How to Install a Recessed Door Contact

Why this matters

A recessed contact is invisible when the door is shut, which is why customers want them and why installers get them wrong. The holes are drilled in two separate pieces of wood that only meet when the door closes, and a quarter inch of misalignment between them leaves a contact that reads closed on the bench, closed on install day, and then chatters open on a windy night after the door settles. Drill the head jamb hole too far toward the hinge and the contact barely moves until the door is half open. Drill into a labeled fire door and you have voided its rating. The procedure below gets both holes on one line, the contact where it moves the most for the least door travel, and the cable out of sight, then proves the zone faults within an inch of the door opening.

Start state

You need: the recessed contact and magnet (wired, here, on a series zone), the maker's instruction sheet with its hole diameter, depth and operating gap for the door material, a drill with a sharp spade or Forstner bit of that diameter, a long flexible installer bit and fish tape or glow rods, a square, a tape, a HEPA vacuum, and a multimeter.

Check before you begin:

• Is the door a labeled fire door? Look on the hinge edge of the door and on the hinge-side jamb for a metal or embossed label. Garage-to-house doors are often required to be fire-rated or solid-core under the residential code. Drilling a labeled door or frame outside what its listing allows voids the label. If it is labeled, use a surface contact or a contact the door's listing permits, and tell the customer why.
• What is the door made of? A wood or fiberglass door takes a standard contact. A steel door needs a contact and magnet rated for steel, and its operating gap is usually smaller; check the sheet. Many steel doors have a steel top channel that is drilled with a bit made for metal, deburred so it does not cut the cable.
• What is in the wall? The latch-side jamb often has a light switch box in its cavity. The cable in this card comes down the hinge-side jamb, which is usually clear, but sweep both sides with a stud finder that detects AC before drilling.
• When was the house built? Painted trim before 1978 may carry lead paint. Drilling a few holes sits well below the EPA renovation rule's minor-repair thresholds (40 CFR 745, Subpart E), but the dust is still lead dust: hold the HEPA vacuum nozzle at the bit, wipe the area after, and keep it out of the carpet.
• Account on test if the system is monitored and already live. See related: How to Put an Alarm Account on Test and Take It Off.

Where on the door, and why

Recessed contacts go in the top of the door and the head jamb above it, on the latch side. A door pivots on its hinges, so a point near the latch edge moves almost the full distance the latch edge moves, while a point near the hinges barely moves. Put the contact near the latch side and the magnet leaves the contact's field after a small opening. Put it near the hinge and the door opens several inches before the zone faults.

Keep it far enough from the latch edge to stay clear of the weatherstrip, the strike and the corner of the frame: 3 to 5 inches in from the latch-side jamb is the usual range, so the bit does not split the corner.

Across the thickness of the door, both holes sit on the same line. On the door top that is the centerline of the door's thickness. On the head jamb, it is the point directly above the door's centerline when the door is closed against its stop.

LOOKING DOWN ON THE DOOR TOP AND UP AT THE HEAD JAMB
(door closed against the stop)

 HINGE SIDE                                LATCH SIDE
 HEAD JAMB  =============================[ C ]=====|
                                           ^ contact
 DOOR TOP   =============================[ M ]=====|
                                           ^ magnet
            |<-- 32 in, hinge to holes ->|<-4 in->|
            |<---------- 36 in door ------------>|

 C and M: same line, centered on door thickness
 CABLE: from C up into the header cavity, across
 the header to the hinge side, down the hinge-side
 jamb cavity to the basement, then to the panel

The steps

1. Mark the door-top hole, then the head-jamb hole from the same reference. With the door closed against its stop, measure 4 inches in from the latch-side jamb face along the head jamb and mark it. On the door, measure from the door's latch edge, subtracting the reveal (the gap between the door edge and the jamb, often around 1/8 inch), so the two marks line up. Across the thickness, mark the door's centerline on its top edge, then find the same position on the head jamb by measuring from the face of the stop. Why: two pieces of wood measured from two different references put the holes a reveal apart. A contact and magnet that are offset sideways still read closed when the door is shut, but they break with less door movement on one side and drift toward a chattering threshold as the door sags. Hazard: for the door-top work, open the door and wedge it so it cannot swing while you work over it; stand on a stable step ladder, not on a chair.

2. Drill the door-top hole to the maker's diameter and depth. Drill straight down, square to the top edge. A hole that wanders toward a face of the door can break through the skin of a hollow-core or veneered door. Why the depth matters: the magnet must seat flush, and a hole too deep leaves it sunk below the surface, which adds to the gap between magnet and contact.

