Neutral melted insulation on AFCI

[ppainterjl]

Has anyone ever seen or experienced the insulation on an AFCI, the one that connects to the neutral busbar. melting ? The AFCI is for a spare bedroom that is almost never used except for an occasional vacuuming of the carpet. When the vacuum cleaner is used the current draw after start-up is less than 8 amps. The AFCI is a 15 amp. Siemans in a 200 amp residential panel board and the spare bedroom is the only area being served by this AFCI. The insulation melted for a distance of approx. 4 inches beginning at the busbar connection. Any ideas as to why this occurred would be appreciated.

 

[ptonsparky]

Has anyone ever seen or experienced the insulation on an AFCI, the one that connects to the neutral busbar. melting ? The AFCI is for a spare bedroom that is almost never used except for an occasional vacuuming of the carpet. When the vacuum cleaner is used the current draw after start-up is less than 8 amps. The AFCI is a 15 amp. Siemans in a 200 amp residential panel board and the spare bedroom is the only area being served by this AFCI. The insulation melted for a distance of approx. 4 inches beginning at the busbar connection. Any ideas as to why this occurred would be appreciated.

First guess. Improper torquing. Too little or too much.

 

[peter d]

That terminal was never tightened.

 

[mopowr steve]

I've been noticing that the neutral and/or ground terminal bars at times have very tight screws (the tap the machines uses for the screws must be out of spec) and it's hard to tell if the screw is tight against the wire or not.

I wonder how this affects torquing?

Very badly.
The torque resulting from pressure against the wire is less than the applied torque by the amount of any "unloaded" friction of the screw in its socket.
Normally the torque you read is the result of metal to metal friction (unlubricated) with the normal force supplied by the pressure on the end of the screw against the wire.

 

[TobyD]

Most likely it wasn't tightened.Probably someone used a drill driver, and as mentioned the terminal screw never seated on the neutral conductor.I had a neutral bar with a cross bar jumper, in a Siemens load center, that was not seated under the screw terminals.Yes it felt tight.The screws were not tapped correctly.The electrician made up the connections installing the neutral conductors with some on the left side and right.I always land all my neutrals /grounded wires directly on the terminal attached to the incoming neutral grounded wire.And now of course I hand torque the terminals

 

[kwired]

I always land all my neutrals /grounded wires directly on the terminal attached to the incoming neutral grounded wire.And now of course I hand torque the terminals

Where do you land the rest of the conductors once that side is full?

 

[TobyD]

Where do you land the rest ofthe conductors once that side is full?

I actually instal all the grounding conductors on opposite side from the grounded conductors.Siemens ,provides an adequate amount of room and if need be there are tapped holes to add any grounding bar directly to the can..I do this even if on back to back service .The neutrals are all,on,the same side as the incoming neutral grounded wire.

 

[kwired]

I actually instal all the grounding conductors on opposite side from the grounded conductors.Siemens ,provides an adequate amount of room and if need be there are tapped holes to add any grounding bar directly to the can..I do this even if on back to back service .The neutrals are all,on,the same side as the incoming neutral grounded wire.

If it normally works for you then great. Here is a Siemans panel that was used for a short time then removed and is sitting in my shop.



It doesn't even have "split neutral", but there are 20 spaces for breakers, and 20 load terminals on the neutral bus. If this were service equipment and you had 20 circuits with 20 neutrals - there is no place left for a GEC. Also there is only 15 spaces on the EGC bus, though it looks like they are rated to accept up to 3 -14's, 2 - 12's or 2-10's.

 

[TobyD]

If it normally works for you then great. Here is a Siemans panel that was used for a short time then removed and is sitting in my shop.



It doesn't even have "split neutral", but there are 20 spaces for breakers, and 20 load terminals on the neutral bus. If this were service equipment and you had 20 circuits with 20 neutrals - there is no place left for a GEC. Also there is only 15 spaces on the EGC bus, though it looks like they are rated to accept up to 3 -14's, 2 - 12's or 2-10's.

I see why you have asked now.That design isn't like the Siemens that I use.I suppose I have been using Siemens 15 years now,Prior to that I always used SquareD.

 

[kwired]

I see why you have asked now.That design isn't like the Siemens that I use.I suppose I have been using Siemens 15 years now,Prior to that I always used SquareD.

Well it is a Siemens panel, I did not modify it either. I put it next to a panel that was full to add some load. About a year later that panel got upgraded - to a NQO panel with 84 spaces, as a part of a bigger project. I find even on other brands there is not always that many neutral terminals on the 20 or less space panels for some reason, but for 40+ circuit panels there usually is more neutral terminals per ungrounded conductor space in comparison.

 

[peter d]

That's the Siemens ES series. I'm so glad they save $4 in the manufacturing process by eliminating the second ground/neutral bar on the other side. :roll:

 

[kwired]

That's the Siemens ES series. I'm so glad they save $4 in the manufacturing process by eliminating the second ground/neutral bar on the other side. :roll:

My experience with many of their products is they seem to like to save money by eliminating things in the manufacturing process.

Pump panels which there is a lot of around this area - Siemens are less cost then most others not by a whole lot but just enough to make them attractive based on price. I will say I have more service calls for problems with the Siemens pump panels then the Square D or Allen Bradley pump panels which are the next two most popular ones in the area. Failed coils on the contactors and failed electronic overload units seem to be most popular failures with them as well.