Circuit Breakers - What is AF & AT?

On engineering documents that refer to molded case circuit breakers, it is common practice to designate the "Frame" and "Trip" sizes of the breaker.

Modern breakers have adjustable or interchangeable trip units, to allow the trip settings to be adjusted to meet the required protective levels.

Your "100AT" designates that the circuit breaker should be configured with a 100 Amp trip unit, or perhaps a trip unit that can be set at 100 Amps.

Depending on the details of the breakers you are using, this 100 Amp Trip breaker will require a frame size of 100 Amps minimum. So, you might see 100AF/100AT, or 250AF/100AT, for example.

The frame size is the designation of the maximum continuous current the breaker can carry, and also an indication of its physical size. A 100 AF breaker will be smaller than a 400 AF breaker.

Frame sizes are determined by what the manufacturer offers in their breaker catalog. Typical values for molded case circuit breaker (MCCB) frame sizes are 100, 250, 400, 600, and 800. Above this size, they go to low voltage power circuit breakers (LVPCB) which are much larger and more expensive.

Cast Resin Transformer Specifications

Some Good Guides for Transformer Losses and Earthing Cross Sectional Area Requirements - Extracted From JKR Specs

 

Comparison of Fluorescent Lamps - T8 vs T5

New TNB Guidelines

Substation_design_booklet.pdf
http://www.mediafire.com/?8iqyy80sppg8791

The handbook of bulk supply interconnection
http://www.mediafire.com/?3xtx9lt252h6ac6

Latest Guidelines For The Fiber To The Premise (FTTP) Guidelines

Kindly find the following links for download of the latest

1) Latast Guidelines Provided By Malaysian Standards
http://www.mediafire.com/?s3x5e1jd5tw5bjj

2) Suggested Single Line Diagram
http://www.mediafire.com/?h8865fidxns24ps

UBBL Excerpts Item 253 Emergency Power Supply System

(3) Emergency systems shall have adequate capacity and rating. for the

emergency operation of all equipment connected to the system including

the simultaneous operation of all fire lifts and one other lift.

(4) All wiring for emergency systems shall be in metal conduit or of fire

resisting mineral insulated cables, laid along areas of least fire risk.

(5) Current supply shall be such that in the event of failure of the normal

supply to or within the building or group of buildings concerned, the

emergency lighting or emergency power, or both emergency lighting and

power will be available within 10 seconds of the interruption of the normal

supply.

More Excerpts From Uniform Building Bylaw

194. Building with single staircase.

A single staircase may be permitted in any building the top most floor

of which does not exceed 12 metres in height:

172. Emergency exit signs.

(1) Storey exits

signs and shall. not be obscured by any decorations, furnishings or other

equipment.

and access to such exits shall be marked by readily visible

(2) A sign reading "KELUAR" with an arrow indicating the direction

shall be placed in every location where the direction of travel to reach the

nearest exit is not immediately apparent.

(3) Every exit

letters not less than 150 millimetres high with the principal strokes of the

letters

a black background.

(4) All exit

occupancy.

sign shall have the word "KELUAR" in plainly legiblenot less than 18 millimetres wide. The lettering shall be in red againstsigns shall be illuminated continuously during periods of

(5) Illuminated signs shall be provided with two electric lamps of not

less than fifteen watts each.

My comments: UBBL needs to updated. We are now using Green signages and LED lights. Does that mean we dont follow BYLAW....need to change this before somone from other parts of the world LAUGH at us!

197. Protected lobbies.

(1) Protected lobbies shall be provided to serve staircases in buildings

exceeding 18 metres above ground level where the staircase enclosures are

not ventilated through external walls.

(2) In buildings exceeding 45 metres above ground level, such protected

lobbies shall be pressurised to meet the requirements of Section 7 of the

Australian Standard 1668, Part I - 1974 or any other system meeting the

functional requirements of the D.G.F.S.

(3) Protected lobbies may be omitted if the staircase enclosures are

198. Ventilation of staircase enclosures.

(1) All staircase enclosures shall be ventilated at each floor or landing

level by either permanent openings or openable windows to the open air

having a free area of not less than 1 square metre per floor.

(2) Openable windows

shall meet the operational requirements of the

D.G.F.S.

(3) In buildings not exceeding three storeys above ground level, staircase

enclosure may be unventilated provided that access to them at all levels

except the top floor is through ventilated lobbies.

199. Ventilation of staircase enclosures in buildings not exceeding 18

metres.

In buildings not exceeding 18 metres above ground level, staircase

enclosures may be unventilated provided that access to them at all levels

except the top floor is through ventilated lobbies and the staircase enclosures

are permanently ventilated at the top with at least 5% of the area of the

enclosures.

200. Ventilation of staircase enclosures in buildings exceeding 18 metres.

For staircases in buildings exceeding 18 metres above ground level that

are not ventilated in accordance with by-law 198, two alternative methods

of preventing the infiltration of smoke into the staircase enclosures may be

permitted by providing-

(a) permanent ventilation at the top of the staircase enclosure of

not less than 5% of the area of the enclosure and in addition at

suitable intervals in the height of the staircase a mechanically

ventilated shaft to achieve not less than 20 air changes per hour

to be automatically activated by a signal from the fire alarm

panel; or

(b) mechanical pressurisation of the staircase enclosure to the

standard of performance as specified in section 7 of the Australian

Standard 1668, Part 1 - 1974 or any other system meeting the

functional requirements of the D.G.F.S.

201. Staircase enclosure below ground level.

All staircase enclosures below ground level shall be provided with

suitable means of preventing the ingress of smoke.

pressurised to meet the requirements of by-law 200.