Specifications

NAIROBI OPERATIONAL HUB
UNOPS Building, UN Lane, Off UN Avenue Tel: [phone]
P.O Box 783,Village Market, 00621 E-mail: [e-mail]
Nairobi, Kenya Website: www.unops.org
UNOPS is ISO 9001 certified
mentioned on the drawings. MCB can be reverse fed without reduction in
performance. Trip setting as indicated on the schedules of points. The
MCB shall have thermal overload trip to accept 5% overload and to trip at
30% of rated current as per IEC 947-2. The instantaneous magnetic trip
shall operate at 5 to 10 times the rated current for 1P, 2P, 3P or 4P
breakers. It shall be possible to replace 3 single phase units with one 3
phase unit. The breakers shall be of current limiting type (DIN type). The
quick lag type breakers (QL/plug in type) are not acceptable. Evidence of
the ultimate breaking capacity (Icu) shall be produced by test certificates
from one of the internationally recognized High Voltage Laboratories
(ASTA, CESI, ESEF/ASEFA, KEMA, PEHLA or SATS).
The operating mechanism shall be mechanically trip free from the
operating handle so as to prevent the contacts from being held closed
against short circuit and overload conditions. It shall be “automatic
resetting type”. The individual operating mechanism of each pole of a
multi pole MCB shall be directly linked within the MCB casing and not by
operating handles. The operating handle shall be of the toggle type with
possibility of padlocking facility and rotary handle. Each pole shall be
provided with bi-metallic thermal element for overload protection and
magnetic element for short circuit protection. Current discriminations
tables shall be provided for each rating of the breaker. The terminals shall
be of the tunnel type (IP 20) in order to minimize the risk of direct contact.
It shall be possible to fit on site auxiliaries like shunt trip coil,
undervoltage release, ON-OFF switch, alarm switch or residual current
device 30 or 300 mA with remote tripping possibility.
The term ‘rcb’ /’rcbo’ shall denote an mcb with built-in earth leakage
protection.
H. RESIDUAL CURRENT CIRCUIT BREAKER (RCCB)
RCCB shall comply with CEE 227 or IEC 1008 standards. The RCCB
shall provide the functions of isolation, switching and earth leakage
protection of electrical circuits.They shall have a residual current operated
electromechanical release which operates without auxiliary source of
supply to an earth leakage fault between active conductors and earth.
RCCBs shall incorporate a filtering device preventing the risk of unwanted
tripping due transient voltage. They shall provide a high degree of
protection against earth faults, fire hazards and electric shock.