Security Systems for Trades That Open Doors, Walls and Windows

Why this matters

A window installer pulls a sash, a door contact opens, and twenty minutes later a patrol car is in the driveway. A drywall crew sands near a ceiling detector and the fire department arrives with lights on. A handyman cuts what he thinks is a dead phone wire behind a baseboard, and the homeowner's alarm will not arm that night. None of these involve touching the security panel. They involve opening the doors, windows and walls a security system watches, and the fix for all three is the same: know what the system is watching, get it put in the right state before you start, and leave its wiring the way you found it.

For the system's parts and how monitoring works in general, see related: Security + Alarm Systems Reference. This card is for the trade whose work happens to open the things it watches.

What the system is watching

Door and window contacts. A contact is a magnetic switch in two halves: a switch on the frame and a magnet on the moving door or sash. Separate them and the switch changes state. Surface contacts are small plastic blocks you can see. Recessed contacts are drilled into the top of a door jamb or the frame of a window, with only a small round face showing; their wire runs into the wall cavity.

Glass break sensors. A ceiling or wall device that listens for the sound pattern of breaking glass, covering a room's windows from one spot. A pane cracking or a glass sheet dropped in that room can trigger it.

Motion detectors. Usually in corners, active only when the system is armed in a mode that uses them.

Wired zones in the walls. On a wired system, each contact or group of contacts is a zone (a circuit the panel watches) wired back through the walls, attic or basement to the panel. Many zones end in a resistor (an end-of-line resistor) so the panel can tell a normal closed circuit from a cut wire or a short. A cut wire shows up as an open zone or a trouble condition. Wireless devices have their own batteries and talk to the panel by radio, so there is no wire to cut, but they still trip.

Life-safety devices on the system. Some smoke and carbon monoxide detectors are wired or paired to the security panel and monitored, which means they report to the monitoring center around the clock whether the system is armed or not.

The panel. Usually a metal or plastic box in a closet, basement or utility room, with a backup battery, separate from the keypad by the door. On many panels the cover carries a tamper switch, and the tamper is often a 24-hour zone: opening the cover reports, armed or not.

Disarmed is not enough, and test mode is not the same thing

These are two different states and other trades routinely confuse them.

Disarmed means the panel ignores most perimeter and interior zones: open a door or a window and nothing happens. It does not silence 24-hour zones. A tamper, a monitored smoke detector or a panic button still reports when the system is disarmed.

Test mode (often called putting the account "on test") is set at the monitoring center, by the account holder calling in with their passcode or using the company's app. For a set period, signals still reach the center but nobody is dispatched. It covers what disarming does not: the 24-hour zones, a cut zone wire, and someone arming the system by habit or from a phone while you are still working.

So: disarming stops the beep at the keypad. Test mode stops the patrol car and the fire truck. For work that opens the perimeter, raises dust near a monitored detector or disturbs zone wiring, ask for both.

You do not do either one. Only the account holder, or the security company, changes the system's state. You never ask for the passcode, never key in a code you were given casually, and never open the panel.

The conversation before you remove anything

The window crew lead on arrival, with the homeowner:

TECH: Before we pull the first window, your alarm: is it
      monitored?
CUSTOMER: Yes, it calls the company.
TECH: Then I need two things from you. Disarm it, and call
      the monitoring center to put the account on test
      for the whole job. We're here until about 2:30.
CUSTOMER: Disarming isn't enough?
TECH: It covers the windows. It doesn't cover the smoke
      detector in the hall, and that's monitored around
      the clock. Cutting out trim makes dust.
CUSTOMER: How long do I ask for?
TECH: Through 3:00. If we're running late I'll call you
      before it runs out, not after.
CUSTOMER: And the sensors on the old windows?
TECH: Two of them have wired contacts. We'll disconnect
      them, tag the wires and leave them coiled. Your
      alarm company installs the new contacts. I'll write
      down which windows.

The detail that matters is the end time. A test period that expires mid-job is the most common way a careful crew still gets a dispatch.

Worked example: three windows, one smoke detector, one test window that runs out

A window crew is replacing three double-hung windows: two in a bedroom, one in the hall at the top of the stairs. The homeowner's system is monitored. A walk-through shows recessed wired contacts on both bedroom windows, a glass break sensor on the bedroom ceiling, and a monitored smoke detector in the hall about 8 ft from the hall window. The panel is in the hall closet; nobody touches it.

