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, with delivery across India from our Chennai store. For site, contractor or bulk quantities, contact us for a quote.