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I am a new homeowner and have started doing some electrical upgrades. The problem I've run into is that the house was built in 1960 and the electrical system as a whole is grounded via the conduit with no ground wire present. Most components I've been purchasing require a ground wire. I've added a few pigtail grounds to the electrical boxes and that seems to have worked out fine. However, I'm seriously starting to consider gradually rewiring the house.

  1. I have a licensed electrician (also a friend) that is going to replace the old, recalled circuit breaker panel and install a whole-house surge protector. He can also advise/assist/inspect any work that I do myself.

  2. I have access via the unfinished basement and attic.

  3. What I'm considering is using the existing wiring as a wire pull to replace it with up to code Romex.

Is this even worth doing or is it a foolish ambition?

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    You should be asking your friend! IMHO (from an electrical engineer, not an 'electrician') is that there's nothing wrong with wire in conduit. The conduit is definitely an acceptable grounding path per NEC last I checked. So long as you're doing the bonding correctly, I think you're fine. I also think you're grossly underestimating the effort involved in rewiring an entire house!
    – Kyle B
    Jun 15, 2022 at 16:27
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    Usually wires in metal conduit is SUPERIOR to romex. They are better protected, rodent proof. Unless you are having some specific problems, I'd say let it be. If you do have a circuit or two with issues, pulling new WIRES (not Romex cable) in the existing conduit would be best. Also you need to consider fill capacities of conduit, individual wires will always allow for more wires than cable. Jun 15, 2022 at 17:29
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    Plus pulling Romex (or any cable) through conduit is not so easy. It is easy with really big conduit, but inside houses in sections designed for a circuit or two, the conduit may not even be larger (by code) to pull cable as larger conduit costs more and builders generally don't like to spend extra. Jun 15, 2022 at 19:45
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    I will echo what others have said about conduit, individual wires and romex. If the idea of a ground conductor separate from the conduit gives you peace of mind, why not pull just a ground wire through the existing conduit and leave the other perfectly good wires in place? I can't comment on the right way to bond those might be.
    – spuck
    Jun 15, 2022 at 20:09
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    What would be your primary reason for doing so? Personally, if you're just doing it to run new wires I wouldn't bother. It'd be pretty pointless if your existing wires are working just fine. I'm with Kyle B on this one (thanks for pointing out there's a difference between an electrician and an electrical engineer). I ain't either one of those things but I know you are underestimating not only the effort but the time and cost involved in rewiring an entire house. I wouldn't do it unless you have knob-and-tube or some grossly outmoded antique electrical system that's making you nervous.
    – Justa Guy
    Jun 16, 2022 at 3:15

6 Answers 6

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You don't know what you have! You already have the best wiring method made. 90% of my brand new work is exactly this stuff, and it's required in industrial installations.

We just need to get you up to speed on the stuff, so you can hold your head proud.

Also if you rewire your house, you'll need to come up to all the current codes, which will mean AFCI and GFCI everywhere.

The rules for grounding devices to metal boxes.

  • If the device is not a receptacle, and has a metal yoke, it will automagically pick up ground via the mounting screws.
  • If the receptacle is marked "Self-Grounding" on a stamp somewhere (usually on the yoke), then it will pick up ground via a wiper that touches the mounting screws.
  • If the receptacle's metal yoke has clean hard flush metal contact with the box flange, that grounds it.

The only case you have to worry about is a) it is a receptacle, b) it is NOT marked self-grounding, and c) it is held above the metal box by its drywall ears (or contaminants or crud are in the way). In that case you need a ground jumper to the metal box.

You can cause any metal box to have a ground "wire"

  • In the back of the box is probably a hole already tapped for a #10-32 screw.
  • You may use a "ground clip" to attach to the side of the metal box.
  • You can drill your own #10-32 hole, and even get special self-drilling screws.

Let's get you up to speed on what you have

The problem I've run into is that the house was built in 1960 and the electrical system as a whole is grounded via the conduit

Yes. This is the best system made. Even today. In fact when you get into commercial/industrial, Romex isn't allowed and you MUST build that way. Chicagoland also requires this. It is a better system.

I've done live testing of the grounding capacity of 60 year old conduit in a condensing environment, and it definitely works.

