before poking around too much. Whoever installed the electrical did a pretty good job the wiring was very tidy however in the name of neatness they cut off a lot of excess wiring which made it very difficult to reposition breakers because there is very little slack on the wires. Since I had to use the neutral wire as a hot wire, I had to take the neutral from where it was connected to the neutral bus and run it all the way down to the lower portion of my panel where the breaker will sit. But because of the neat routing it would not reach. Fortunately I was able to pull another inch or so of romex down from where it enters the box and by stretching the wire straight (not routed along the sides as it was) I was able to get just enough reach. Actually I had to go back to Home Depot (that's 3 trips now) and get a 20A tandem breaker so I could condense 2 existing 20A breakers down into 1 slot so i could put in the new breaker one slot higher and that enabled me to get the short neutral wire to reach.

Anyway got all the wiring squared away, wrapped the neutral wire with black electrical tape on both ends, installed the new socket, and I measure 240V at the wall now

Just have to get the inspector scheduled. Which leads me to my next question:

My house was built in 2006. Based on what I understand, at the time garage circuits were not required to have GFCIs, but now they do. So when I bought my 2-pole 20A breaker I got the GFCI version. However my existing garage circuitry (GDO and overhead lighting) do not have GFCI not at the socket or the breaker. Will my inspection fail since my garage circuits are not to code? Do I have to fix the existing circuits and install GFCI breakers for my garage circuits? Will this require another permit, or at least a more expensive permit than I already got (since on my permit application I only wrote to modify 1 circuit, I think there is additional charge for additional circuits?)? Or is it all OK since the circuitry was there before the code was changed?

Last thing, since I had to replace 2 existing 20A 1-poles with one tandem 20A 1-pole, is that another modification that requires a permit? Or does it all fall under the one permit I got?

Anyhow I feel pretty good about being able to do this one myself, I definitely learned new things, got to use my tools, and saved myself some money I'm sure (knowing now what the permit and the special breaker cost, I'm sure an electrician would have been several hundred dollars to do this). But I guess I will not get too excited until the inspection is done.

Ruahrc

 

[wyliesdiesels]

Wow too much to read.

Anyway, code only requires 120v outlets in garages to be GFCI protected.

The new 240v outlet u put in doesnt need GFCI protection. Return the expensive GFCI breaker and get a regular 2-pole breaker.

Any existing electrical not to current code is gramd fathered in.

BTW GFCI protected outlets have been required in garages for a long time.

AFA as the permit questions u would have to ask the AHJ. Every AHJ has different rules and policies.

 

[75gmck25]

I agree. In general, circuits that you did not touch or change are grandfathered and do not need to be brought up to current code. However, GFCI on 120 volt garage circuits has been a requirement for a long time. My house built in 1996 needed them, and I have seen them in much older houses.

Bruce

 

[Ruahrc]

It's odd then how my wiring could be the way it is now. I mean how could it have passed prior inspection with such an obvious flaw? As I said the house was built in 2006 if the code required GFCIs in garage for many years prior how then could this have passed inspection at the time of construction? It does not look like any of the circuits in question were modified since the house was built (the breakers match those of the rest of the circuits in the house in type and appearance, wiring looks consistent with rest of wiring, etc). If the city says I need another permit can't I put it back on them and ask to see the passing permit from when the house was built?

One thing I was wondering about is if I just go ahead and fix it, would the inspector even know that it was not up to code to begin with?

I had another question about GFCIs: I went out and bought a regular 20A 2-pole breaker to use instead of the GFCI model I installed. I got to thinking though, if there really is a safety benefit to having the GFCI installed, maybe I just leave it alone and leave the better unit in place. However my next thought was whether the GFCI is actually protecting anything since my circuit consists of 2 hot wires and a ground (no neutral)?

If a circuit consists of just a hot and ground and no neutral, is a GFCI providing any benefit? My understanding is that GFCI compares current in neutral wire to current in hot wire and if they don't balance it trips.

FYI the GFCI breaker I installed has a lead screw for neutral connection (if it were to be used with a 4-pole 240V plug) and a white "pigtail" wire that I connected to the neutral bus of the breaker box.

Ruahrc

 

[Radix2]

your 240v GFCI will compare the current in the two hot leads - basically the same thing as comparing the hot and neutral in a 120v circuit - as the name implies it is looking for current sneaking out of the circuit in a fault to ground.

I think you r GFCI money would be better spent on 120V GFCI outlets in the garage where you are more likely to mess with extension cords, water, cut cords, tools, etc than spent on a seldom messed with dedicated vacuum circuit. IMO.

 

[wyliesdiesels]

It's odd then how my wiring could be the way it is now. I mean how could it have passed prior inspection with such an obvious flaw? As I said the house was built in 2006 if the code required GFCIs in garage for many years prior how then could this have passed inspection at the time of construction? It does not look like any of the circuits in question were modified since the house was built (the breakers match those of the rest of the circuits in the house in type and appearance, wiring looks consistent with rest of wiring, etc). If the city says I need another permit can't I put it back on them and ask to see the passing permit from when the house was built?

