THHN/THWN-2 is a type of building wire. This means it is used inside the building or house. THHN/THWN-2 is made of flame retardant PVC that self-extinguishes flame.

Solid conductor is used for simple circuits.
Stranded conductor is used for circuits that has complex runs. Stranded wires are more flexible than solid wires.

This is usually computed by a designer, however there is a typical rule-of-thumb that is used:

  • 2.0mm2 : small lighting, lighting switches
  • 3.5mm2 : multiple lighting (around 20 lights per line), convenience outlet (CO) (6-10 COs depending on the design and expected load)
    Usual CO rating is 180Watts/CO.

    • Though 3.5mm2 is rated more than the additional rating as mentioned, Voltage Drop should also
      be considered. More lighting or CO’s means longer wire length that also means bigger voltage drop.
  • 5.5mm2 : motor loads and air-conditioner
    • 1HP motor = 8 amperes
    • 1.5HP motor = 10 amperes
    • Though running amp is small, motors have very high starting current. Around 3 times of its rated amp rating
  • 8.0mm2 and bigger : feeder lines, bigger loads like (commercial and industrial applications), malls air conditioning system (FCU, CHW Pumps), pumps, elevators, escalators

Minimum feeder size is 5.5mm2 but actual load should be computed to know the proper sizing of wire.

There is no specific number of years that dictates rewiring schedules. However, by visually inspecting the wire, rewiring may be done if you see that the PVC color is fading or cracks appear in the insulation.

THHN/THWN-2 is rated 600V. This means it can accommodate both 110 or 220V.

Theoretical computation can be done:
2.0mm2 = 24kg/km
3.5mm2 = 37kg/km
5.5mm2 = 58kg/km
8.0mm2 = 96kg/km
14mm2 = 147kg/km
22mm2 = 232kg/km
30mm2 = 311kg/km
38mm2 = 414kg/km

Fumes will be released, then its insulation will melt. When the melted insulation touches other materials in the line, it can cause fire.

There is no such thing as a 70ºC wire. The usual ratings are 60ºC, 75ºC, and 90ºC. Failure that can lead to fire is a possibility when the wire is not properly used.

Usually used for low cost housing because it is made of 2 TW cables with jacket

No need to use wire cladding.

Meralco uses it as service drop cable. With its construction, it lessens power pilferage (anti-theft cable).

Designed for use in portable and movable tools and equipment, portable appliances, small motors and associated machinery

There is a wide variety of electrical wires – typical standard wires, and wires made for special cases. Phelps Dodge has the largest manufacturing capability in the country to produce different kinds of wire, for different needs.

Use Aluminum polyethylene (PE) wires, because aluminum is lighter, and PE is sunlight and weather resistant.

Look for the seal, weigh the box, match the color.


– How to tell fake wires guide