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Author Topic: 240VAC passing thru 120VAC outlets..  (Read 4034 times)
NA4IT
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« Reply #30 on: March 23, 2019, 05:52:21 AM »

I am a disabled / retired master electrician. Here is what I did regarding conduit and grounding.

1) I ALWAYS ran a green or bare copper ground inside the conduit, bonded to every box under the ground screw location built into the box, with a tail left hanging to connect to grounding screws of outlets and switches. Conduit box fitting can loosen in time.

2) I usually ran solid THHN wire because it's easier to wire. I NEVER used to "push in" connections on the back of an outlet or switch. I always used the screws, and some devices had a hole you put the wire into and then tightened the screw.

3) As long as the 240 circuit is "3 wire" (two hots and a ground) I'm OK with a shared ground. If it is a "4 wire" 240 circuit make sure you size the neutral wire properly (enough to carry the amp rating of the breaker).

4) If the run is short, sometimes you can save money by buying NM cable (12-2w/G) and stripping off the sheath, then putting just the wires in the conduit.

Disclaimer... I offer this as information only. YOU are responsible for how you use this information and the safety of your person.
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KD6VXI
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Posts: 177




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« Reply #31 on: March 23, 2019, 07:09:43 AM »

Have you looked at a 4S box lately? I just bought a case, and they have concentric knockouts. If yiu used half inch, you'd need bond bushings.

I can't see from his pictures what types of boxes he has. 

Even a handi box can have concentrics.

Im not getting into a pissing contest with you.  As I stated, I based my statements in what I've experienced as a solar installer and electrician for the last 5 years plus in my jurisdictions (California, in many cities and various counties both northern and Southern).

You want to base your answers in a poor homeowner arguing with his insurance company about what he read on the internet, that's fine. What I told him WILL pass code and an inspection almost universally.  Your answer, better be prepared for a fight around here.

That green run of wire is SO expensive....!


Have a good weekend, done with arguing.


--Shane
KD6VXI
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KD0REQ
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Posts: 2389




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« Reply #32 on: March 23, 2019, 10:59:58 AM »

ground wires must be able to carry all the potential current rated for all conductors in the box. so, if I didn't misread a post further up... you cannot rely on an existing 14 or 12 gauge ground wire for a 115 volt circuit AND a 240 volt circuit in the same run.

either use an oversize ground lead, or pull a new ground with the new circuit. assuming 20 amp 240 volt and existing 15 amp 120 volt, you need to have protective ground capable of 35 amps carrying current, which is halfway between a #8 and #10 AWG. size up to the #8 and party on.
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K3GM
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Posts: 2549




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« Reply #33 on: March 23, 2019, 12:11:36 PM »

Thanks again everyone for the advice, debate, etc.  Just to provide some info, the boxes are standard Steel City, 1 gang, old work boxes that are available at the Home Depot for $.99 each.  Each box is not loaded with a ground screw on the inside back of the box.  I will run a ground wire with the hot and neutral conductors. The 240VAC box will be the 5th box from the panel, so it is simple to run a separate and continuous green wire to that box.  I purchased a standard breaker at the panel rather than an AFCI/GFCI breaker as guys in my club are having tripping problems with them.  Experiments are underway to see what can be done to harden them by way of ferrite or possibly something else.

But here's a question:  There is a recommendation by Scott, NA4IT to use NM cable (aka. Romex) and strip the jacket off.  This is a great idea and certainly cheaper than THHN.  But the jacketed conductors inside NM cable aren't identified in any way, and I thought and read somewhere that this wasn't allowed because of that (not trying to sell you short, Scott). Any comments before I buy the wire?
« Last Edit: March 23, 2019, 12:32:52 PM by K3GM » Logged
AA4PB
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Posts: 15046




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« Reply #34 on: March 23, 2019, 12:54:22 PM »

The conductors inside Romex cable have color coded insultation on them. 12/3 with ground will have a Red, Black, White and bare (ground) conductor.
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Bob  AA4PB
Garrisonville, VA
K3GM
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Posts: 2549




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« Reply #35 on: March 23, 2019, 01:57:35 PM »

I realize that, Bob, but the wire conductors jacket inside NM cable has no identifying nomenclature on it to show that it conforms to a particular set of parameters; like THHN or THWN wire has on its jacket.
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W9FIB
Member

Posts: 2509




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« Reply #36 on: March 24, 2019, 02:43:13 AM »

Have you looked at a 4S box lately? I just bought a case, and they have concentric knockouts. If yiu used half inch, you'd need bond bushings.

I can't see from his pictures what types of boxes he has. 

Even a handi box can have concentrics.

Im not getting into a pissing contest with you.  As I stated, I based my statements in what I've experienced as a solar installer and electrician for the last 5 years plus in my jurisdictions (California, in many cities and various counties both northern and Southern).

You want to base your answers in a poor homeowner arguing with his insurance company about what he read on the internet, that's fine. What I told him WILL pass code and an inspection almost universally.  Your answer, better be prepared for a fight around here.

That green run of wire is SO expensive....!


Have a good weekend, done with arguing.


--Shane
KD6VXI

When you bid a job, making extra cost for yourself is self defeating.

Never said you CAN"T get that style of box, simply that you can also get boxes just as cheap without the concentric knockouts and avoid the extra costs.

Its the difference between being an installer that will use anything and a contractor maximizing profit on a bid project and following the rules.

