# What's neutral wire size should I use ?

#### meowsoft

Joined Feb 27, 2021
353
What's neutral wire size should I use, when use two 16mm2 wire in parallel for phase wire, 16mm2 wire capacity is 80a, that system is single-phase, can I use 25mm2 wire for neutral ?, 25mm2 is 105a, 35mm2 is 130a, and 50mm2 is 160a, electrical load is 100a

#### meowsoft

Joined Feb 27, 2021
353
or better to use same wire size ?, two 16mm2 wire in parallel for neutral ?

#### meowsoft

Joined Feb 27, 2021
353

#### meowsoft

Joined Feb 27, 2021
353
Note : Use Parallel wire is allowed, but it's recommended to use same sectional area and type
2x16 is also same insulated triple insulation and I think's also same resistance, capacity is same, 80a per core, this is underground cable with two core
1x16 is 108a per core, insulation is only two, because this is underground cable with one core
3x16 that used by phase wire is 80a per core, also underground cable with two core
1x35 is 160a per core, insulation is only two
Is use 3x16 (for phase) and 2x16 (for neutral) is best solutions ?, or 3x16 (for phase) and 1x35 (for neutral) ?
one core in 3x16 isn't used, is allocated if we upgrade capacity to three phase 3x50a, also if we moved to 3x50a from 1x100a, we plan to still used thicker neutral, because majority load is single phase, also harmonics problem, move to 3x50a is planned to about next year

can we have problem's if use bigger neutral is single phase ?, can phase wire be burnt ?

#### Ramussons

Joined May 3, 2013
940
In a Single Phase setup, the Neutral wire will carry the same current as the Phase wire. So the Area of both should be the same, whatever be the combination. (The Neutral wire can have a larger area, no harm done).

The Maximum working Load Current should be <= Current carrying Capacity of the Phase / Neutral wire.

#### GetDeviceInfo

Joined Jun 7, 2009
1,844

Joined Jul 18, 2013
22,841
Each supply conductor should be of the same gauge.
i.e. The neutral conductor should always be the same gauge as the line.
Same goes for GND conductor.

#### BobaMosfet

Joined Jul 1, 2009
1,636
@meowsoft

Wire ampacity per electrical code (whether North American or Canadian), is not based on what the conductor can actually carry. The numbers given in the local code tables are very conservative (for a reason). Such ratings are actually designed around the things around the wire- those things that can burn/flame. Insulation, breakers, etc. Don't run more amperage than your breakers, fuses, etc, can handle- in conjunction with knowing what your upstream/downstream can handle as well.

I recently had to evaluate such codes and reverse engineer the mathematics behind how such standards are derived, because (from an engineering standpoint), such tables are useless when dealing with wire gauges and materials that are NOT covered by such tables. One must know specific resistivity, conductivity, thermal limits, derating, electron counts and all matter of physics related aspects into order to generate the equations to empirically determine how much current a conductor can actually handle before it will melt, as well as what it would handle if using the same rules of thumb the standards bodies use.

Having said that, you are limited to using what the local codes require (for liability & safety reasons), and as @MaxHeadRoom said, it is safest to use the same gauge as the line.

Joined Jul 18, 2013
22,841
Also not permitted to use a wire gauge of smaller amerage rating than that of any protection device it is fed from.

#### meowsoft

Joined Feb 27, 2021
353
Also not permitted to use a wire gauge of smaller amerage rating than that of any protection device it is fed from.
Yes... I use two 16mm core wire in parallel (inside underground cable with three core, 1 core isn't used) for phase wire, each capacity is 80a, x2 80 capacity is 160a
1. Can I use one 1x 35mm with 130a capacity ?, but load is only limited at 100a
2. Can I use one 1x 16mm wire (1x 16mm single core underground cable is rated at 100a, ONE CORE, NOT THREE CORE like number one) ?

Joined Jul 18, 2013
22,841
The wire gauge can be larger than the current required and the size of protection device.

#### GetDeviceInfo

Joined Jun 7, 2009
1,844
Also not permitted to use a wire gauge of smaller amerage rating than that of any protection device it is fed from.
While I generally agree with this, there are allowable exceptions. Motors, transformers, and capacitors come to mind. The myriad of conditions that derate ampacity, specifics around paralleling conductors, industry and geographical application of codes, suggest that the OP has come to the wrong place for answers.

Joined Jul 18, 2013
22,841
Also not permitted to use a wire gauge of smaller amerage rating than that of any protection device it is fed from.
I am just quoting the code that applies to most of N.A.

#### shortbus

Joined Sep 30, 2009
8,468
I am just quoting the code that applies to most of N.A.
But the TS is from China, don't know why he doesn't access the electrical codes there.

Joined Jul 18, 2013
22,841
But the TS is from China, don't know why he doesn't access the electrical codes there.
Do they have them there?

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,634
Country? Distance? Ring main (uk)? Attached/detached structure (NEC)? Continuous load (NEC)?

#### meowsoft

Joined Feb 27, 2021
353
Country? Distance? Ring main (uk)? Attached/detached structure (NEC)? Continuous load (NEC)?
Beijing, China / PRC, Please Read Carefully all information was specified, in local code all continuous and non continuous treated as same, all capacity need's is 125%

#### click_here

Joined Sep 22, 2020
96

#### Wendy

Joined Mar 24, 2008
22,367
There should be no difference in wire size between hot and Neutral. Ground should be the same too. Just my 2¢.