How to Mount and Power an Alarm Panel

Why this matters

The panel is the one part of an alarm system that has to keep working when everything around it is going wrong: the power is out, someone is in the house, a storm is throwing surges down the lines. A panel mounted in the open gets smashed before it can report. One on a switched outlet loses AC every time someone flips the closet light off, and calls in AC troubles until the customer stops trusting the system. One without its earth ground takes a nearby lightning surge through its communicator. One with the battery landed before the board is ready can spark at the terminals and, on some boards, damage the charger. Mounting and powering the panel is a short job done in a fixed order, and each step in that order exists because skipping it produces one of those calls.

Start state

You need: the panel can and board, the panel's installation manual, the plug-in transformer the manual names (its voltage and VA rating are per the documentation; do not substitute one from the truck stock that "looks the same"), the standby battery sized for the job, transformer wire of the gauge the manual calls for at your run length, ground wire and a clamp, anchors suited to the wall, a plug-in receptacle tester, and a multimeter.

Check before you begin:

• The account is on test with the central station if this is a replacement on a monitored system. See related: How to Put an Alarm Account on Test and Take It Off.
• The spot the survey picked is still the spot: hidden from view, inside the protected area, ventilated, not in an unconditioned garage or attic, within the transformer run the manual allows.
• The outlet is unswitched, on a circuit nothing else commonly turns off, and is a receptacle you can plug into without an extension cord. If there is no suitable outlet, stop here: a new receptacle is electrical work, and an electrician runs it where local rules require one. The panel does not go on an extension cord or a power strip.

Battery sizing is its own calculation; see related: How to Size a Standby Battery for an Alarm Panel.

The steps

1. Mount the can level, at working height, on solid backing. Hold the can so the terminal strip sits around chest height, which keeps the tech's hands at the board without a ladder. Mark through the mounting holes, check behind the wall for wiring and plumbing before you drill (a stud finder with AC detection, and a look at what is on the other side), and use anchors rated for the weight of the can with a battery in it. Fasten to a stud where you can. Why: a can that sags on drywall anchors loosens over the years until its knockouts strain the cables, and a can mounted overhead in a closet guarantees every future service tech works off a ladder. Hazard: eye protection while drilling overhead or into masonry; masonry dust is silica, so drill with a vacuum at the bit.

2. Pull every cable into the can before the board goes in, through the knockouts, with slack. Zone runs, keypad bus, siren, communicator, transformer and ground each get labeled at the can end. Leave enough slack to reach any terminal on the board. Why: labeling at the can end is the only labeling the next tech will see, and slack lets a zone move to a different terminal later without a splice.

3. Mount the board on its standoffs, with the can's tamper switch in place if the panel uses one. Why: the standoffs keep the board off the metal can. A board resting on the can, or held on with the wrong screw, can short a trace to ground.

4. Land the low-voltage wiring: zones, keypad bus, siren, communicator. Follow the terminal labels on the board, not color habits from a different maker. Leave the transformer and the battery unconnected. Why: landing these with the board unpowered means a slipped conductor cannot short a powered terminal.

5. Bond the earth ground to the board's ground terminal, per the panel's documentation. The manual names what to bond to, commonly a metal cold-water pipe that is itself bonded to the building's grounding system, or another electrode it lists. Never a gas pipe. Use the gauge and the maximum length the manual gives, and route it as straight as you can. Why: the ground terminal is where the board's surge protection dumps a transient. With no ground, that transient has nowhere to go but through the board and the communicator. Long, coiled ground runs work poorly for surges.

6. Run the transformer wire to the AC terminals, then secure the transformer to the outlet, then plug it in. Land the wire at the board first. Securing the transformer means fastening its tab to the receptacle with the cover-plate screw so it cannot be knocked or pulled out. That screw threads into the receptacle's strap, a few inches from energized terminals: turn the circuit off at the breaker, prove the receptacle dead with the meter, hot to neutral and hot to ground, checked on a known live source before and after (a plug-in receptacle tester can go dark on a live receptacle with an open neutral and ground, so it does not prove dead) (NFPA 70E Article 120), swap the plate screw for the transformer's retaining screw, then restore the breaker and plug the transformer in. Where the outlet is a duplex, check the remaining half still works for the customer. Why: an unsecured transformer is the single commonest cause of AC trouble calls. A vacuum cord, a shelf being moved, a child, and the panel is on battery until it dies.

7. Read the AC voltage at the panel's AC terminals. It should be close to the transformer's rated output; an unloaded plug-in transformer commonly reads somewhat above its rating. A reading far below points at a long, thin run or a loose terminal.