Most components I've been purchasing require a ground wire. I've added a few pigtail grounds to the electrical boxes and that seems to have worked out fine.

Well, that's how you do that, and that's fine.

Per NEC 110.2, all equipment installed must be UL Listed or equivalent from ETL or CSA. You cannot use random Chinese garbage bought mail order because it is unsafe, but also won't have competent instructions. Competent instructions ought to provide for metal-box installations, since there are a lot of metal boxes in North America.

Even if the wiring is Romex, the Romex must be grounded to the metal box first, and then most things can pick up ground automagically as discussed above.

If a receptacle can't ground by hard-flush metal contact, install a "Self-Grounding" receptacle and let it pick up ground off the screws. These are the $3 ones that come in their own box instead of loose in a bin. They are better made, also.

As discussed above, almost everything will self-ground via its metal yoke, and any ground pigtails are simply superfluous and can be left to dangle.

If you have kit with a plastic yoke, then first make sure it is actually UL listed (and if not send it back). Then you'll have to use a ground screw or ground clip.

In rare cases, you have smart switches with BOTH a bare AND a green wire. Follow those instructions CAREFULLY but the green wire is functionally neutral, but they have gotten UL approval to bootleg neutral off ground for that switch alone. In that case either a) since you are in conduit, just pull a real neutral wire! Or b) ground it to the box.

I have a licensed electrician (also a friend) that is going to replace the old, recalled circuit breaker panel

Do you want a second opinion on whether that's even necessary? Zinsco and FPE -> replace, otherwise you can probably flip it and make it a subpanel of a new main panel, and save yourself a world of wiring lol.

What's far more helpful to DIYers is having a "Meter-Main" so you can fully de-energize the main panel. (well master panel as the "main" is now at the meter).

However, I'm seriously starting to consider gradually rewiring the house.

What I'm considering is using the existing wiring as a wire pull to replace it with up to code Romex.

Is this even worth doing or is it a foolish ambition?

I would say it's ... under-informed, but we'll fix that right now.

Does wire get old and rotten? Sure. It can. You inspect it. If you don't like what you see, wire is cheap.

However you seem to have a misconception that Romex is better than 62-year old TW wire. That would be "a bit of a horse race"... if the conduit has water ingress it's no contest, the Romex loses.

Anyway, no more TW for you. You'll use the new good stuff, dual-rated THHN and THWN-2.

  • T = thermoplastic
  • H and HH = "high heat" (your only limit is the thermal rating of the terminals, and 240.4(D) as usual).
  • W = wet rated
  • N = nylon outer shell for easy pulling
  • -2 = 2nd revision of THWN raising its thermal rating to match THHN

Yeah, you can use the old wires to pull in the new wires, just try to do all the wires in the conduit at the same time (this will go FAR easier). Note that it's common for some wires to pass through a box on their way to somewhere else, you'll want to preserve that, because if you cut and splice you need to add more than a 12" loop to do that splicing, and it will add cubic inch fill to the box.

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  • @Steve Well grounding started going in during the 50s and was universal by 1966. Plastic boxes wouldn't come along until much later, so everything was metal boxes back then. They had to put the grounds somewhere. Jun 16, 2022 at 18:53
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    To add a bit, metal conduit allows you to (relatively) easily pull more conductors if the need arises. Romex must be stapled on a schedule, so adding wires usually involves opening up the walls. Metal conduit is definitely superior for upgrades/repairs.
    – JS.
    Jun 16, 2022 at 22:32
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    “ I've done live testing of the grounding capacity of 60 year old conduit in a condensing environment” … I feel like there’s a great story hiding in here Jun 16, 2022 at 23:20
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    @JacobKrall I feel like Harper's entire life is a great story. I hope they release a highly opinionated autobiography one day. Nov 18, 2022 at 18:09
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the electrical system as a whole is grounded via the conduit with no ground wire present

That is perfectly fine. As long as it is all metal conduit (conduit can also be PVC) and connects to metal boxes, you have a valid grounding path. Many receptacles and switches will automatically ground via yoke to the metal box. For anything that has a separate ground wire, connect it to the metal box with a grounding screw. No reason to replace the conduit. If you have individual wires with problems, you can replace them. But no need to add separate ground wires or to do a wholesale replacement.

