Converting 5-20 receptacle to 6-20 receptacle

[cyoungster]

I have an existing 5-20 receptacle in my garage. I want to convert it to a 6-20 for 240V charging. The existing 5-20 receptacle is currently connected to a central vacuum, which I plan on plugging into a 15-Amp receptacle instead.

At the breaker panel I know I need to replace the existing 1-pole 20A breaker with a 2-pole 20A breaker, and then use the existing neutral wire as the second hot wire for the 240V circuit.

It seems pretty straight forward, but as I inspect the wiring I see that there is a red wire going into the circuit breaker, but at the receptacle in the garage it is black (not red). So I am confused. If this is a dedicated circuit then the hot should be the same color on each end, I think.

What am I missing here? Am I wrong in thinking I can use an outlet that was dedicated to a central vacuum?

 

[jcanoe]

I have an existing 5-20 receptacle in my garage. I want to convert it to a 6-20 for 240V charging. The existing 5-20 receptacle is currently connected to a central vacuum, which I plan on plugging into a 15-Amp receptacle instead.

At the breaker panel I know I need to replace the existing 1-pole 20A breaker with a 2-pole 20A breaker, and then use the existing neutral wire as the second hot wire for the 240V circuit.

It seems pretty straight forward, but as I inspect the wiring I see that there is a red wire going into the circuit breaker, but at the receptacle in the garage it is black (not red). So I am confused. If this is a dedicated circuit then the hot should be the same color on each end, I think.

What am I missing here? Am I wrong in thinking I can use an outlet that was dedicated to a central vacuum?

Do not attempt to convert the 5-20 receptacle without the help of a licensed electrician. The conversion of 120V (5-20) to 240V (6-20) can only be performed when the 120V (5-20) receptacle is the only receptacle on the circuit. The existing wiring needs to be connected to a new 2-pole circuit breaker for 240V at the service panel.

 

[cyoungster]

The conversion of 120V (5-20) to 240V (6-20) can only be performed when the 120V (5-20) receptacle is the only receptacle on the circuit. The existing wiring needs to be connected to a new 2-pole circuit breaker for 240V at the service panel.

That is exactly what I mentioned in my original post. The existing 5-20 is dedicated to the central vac. I can find no other receptacles anywhere that are controlled by the same breaker

 

[jcanoe]

That is exactly what I mentioned in my original post. The existing 5-20 is dedicated to the central vac. I can find no other receptacles anywhere that are controlled by the same breaker

Plugging the Central Vacuum into a 15 amp circuit may not be meet code. Ref NEC 2011 210.23 Permissible Loads: Synopsis - Electrical equipment fastened in place (such as a central vacuum unit) cannot exceed 50% of the circuit rating where lighting or other non-fastened in place cord and plug equipment is on the same circuit. What is the amperage spec of the Central Vacuum?

If there is room in the service panel for a new double pole breaker then the existing dedicated 120V 20 amp circuit could be repurposed for 240V and changing the receptacle from 5-20 to 6-20. Unless you are experienced working inside the service panel hire an electrician.

 

[brkaus]

If the wire is changing color, it’s not as dedicated as you are hoping.

what other wires go together at the panel side? Is it nm-b or conduit?

 

[cyoungster]

If the wire is changing color, it’s not as dedicated as you are hoping.

what other wires go together at the panel side? Is it nm-b or conduit?

It is NM-B

And you may very well be right about it not being dedicated. I am thinking that a central vacuum system must by it's very nature be power-activated at each hose plug-in location. I guess I can't do this after all.

 

[brkaus]

It is NM-B

And you may very well be right about it not being dedicated. I am thinking that a central vacuum system must by its very nature be power-activated at each hose plug-in location. I guess I can't do this after all.

Are there more wires going into that nm-b (at both ends)? Maybe multiple circuits?

You might be right on the complication. Either switches fir the unit or power for each outlet for a power wand.

 

[Watts_Up]

It seems pretty straight forward, but as I inspect the wiring I see that there is a red wire going into the circuit breaker, but at the receptacle in the garage it is black (not red). So I am confused. If this is a dedicated circuit then the hot should be the same color on each end, I think.

What am I missing here? Am I wrong in thinking I can use an outlet that was dedicated to a central vacuum?

One possibility is that the red and the black wires are connected to a switch controlling the vaccum cleaner?

My concern will be to be sure that the neutral is dedicated and not used by other circuits BEFORE using this wire as the second hot phase wire !!!

 

[WheresMyKeys]

As mentioned above you've either got an external switch in the circuit somewhere, and / or more likely, you've got 2 circuits on a single 12-3 or 10-3 wire that's sharing a common neutral (multi-wired branch circuit). Red is typically only included in 3 conductor cables, or when ran as individual conductors, and typically only used to separate itself from the standard black (unless it was friday at 5:30 and that's all that was left on the truck).

If you've got a shared neutral the second breaker will on on the opposite leg of the 240v breaker panel. Sometimes these 2 circuits share a 2-pole breaker, but sometimes they don't so you have to be really careful about inspecting existing conditions and understanding what you're looking at before making any changes.

