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What is the Difference Between Dry, Wet, and Damp Locations?

(NEC) National Electric Code Definitions: UL Standard 1598 Definitions:

Dry Locations: A location not normally subject to dampness or wetness. A location classified as dry may be temporarily subject to dampness or wetness, as in the case of a building under construction.

Damp Location: Locations protected from weather and not subject to saturation with water or other liquids but subject to moderate degrees of moisture. Examples of such locations include partially protected locations
under canopies, marquees, roofed open porches, and like locations, and interior locations subject to moderated degrees of moisture, such as some basements, some barns, and some cold storage buildings.

Wet Locations: Installations underground or in concrete slabs or masonry in direct contact with the earth; in locations subject to saturation with water or other liquids, such as in vehicle washing areas; and in
unprotected locations exposed to the weather.


UL Standard 1598 Definitions:


Dry Locations: A location not normally subject to dampness, but may include a location subject to temporary dampness, as in the case of a building under construction, provided ventilation is adequate to prevent
an accumulation of moisture.

Damp Location: An exterior or interior location that is normally or periodically subject to condensation of moisture in, on, or adjacent to, electrical equipment, and includes partially protected locations.

Wet Locations: A location in which water or other liquid can drip, splash, or flow on or against electrical equipment. A wet location luminaire shall be constructed to prevent the accumulation of water on live parts, electrical components, or conductors not identified for use in contact with water. A luminaire that permits water to enter the luminaire (during the rain test of Clause 16.5.2 or the sprinkler test of Clause 16.5.3) shall be provided with a drain hole (Clause 13.4.3).

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Elements of the IP Code and their meanings

A brief description of the IP Code elements is given in the following chart (see Fig. E67).

What is the external influences IEC 60364-5-51 ?

Each condition of external influence is designated by a code comprising a group of two capital letters and a number as follows:

First letter (A, B or C)

The first letter relates to the general category of external influence:

    A = environment
    B = utilisation
    C = construction of buildings

Second letter

The second letter relates to the nature of the external influence.
Number

The number relates to the class within each external influence.
Additional letter (optional)

Used only if the effective protection of persons is greater than that indicated by the first IP digit.

When only the protection of persons is to be specified, the two digits of the IP code are replaced by the X's.

Example: IP XXB.

Example

For example the code AC2 signifies:

A = environment
AC = environment-altitude
AC2 = environment-altitude > 2,000 m













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Flat cables twisting problems and solutions

If you want less rotation, the winding angle should be narrow.

501.10(B)(1) Wiring Methods. Class I, Division 2.,

Code Change Summary: Changes were made to the allowable wiring methods used in a Class I Division 2 location.

Article 501 is all about Class I hazardous locations. The Class represents the type of flammable material, whereas the Division represents the conditions where the flammable materials are used or stored and the likelihood of the flammable material being present.

Examples of Class I locations include fuel dispensing, spray booths where volatile flammable solvents are used, gas generator rooms and other portions of gas manufacturing plants where flammable gas may escape.

Section 501.10(A) specifies all of the types of wiring methods permitted to be used in a Class I Division 1 hazardous location. Those methods are also permitted to be used in a Class I Division 2 location which is less restrictive than a Division 1 location. Two of the allowable wiring methods for a Class I Division 1 location are threaded rigid metal conduit (RMC) and threaded steel intermediate metal conduit (IMC).

In the 2017 NEC, revisions were made to 501.10(B), pertaining to Class I Division 2 locations, to allow RMC and IMC with listed threadless fittings. Requiring only threaded fittings as in 501.10(A) was too restrictive since many cable types permitted in Class I Division 2 locations were only required to use listed fittings. Many listed cable fittings are threadless and permitted in Class I Division 2 locations.

Another change was the addition of Cablebus to the permitted wiring methods in a Class I Division 2 location. Cablebus is similar to cable tray with spacers between the conductors. Since tray cable is allowed in a Class I, Division 2 location, there is no reason a cablebus with insulated cables shouldnt also be allowed.

Below is a preview of the NEC. See the actual NEC® text at You are not allowed to view links. Register or Login for the complete code section. Once there, click on their link to free access to the 2017 NEC® edition of NFPA 70.

2014 Code Language: 501.10(B) Class I, Division 2.

(1) General. In Class I, Division 2 locations, the following wiring methods shall be permitted:

(1) All wiring methods permitted in 501.10(A).

(2) Enclosed gasketed busways and enclosed gasketed wireways.

(3) Type PLTC and Type PLTC-ER cable (see NEC® text for remainder).

(4) Type ITC and Type ITC-ER cable as permitted in 727.4 and terminated with listed fittings.

(5) Type MC, MV, TC, or TC-ER cable (see NEC® text for remainder).

(6) In industrial establishments with restricted public access (see NEC® text for remainder).

(7) Optical fiber cable Types OFNP, OFCP, OFNR, OFCR, OFNG, OFCG, OFN, and OFC (see NEC® text for remainder).


2017 Code Language:501.10(B) Class I, Division 2.

(1) General. In Class I, Division 2 locations, all wiring methods permitted in 501.10(A) and the following wiring methods shall be permitted:

(1) Rigid metal conduit (RMC) and intermediate metal conduit (IMC) with listed threadless fittings.

(2) Enclosed gasketed busways and enclosed gasketed wireways.

(3) Type PLTC and Type PLTC-ER cable in accordance with the provisions of Article 725, including installation in cable tray systems. The cable shall be terminated with listed fittings.

(4) Type ITC and Type ITC-ER cable as permitted in 727.4 and terminated with listed fittings.

(5) Type MC, MV, TC, or TC-ER cable, including installation in cable tray systems. The cable shall be terminated with listed fittings.

(6) In industrial establishments with restricted public access (see NEC® text for remainder).

(7) Optical fiber cable Types OFNP, OFCP, OFNR, OFCR, OFNG, OFCG, OFN, and OFC (see NEC® text for remainder).

( Cablebus.

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Basis of Calculation Capacitance of Cables, Charging Current, and Charging Reactive Power

Where:
C = Total capacitance of the cable (microfarads)            Icharge = Charging current of the cable
SIC = Dielectric constant of the cable insulation (Table-3)    D = Diameter over the insulation (in)
d = Diameter of the conductor (in)                            VLL = System operating voltage in (kV)
f = System operating frequency (Hz)                            L = Length of the Cable in Feet
Icharge = Charging current (amps)                            KVARcharge = Single-phase KVAR or charging VARs per cable







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What is L/R Time Constant.
When a short-circuit occurs across the terminals of a DC circuit, the current rises from the load current (y In) to the short-circuit current Isc over a period of time that depends on the value of the resistance R and inductance L of the short-circuited loop.

The equation determining the current in the loop is:
U = Ri + L Di/Dt

The curve of I versus time is defined (neglecting In) by the equation:
I= Isc (1 - exp(t/t))
where t = L/R is the time constant for the rise to Isc.

Practically speaking, after a time t = 3t, the short-circuit is considered to be established, because the value of exp(-3) = 0.05 is negligible compared to 1 (see the
curve opposite).

The lower the time constant (e.g. battery circuit), the shorter the time required for the current to rise to Isc.

To express breaking capacity, the interrupted short-circuit current with the following time constants is used:
L/R = 5 ms, fast short-circuit
L/R = 15 ms, standardised value used in standard IEC 60947-2
L/R = 30 ms, slow short-circuit.

What is the Bird Caging effect in the wire?

A bird caging is a short section of rope in which the outer strands are much longer than the rope.