I am installing an infrared sauna and came across an electrical outlet problem. I had two people (one an electrician) check it out and both were stumped on why there are 2 white wires (along with 1 black and the ground). The house is approximately 115 years old and I have lived here 35 years.

It appears one is 14 and the other 12. Someone had put a 25 amp circuit breaker. The electrician recommended replacing it with 15 amp which I have done but also got a blown fuse when having TV on, little electric heater and turned coffeemaker on which i hadn't had happen before. (this circuit is for my den and workout room). I didn't use the heater this morning and no blown fuse. Unfortunately it would be a huge project to rewire so beyond my budget.

But for my own piece of mind and for safety issues, does anyone have ideas why this was done? enter image description hereenter image description here

  • Can you post a photo looking into the back of the box please? – ThreePhaseEel May 29 '19 at 23:15

That 15A breaker and the trip

Remember this: Breakers protect wires. Breakers come between you and wires overheating and starting a fire in your walls where it's almost impossible to put out.

Code is very clear: #14 wire gets a 15A breaker. #12 wire gets a 20A breaker. (NEC 240.4). You are not allowed to put common receptacles on a larger breaker (210.21B3). That is because breakers also protect appliances. A 15A breaker allows 1800 watts (20A allows 2400W).

Appliances which make heat (and have standard plugs) are hard capped at 1500 watts (UL) - and that's not very much, so most heat-making appliances use all of it.

People have no concept of what appliances actually draw -- you use the word "little" to describe the heater, as if that makes it a small draw -- it's a 1500 watt draw. Go look :) Your coffeemaker is probably around that too, since it also wants to heat the water as quickly as possible.

If you're noticing, two heat appliances is 3000W and won't even fit on a 20A breaker. Correct. Heat appliances are like Sauron; they do not share power!

If you need to run 2 large loads, run 2 circuits or position them so they are on different circuits. No way around it!

Some fool had the same problem, and that's why he fit the 25A breaker. Why did it work then, since 25A=3000W and your draw was slightly above that? Breakers operate in "thermal trip" mode, where they allow the overload, allow the wire to heat up, and only trip before the heat becomes dangerous. This scheme depends on the wires being the proper size.

It also depends on Do not immediately reset a breaker after a thermal trip. Wait 10 minutes for the wires to cool off, since breakers cool off faster than wires. Well, okay... the first trip, go ahead and reset immediately but remove some large loads.

"Equal currents" is a basic principle

As you know, current flows in loops. (kinda like hydraulic fluid). Out the hot, back the neutral. These partner wires must travel together in the same cable or conduit. If power goes out to a lamp, the return must come back on the same cable. Why? A bunch of reasons.

First, Unlike hydraulic fluid, electricity throws a large magnetic field - and because it's AC power, this field vibrates. If the wires are tightly bound to each other, the fields cancel each other out and the effect is null. But if the wires are separated at all, it causes physical vibration (damaging the wires) and eddy current heating in metals.

But second, neutrals don't have circuit breakers. It is supposed to be protected by the idea that current on a neutral can only come from its partner hot wire, which does have overcurrent protection.

Third, GFCI detection requires this - they check whether currents are equal to see if any current is leaking or shocking someone.

You are allowed to split; say for a ceiling fan, you can split power to lamp and fan, both returning current on the same neutral. The 3 wires add up, and cancel each other out.

You're usually safe if you physically run cables in a tree fashion -- branches can branch and re-branch, but they can't loop back to another branch.

And there will always be at least 1 partner wire. And the pair (3+?) will always be the same size as each other.

So this neutral wire is an anomaly

Since the electricians looked for other cables in the back of the box, we know this must be a weird single wire that's been bridged over from somewhere else. No doubt that circuit had a problem with its neutral wire, so they "stole" neutral from here. Great: if it's a 15A breaker, then this circuit's neutral can carry 15A + the 25A from your breaker = 40A. That's not good!

My thought is, figure out which neutral is the partner to the hot, and remove and cap off the other one. Treat it like it might be hot; it will be once you remove it, because it will get pulled up to 120V by the appliance trying to return current.

If a nearby switch has a powered switch, it's possible that switch is wired as an old-style "switch loop" and he stole neutral from here. Roll it back to a switch that doesn't require neutral. For instance timer switches that crank (instead of pushing buttons) don't need neutral.

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  • Thank you so much for the info. There was also a 30 amp breaker (14 wire) that they said should be changed out which they did. Very scary that those breakers were in there for so many years. – Darbie May 29 '19 at 18:17
  • Interesting, because single pole breakers are basically useless. The only application I have ever found for them is small campers, though two of them can be handle-tied for an A/C unit or water heater. The same can be said of 25A breakers. – Harper - Reinstate Monica May 29 '19 at 18:19

This is just a guess, but the second white wire could have been run as a repair to a nearby box or to add a neutral to a switch that did not have one. This is not legal (running only a neutral wire on its own), but the sloppiness of the wire connections in your picture point towards a homeowner or handyman doing the work. Black and white wires should always travel together. A ground can be run on its own, but that's the exception.

As far as the tripped breaker - a 15A breaker is the max on any circuit that contains 14ga wire. Running a heater and a coffee maker (another heater) is too much power for a 15A circuit, so it is working as designed. Even a small heater can max out a single 15A circuit.

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  • That is interesting. I know when I bought the place, they had had to update the wiring previously due to the loan they received. Kind of weird as both outlets in that room and one in a hallway were the same.....I haven't checked the other room that is on the same breaker yet. – Darbie May 29 '19 at 16:04
  • So multiple outlets have this second white wire? That is very strange. – JPhi1618 May 29 '19 at 16:05
  • I am sure you can tell I am electricity illiterate which is why I am asking. ;) I take it back on both outlets. I had thought all three were but its not. The one outlet in the "workout" room had the two wires and then the outlet in the neighboring hallway that has a light switch and outlet on it has 2 also. But the other outlet in the "workout" room has just the one. So I would bet someone did something to get the hallway to be a switch/outlet combo? – Darbie May 29 '19 at 18:14
  • Possibly. some switches will have only a hot running to them using a technique known as a "switch loop". That doesn't support an outlet (or a new smart switch) because there is no neutral. That is no longer allowed in new construction because of the issues around not having a neutral, so this could indeed be a workaround. Open up that switch/outlet combo and see if there is a lone white wire coming in the box. – JPhi1618 May 29 '19 at 18:19

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