40A three phase (TPN) double door DB with a phase selector section — move circuits to a healthy phase when one phase fails. 4, 6, 8 and 12 way.
- Rated 40A, in 4, 6, 8 and 12 way sizes (listed as TPNL/T).
- Separate phase selector section, punched for three rotary selector switches.
- Three round cut-outs, commonly used for R, Y and B indicator lamps, behind a clear window in the outer door.
- MCB windows on the inner cover with ON/OFF marking and numbered label strips.
- Double door build: hinged outer door with a catch in front of a screw-fixed inner cover.
- White finish with grey corner caps and a warning label on the door.
- Sold empty, as pictured — the MCBs, selector switches and lamps are fitted to suit your supply.
A phase selector DB is a three-phase (TPN — three phase and neutral) distribution board with an extra section for phase selector switches. Single-phase circuits are shared out across R, Y and B; if one phase fails or runs low, the selector for a group of circuits can be turned to a healthy phase, so the lights, fans and fridge on that group keep working.
The 40A figure is the listed rating of the board: keep the incoming protective device within it. The way count is usually per phase — a 4 way board typically takes four SP MCBs on each phase. For a plain three-phase board, see our three phase double door DB; for each phase in its own compartment, see our 7 segment (phase segregated) DB.
What goes in a phase selector DB
- Incomer: a four pole (TP+N) MCB, four pole isolator or 4-pole RCCB, within the 40A rating.
- Three rotary phase selector switches in the selector section, for example our 40A cam-operated rotary switch.
- SP MCBs for the outgoing single-phase circuits.
Your electrician decides which circuits go through each selector.
Where to use it
- Homes and villas with a three-phase connection where one phase often fails.
- Shops, clinics and offices that need essential circuits to keep running.
- Buildings where single-phase loads are spread across three phases.
How to install
- Plan the circuit groups, selector switches and MCBs with your electrician.
- Fix the board level at an accessible height, away from water, and bring the cables in neatly.
- Fit the incomer, selector switches, lamps and MCBs, and wire them to your electrician's layout.
- Refit the inner cover, close unused openings, label the circuits and test each selector position with the loads switched off.
Three-phase work should be done by a licensed electrician with the supply switched off. Use proper phase selector switches (one phase at a time) and switch heavy loads off before changing phase.
Frequently asked questions
- What does a phase selector DB do?
- It lets you move a group of single-phase circuits to another phase with a rotary selector switch — useful when one phase of a three-phase supply fails or runs low.
- Is the phase change automatic?
- No. The selector section is made for manual rotary switches — you turn the switch to a healthy phase. The switches and lamps are fitted separately.
- Does it protect against overload or short circuit?
- Not by itself. The board and the selector switches only route the supply; protection comes from the MCBs and the RCCB fitted in the board.
- What does 40A mean?
- It is the listed current rating of the board. Your electrician keeps the incomer, and the load through each selector, within it.
- Phase selector DB or normal three phase DB — which do I need?
- If single-phase failures are common where you live and you want essential circuits to keep running, choose a phase selector DB. Otherwise a normal three phase double door DB is enough.
Buy phase selector double door DBs online from Electric Market, Chennai. For site, contractor or bulk quantities, contact us for a quote.