1

I'm dealing with a 1970-built home and the oven has 6-3 without ground running to the oven. 2 hots and the neutral. Got a new oven coming in and want to make sure it's wired right. I could run new wire, it's not impossible but daunting for a DIY'er. I'm curious about running a separate 6AWG ground wire along side the 6-3 from the panel. I see conflicting info online about how NEC 2014 allows this but then there's NEC 303.3(B) that says all wires need to be together or is that only for running in conduit? The oven wire currently is running up a wall and along a 2nd story floor joist to a junction box, only after the junction box is it in metal conduit with a ground wire bonded to neutral. I plan to remove the junction box and run the 6-3 through the floor to a new junction box up stairs with a 4-prong receptacle. Here's some pictures: https://imgur.com/a/Asq4c9R

  • I'm slightly puzzled why running a new grounding wire is OK, but running a new cable with four wires is challenging (or is it not so much running the cable as connecting the two hots that is challenging)? – Martin Bonner supports Monica Jun 26 at 16:22
  • A #10 wire will suffice. There's a chart indicating which ground wire sizes are called for which ampacities. – Harper - Reinstate Monica Jun 26 at 17:45
  • 1
    @MartinBonner It's about 3ft vertical then 4ft horizontal of a run from the breaker panel to where the new junction box will be. That part is easy. However, it's run through the top of a panel box that is surrounded by 2x4 framing, it would be difficult to get the existing 6-3 unsecured/unclamped and fish 6-4 through that same hole. While I can fish a ground conductor up another hole, grab it when it comes out at the top of the 3ft vertical run and run it horizontal to the new junction box. Probably easier for an experienced electrician but I'm trying to keep this DIY. – Nate Jun 26 at 20:23
2

You can retrofit ground. See many answers about that - e.g., What does this answer about old residential home grounding mean?

Options include running a new separate ground wire or connecting with another ground wire. However, while you may be able to use a smaller than 6 AWG wire for the ground (10 AWG according to Harper's comment), you can't just connect to a 12 AWG or 14 AWG ground from a 20A or 15A circuit - that's not quite big enough.

As far as all the wires being together - ground is the exception. That's because ground only carries current in an emergency (and then hopefully only long enough for the overcurrent situation to trip the breaker). However, one key to that is make absolutely certain that any neutral-ground bond in the oven is removed. Sometimes a neutral-ground bond is included in the oven but that is only used when connecting without a separate ground to the panel (which should not be the case on any new installation).

As far as why this is all even an issue: When grounding was added as a requirement for most residential circuits, appliance manufacturers (specifically electric ovens/cooktops/ranges and clothes dryers) were concerned that requiring a potentially significant amount of electrical work (e.g., if the wires were not in conduit and the path not easily accessible to run a ground wire or a new cable) would affect sales of new appliances - you would replace it if it was broken and you had no way to fix it, but you wouldn't "upgrade" and you would fix rather than replace when possible. In other words, money. So they got an exception to allow ground to share the neutral connection. In certain situations this provides the same safety benefits of a separate ground wire. But in many other cases it does not. At this point (and for many years now), new installations and changes to existing installation require full separate grounding. But the manufacturers are still resistant to losing any sales due to lack of a ground wire so they continue (legally) to sell appliances that can be connected either way, and in many areas it is totally legal to keep using a ground-via-neutral provided it is a simple appliance replacement, but not recommended.

As far as neutral-ground bond in the main panel, the basic idea is that neutral & ground should be connected in exactly one place. In fact, they need to be connected for certain aspects of the entire electrical system to work properly. But having them connected in multiple places ends up defeating the purpose (partially) of ground wires.

  • 1
    Thanks. I do see in the new oven's manual a mention about a strap from neutral to ground that you're supposed to bend out of the way for a 4-wire/prong installation. Maybe you can answer a curiosity question of mine though... why is it ok to have both neutral and ground together at the panel but not at the oven? – Nate Jun 26 at 15:44
  • @Nate Your curiosity question is an interesting one - but the answer is likely to be quite long. Check if it has already been asked here, and if not, ask it as a separate question. – Martin Bonner supports Monica Jun 26 at 16:20
  • 1
    @Nate short version: because at the panel and the oven would be 2 places not one. It does nothing to improve safety and many things to harm safety. – Harper - Reinstate Monica Jun 26 at 17:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.