- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
It took almost 20 posts before you actually asked the question we can answer. lol.
Neutrals in parallel
- Thread starter domnic
- Start date
Frank DuVal
Senior Member
- Occupation
- Electrical Contractor, Electrical Engineer
Where does one buy THHN that is also not rated THWN? 
ptonsparky
Tom
- Occupation
- EC - retired
Refer to post 13.
What do you not understand about overloading of one conductor? Overload usually shows up in overheating. Overheating can cause damage which leads to additional heating, etc..
ptonsparky
Tom
- Occupation
- EC - retired
I don't think I've ever seen it.Where does one buy THHN that is also not rated THWN?
Tulsa Electrician
Senior Member
- Location
- Tulsa
- Occupation
- Electrician
Please confirm.
Your question is a #3 and #6 in parallel for a service netural. Also please include the ungrounded conductor size and service size in amps. For the hypothetical question.
Your question is a #3 and #6 in parallel for a service netural. Also please include the ungrounded conductor size and service size in amps. For the hypothetical question.
Eddie702
Licensed Electrician
- Location
- Western Massachusetts
- Occupation
- Electrician
I realize all the wire like THHN/THWN/MTW is dual rated or triple rated but it has not always been that way.
I just wish when people say THHN and they are underground or outdoors it leads me to believe they don' know what the W means.
Also, if I am not mistaken THHN dry is 90C and THWN wet location is 75C so it makes a difference on de rating as well
I just wish when people say THHN and they are underground or outdoors it leads me to believe they don' know what the W means.
Also, if I am not mistaken THHN dry is 90C and THWN wet location is 75C so it makes a difference on de rating as well
EMF issues because of parallel neutral , what problem could it cause ?
ptonsparky
Tom
- Occupation
- EC - retired
Supposedly health issues but you would have to be between the conductors. Maybe in electronics.
what i want to know is what is the problem with using two neutral wires of different sizes for a 100 amp service #6 and #3 the neutrals would be in parallel . what electrical problem could this cause ( hypothetical Queston )
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
This is too much of an open question.
Are you concerned about an intentional parallel installation or an inadvertent one?
Are you worried about inductive heating or EMF if the paralleled conductors are not following the same path?
Do you want to know how the currents are shared and any possible impact on their load carrying capacity?
ALL i want to know is what problem it could cause. if any !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Overheating of the smaller conductor.
ptonsparky
Tom
- Occupation
- EC - retired
We've told you what it could do. It does not mean it will!
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
My question was a list of possible concerns.
You need to tell us more of the hypothetical conditions. Are the conductors run in the same magnetic conduit and with their respective ungrounded conductors? Are the conductors in an NM cable with different routing and lengths?
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I envisioned a typical residential service where someone mistakenly installed an EGC to the meter.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
For normal conditions (no faults) and equal lengths, it's more likely the larger conductor will overheat. And of course that depends on how you have protected the unequal parallel conductors.
E.g. #3 AWG (100A 75C ampacity for Cu) has twice the area of #6 (65A 75C ampacity for Cu), and hence twice the conductance, half the resistance. If you paralleled them in equal lengths, the current would divide 2:1. So if you tried to protect them at the sum of their ampacities, 165A, then you'd get 110A on the #3 and 55A on the #6. The #3 is seeing in excess of its ampacity, while the #6 is still below its ampacity.
If you protect the pair at a lower value, say 100A, or even just protect the #3 at 100A, with no OCPD on the #6 (other than the fact that it will always see only half the current on the #3), then you can't overload either conductor without the OCPD seeing more current than it is rated for. Again, that's for equal length and no faults.
So I think the technical reasons to avoid such paralleling have to do with behavior in faults .
Cheers, Wayne
kwired
Electron manager
- Location
- NE Nebraska
Most if not all of it today also has THWN-2 designation which can be used at 90C for wet locations.
kwired
Electron manager
- Location
- NE Nebraska
Most instances probably little to none. The neutral only carries imbalanced current of the ungrounded conductors, your typical 100 amp dwelling service may not ever see over 30 or 40 amps on the neutral. If you actually had 100 amps of neutral load it would divide between the two paths, but since they are different size and different resistance it won't divide equally. I seriously doubt the #6 draws enough to overload it though. Would have to loose the #3 altogether for the #6 to carry all the current.
ptonsparky
Tom
- Occupation
- EC - retired
These are theoretically paralleled neutral conductors so the chance of them seeing any thing over their ampacity would be only during fault condition.