Door Position Switches: Recessed, Surface and Overhead Door Contacts, Gap Size and Resistor Packs

Replacing an old door contact, or picking one for a new door, comes down to three questions: how the switch mounts, what gap it is rated for, and which loop type your alarm panel or door controller expects. The George Risk Industries (GRI) and SDC spec sheets cover all three.

In SDC's description, a door position switch (DPS) reports whether the door is open or closed. Its MC series contacts go in the edge of the door and the frame and are wired to remote devices, typically an alarm panel or a door controller. The switch locks nothing, and SDC advises using it together with a locking device and some form of lock status monitoring. See our posts on fail safe and fail secure hardware and on Securitron Magnalock models, where a door position switch is an ordering option.

Recessed, surface or concealed: which door contact fits your door

GRI's recessed contacts range from a 1/4 inch super miniature set up to 3/4 and 1 inch diameters. For steel doors it makes the 180, 184 and 8080-T series, and its recessed range also lists a 3/4 inch series for wood, aluminum and vinyl (120T-12 and 4473). SDC's MC-4 and MC-7 are 3/4 inch recessed contacts, and the MC series datasheet names hollow metal and aluminum doors and frames as the application. The MC-7 is biased, which according to SDC guards against a false status caused by an additional magnet.

On the surface side, the GRI 100 and 110 series is a 2 inch miniature set that GRI describes as suited to residential and light commercial work. The 28, 29 and 29P series is its 2-1/2 inch commercial set, supplied with covers, spacers and mounting hardware.

For a concealed installation, SDC makes a separate model, the MC-4MU in the datasheet's model list. It has a stainless steel faceplate and needs 1/2 inch of depth, against 1 inch for the recessed MC-4. SDC designed it for vandal resistance: it mortises into a hollow metal or aluminum frame and a wood, hollow metal or aluminum door.

Gap size: standard gap, wide gap and the figure on steel

Gap ratings from the spec sheets, a selection:

WG stands for wide gap and XWG for extra wide gap. Check whether a figure applies to steel. The 28, 29 and 29P sheet rates the standard gap at up to 1 inch, but 5/8 inch on steel, while the 180, 184 and 8080-T figures are stated on steel to begin with.

GRI overhead door contacts: 4532, 4532L and 200-36

GRI lists overhead door sets designed especially for loose fitting, worn or damaged overhead doors. The 4532 is a miniature floor mount set in a cast aluminum case with 24 inch armored cable and a universal magnet. Order the 4532L for the version with the optional L bracket. The sheet's part number table gives a gap of up to 2-1/2 inches; its application text says up to 3 inches.

The 200 and 250 series are extruded aluminum sets with #22 AWG wire in 36 inch stainless steel armored cable. According to GRI, the 200 is used mainly on overhead doors where heavy motorized traffic would make a plastic encapsulated switch impossible to use. The loop type is part of the number:

• Floor mount: 200-36 closed loop, 210-36 open loop, 220-36 SPDT, 230-36 DPDT
• Wall mount: 250-36, 260-36, 270-36 and 280-36, in the same order
• Heavy duty, 3 inch gap: 200-36HD and 250-36HD, both closed loop

Closed loop, open loop, SPDT and DPDT: reading a GRI part number

GRI's glossary defines the loop types by the switch state with the magnet close: a closed loop switch is closed, an open loop switch is open. An SPDT switch has common, open and closed sides, and a DPDT contact holds two such switches. Match the loop type to what the manual of your panel or controller asks for. The electrical tables on these GRI sheets also print N/O and N/C: closed loop sets such as the 180-12 appear there as N/O, open loop sets as N/C.

From the steel door sheet:

• 180-12: 3/4 inch, closed loop, 12 inch leads. Open loop, SPDT and DPDT: 185-12, 190-12, 195-12.
• 184-12: the 1 inch closed loop set, with 189-12, 194-12 and 199-12.
• -T, as in 8080-T (3/4 inch) and 8484-T (1 inch): a terminal switch, with screw terminals.
• WG after the number: wide gap.
• Color suffix, from GRI's glossary: -W white, -B brown, -G gray, -BL black, -AL almond.

So a 184-12WG-G is a 1 inch closed loop set with 12 inch leads, wide gap, in gray, and an 8080-T-W is a 3/4 inch closed loop terminal set, standard gap, in white. On that sheet the UL 10C mark sits next to the closed loop 180-12 and 184-12 and their WG versions. SDC lists UL 10C for the MC-4, MC-4-2 and MC-4PAK only.

What the resistor pack is for: GRI 6644

A resistor pack holds end of line (E.O.L.) resistors, which GRI offers for supervision of open and closed loop systems. The five GRI contact sheets behind the gap table (180, 100, 28, 4532 and 200 series) all offer E.O.L. resistors built into the contact on request, and GRI also makes resistor-only packs for retrofits. In its contacts with built-in resistors, closed loop switches have the resistor in series and open loop switches in parallel.

GRI's resistor sheet describes the 6644 as two 1K, 1/8 watt resistors in a brown 50R case with blue and black 12 inch leads; our 6644-1 card lists a 2-1K, 1/8 watt pack. Before you choose a pack, check the resistor value your zone needs in the panel's manual, and follow the panel and GRI instructions for the wiring.

Door contacts at The Builders Supply

• George Risk Industries (GRI)
• SDC (Security Door Controls)
• Pushbuttons, keyswitches and sensors

Not sure which contact suits your door or panel? Our customer support team is available Monday - Friday, 8 AM - 4 PM Central Time, at 1-888-800-7789 or [email protected].