By Kent · Lock Depot Staff Writer

Altronix ACM8CB: One Panel, Eight Doors, No Guessing on the Power Distribution Module

A single-door retrofit only needs one power supply feeding one lock. The wiring gets harder the moment a job has four, six, or eight openings on the same access control panel, because now every output needs its own fuse, its own polarity, and in most jobs its own fail-safe or fail-secure setting. Stack six separate power supplies in a head-end closet and you have burned the whole enclosure on boxes that mostly sit idle. Altronix builds three different boards to solve that problem, and picking the wrong one means re-pulling wire later. Here is how the ACM8CB, PD4UL, and MOM5 actually differ, and which one belongs on your job.

Altronix ACM8CB: the access power controller for doors that need to be switched, not just powered

The Altronix ACM8CB takes one 12 to 24 volt AC or DC input and turns it into eight independently controlled Class 2 rated, power-limited, PTC-protected outputs. That word "controlled" is the whole reason to spec this board over the other two. Each output is triggered by a dry contact or open-collector signal from your access control panel, card reader, keypad, or PIR, and each one can be set to fail-safe or fail-secure on its own. On a mixed job, that is normal: the server room maglock needs to drop on fire alarm, the warehouse strike needs to stay locked on a power loss. One ACM8CB handles both without a second board.

It also carries a FACP interface for tying into the fire alarm control panel, so an integrator running emergency-egress or alarm-monitored doors off one system does not need a separate relay stage bolted on after the fact. If the spec calls for door-by-door switching, individually assignable lock logic, and a fire tie-in on a multi-door job, the ACM8CB is the board built for it, not the one you patch together to get there.

Altronix PD4UL: the simple fused distribution module for a job that doesn't need switching

By contrast, the Altronix PD4UL is a much plainer board, and that is the point. It splits one AC or DC input, up to 28VAC/28VDC, into four individually fused outputs rated at 3.5 amps (up to 5-amp fuses accepted), with surge suppression and a power-LED per output. There is no access-control trigger input here and no fail-safe/fail-secure logic. Every output is live all the time, protected by its own fuse, which is exactly what you want when you are powering four cameras, four door contacts, or four accessory devices off one 24VDC supply and you just need each leg to blow its own fuse instead of taking the whole board down. If nothing on the job needs to be switched by an access event, the PD4UL is cheaper and simpler than either of the other two, and simpler is correct when simpler is all the job asks for.

Altronix MOM5: PTC-protected distribution with a fire-alarm tie-in, no per-output control

The Altronix MOM5 sits between the other two. It takes one 12VDC or 24VDC input from a UL-listed power supply and splits it into five individually PTC-protected, Class 2 power-limited outputs at 2 amps each. PTC protection means each output self-resets after a short instead of needing a fuse swap, which matters on a maglock or strike job where a wiring nick at one door should not take the rest of the openings down with it. The MOM5 also includes a FACP interface for fire alarm release, same as the ACM8CB, but it does not give you independently switched access-control outputs. Every output is powered together; the fire tie-in drops them together. That is the right board when you are running five locking devices off one supply and need the fire-alarm drop, but you are not asking the panel to open one door and not another.

Which power distribution module fits your job

Run it by what the job actually needs, in this order: if any door has to be opened by a card read or keypad while the others stay locked, and you need mixed fail-safe/fail-secure on the same board, spec the ACM8CB. If you are powering five or fewer locking devices off one supply as a group, with a single fire-alarm drop for all of them, the MOM5 covers it at a lower cost. If nothing on the board needs access-control logic at all, cameras, contacts, LEDs, accessory devices, the PD4UL is the cheapest correct answer and there is no reason to pay for switching logic you will never wire in. All three run off a standard Altronix supply like the AL600ULACM; the board you pick downstream of it is a function of how many outputs need to think for themselves, not how much current the job draws. If the same panel also needs dry-contact relay logic instead of distribution, see our Altronix RB30 vs RB1224 relay module breakdown, a different board for a different job.

Common questions

Can I mix fail-safe and fail-secure outputs on one Altronix board?

Yes, on the ACM8CB. Each of the eight outputs is independently set, so a maglock on a fire-rated corridor door can be fail-safe while an electric strike two doors down stays fail-secure, all off the same board. The MOM5 and PD4UL do not offer per-output fail-safe/fail-secure selection; every output on those boards behaves the same way as a group.

Do the PD4UL and MOM5 need an access control panel to work?

No. Both are pass-through distribution boards. They take one power source and split it into protected outputs, but nothing on either board reads a card, a keypad, or a REX signal. If a door needs to be switched by an access-control event, that logic has to live upstream in the panel itself, or you need the ACM8CB, which does have a trigger input per output.

What happens if one output shorts on the MOM5 versus the PD4UL?

On the MOM5, a shorted output trips its PTC and resets on its own once the fault clears, no maintenance visit required. On the PD4UL, a shorted output blows its fuse, and someone has to physically replace that fuse before the output comes back. Either way the other outputs on the board keep running; neither design lets one bad leg take down the whole board.

Can the ACM8CB power a maglock directly from its outputs?

Yes. Each output is rated to route power to maglocks, electric strikes, or magnetic door holders directly, and the board can be powered by one shared source for board logic and lock power, or by two separate sources if you want board control isolated from lock power. Confirm your total maglock draw against the ACM8CB's per-output rating before wiring more than one high-draw lock to a single output.

Is a distribution module the same thing as a power supply?

No. A power supply like the AL600ULACM converts building AC into regulated low-voltage DC or AC for locking hardware. A distribution module like the PD4UL, MOM5, or ACM8CB takes that already-regulated output and splits it into multiple protected, and on the ACM8CB switchable, legs so one supply can safely feed several doors instead of one.