Need some input

I was doing a practice inspection of my brother’s house yesterday, and some electrical issues popped up. First, the main panel has multiple cases of double tapped grounded and grounding conductors Sorry, my picture is too large to upload. The issues he is having is frequent AFCI tripping in one bedroom, light bulb exploding multiple times in one bathroom 100W bulbs fixture rated for 660 W. Several of the circuts showed a voltage drop of 7-8% but they were not in the rooms of concern. Obviously, this needs to be looked at by an electrician, but just wanted to get some of your thoughts for an overall explanation.

Hi Jackie,
Welcome to NACHI and the world of home inspection.:smiley:

Grounding ( A.K.A green grounding conductors, branch circuit), two conductors, I believe can share a connection point under a screw on the “neutral” bus in the main service panel. Since there really is no current flow until something really goes wrong it’s allowable. We’ll get some feedback from the board “sparkies” as they are referred to shortly.:wink:

Grounded conductors (A.K.A Neutral or white wires) should never share a point on the bus under one screw since these have current flowing back to the panel. One conductor per screw. Tight is right loose will cause arching…

Is the Main service panel clean? No burned wires or breakers , smoke, melting or other signs of trouble? How old is the panel , what brand , type? Some brands are known for trouble : Zinco, FPE , Bulldog pushmatics…

Did you check the service entrance conductors outside? From electrical pole to the house?
Maybe you can’t see that since a lateral ,underground cable ,could be the connection to house.:wink:
Anyway if there are three conductors connected (visible) that a good starting point with a nice drip loop not under strain by tree branches.

None should be loose and free floating like the neutral (usually used for strain relief too) If that would be the case then you would end up having only 240 volt service to the service panel. Blowing light bulbs is condition of this…
Could be one of many factors here. Remember 120 volts is from one side of “hot” conductors to ground if by some reason that the neutral conductor is disconnected you may have 240V only in the house . Lights get really bright and then blow at some point.

How about checking receptacles with some test equipment in the bedroom to see what you have there.
The push is for new homes to have Arc Fault circuit interruptors AFCI’s to kill the power when arcing is detected nowadays in the bedroom circuit only.
Investigate what is plugged in the bedroom and connected the ceiling boxes. Is there a Ceiling fan with a dimmer that is wrong. Do the lights require something special when it comes to bulbs.

It could also be a floating neutral (grounded) conductor somewhere . Loose arching in a box or poor connection with a wire nut in a junction box… It may take some time to find out what is causing it but arcing is dangerous and will cause home fires, so stress the importance of having a electrician / contractor/ sparkie fix it ASAP.:smiley:

Investigate but Stay safe…Be careful around electricity!!:wink: When in doubt always consider it hot and test before you touch anything.

AFCI’s will trip frequently when used in a multiwire circuit with a shared neutral, even if no problems exist.

I’m not sure if there has been an AFCI breaker developed yet that corrects this issue, but it’s likely that these will need to be rewired.

The exploding light bulbs are a new one to me. Sounds like the POCO may have a surge problem.

Hmmm…I think I missed something as when I read the message it did not say anything about a multiwire circuit…I will read it again…

But I will tell you multiwire circuits on AFCI’s is a no-no…the AFCI can’t do its job correctly in this manner…due to the different phases of the HOT lines…to a shared neutral will cause issues.

I am not aware of any new product that will allow this. Multiwire circuits are not for the beginner…they should only be done with guidence and caution.

As for the exploding light bulb, most cerainly sounds to me like an isoloated issue or a POCO surge issue…did anything ELSE in the house suffer any damage…

While you are doing a practice inspection…learn first hand that it is easier to defer things you can’t explain versus trying to explain it…just may serve you later in your career as good advice…I know I HEED it now and then.

That was just a guess Paul, as to the comment about the AFCI tripping frequently.

Ahhh…got ya Jeff…I thought I was seeing things…YOU are right fella…someone goes messing in the panel on a multiwire circuit and whamo…240V to the light bulb…Just might POP her…lol

Ta DA… Board sparkies Amazing… :smiley:


A high resistance neutral connection at the fixture can cause lamps to explode, BTDT. It can be at the splice or at the lampholder rivets. Is this a porcelain lampholder?

Thanks, I appreciate all the input. I wish I could have gotten the picture to load, the house is less than a year old, great looking Sieman’s box (minus the double tapped grounded conductors). Nothing else in the house suffered any damage, the bulb is in a vanity lighting fixture in the bathroom. The service entrance is lateral, so I can’t comment on its condition. I have never heard the term POCO surge, what is it?

The bedroom voltage readings for volts, voltage drop, and wiring were all normal, other areas of the house did register up to an 8% voltage drop. All of the AFCI’s tested properly. Again, the only abnormal indictions were one bedroom AFCI trips frequently, multiple instances thoughout the house of voltage drop of 7-8%, and double tapped grounded conductors. As far as the loads are concerned, a typical ceiling fan is in the room but it is on an on/off switch not a dimmer, two outlets have one plug in them. I have already deferred to an electrician, once I hear an explanation I’ll pass it on.

I forgot to add that I have found out that many of his neighbors have problems with the AFCI’s tripping frequently.

More information wanted what is the incomming voltage Hot to hot and hot to neutral both legs. . Also check hot to Grnd is it the same as hot to neutral .
You say there is a voltage drop is that with load and what was the load and what is the distance from the panel. Size of wire to the bed rooms did you check the voltage in the bath room with and with out the load on the circuits that had the voltage drop during the test.
Roy Sr …

122 volts incomming hot to neutral, did not check hot to ground.

The voltage drop was without any load on the circuit, the wire was #12 copper, about 40-50 feet from the panel. To make matters more confusing the bathroom checked normal.

Good read.

Did not want to insert two pages.

Power Company

Ahh, so obvious now. Thanks

Great info, thanks!

Just thought I’d give you a quick update, went back to my brother’s house today and he asked me to look at his fireplace, well the pilot light was not lit, so I reached down to light it and ZAP as soon as I touched the metal exterior of the firebox I got a little shock. Whenever the wall switch is on, the entire firebox is hot. If he didn’t believe me about a licensed electrician before, he does now.