What Size Wire Do I Need For A 100 Amp Service

When determining feeder conductor size, you'll want to consider the "everyman temperature rating of any connected termination, usher, or device" as per National Electrical Lawmaking (NEC) Commodity 110.14(C).

While the cablevision/wire may be rated at 90°C, you'll probable find that the terminals are rated at 75°C, or not labeled at all. 110.14(C)(1)(a) tells us, that since we're working with 100 amperes or less. Nosotros should use the 60°C cavalcade of Table 310.15(B)(16) to determine the conductor size, unless the equipment is listed and labeled for a higher temperature.

National Electric Code 2014

Article 110 Requirements for Electric Installations

110.14(C)(1) Equipment Provisions. The conclusion of termination provisions of equipment shall be based on 110.fourteen(C)(i)(a) or (C)(one)(b). Unless the equipment is listed and marked otherwise, usher ampacities used in determining equipment termination provisions shall be based on Table 310.15(B)(sixteen) (formerly 310.xvi) as appropriately modified by 310.15(B)(6).

(a) Termination provisions of equipment for circuits rated 100 amperes or less, or marked for fourteen AWG through one AWG conductors, shall exist used only for one of the following:

(1) Conductors rated 60°C (140°F).

(2) Conductors with higher temperature ratings, provided the ampacity of such conductors is determined based on the 60°C (140°F) ampacity of the conductor size used.

(iii) Conductors with higher temperature ratings if the equipment is listed and identified for use with such conductors.

(4) For motors marked with pattern letters B, C, or D, conductors having an insulation rating of 75°C (167°F) or higher shall be permitted to be used, provided the ampacity of such conductors does not exceed the 75°C (167°F) ampacity.

Since the cable volition run from a breaker in the master service panel, to either a breaker or lugs in a subpanel. We take to consider the temperature rating of...

• The conductors
• The terminals in the main panel where the conductors will connect.
• The terminals in the sub panel where the conductors volition connect.

We'll and so employ the lowest value, or 60°C if any of the higher up are not labeled. In one case we know the size of the overcurrent devices, and the lowest temperature rating, we can apply Table 310.15(B)(xvi) to determine the conductor size and cloth we'll need.

This will give usa the current carrying conductor size required for our feeder.

But wait...

If you're working in a i-, two-, or multi-family domicile unit, is Commodity 310.xv(B)(7) applicable?

National Electric Code 2014

Commodity 310 Conductors for Full general Wiring

310.fifteen Ampacities for Conductors Rated 0–2000 Volts.

(B) Tables. Ampacities for conductors rated 0 to 2000 volts shall exist as specified in the Commanded Ampacity Table 310.xv(B)(16) through 310.15(B)(19), and Ampacity Tabular array 310.15(B)(twenty) and Table 310.fifteen(B)(21) every bit modified by (B)(1) through (B)(7).
The temperature correction and adjustment factors shall be permitted to be practical to the ampacity for the temperature rating of the conductor, provided the corrected and adjusted ampacity does not exceed the ampacity for the temperature rating of the termination in accord with the provisions of 110.14(C).

(7) 120/240-Volt, three-Wire, Unmarried-Stage Dwelling Services and Feeders.

(a) For individual dwelling units of ane-family unit, two-family, and multifamily dwellings, conductors, equally listed in Table 310.15(B)(seven), shall be permitted as 120/240-volt, single-phase service-archway conductors and service lateral conductors.

NO.

Detect the codes says

"shall exist permitted equally 120/240-volt, unmarried-stage service-entrance conductors and service lateral conductors ".

After reading the definition of these terms, it'south clear that this does not utilise to the wire betwixt the main console and a subpanel.

Service-Entrance Conductors, Overhead Organization. The service conductors betwixt the terminals of the service equipment and a point unremarkably outside the building, articulate of building walls, where joined by tap or splice to the service drop or overhead service conductors.

Service-Archway Conductors, Underground System. The service conductors between the terminals of the service equipment and the point of connection to the service lateral or secret service conductors.

Service Lateral. The underground conductors between the utility distribution system and the service signal.

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tl;dr

Conductors and all terminals rated at or above 75°C.

Utilize 3 AWG copper or 1 AWG aluminium for the current carrying conductors.

Conductors rated at or above 75°C, terminals rated at lx°C or unlabeled.

Use 1 AWG copper or 1/0 AWG aluminium for the current carrying conductors.

Conductors and terminals rated at lx°C.

Use ane AWG copper or i/0 AWG aluminium for the current carrying conductors.

Conductors rated at 60°C, terminals rated higher than 60°C

Use 1 AWG copper or 1/0 AWG aluminium for the electric current carrying conductors.

What Size Wire Do I Need For A 100 Amp Service,

Source: https://diy.stackexchange.com/questions/29057/what-wire-gauge-do-i-need-for-a-100-amp-subpanel-at-the-end-of-a-60-wire-run

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