DB (DISTRIBUTION BOARD)

SP DB, TPN DB – 4 Way TPN DB, 6 Way TPN DB, 8 Way TPN DB…

DB – Distribution board is set of MCBs, ELCBs/RCCBs which are installed in a metal box & is used to distribute electrical power to different loads.

Classification of DB  –1) according to usage, 2) according to supply,

  1. Classification of DB according to usage –

  • LDB (Lighting DB) – It is used to distribute power to lighting circuits, 6A power points, exhaust fans etc. It is used for maximum 6A/10A current loads.
  • PDB (Power DB) – It is used to distribute electrical power /supply to power loads such as Geyser, Fridge, AC etc. All these items draw high current. MCBs of current rating 16A,20A,25A are used.
  • L&P DB – When DB is use for both lighting & power loads.
  • NDB (Normal DB) – It is used for normal AC supply where load is to be fed from normal power.
  • UPS DB – It is used for UPS supply where load is to be fed from UPS power.
  1. 3- phase DB –

A 3 Phase DB consists of one no. three phase incoming MCB and a set of single phase outgoing MCBs. A 3 phase DB can be used for Lighting & Power load.  It can be arranged in two ways –

  1. Incomer – One TPN /4P MCB/ISOLATOR along with equal rating of ELCB /RCCB is used and outgoing– single phase MCBs – 4 nos/6 nos/8 nos/10 nos/12 nosper phase are used .  Such arrangements are called 4Way TPN DB/6Way TPN DB/8Way TPN DB/10Way TPN DB/12Way TPN DB. One no. neutral bar per phase & one no. earth link per phase are fitted in the DB for neutral &earthing wire connections of each circuit.
  2. Incomer – One no. TPN /4P MCB/ ISOLATOR and outgoing single phase MCBs 4 nos/6 nos/8 nos/10 nos/12 nos SP MCBs per phase alongwith SP/DP ELCB per phase are used.  Such arrangements are called 4Way TPN DB/6Way TPN DB/8Way TPN DB/10Way TPN DB/12Way TPN DB. One neutral bar per phase & one earth link per phase are fitted in the DB.
  1. Single phase DB –

A Single phase DB consists of one incoming and a set of outgoing MCBs. These can be arranged in following way –

Incomer – One DP MCB and outgoing–  4nos/6 nos/8 nos/10 nos/12 nos  SP MCBs along with SP/DP ELCB are used.

IMPORTANT TERMS –

  • SP – Single Pole (only one point isolation contact where one phase is connected).Application – Switching & protection is done in one phase only.
  • SPN – Single Phase with Neutral. Application – same as above.
  • DP – Double Pole (Two point isolation contacts where Phase & Neutral are connected). Application – Switching & protection is done in one phase & neutral only.
  • TP – Triple Pole (Three point isolation contacts where R,Y,B phase are connected). Application – Switching & protection is done in all 3 phases only.
  • TPN – Triple Pole with Neutral (Four point isolation contacts). R,Y,B phase & Neutral are connected but protection is given for 3 phases only, not for neutral.
  • 4P – Four Pole (Four point isolation contacts. R,Y,B & Neutral are isolated & protection is given for 3 phases & neutral)
  • 4 Way TPN DB/6 Way TPN DB/8Way TPN DB/…. – In this, each phase would have 4 outgoing MCBs in case of 4 Way TPN DB, hence 4-Way TPN DB would have 12 outgoing MCBs. Similarly, 6Way TPN DB will have 6 outgoing MCBs per phase and 8 Way TPN DB would have 8 outgoing MCBs per phase & so on.
  • Phase– Live wire (from where current flows),
  • Neutral – where current returns
  • Earth/Ground – Point which is connected with earthling.
  • Insulator – Material which does not allow current to flow. It is used as a support in DB.

FAQs – 

Q1- What is the difference between 4 way TPN DB & 6 way TPN DB?

Ans – Both 4way & 6 way DBs are three phase DBs. In three phase DB, each phase has certain number of outgoing MCBs according to ways. For example – 4 nos of outgoing MCBs per phase make 4 Way TPN DB (where user will get 12 (4X3) outgoing MCBs in the DB). Similarly, 6 nos outgoing MCBs per phase will be there in 6 way TPN DB (where user will get 18 nos outgoing DB). This formula is applied for 8way TPN DB (where 24 outgoings will be there in DB) & so on.

Q2 – What kind of precautions to be taken while doing wiring work in DB?

Following precaution should be taken when DB installation work is going on

  • Incoming cable should be connected with incoming MCB from bottom side while upper side should be used for outgoing purpose.
  • Neutral wire should not be interchanged from one phase to other phases. This is very important point when RCCB/ELCB is installed in the DB.  Interchange of neutral wires between two different phases will create problem & RCCB/ELCB will not hold.
  • Create separate neutral section for each phase. Neutral wire from each point should be connected with the neutral of individual phase.
  • Neutral & earthing links should be installed on the insulators. These links should not be installed directly on DB box.
  • Use insulated shorting links for connecting multiple SPN MCBs from one phase. Insulation on shorting link will protect the user from shock during maintenance of the DB.
  • Circuit wires in the DB should dressed properly.
  • Thimble/Lugs should be used with wires while terminating them in the MCB/ELCB/RCCB etc.
  • TPN DB should be double earthed.
  • SPN DB should be connected with single earthing.
  • Door of the DB should be connected with DB box through wire to ensure that the door is earthed also.
  • Vacant MCB space in the DB should be covered with blanker to avoid ingress of foreign objects like lizard etc.
  • Each wire (phase, neutral & earth) should be identified with help of ferrules. Ferrules are available in market according to wire size & are available from A-Z & O-9 range.
  • SLD (Single Line Diagram) of DB should be pasted on the back side of the front door. SLD should cover incoming supply source & outgoing load details.
  • Each DB should be identified by mentioning DB name which may be LDB or PDB or UPS DB etc. Each DB should be should be numbered also such as LDB -1, LDB-2, PDB-1 .. and so on.
  • Incoming supply of the DB should be mentioned on front side of the door for safety reasons so that supply of DB should be disconnected without wasting time in case emergency.

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