OT electrical code question and aesthetics…

[DS_park]

I have been allowed the 5’ x 10’ space in our basement under the stairs landing (7’ ceiling) for a small workbench / shop area which will be nice in the winter. I'm in the process of reworking the basement lighting.

All around the basement at 23” off the floor are numerous 120ac receptacles in metal boxes with metal conduit up to the ceiling. These have been there since the house was built (50+ years) so they are grandfathered.

US Code question: Can I install a second box in the conduit at 48” off the floor to use for a light switch? There is room in the conduit for a second piece 14-3 in the two conduits in question.

This is the only new switch location proposal that has made it past the design approval committee who has the majority vote and veto power on such aesthetic considerations.

DS

[becksmachine]

Allowed? By who or what? Your wife, the building owner, electrical inspector?? Who or what comprises the "design approval committee?

They are "grandfathered" in what sense? Why would they not be allowed in new construction?

Dave

[J Tiers]

You could add a box, there is no specific problem with that by itself. There are some other issues though.

First, you do NOT put multi-conductor cable, such as 14-3 in conduit. Conduit gets individual wires (the extra insulation could cause over-heating). For a light, you would only need 2 wires, the "hot" to the switch, and the return to the light, plus any needed earthing wires. If you have cable in conduit, that would not be per present-day code.

Second, there is a limit on the number of wires in any "raceway" such as conduit. This is based on cross-sectional area, but usually given as "X" number of such and so gauge wires. I have NO idea what 14-3 would be counted as (I can't see it from here), but it would appear likely that it would already "fill" the conduit to the maximum percentage, leaving no extra room.

Thirdly, if more than 3 current-conducting wires (not earthing wires) are in a conduit, the allowed current capacity of the wires is reduced to account for the extra heating. So if the existing wires are fused at their limit of 15A, the fuses would technically need to be changed to lower rating when more wires are added.

You should probably leave the "grandfathered" stuff in place and not disturb it, if it is not to present-day code. Messing with it might both damage it, and also would technically bring up the possible need to upgrade to current code.

Can't you use switched lights and simply plug them in?

[lakeside53]

Here you can run a short length (say to the switch) of your 14-3 in conduit for "physical protection" but it must not be closed at the end. If you close with say a cord grabber or box, code defines it as a "system" which then need as Jerry mentions above, separate wires. You certainly can not add another 14-3 to any existing conduit installation If you have concerns about what meets "code" in your area you need to ask your local AHJ. if you are modifying any existing installation, you'll need to strip out any existing 14-3 and do it right.

Grandfathering only works for past code compliant installations. If it was not code compliant when installed, it still isn't.

[becksmachine]

You could add a box, there is no specific problem with that by itself. There are some other issues though.

Thirdly, if more than 3 current-conducting wires (not earthing wires) are in a conduit, the allowed current capacity of the wires is reduced to account for the extra heating. So if the existing wires are fused at their limit of 15A, the fuses would technically need to be changed to lower rating when more wires are added.

Ok, correct me if I am wrong, but I don't think this is exactly correct.

Don't you use the higher ampacity rating when calculating rated ampacity for three or more conductors?

In the case of #14 wire, the calculation for derating for 4-6 wires in a raceway, would be 80% of 20 amps rather than 80% of 15 amps?

Since #14 is already required to be fused at 15 amps, .8 X 20amps = 16 amps, so adding 2 or 3 more wires doesn't require a reduction in overcurrent protection.

Dave

[Paul Alciatore]

I see several issues here. Just what is it that you want or need? Do you just need outlets at a higher level for use with a work bench? Or do you need more circuits for more current? Chances are that all the outlets in that area are on one 15A or 20A circuit and that is not a lot but I have had small shops that ran on one duplex outlet. One person can only use one or two tools at a time. So this question needs to be answered first.

If you just need to have the outlets at a higher level, there is no reason why the existing conduit runs could not be either shortened, raising the existing outlets or an additional outlet could be added to each one. The additional outlet could be added by cutting the existing conduit or by running new conduit back upwards (and perhaps sideways for a better position) up to the level you want.

If you need more circuits, it is very likely that a single extra hot wire could be added to the existing conduit. If you use the other phase from the existing outlet, you would not need an additional neutral or ground wire. As others have already said, you do NOT run multi-conductor cable in conduit. There is no need and there is the heat issue. But actually running an additional wire may be problematic. For most conduit runs all the wires are pulled at one time. When you try to add an extra one it gets difficult. The electrician may not even consider it.

This is obviously a commercial situation, an apartment or condo. You need to use a qualified electrician. DO NOT DO THIS YOURSELF. You could be liable for any present and FUTURE property damage or loss of life or limb. DO NOT DO THIS YOURSELF! Even if your condo board or other "authority" says you can, DO NOT DO THIS YOURSELF! If you do, then get a lifetime insurance policy that will pay ALL CLAIMS (good luck on that).