If you have a multi-wired branch circuit stealing the neutral to give the 1 circuit's existing outlet 240v will royally mess up the 2nd circuit - to the extent of which I'm not sure.

Given where you're at with what you see, and what you're trying to do, and your comfort level / knowledge a car forum isn't the right place to be asking these questions and I'd strongly recommend reaching out to a local licensed electrician to see if you can do what you are looking to do with what you've got or if any further alterations would be required.

Central Vac is a power hungry appliance and code may dictate it needs to be on a dedicated circuit.

 

[cyoungster]

Yeah you guys are correct. Upon further inspection I have a 12-3 that has the red wired to one 20A breaker and the black wired to a different 20A breaker. The neutral is shared between them.

So I guess I am SOL.

 

[brkaus]

Yeah you guys are correct. Upon further inspection I have a 12-3 that has the red wired to one 20A breaker and the black wired to a different 20A breaker. The neutral is shared between them.

So I guess I am SOL.

Those two breakers probably should have their handles tied for safety. If you didn't look a second time, you could have turned one of the breakers off and not realized the other end of the wire was still live.

Where do the two circuits go to?

 

[cyoungster]

Those two breakers probably should have their handles tied for safety. If you didn't look a second time, you could have turned one of the breakers off and not realized the other end of the wire was still live.

Where do the two circuits go to?

One goes to my central vac and the other goes to my entertainment center in the family room. I am really unhappy with my electrician. I think he cut corners.

 

[brkaus]

One goes to my central vac and the other goes to my entertainment center in the family room. I am really unhappy with my electrician. I think he cut corners.

Ouch. Yes, I would strongly prefer shared neutrals are avoided. But I *think* code does allow it.

I have one of those in my house too. The microwave outlet and a light circuit are powered off a red/bkack/white/ground nm-b. I haven’t quite figured out where they are split out. I think I have to pull the oven to find it. Ugh.

 

[ATPMSD]

The neutral is shared between them.

“Although technically acceptable under the NEC, it is considered “bad practice” by industrial standards.”

 

[cyoungster]

I have abandoned the 6-20 idea obviously, since I have no dedicated neutral wire to apply to the 240V circuit. I will continue to use the 5-20 for the foreseeable future, until such tome as my Electric Dryer goes caput. When that happens I will invest in a gas dryer so I can re-purpose the 240V 30A dryer outlet as my new EV charger outlet for the garage. Just need to turn that around and have it face the garage instead. Then get a Tesla 10-30 adapter for the mobile charger.

 

[blue y]

“Although technically acceptable under the NEC, it is considered “bad practice” by industrial standards.”

It's a multi wire branch circuit (mwbc). Perfectly acceptable when wired correctly.

Is your panel full or why are you trying to repurpose all the existing circuits and not just adding a new one?

 

[Watts_Up]

It's a multi wire branch circuit (mwbc). Perfectly acceptable when wired correctly.

How do you estimate the Ampacity of a multi wire branch circuit (mwbc),
I mean what wire gauge and circuit breaker to use then to protect the Neutral wires from overheating?

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[blue y]

How do you estimate the Ampacity of a multi wire branch circuit (mwbc),
I mean what wire gauge and circuit breaker to use then to protect the wires from overheating?

Huh? In a normal residential setting it's going to be a 20a (12/3 nm-b minimum) or 15a (14/3 nm-b minimum) circuit. Remember the neutral is only going to carry the difference of the currents on each leg back to the panel (though there will be additional current between the two loads, but it will never exceed the higher leg amp draw). Wire it to code and you'll be fine.

 

[ATPMSD]

It's a multi wire branch circuit (mwbc). Perfectly acceptable when wired correctly.

I found your comment interesting and did a little more digging and you are of course correct, when wired correctly. I found this reference:

The element of multiwire branch circuits that makes them potentially dangerous is the “shared neutral.” When sharing a neutral between two circuits, you must remember to use opposing power bus connections at the source. In other words, always make sure to use L1 + L2 + shared neutral in order to cause the two currents to subtract (or cancel each other out) and produce a net neutral current of zero. This is called a “balanced” system. NEVER use either L1 + L1 + shared N or L2 + L2 + shared N. Using “non-opposing hots” will cause the two currents to add and, thus, create a neutral current which could exceed the ampacity of the neutral conductor (possibly causing a fire).

Electrician's Journal-The Dangers of Multi-Wire Branch Circuits

Introduction Multiwire branch circuits have the following advantages: More cost effective. Fewer conductors required for a given number of circuits. Smaller raceways required. However, extreme care must be taken to ensure safety is not compromised. The element of multiwire branch circu

www.electriciansjournal.com

 

[fholbert]

Is your panel full or why are you trying to repurpose all the existing circuits and not just adding a new one?

I wondering the same. Is installing a new dedicated 240v circuit an option? If so, that’s the best solution by far.

Audit your breaker panel. I’m the second owner of the house, after living here 22 years I found an abandoned 240v 50a circuit in my main breaker panel. As luck would have it, the abandoned pathway went into my garage. I added some conduit, pulled new wire and used it for my Tesla charger.