TECHNICAL DATA SHEET Sentry Miniature Circuit Breakers 1:3 Sentry MCBs Description Sentry MCBs are of the thermo-magnetic, Modes of operation PRODUCT RANGE current limiting type and are available with The mechanism of the Sentry MCB has been Type B Single pole Rating either Type B or Type C operating characteristics. carefully designed and engineered using ther- 5903s 3A The operating dolly may be locked in either mal and magnetic elements to detect over- the ON or OFF position without affecting the currents due to both overload and fault 5906s 6A ability of the trip mechanism to operate. The currents. The MCB will operate and interrupt the 5910s 10A contacts themselves are manufactured from supply to prevent damage to the installation. 5916s 16A carefully chosen materials, selected specifically The thermal component is a carefully cali- for their low electrical resistance and low 5920s 20A brated, thermally operated bi-metal element. propensity to weld under fault conditions. 5932s 32A Larger overloads and fault current situations Positive contact status indication 5940s 40A are dealt with using the magnetic tripping When the green portion of the dolly is visible, mode of the MCB. This acts very quickly, 5945s 45A then a contact gap of 4mm has been achieved. overriding the thermal operation. 5950s 50A Sentry MCBs may therefore be used as single BS EN 60898 requires the tripping to occur Type C Single pole Rating pole isolating switches where appropriate. within 100 milliseconds and the design of the 8703s 3A Terminals Sentry MCB allows fault currents of up to 8706s 6A 6000A (M6) to be safely interrupted well The Sentry MCB features tunnel terminals of within this time scale. 8710s 10A 2 generous capacity, with 25mm on ratings up 2 8716s 16A to and including 20A, and 35mm on all Operating characteristics ratings 32A and above. The terminal screws 8720s 20A TYPE B are touch proof to IP2X, captive and feature The magnetic operating limits are between 3 8732s 32A combination heads. and 5 times the current rating of the MCB. 8740s 40A Retrofit kit 5567s Under these conditions the mechanism of a 8750s 50A 10A MCB will operate between 30A and 50A The Sentry MCB/RCBO retrofit kit is designed in an overcurrent situation. Retrofit kit for use when installing MCB/RCBOs into 5567s superceded Sentry Consumer Units. The kit TYPE C contains a busbar extension terminal (5562s), In the case of Type C MCBs, the magnetic 2 a 100A rated cable and a 25mm capacity operating limits are between 5 and 10 times spade connector terminal with clamp screw. the current rating of the MCB. Under these Standards and approvals It may be used to fit up to 3 Sentry conditions the mechanism of a 10A MCB will Sentry MCBs are designed to fully comply with the MCB/RCBOs. If more need to be installed, operate between 70A and 100A in an over- relevant requirements of BS EN 60898: 1991. then use the MK 5511s busbar with kit. current situation. The MCBs feature positive contact status indication in accordance with 16th edition IEE Wiring regulations (537-02-03 and 537-03-02). 2002 MK Electric Limited The Arnold Centre, Paycocke Road, Basildon, Essex SS14 3EA, United Kingdom Tel: +44 (0)1268 563720 Fax: +44 (0)1268 563064 email: more mkelectric.co.uk www.mkelectric.co.uk Edition 09-02TECHNICAL DATA SHEET Type C devices are capable of supplying the TYPE D majority of inductive and capacitive loads (not offered in the Sentry Range) Sentry such as motors, transformers and tungsten The Type D MCB is suitable for applications Miniature Circuit Breakers or fluorescent lighting. involving equipment generating very high 2:3 Time/Current and Energy let through inrush currents, e.g. x-ray equipment, trans- characteristics of Sentry MCBs are shown mitters and computer power supplies. The graphically on the Time current characteristics magnetic operating limits are between 10 and chart (See separate document). 20 times the current rating of the MCB. Features Meet BS EN and IEE Wiring Regulation Tunnel type, touch-proof, captive requirements terminals Trip-free mechanism Generous terminal capacity Positive contact status indication Can be used as single pole isolating switch Installation TECHNICAL SPECIFICATION Selection of the most suitable MCB should take 3. Fault breaking capacity Electrical into account the following considerations: All Sentry MCBs have a short circuit breaking Voltage rating: 1. Operating voltage and frequencies capacity of 6,000A (M6). 250V/415V a.c. Operating frequency: It is possible to use the Sentry MCB on other For applications where the prospective fault 50Hz voltages than 240/415V a.c. 50Hz, but it current is in excess of this, a BS 88, 100A Rated short circuit capacity Icn: should be noted that this takes the MCB (maximum) fuse should be used upstream of 6000A outside the scope of BS EN 60898. the MCB to provide a system breaking Service short circuit capacity Ics: capacity of 20,000A. 2. Type of load 6000A 4. Discrimination with HRC fuses RESISTIVE Energy limiting class: 3 No derating is required in the case of resistive A Sentry MCB consumer unit will normally be Physical loads. supplied via an HRC fuse. The HRC in such Ambient operating temperature: instances will be the major device and remain INDUCTIVE 25C to +60C unaffected by any fault current which causes In the case of inductive loads from direct-on- Calibration temperature +30C the MCB to operate. line motors, the surge on energisation can IP rating: produce up to 9 times full load current, The level of fault current up to which this can Front face IP4X, screw IP2X 2 which may be present for several seconds. It be assured is determined by comparing the I t Max. installation altitude: is therefore recommended that Type C MCBs characteristics of the two devices. Discrimi- 2000 metres are used for such circuits. nation will theoretically occur up to the level at 2 which the value of the total operating I t of the When using assisted start motors, the usually 2 MCB is below the minimum pre-arcing I t of quoted figures are 2.5 times the full load the fuse, although in practice, discrimination current, for periods generally longer than will be achieved at higher levels than this. those for direct-on-line starters. It is thus important to establish the degree of inrush 5. Cable protection current in order to select a suitable MCB. In The current carrying capacity of the cable all instances, reference should be made to should always exceed the current rating of the both the motor manufacturers curves and MCB to prevent damage. MKs circuit breaker curves in order to select However, should this not be the case, a further the compatible miniature circuit breaker. calculation may show that the MCB can still CAPACITIVE interrupt the current in a sufficiently short time Surges on energisation, for example with dis- to prevent overheating of the cable insulation. charge lighting, may well reach 25 times the Although this will prevent mechanical damage rated current of the device, but only for very to the cables, further overload protection short duration. Type B devices will often be should be provided by a separate device, e.g. adequate, but for more specialised circuits, a a motor overload relay. Type C may be required. The lighting fitting In case of doubt please contact the MK Tech- manufacturers recommendations should nical Sales and Service Department. be observed. 2002 MK Electric Limited The Arnold Centre, Paycocke Road, Basildon, Essex SS14 3EA, United Kingdom Tel: +44 (0)1268 563720 Fax: +44 (0)1268 563064 email: more mkelectric.co.uk www.mkelectric.co.uk Edition 09-02