3. Drill the head-jamb hole, then continue up into the header cavity with the flexible bit. Drill the contact's diameter through the jamb, then steer the long bit up through the header and toward the hinge side. Vacuum at the bit. Hazard: drilling overhead throws chips down: safety glasses, not prescription glasses. Before the long bit goes into the header, know what is in it; on an exterior wall, a header may carry a porch light or a doorbell cable, and the flexible bit will find it.

4. Fish the cable from the hinge-side jamb cavity up into the header and out through the head-jamb hole. Drill a small hole at the bottom of the hinge-side jamb cavity from the basement or crawlspace (or come down from the attic on a second story), fish up with glow rods, and pull the cable to the contact hole. Leave 6 inches of slack at the hole. Why the hinge side: the latch side carries the strike, often a switch box and sometimes a deadbolt bore, and every one of those is a cable obstruction.

5. Splice or land the contact, and seat it flush. On a series zone, the contact goes on the switched leg, and if it is the last device, the end-of-line resistor goes in with it; see related: How to Wire a Hardwired Zone With the Resistor at the Last Device. Tuck the slack into the header, press the contact flush with the jamb surface. A contact proud of the surface catches the door top and eventually snaps.

6. Seat the magnet flush in the door top. Press-fit as the sheet describes. A drop of the adhesive the maker recommends keeps a loose magnet from walking out over years of slamming.

7. With the door closed, confirm the gap. Measure from the face of the magnet to the face of the contact. With both flush, that gap is the clearance between the door top and the head jamb. It must be inside the maker's operating gap for this door material, with margin for seasonal movement.

8. Prove the zone faults within an inch. With the meter on the loop (or the zone landed and the keypad showing zone status), open the door slowly, measuring at the latch edge. The zone must fault before the latch edge has opened 1 inch, and restore when the door closes. On a monitored system, confirm the fault and restore reached the station with the right zone and name, then take the account off test.

Worked example: a front entry door on a series zone

A wood exterior door, 36 inches wide and 1-3/4 inches thick, no fire label. The contact's sheet gives a 3/4 inch hole, a depth to match, and an operating gap for wood that, for this model, opens at about 1/2 inch of separation.

• Marks. 4 inches in from the latch-side jamb on the head jamb; on the door top, 4 inches from the latch-side jamb minus the 1/8 inch reveal, so 3-7/8 inches from the door's latch edge. Centerline at 7/8 inch from either face of the door; on the jamb, the same position measured from the stop.
• Where the holes sit. 36 inches minus 4 inches leaves the holes 32 inches from the hinge side, as the diagram shows.
• Gap closed. The door top clears the head jamb by 1/8 inch, so with both parts flush the closed gap is 1/8 inch, well inside the 1/2 inch opening point.
• How far the latch edge must open before the zone faults. The magnet sits 32 inches from the hinge, the latch edge 36 inches. A point on the door moves in proportion to its distance from the hinge, so when the magnet has moved 1/2 inch, the latch edge has moved 1/2 x 36 / 32 = 0.56 inch. Check it from the other side: at 0.56 inch at the latch edge, the magnet has moved 0.56 x 32 / 36 = 0.50 inch.
• On test. Opening the door slowly with a tape at the latch edge, the zone faulted at about 9/16 inch and restored on closing. Inside the 1 inch finish test.

Had the holes been drilled 12 inches from the hinge instead, the latch edge would have had to open 1/2 x 36 / 12 = 1.5 inches before the zone faulted, failing the finish test with the same contact and the same gap.

How to verify it stays right

Slam and push. Close the door hard, then push and pull on it against the latch. The zone must stay closed. A zone that flickers when the door is rattled against the latch has its gap near the operating limit; that is the door that faults on windy nights. See related: The Alarm That Tripped on Windy Nights.

Deadbolt and no deadbolt. Some doors sit tighter against the stop when the deadbolt is thrown. Test both ways.

Weather. A door that swells shut in summer can sag in winter. If the closed gap is already more than half the maker's operating gap, expect trouble when the seasons change, and fix it now by checking the door's hinges and seating the parts fully flush.

References

• Contact manufacturer's instruction sheet: hole size, depth, operating gap for wood and steel
• 40 CFR 745, Subpart E, EPA lead renovation, repair and painting rule, for pre-1978 painted surfaces
• See related: Door and Window Contact Types and Gap Ratings
• See related: How to Wire a Hardwired Zone With the Resistor at the Last Device
• See related: How to Put an Alarm Account on Test and Take It Off