BTW...never did see your citation of the NEC that you were so proud of.
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73, Stan
Wisdom is knowledge you gain after you know it all.
W9FIB
Member

Posts: 2509




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« Reply #37 on: March 24, 2019, 02:49:17 AM »

I realize that, Bob, but the wire conductors jacket inside NM cable has no identifying nomenclature on it to show that it conforms to a particular set of parameters; like THHN or THWN wire has on its jacket.

That is correct as the NM cable is specified and built as a cable assembly. So the ratings apply to the assembly, and the interior parts do not require the same markings as THHN which is installed as an individual component.
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73, Stan
Wisdom is knowledge you gain after you know it all.
W2RWJ
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Posts: 336




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« Reply #38 on: March 25, 2019, 04:08:59 PM »


Are you going to run into box fill issues between the device, grounding wire, the wire nuts, and pass-through cabling?
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AA4PB
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Posts: 15046




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« Reply #39 on: March 25, 2019, 05:01:21 PM »

I realize that, Bob, but the wire conductors jacket inside NM cable has no identifying nomenclature on it to show that it conforms to a particular set of parameters; like THHN or THWN wire has on its jacket.
Is the inspector going to pull the wires out of the conduit to check for the proper markings? If you need a few inches of THHN for a jumper do you have to make sure you cut a piece that includes the marking? Around my area you can use a white wire for a hot lead if you mark each end with a piece of black tape or a black magic marker. I've never seen anyone worry about the markings on the wire - but every area is different.

In my area places like Home Depot sell THHN by the foot off a reel although for as much as you will probably need it might be less expensive in bulk rolls.

It's probably going to be a problem pulling around those four 90's going around the post.
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Bob  AA4PB
Garrisonville, VA
K3GM
Member

Posts: 2549




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« Reply #40 on: March 25, 2019, 08:26:56 PM »

......It's probably going to be a problem pulling around those four 90's going around the post.
The photo doesn't show it well, but there are inside and outside pull elbows at the four corners.

Your other comments regarding jacket nomenclature are certainly valid.
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K3GM
Member

Posts: 2549




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« Reply #41 on: March 25, 2019, 08:42:13 PM »

Are you going to run into box fill issues between the device, grounding wire, the wire nuts, and pass-through cabling?

Remains to be seen.  This is a second residence, so I work on it sporadically when I'm there. The only wire nut in each box will be a Greenie for the ground run, while each loop outlet hot and neutral screws will serve as the "gozinta" and "gozouta" for each box.
« Last Edit: March 25, 2019, 08:49:37 PM by K3GM » Logged
K3GM
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Posts: 2549




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« Reply #42 on: April 20, 2019, 04:13:34 PM »

Follow up:
If I could have a do-over.... The "handy boxes" I used were way too small for four 12 guage wires, two conduit fittings, and a greenie wire nut for grounding.  It was impossible to pass the 240V wires thru the boxes.  While I was able to cram everything in, I should have used 4x4 boxes with a cover for one duplex outlet.  They would have provided adequate room for everything plus the 240V wires.  I know this because the #1 outlet which holds a GFCI outlet would not fit in the handy box.  I replaced it with a 4x4 box, and then getting everything in was a breeze.  So I'm going to run a separate conduit for the 240V line.  Live and learn I guess....
« Last Edit: April 20, 2019, 04:24:01 PM by K3GM » Logged
W3TDH
Member

Posts: 17




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« Reply #43 on: June 17, 2019, 06:53:59 PM »

conduit is not recognized as a protection ground in a life-safety environment. corrosion and loose connections break it. as a personal note, you can always exceed the code requirements. what I'd do is pass a over-rated ground wire and use that for all the protection grounds. thus, no ground loops, no differential currents.

the AFCI also has GFI capabilities, and that's now the NEC code standard for all liveable spaces, so don't chain them. you'll have false trips till Hell freezes over. 

There is no gentle way to say this.  You are misinformed. 

The only place that Electro Metallic Tubing cannot serve as the only Grounding (Bonding) Electrode Conductor is in patient care areas of healthcare facilities.  All patient care areas of such facilities must have two independent Equipment Grounding Conductors either of which would otherwise be adequate on their own.  There are several places you cannot use EMT at all but that is a totally different situation.  The only application that allows the wire Equipment Grounding Conductor to not be bonded to the box through which it passes is were the wire EGC is serving Isolated ground receptacles.  Those are only used to supply equipment that is so sensitive to electrical noise on it's ground that it will cause operational failure. 

AFCI Breakers do provide Ground Fault Protection of Equipment because they will open on any leakage current which exceeds 30 miliamperes.  The required trip level for Ground Fault Circuit Interrupters is 5 miliamperes.  So unless you are talking about one of the combination AFCI GFCI breakers; which are now readily available even at big box stores; the two types of circuit breakers serve different functions.  Since an unfinished basement is not defined as an living area by the building codes they are not required to have AFCI protection.  All unfinished basement areas are required to have GFCI protection of all 120 volt receptacles including the required 20 ampere circuit for laundry outlets if present.  Since concrete floors are definitely conductive you may want to install a two pole GFCI breaker on the 240 volt circuit. 

As for the likelihood of nuisance tripping of GFCI receptacles that protect the receptacles that are attached to the load terminals of the receptacle it is no worse than the likelihood of nuisance tripping of a GFCI breaker.  All of the principles of operation are the same.  The only difference between the two devices is where they are located.  One is in the box were the first receptacle needing protection is located.  The other is in the electrical panel that supplies that circuit. 

--
W3TDH
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