8. Read the battery charging voltage at the battery leads, then connect the battery last: red to positive first, then black. The manual gives the charging figure; many panels charge at roughly 13.5 to 13.8 V on a 12 V sealed lead-acid battery. Connect only after the panel is powered from AC and the charging voltage reads right. Why last: the board brings its charger and its supervision up in a known state on AC. Some boards do not start from battery alone, and landing a battery onto a board with a fault on it puts the battery's short-circuit current through that fault. Hazard: a sealed lead-acid battery can deliver hundreds of amps into a short. Keep the leads apart, never let a tool bridge the terminals, and do not wear a ring or a metal watchband while handling it.

TYPICAL TERMINAL STRIP, LEFT TO RIGHT (check the board)

[AC][AC]  [EGND]  [AUX+][AUX-]  [KP +][KP -][DATA][DATA]
  |  |       |       to motion,    keypad bus, colors
  |  |       |       glass-break   as the maker assigns
  |  |       +-- ground wire to bonded cold-water pipe
  +--+-- 2-wire run to plug-in transformer, outlet
         secured with retaining screw, unswitched

[Z1][COM][Z2]  [Z3][COM][Z4]  [BELL+][BELL-]
  zone loops,   two zones       siren output
  share COM     per common

BATTERY LEADS:  red -> BAT+   black -> BAT-
                connected LAST, after AC is on

Worked example: a hybrid panel in a laundry closet

The survey put the panel in a laundry closet with an unswitched duplex receptacle 4 feet below the can and a bonded copper cold-water line on the same wall. The panel's manual names its plug-in transformer by output and VA, specifies 18 AWG for transformer runs up to the length it lists, and lists the charging voltage.

• Mount. Can on a stud at chest height, two screws in the stud and two in anchors. The other side of the wall is a bedroom closet; nothing in the cavity on the detector's sweep.
• Cables. Two wired zone runs, the keypad bus to two keypads, the siren and the cellular communicator's antenna lead, all labeled at the can: "Z1 front door", "Z3 garage door", "KP bus", "siren".
• Ground. 6 feet of ground wire to a clamp on the cold-water line, straight down the wall, no coils.
• Transformer. 6 feet of 18 AWG from the AC terminals to the outlet. Breaker off, the meter checked on a live outlet in the hall, the receptacle read 0 V hot to neutral and hot to ground, the meter checked on the hall outlet again, plate screw swapped for the transformer's retaining screw, breaker on, transformer plugged in and screwed down. The other half of the duplex still powers the washer.
• AC reading. The board read slightly above the transformer's rated output, as expected unloaded with the battery not yet connected.
• Charging voltage. 13.7 V at the battery leads before connection, inside the manual's figure.
• Battery. Red to positive, then black. The keypad showed AC present, no battery trouble.

How to verify it is right

The AC-loss test. With the account still on test, unplug the transformer. The keypad should show an AC loss indication within the delay the panel is programmed for, the panel should keep running on battery, and the AC trouble should report to the central station if it is programmed to. Plug it back in: AC restores. If AC loss does not report, the customer will find out about a dead outlet when the battery dies.

The battery trouble test. Disconnect the battery's negative lead with AC on. The panel should flag a low or missing battery at its next battery test (some panels test immediately on a keypad command). Reconnect. A panel that never notices a missing battery will not notice a dead one. Load testing the battery properly is its own procedure; see related: How to Replace an Alarm Panel Battery and Load Test It.

The ground check. With the meter on resistance and the panel powered down for the check, read from the board's ground terminal to the pipe clamp. It should read near zero ohms. A high reading means the clamp is on a painted or corroded section. Power back up in the same order as before, AC first and the battery last, and confirm the keypad shows AC present and no battery trouble.

Signals arrived. AC loss and restore, and battery trouble and restore, appear on the account history before the account comes off test.

What changes the job

A metal-framed closet or a basement corner with poor cellular. The panel can stay; the communicator may need a remote antenna. Decide that at the survey, not when the activation fails.

A commercial building. Panel location is often in a locked electrical or telecom room, and the 120 V source may need to be a dedicated circuit with a breaker lock; check the local code and the panel's listing instructions, and route the circuit to an electrician.

A combination fire and burglary panel. Fire listings add requirements for the power source, the battery and the circuit identification, under NFPA 72 in the edition adopted, often for a separately licensed contractor. See related: Combination Fire and Burglary Panels and the License Line.

References

• The panel manufacturer's installation manual: transformer, wire gauge, grounding, charging voltage and battery connection
• NFPA 70E, Standard for Electrical Safety in the Workplace, Article 120 (verify absence of voltage with a tester proven before and after), current edition
• See related: How to Size a Standby Battery for an Alarm Panel
• See related: How to Put an Alarm Account on Test and Take It Off
• See related: How to Replace an Alarm Panel Battery and Load Test It