Incorrect voltage at light sockets

Question

Light bulbs on our kitchen lighting circuit need frequent replacing (lasting only a few months.) All other circuits in the house behave normally. There are three switch legs on this circuit:

1. 6 recessed lights, on a 3-way switch, with LED bulbs. Distance from switch to first light is ~10'. Each can is ~3' from the next.
2. 5 pendant lights, on a single dimmer, incandescent bulbs. Distance from switch to first light is ~15'. Pendants are ~3' apart and ~5.5' long.
3. Chandelier with 5 light sockets, on a single dimmer, incandescent bulbs. Distance from switch to light fixture is ~15'. Light sockets are ~6' from ceiling.

An electrician came out and discovered that the voltage at each switch is 120v, yet each light socket only reads 113v. The electrician checked in the attic and didn't see anything odd; the wires looked fine, no extraneous junction boxes, no damage, etc... The advice was to try out bulbs rated for 110v instead of 120v or re-run the switch legs.

What could cause such a voltage drop over short runs and three distinct switch legs? Do I have any other options besides the two offered by the electrician?

Answer 1

It's a floating neutral.

But it's only the one circuit.

Find, re-strip, re-splice, and tighten down all of that circuit's neutral connections. If it goes directly through an outlet, pigtail it.

Answer 2

In residential interior wiring, voltage irregularities generally are only a concern when over-voltages are seen and not under-voltages. Incidentally however, when there is an under-voltage, there is usually an over-voltage on the opposite phase somewhere else to balance it out.

113V is fine. Light bulbs, except for the LEDs, are pure resistive loads and will not burn up from under-voltages. Now 130V would be a problem if the bulb is not rated for 130V.

I would also consider hiring a different electrician as what he suggested is nonsense.

Answer 3

Everything you are saying depends on where the electrician checked the voltages. Dimmers will affect the voltages on the load side. So did the electrician check for voltage drop across the dimmers themselves? If there is a drop it would be there. The other thing that causes abnormal voltage drop are joints not making a solid electrical connection. So look for loose wires or corrosion or anything that would cause the drop at connection and splices. On the least likely side you might check to see if the circuits cross an area that produces a high amount of heat. The only thing a 113V load would do to an incandescent is make the lamp put out less light and actually burn cooler.

I know this may sound a little snobbish but we have found the main reason incandescent lights burn out at an abnormal rate is that they are poorly manufactured lamps. The other main reason is a lot of surges from the utility company. Such as when you are in a new development and there is construction all around you. In construction, before energy management codes took effect we installed incandescent lamps using 130V filaments. It's a heavier filament and does not burn out for a long time. Unfortunately these are not available to the normal consumer and all the advertising about longer lasting lamps you see on the labels from retail outlets are generally hogwash. I know since over the years I and the companies I have owned and worked for have bought every style imaginable only to find there are no noticeable changes in longevity worth the extra cost.

You might try going to LED but if you do make sure your dimmers match.

Hope this helps.

Answer 4

Many LED lights are not equipped to deal with dimmers and those that are need dimmers rated for LED loads. Since you replaced the existing bulbs with LEDs I bet you have the wrong dimmers. Further since you mentioned a seven volt drop over a short distance I bet you have really old dimmers as newer dimmers do not show a voltage drop when full on. I would recommend one of the following:

• go back to incandescent bulbs.
• replace the dimmers with switches.
• replace both dimmers and led fixtures with ones known to work together.
• replace the dimmers with blank plates and use self dimming bulbs.

Answer 5

1. As mentioned above check the wiring for a floating neutral, bad grounds via a polarity checker.
2. You might also be getting spikes on the line from anything with a motor eg: an appliance (particularly an old appliance) or treadmill :)
3. Check each socket for rust or corrosion
4. Check each ground for rust, corrosion or loose connection
5. Go to the fuse box and pull the the fuse or breaker (electrician required :)

Note, IMHO, 80% of electrical issues are due to rust or corrosion.

Note, Note, RESPECT electricity and turn OFF the circuit before any cleaning, removal, etc.