The one exception, which really doesn't apply here, is that in buried outdoor conduit a separate ground wire may make sense as it ensures a good ground even if the conduit corrodes.

I have a licensed electrician (also a friend) that is going to replace the old, recalled circuit breaker panel and install a whole-house surge protector.

That is a very good idea. Make sure that it is not just a straight replacement but, unless the old one had lots of empty breaker spaces, larger. That way you can add new circuits as needed.

What I'm considering is using the existing wiring as a wire pull to replace it with up to code Romex.

You need to check your local code. Most places in the US allow conduit or NM cable (Romex). However, some places require conduit. Since conduit generally costs more than NM cable, if you have an entire house of conduit it is quite likely that it is required. If it was required in 1960 it may still be required today, or it may not. Find out what your local rules are.

If NM cable is allowed, that is great for new circuits. But for existing circuits, stick with the conduit. Even if you have to replace the wires due to decaying insulation, doing so with individual wires in conduit will be less expensive and less work than replacing with NM cables.

Is this even worth doing or is it a foolish ambition?

Opinion. But my opinion is: Replace the panel (definitely), replace ungrounded receptacles with grounded receptacles, add GFCI where appropriate (kitchen, bathrooms, etc.). Replace other items only "as needed".

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I would certainly not replace the metal conduit in a house. Replacing it with romex is arguably a lower-quality installation.

As to the need for grounded receptacles, a proper quality receptacle will bond the metal yoke with the ground prong, which means that the metal machine screw used to secure the receptacle to the metal device box will create the ground bond between the receptacle and the house’s ground system.

You don’t even need the pigtail. If it’s a properly installed UL listed three-prong receptacle, just the act of attaching it to a metal device box grounds it.

If I had a house with entirely metal conduit for all circuits, I would be happy that I had such a high quality electrical installation.

Replace the panel and rest assured there’s nothing wrong with metal conduit.

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  • "You don’t even need the pigtail. If it’s a properly installed UL listed three-prong receptacle, just the act of attaching it to a metal device box grounds it." I thought that required a "self-grounding" receptacle. Does this mean that I can ignore the green ground connection on the receptacle?
    – JackTrade
    Jun 15, 2022 at 17:16
  • @JackTrade I have to assume you are quoting because you disagree? Jun 15, 2022 at 17:17
  • No, I'm asking. I used quotes because I haven't yet learned coding to format the quote in your comment.
    – JackTrade
    Jun 15, 2022 at 17:19
  • @JackTrade self-grounding outlets are very common and in the latest NEC 2020 code book they appear to be required. If there’s every any doubt, use a multimeter to check the voltage between hot, neutral and ground. Jun 15, 2022 at 17:21
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If the conduit is all installed correctly and in good shape, there's absolutely nothing wrong with it serving as the ground path. This kind of installation is in fact required in Chicago and surrounding areas. Other, more experienced contributors may chime in here with some other things to look out for to make sure that your electrical system is in good shape, but "conduit serving as ground" is perfectly safe and not a reason to rewire the house.

If you have a device which needs a ground wire, you can keep adding a pigtail as it sounds like you have done by screwing it into the metal junction box. Some metal junction boxes will have a raised area at the back with a hole which is intended for attaching a ground pigtail.

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    Since the OP has grounded metal boxes, he can avoid group pigtails but installing self-grounding outlets. These are certified to properly ground through the mounting screws. I also believe that most/all standard switches are self-grounding.
    – DoxyLover
    Jun 15, 2022 at 16:55
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    @DoxyLover And the better quality receptacles that are self-grounding also have screw-to-clamp connections which are easier to install than plain screws and more reliable than backstabs. The extra $2 is money very well spent. Jun 15, 2022 at 17:01
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If you insist on the need to pull new cable, it's highly recommended to use individual wires (THHN or similar, as appropriate for your situation). I'll let others chime in with code and conduit fill capacity information, but pulling Romex (i.e. 14/2 with ground all in one jacket) is going to be really tough, and will max out any conduit fill requirements pretty much as soon as you put one Romex cable into most residential metal conduit sizes.

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I'd check the quality of your ground at each outlet and receptical box before counting on it. Unless you open each wall, can't be sure what was installed or repaired before. Testing continuity will tell you about the quality of the ground at each location.

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