Personally, if they are in good condition, I would try to use the existing outlets with a power strip mounted on the bench plugged in to them. You could do that yourself and if you need a second circuit you may be able to use a second power strip with a longer extension cord. If the outlets are not in good condition, replacing one or two would be a routine maintenance job which should have no problems attached. Again, have an electrician do it or let the condo or owner take care of it, even if you pay for it. Let it go through their hands and become their liability.

[lakeside53]

Beck : That is correct. You start with the ampacity, then derate (for fill and ambient temp ). For example, 12 awg ampacity is 30amps (if Thhn) but limited to a max of 20 amps; 14 awg Thhn is 20 amp, limited to 15. Derating for fill at normal ambient temps (i.e not attic) is usually of no concern unless you exceed 6 current carrying wires.

However.. the existing wire is 14-3 which you can't add to or modify in conduit anyhow. For temp - all romex has to be considered 60C no matter the internal wire.

Paul : you cannot add an extra wire to a 3 wire romex, in conduit or not.

[Doozer]

It is soooo interesting to me how all you people
(take offense as necessary)
are sooo concerned about
codes, permits, approval, liability, litigation, insurance, inspection,
and burning the effing place down.
Monotheistic civilization started out with 10 basic rules.
Now all the shepherds have made so many rules,
that the sheep are afraid to piss on green grass.
Cost of a light switch, $3.
Cost to install it to the satisfactions of God and country, $3000.

-Doozer

[J Tiers]

Yes, for the smaller wires as here it is. But the existing old wire will most likely NOT be any higher than 60C rated, and it will control all if it so happens that it is not some form of romex. So yes, it could stay at 15A, IF there is no temperature derate.

Reviewing and noticing that this is in the *basement*, probably no temp derate applies. Elsewhere in the house, the 86 deg temp might not apply, and so the 20A ampacity wouldn't either.

Dunno why I thought this was somewher that a temp derate might apply.

[Fasttrack]

Paul : you cannot add an extra wire to a 3 wire romex, in conduit or not.

Well you can do whatever you want if the inspector never sees it...

Code does allow for a separate and appropriately marked safety earth to be run alongside NM cable if the cable does not include a ground conductor (e.g. in old NM cables).

[RichR]

Personally, I would leave whatever has been grandfathered alone. I'm pretty sure once you start to modify it, it is no longer considered to be
grandfathered and you would be require to bring it up to code.

[lakeside53]

Don't assume it ever was to code... no grandfathering unless it was at the time, and was inspected. Also, the AHJ can simply invalidate any so called "grandfathered" work if he thinks it's not suitable for today. Good luck on arguing with them.

As for "code" naysayers... it's not just a collection of moronic ideas - the NEC has been refined for decades and is GOOD. Following it isn't hard; and it's simply for life and fire safety. If you live in a shack in the woods on your own and never have visitors, do what you want, otherwise do it right. Even if you don't get an inspection, do the work as if you would.

[J Tiers]

As for "code" naysayers... it's not just a collection of moronic ideas -

There are a few questionable items (some parts of the "tap rule", for instance)..... but by and large it is reasonable and good to go by.

Of course, the local AHJ does not necessarily have to accept it. Only if the local law accepts it and does not defer to the inspector.

And even if they do by law, they usually have to accept each successive version as it comes up. That isn't always done in a timely manner, so the applicable version may not be the most recent. In fact, it usually is not, for at least a year after it comes out.

[kendall]

Avoid cord issues, if it is just a light, plug into an outlet, install a box for the switch, everything is considered a lamp not a fixture.

[Paul Alciatore]

If this is an apartment or condo, I VERY SERIOUSLY doubt that there is Romex in conduit. No competent electrician would do that. It would cost more. It would be harder to pull. It would not pass inspection at any time in the past that I know of and a commercial building would certainly have been inspected. I doubt that the OP has opened up the boxes to see the wiring and is just assuming it is Romex. It is almost certainly individual wires.

I don't know what the code would say about adding a fourth wire, IN CONDUIT, to a box that is wired with Romex, but if it is on a different phase, then it would work. The neutral and ground in the Romex would function just as well as separate wires for those functions and if it is on the opposite phase, then the current in the neutral would not exceed the original capability of the Romex neutral - as long as we are talking about 15 or 20 Amp circuits. As I said, I DO NOT KNOW what the code or an inspector would say. From a lot of what I have seen done, I would suspect the chances of a QUALIFIED ELECTRICIAN getting away with it are good. And AGAIN, I do not recommend that he do any wiring on his own IN ANY CASE. He must get a licensed electrician.

Beck : That is correct. You start with the ampacity, then derate (for fill and ambient temp ). For example, 12 awg ampacity is 30amps (if Thhn) but limited to a max of 20 amps; 14 awg Thhn is 20 amp, limited to 15. Derating for fill at normal ambient temps (i.e not attic) is usually of no concern unless you exceed 6 current carrying wires.

However.. the existing wire is 14-3 which you can't add to or modify in conduit anyhow. For temp - all romex has to be considered 60C no matter the internal wire.

Paul : you cannot add an extra wire to a 3 wire romex, in conduit or not.