> size neutral for harmonic load

[ron]

We've heard of triplen harmonics adding on the neutral (grounded conductor) causing some folks to request increasing the size of the grounded conductor as compared to the phase conductors in a three phase four wire circuit.
How about harmonics present in a 120V circuit? I have someone telling me that the reduced impedance in a larger grounded conductor will help reduce the harmonic draw of the load.

 

[winnie]

_Reduced_ impedance in the source will permit the load to draw _greater_ harmonic current, however it will reduce the _voltage_ distortion (voltage harmonics) caused by the harmonic current.

I doubt that an increased neutral will make a significant difference in the harmonic current flow.

If this is a 120V two wire circuit, the harmonic current on the phase conductor will exactly match the harmonic current on the grounded conductor.

-Jon

 

[ron]

Jon,
I agree. I'm hoping someone has the opposing opinion so I could understand that perspective too.

 

[sparky59]

have you noticed how the companies that sell wire are always talking about this big harmonics problem. (always increase your neutral.... and whatever you do....don't use the conduit for the EGC.)

 

[robbietan]

in a residential circuit, I would NOT recommend sizing the neutral bigger than the 'hot' wire.

increased neutrals are useful for 3 phase circuits full of single phase non linear loads. this is where the 'increased' neutral comes in. But in increasing the neutral, it is because of the olde practice of having the neutral conductor a shade smaller than the 'hot' conductors. in essence, it just says that the neutral should have the same size as the 'hot' wires.