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How to install a flush PIR sensor

Updated: 23 October 2026

You are about to cut a hole in a plasterboard ceiling and connect a flush PIR sensor to permanent live, neutral, and switched live. Isolate, use the hole the listing states, name three cores, then stop for a new circuit, a bath or shower location, unclear conductors, or an RCD trip. The nine listings are on the [Flush PIR sensor](/hub/electronic-surveillance/flush-pir-sensor) page. Peter F., DIY and tools editor, updated this on 20 October 2026 from those listings and Approved Document P (2013) for England. A qualifying purchase can earn a commission at no extra cost to you.

You are about to cut a hole in a plasterboard ceiling and connect a flush PIR sensor to permanent live, neutral, and switched live.

Our top picks

SEBSON SEBSON IR_ES_A flush

Best overall

SEBSON SEBSON IR_ES_A flush
9.4/10about £13.99
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SEBSON SEBSON IR_ES_E flush

Alternative

SEBSON SEBSON IR_ES_E flush
9.2/10about £14.99
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Sensky Sensky BS041 recessed

Best value

Sensky Sensky BS041 recessed
9.0/10about £12.99
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On this page
  1. 1.Before you cut
  2. 2.Three cores at the ceiling
  3. 3.First switch-on
  4. 4.When you stop

Before you cut

Isolate the lighting circuit and prove it dead before the hole saw comes out. Do not work live. Look for hidden cables, pipes, and joists before you cut. Do not assume 63 mm. Only IR_ES_E states Ø63–66 mm and Sensky BS041 states 65–70 mm. Everyone else leaves the cut-out unstated. A 16 mm note on the mini, and a review guess of about 70 mm on IR_ES_B, are not specifications. IR_ES_D can use a surface adapter instead of a recess. That choice is on flush or surface mount PIR sensor. If the listing does not state the hole, read the flush PIR sensor buying guide before you cut.

Three cores at the ceiling

Every kept listing is 3-wire: a permanent live, a neutral, and a switched live to the lamp. Danlers uses brown, blue, and black on its own trade unit. Do not copy that map, or Autenco’s sleeving, onto IR_ES_A. These amazon rows do not print a terminal diagram, so this page will not invent one. A switch drop often has no neutral. The ceiling rose usually does. If you cannot name the three conductors, stop. Several SEBSON reviews say there is no earth terminal. Do not use the protective conductor as a neutral.
SEBSON SEBSON IR_ES_A flush

Testsieger

SEBSON SEBSON IR_ES_A flush
9.4/10about £13.99
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First switch-on

The first time you restore power, expect a warm-up, and do not treat one brand’s timer as universal. Elkay describes a few minutes of flashing, Danlers about a minute, and IR_ES_B reviews about 30 seconds. Do not treat one of those times as universal. Most of this set is about 10 seconds to 15 minutes. IR_ES_D and IR_ES_E reach 30 minutes. The mini stops at 8 minutes. Draughts cause false triggers. Seal the void if the light cycles with nobody there. If you insulation-test the circuit, disconnect the sensor first. Autenco says that for its flush unit, and the same caution applies here.

When you stop

Stop and call a competent person in four cases. The work is a new circuit. The ceiling is in a bath or shower special location. The three conductors are unclear. The device trips the RCD. In England, work in that special location is notifiable under Approved Document P (2013). The zone rules are on PIR sensor bathroom zones. Scotland and Northern Ireland are not covered by that Approved Document. The work still has to meet BS 7671. This page does not claim a cable cross-section.

Common questions

What size hole do I cut?
Cut the hole your own listing states. Here that is Ø63–66 mm on IR_ES_E or 65–70 mm on the Sensky. If the cut-out cell is blank, do not borrow 63 mm from a Danlers guide or 73 mm from Autenco. The mini head is a different shape, about Ø18 x 25 mm on the saved file, and its cut-out is still unstated.
Which three conductors does a ceiling PIR need?
A permanent live, a neutral, and a switched live. Danlers’ brown, blue, and black map is for that trade unit. It is not a diagram printed on these amazon listings. If the colours in your ceiling do not match a diagram you can point to, do not invent the map from a forum post.
Can I put this on the old switch drop?
Usually no. A switch drop often has no neutral, and every sensor in this set is 3-wire. The ceiling rose is the place that usually has the neutral. If the only cables you can see are at the wall switch, you do not have the three conductors this fitting needs.
What happens the first time I switch the power on?
Expect a warm-up that is not the delay you set. Elkay describes a few minutes of flashing, Danlers about a minute, and IR_ES_B reviews about 30 seconds. Use that only as a warning that the first minute is not the finished setting. Do not apply one of those times to every model in the set.
When do I stop and call a competent person?
Stop for a new circuit, for a bath or shower location, when you cannot name permanent live, neutral, and switched live, or when the device trips the RCD. In England, work in that special location is notifiable under Approved Document P. The electrical work still has to meet BS 7671 even when it is not notifiable.
Should I insulation-test with the sensor still connected?
No. Disconnect the sensor before an insulation test. Autenco says that for its flush unit, and the same caution applies to this set. Do not leave it connected. A test voltage is not the 230 V supply the electronics see in normal use.
Does a bathroom ceiling change this procedure?
Yes. The hole and the three cores are the same idea, but a bath or shower room is a special location. Do not treat it as a like-for-like landing repair. Read the zone page before you isolate anything in that room, and call a competent person if the point sits in zone 1 or zone 2.

Related pages

Best flush PIR sensor for one dry-room job

Flush PIR sensor

PIR sensor bathroom zones and a flush ceiling switch

A flush PIR sensor: the figures that decide the fit

Flush or surface mount PIR sensor for a solid ceiling

Sources

Public UK sources from the research digest. Shelf prices, stars and review counts are the figures stored with these nine amazon.co.uk listings. No laboratory test was carried out. October 2026.

  1. Approved Document P, 2013 (retrieved 22 October 2026)
  2. GOV.UK: building work, replacements and repairs (retrieved 22 October 2026)
  3. GOV.UK: Electrical Equipment (Safety) Regulations 2016 (retrieved 22 October 2026)
  4. SELECT bathroom zones guide, 2022 (retrieved 22 October 2026)
  5. IET: section 701, locations containing a bath or shower (retrieved 22 October 2026)
  6. Danlers CEFL PIR user guide (retrieved 22 October 2026)
  7. Autenco flush PIR data sheet (retrieved 22 October 2026)
  8. Lighting Industry Association: inrush currents (retrieved 22 October 2026)