One thing I was wondering about is if I just go ahead and fix it, would the inspector even know that it was not up to code to begin with?

I had another question about GFCIs: I went out and bought a regular 20A 2-pole breaker to use instead of the GFCI model I installed. I got to thinking though, if there really is a safety benefit to having the GFCI installed, maybe I just leave it alone and leave the better unit in place. However my next thought was whether the GFCI is actually protecting anything since my circuit consists of 2 hot wires and a ground (no neutral)?

If a circuit consists of just a hot and ground and no neutral, is a GFCI providing any benefit? My understanding is that GFCI compares current in neutral wire to current in hot wire and if they don't balance it trips.

FYI the GFCI breaker I installed has a lead screw for neutral connection (if it were to be used with a 4-pole 240V plug) and a white "pigtail" wire that I connected to the neutral bus of the breaker box.

Ruahrc

Forget the double pole GFCI. U dont need it for the vacuum.

And about the house passing inspection. Inspectors miss things all the time. I dont put it pass them.

My house, built in 1996, passed inspection and the ******* plumber didnt plumb a drip leg on the gas line fedding the h2o heater and central heater. Ive seen many electrical installs passed despite several obvious codes being violated.

If u fix it, i doubt he'll notice.

Are u sure the outlets arent protected by a GFCI thats somewhere else?

 

[Ruahrc]

OK I figured it all out

The circuit in the garage DOES have a GFCI, it was just hidden behind one of those "2 to 6 outlet" adapters that was plugged in. I don't know why I assumed this outlet did not have a GFCI nor why I did not look behind the adapter in the first place. Anyhow mystery solved.

I also found that the circuit containing the GDO does NOT have a GFCI, although this is is understandable as I believe the GDO exception went away in 2008 and the house was built 2006 so it was to code at the time of installation.

Before I learned this I actually called the city again and spoke to an electrical inspector on these points to get his input. He basically said the same thing as you guys, there is probably an outlet-based GFCI somewhere on the circuit, rather than the slim chance the wiring was not to code. Regarding my question about if I would need to alter my current permit or get a new one to replace the breakers with GFCI units, he told me that strictly speaking yes the permit would need to be altered to add a couple of additional circuits, but that the cost to the city to re-process my existing permit would undoubtedly exceed the $3 difference in permit fees, so he said it was fine to just get it all inspected at the same time on my existing permit.

So here's what I did (or plan to do):

1) Went and got a non-GFCI 2-pole 20A breaker and replaced the GFCI one I had originally installed. Will return my GFCI breaker and get my $77 back

2) Since the GDO circuit is not a dedicated circuit, and the same circuit actually feeds outlets in my house too (it feeds a den that is next to my garage), I decided I would just take this opportunity to enhance my household wiring and install an AFCI/GFCI breaker on this circuit, and get protection for all covered outlets. I went to Lowe's and got two 15A AFCI/GFCI combination breakers and will install them both on the garage circuits. One is to add GFCI capably to the circuit that does not have it, the other is to centralize the GFCI protection to the breaker rather than the outlet. Is this needed? Not necessarily, but I already have an open electrical permit from the city, am going to get/need an inspection anyway, and in the long run a couple of $40 GFCI breakers is nothing in terms of cost.

3) Looking at the wiring in my breaker box and I will again run into the problem where the existing neutral wires are cut too short. I can stretch the wire almost taut and make the connection but I think the cleaner approach is to splice in an extra foot or so of wire using a wire nut and then route the wire properly along the edge of the breaker box. To get the necessary wire I just bought about 3 feet of yellow romex by-the-foot which I will cut up and take out the white wire.

Tried to get it all done tonight but could not get to the hardware store in time to get a length of white romex to use the white wire from to splice onto the existing neutral wires. I could safely use the 12ga wire from the yellow romex I have on hand to extend the 14g a neutral wires but I guess people look down on mixing wire gauges. Since I have to go back to the store to return this GFCI I will just get the right wire.

 

[mike93lx]

Wow, a permit for an outlet change? That's dedication.

Be careful of how much you change. You could be opening a can of worms at inspection.

 

[wyliesdiesels]

I wouldve used THHN wire as its cheaper by the foot. Plus the conductors in NM-b arent marked so technically it cant be used for splicing in that regard but everyone does it.

 

[Ruahrc]

Just a quick update the inspector came yesterday and approved everything. Went very well no issues whatsoever with anything he saw.

Thanks everyone for the help and tips I learned a lot, didn't get hurt, fixed things, and saved some money by doing it myself can't ask for a better outcome than that Well maybe a better outcome would include getting some new tools out of the process but I already had everything I needed lol.

Ruahrc