Time the job against the test window. The crew figures 2 hours per window and a 30 minute lunch, so 3 x 2 + 0.5 = 6.5 hours. Starting at 8:00, that ends at 14:30. This homeowner had already called the center before the crew arrived and asked for "a few hours", and the center set 4 hours from 8:00. When the crew lead asks for the end time, as in the conversation above, the answer is 12:00, and it goes on the job sheet. That is short by 2.5 hours, and the crew lead decides to call for the extension before noon rather than send the homeowner back to the phone during the walk-through.

The bedroom windows. With the system disarmed, opening and removing the sashes trips nothing. The recessed contacts sit in the top of each frame. As each frame comes out, the installer finds the contact's wire, cuts nothing, unscrews the contact from the old frame, and pulls the wire just far enough to coil it in the rough opening. Each coil gets a tag: "Bedroom east, zone wire, contact removed". The glass break sensor hears both old sashes set down carefully on a drop cloth, and nothing breaks, so nothing reports; and the system is disarmed and on test anyway.

The hall window. It is scheduled third, after lunch, so it starts at 12:30. Its interior returns are drywall and have to be cut back, and the hall detector is 8 ft away. The test period ends at 12:00. If the crew starts cutting at 12:30, any dust that sets off that detector goes to the center as a fire alarm with no test in place, and a fire alarm gets the fire department.

The call. At 11:40 the crew lead calls the homeowner: "Your test ends at noon and we've got about two and a half hours of work after that, mostly near the hall smoke detector. Can you call the alarm company and extend it to 3:00?" From 12:00 to 14:30 is 2.5 hours; extending to 15:00 gives 3 hours, which leaves half an hour of slack. The homeowner calls, the center confirms, and the crew lead writes the new end time down. The crew also keeps the cutting dust down with a shroud and vacuum on the saw, which helps the detector and the lungs both.

What the record says. On the job sheet: system monitored; disarmed and on test 8:00 to 12:00, extended to 15:00; two wired contacts removed from bedroom windows, wires tagged and coiled in the openings; hall window had no contact; homeowner to call the alarm company to install new contacts. At 14:30 the crew tells the homeowner the job is done and the system can come off test, and that the two bedroom zones will show open or be bypassed until the alarm company comes.

What would change the answer.

• A wireless system. No wire to tag. The old contacts come off with the old frames, and their halves go in a bag for the homeowner, because the alarm company may reuse them. The panel will report those sensors as missing or tampered when they are pulled, so test mode matters more, not less.
• An unmonitored system (local siren only). Disarming is all there is. A tripped 24-hour zone still sounds the siren and the homeowner has to silence it at the keypad.
• A homeowner who cannot be reached to extend. The hall window waits. The crew does other work, or stops for the day, rather than cutting near a monitored detector on an expired test.

When the monitoring center calls anyway

If an alarm goes off despite all this, the center will usually call the house or the contacts on the account, and some systems let an operator speak through the keypad.

• Say who you are and why you are there. "I'm with the window contractor the homeowner hired. We opened a window and the alarm went off."
• Do not pretend to be the homeowner, and do not guess at a code. You do not have the passcode, so say so: "I don't have the passcode. Please call the homeowner at the number on the account."
• Do not tell them to cancel. Only someone with the passcode can do that. Say what happened plainly and let them do their job.
• If police or fire arrive, tell them the same thing and have the homeowner's number ready.

Then call the homeowner yourself so they hear it from you first. Some local ordinances fine owners for repeat false alarms; that is between the homeowner and their city, but it is a reason the call before work matters.

Things that look like your problem and are not

• A zone wire inside a wall you are opening. Small multi-conductor cable stapled along a stud and heading toward a door or window is almost certainly a zone. Do not cut it to get it out of the way. Coil it, tag it, and tell the homeowner it needs the alarm company. See related: How to Tell Which Trade Owns a Pipe, Wire or Duct You Found.
• A keypad beeping or showing trouble after your work. That is usually a zone you disconnected, or a power interruption to the panel if you turned off a circuit. Tell the homeowner what you did; the alarm company reads the trouble.
• A detector you want to cover for dust. Covering a smoke detector disables a life-safety device. Ask the homeowner and the alarm company before you do it, take the cover off before you leave the room for the day, and say on the record that you did.

References

• See related: Security + Alarm Systems Reference
• See related: Smart Home Hubs and the Network Closet for Every Trade
• See related: How to Hand Off a Problem You Found in Another Trade's System
• See related: Describing a Problem in Another Trade's Own Words