Standard Operating Procedure for Main Electrical Distribution Board

Contents:                      

1. Purpose
2. Scope
3. Procedure
4. Acceptance criteria ­­­­­­­­­­­­­

4.1.General Definition

4.1.1.      Distribution Boards

4.1.2.      Outlet

4.1.3.      Over Current Protection Device

4.1.4.      Circuit Breaker

4.1.5.      Fuse

4.2.Reference

5. Checklist for M.D.Bs
6. Responsibility

1.      Purpose: The purpose of this standard is to provide inspection and testing procedures and practices for to determine the safety of installed electrical system within and associated with in industrial places or other Places where many people perform their duties or where people live.

2.       Scope:

This standard provides criteria for identification of hazardous condition of electrical system in industrial places (where many people perform their duties or where people live). Because a lot of people work in the textile mills there’s always a risk of life and property loss.

3.     Procedure:   

For Electrical Inspection of the Main Distribution Board. Responsible personnel should have complete electric tools kit and wearing safety equipment like Gloves Helmet, and safety shoes.

Steps for electrical inspection are described below.

1. Switch off the supply feeding MDB, use LOTO (Lock out, Tag out) technique.
2. Check that, the rubber mat is intact (no cracks), and is of appropriate size.
3. Check that, the MDB is clean and no fluff or dirt is there.
4. Check that the distance (clearance) of at least one meter in front the main distribution board with the measurement tapes.
5. Ensure the bus-bar of appropriate size is installed in MDB. The thump rule for bus-bar size is

Bus-bar Size = Area of Bus-bar (mm) = 2* (Breaker Capacity)

6. Check the ampere meter and volt meter or energy flow analyzer installed at the front door of main distribution board are working properly. If the answer not, then repair or replace those meters.
7. Check all four types of sheets on main distribution board including D.B address, Appliances connected list, over current Devices List, and SLD (single line diagram) also check for safety signs and artificial respiration signs.
8. Check the breaker inside the main distribution board to see if there’s any sign of burns due to overload on the breaker. If the signs of burning or overheating present, replace that breaker.
9. Check the cable size to see if they are installed according to the load capacity of the breakers in the main distribution board. (No breaker should be more the load capacity of the cable). Adjust the breaker whose capacity is higher than the load capacity of the cable.
10. Check the earth cable inside the main distribution board to see it is installed according to the size of the main cable. The thumb rule is

Earth Cable Size = 1/2 (Main Cable Size)

11.  Inside the main distribution board the phase separators between the MCCBs terminals are installed or not. If not, inform the In charge, and install the new Phase separators (First switch off the supply of that breaker).
12. Check pair segregation. If there’s need any changing, adopt that changing.
13. Ensure that, wire lugs are being used for the cables connection. If any cable has no wire lug, provide the wire lug.
14. Ensure that, every Glands or any hole of the MDB is filled with Sealant Foam or glass wool.
15. Check that the main distribution board protection sheet to see that it is placed in front of the bus bar or not. If not, adopt the change according to situation.
16. Ensure that the color coding is maintained in MDB.
17. Check that the main distribution board indication lights are working or not. If not replace or repair that Light.
18. Check that the lock of the door is operational or not, if not replace or repair that lock.
19. Ensure no multi-looping inside the breakers terminals in MDB. If there’s any multi-looping install new circuit, to avoid ensure no multi-looping agenda.
20. Check the location of the main distribution board, it should be located 2.5 meter away from the washing area. In case of non-compliance to this point, relocate the MDB.
21. Check the breakers output supply to see they were working properly, by turning breakers ON & OFF with the phase tester.
22. Ensure that the CKT tags should be present. If not inform the responsible personnel.

4.      Acceptance criteria:

1. Distribution boards & Equipment shall be readily accessible.
2. Distribution boards & Equipment shall not show evidence of physical damage, over heating rust, or other deterioration.
3. All cables entering the equipment shall be fastened with approved connectors.
4. All unused opening shall be closed using a material that meet or exceeds the wall thickness or characteristic of the Distribution boards & Equipment.
5. All metal parts shall be effectively grounded or bonded using approved fitting.
6. Each Disconnecting means for motors and appliances and each service, feeder, or branch circuit at the point, shall be legibly marked to indicate its purpose.
7. Over Current protective devices shall be rated for the conductor under the conditions of use.
8. Over Current protective devices shall not show evidence of physical damage or overheating.
9. Connections and terminations of over current protective devices shall not be loose or bad.
10. Listed over Current protective devices, including circuit breakers and fuses, shall be used or installed in accordance with load demand.
11. Cable entering distribution boards, boxes, and devices shall be tied up and supported to ensure that stress is not transmitted to the conductors and terminations.
12. The conductor size shall be not less than the ampere rating of the circuit.
13. Conductor, cables, and cable assemblies shall not show evidence of overheating or burning.
14. Conductor shall be terminated at distribution board, devices, and boxes to ensure a secure connection without damage to the connection or the conductor.
15.  More than one conductor shall not be installed in any terminal.

4.1.  General Definition:

4.1.1.      Distribution boards: A breaker Distribution boards is an electrical box that contains one or more circuit breakers.

An enclose channel designed expressly for holding wires, cables, or bus bars with additional functional as permitted in NFPA 70.

4.1.2.       Outlet: A point on the wiring system at which current is taken to supply utilization equipment.

4.1.3.      Over current Protection Device: A Device that automatically interrupts the circuit when current in excess of given rating flows through the circuit because of a short circuit, over current load, or ground fault.

4.1.4.       Circuit Breaker: A device designed to open and close a circuit by no automatic means and to open circuit automatically on a pre-determined over current without damage to itself when properly applied within its rating.

4.1.5.      Fuse: An over current protective device containing a conductor that melts when heated by an over current condition, thus opening the circuit.

4.2.Reference:  This edition of NFPA 73 standard for electrical inspection for industrial places (where many people perform their duties or where people live) was prepared by the technical committee on electrical system maintenance and released by the correlating committee on national electrical code. It was issued by the standards council on august 30, 2019 with an effective date of September 19.2019 and supersedes all previous edition.

5.      Checklist for MDB:

Name of the Facility
Location
Checklist for MDB # _______ Located at ____________________________
Sr.#		Items to Check	Status			Remarks
			Yes	No
1		1 meter clearance provided in front of D.B.
2		Combustible material is not stored near D.B. within  1 meter
3		Insulated rubber mat is provided in front of D.B.
4		D.B. installed at compliant location
5		Artificial respiration installed beside D.B.
6		Amp, Volt meter and Indication lights are installed & functional with protective devices/ Breaker/ Fuses
7		Clear & Permanent Capacity information label provided
8		Safety sign is present on the door of D.B.
9		D.B. has operate able door
10		D.B. door and C.B. protection door is connected with Earthing
11		Earthing cable size is appropriate
12		D.B. is properly cleaned/concealed dust & vermin proof
13		Clear & Permanent identification marking provided
14		Any breaker damage
15		Phase separators have been installed b/w MCCB terminals
16		No circuit is drawn without incorporated C.B.
17		No higher rated C.B. against low rated cables
18		Wires are separated from iron or other heat source
19		No undermanaged wire found
20		Multi-looping of cables is not observed
21		Color coding is maintained for cables & bus bar
22		Each circuit provided with dedicated neutral and earth
23		Presence of Cables marking & tagging/ Wires identification i.e. CKT 1, CKT 2
24		Glands/Sealant foam/Glass wool is filled properly at top and bottom holes
25		Conductor is provided with wire lugs and color insulation relevant phase
26		Protection Sheet is present on Bus Bar
27		No overheating, overloading & signs of burning is observed through Thermal scanner
28		Earth check at equipment / appliances
29	D.B. installed 2.5 meter away from washing area

6.     Responsibility:

Responsibility is imposed on the electrical engineer/Officer and the electrician who conducts the inspection, who have jointly inspected, then the Electrical Manager / HOD who will make sure that the inspection is done properly.