Ancillary device

What counts as ancillary

Everything the panel drives that is not a detector, a manual station or a notification appliance. The common ones on a Canadian job are magnetic door holders that release on alarm, relays that shut down or reposition air handling equipment, damper controls, elevator recall contacts, and door hardware releases. They sit on the output side, and the panel treats them as loads it operates rather than as devices it interrogates for fire.

The important structural point is that an ancillary device is usually the boundary between two trades. The fire alarm contractor owns the contact. Somebody else owns what happens after it.

Where the standard sits, and how it reaches you

CAN/ULC-S573 is the installation standard for ancillary devices connected to fire alarm systems. It was first published in December 2018 and it is still in its 1st edition, revised four times since.

It is one of six CAN/ULC fire alarm standards that neither Ontario code designates by name. That is not an oversight and it does not make the standard optional. It reaches a job through CAN/ULC-S524 and CAN/ULC-S537, which reference it, and through the product listing. It does mean that anyone telling you "the Ontario Building Code requires S573" is describing the chain loosely. Which edition applies to a given job is inside S524, which is paywalled, so we do not state one. The published against designated position for the whole family is tracked in the CAN/ULC edition tracker.

How it behaves in the field

An ancillary output is almost always a set of dry contacts, either a panel mounted relay or an addressable control module. Nothing crosses that boundary except contact state, and what makes the installation good or bad is what happens when the wire between the two systems breaks.

Elevator recall is the clearest example, and it is worth reading in full in the elevator recall guide. Alberta's fire code joint interpretation on the elevator fire alarm interface is unusually direct: a fault in the elevator signalling wires must cause the elevator to go to its recall position, and the system must be configured with normally closed contacts so a break in the wiring is immediately detected by the cars recalling. Two things have to be true at once there. The contact arrangement fails safe on the elevator side, and the circuit driving it is supervised by the panel in the ordinary way so an open or a ground shows as a trouble.

What goes wrong

Nobody bids the wire. The run between the fire alarm contact and the other system's terminals is a short piece of cable that appears in no scope. On a bad job it never gets installed, or it gets installed by whoever was standing there.

The contact is landed on the wrong pair. It looks perfectly correct from the fire alarm side and does the wrong thing at the far end. Get the other trade's terminal designations in writing before you terminate.

No signed matrix. Every job with ancillary outputs should have a fire alarm matrix showing which input drives which output. Without one, nobody can prove at verification that the mapping is what the design intended, and nobody can retest it in five years.

It was never tested with the other trade present. Somebody heard the relay click and signed the sheet. Nobody watched the damper, the door or the car.

Related terms

Where ancillary functions cross into other life safety systems and have to be proven as a whole, the governing standard is CAN/ULC-S1001 integrated systems testing, not S573.

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Fire Alarm Academy provides educational content only. It does not confer any certification, licence or credential, and it is not affiliated with, endorsed by, or accredited by the Canadian Fire Alarm Association, the Electrical Contractors Association of Ontario, ULC Standards, UL Standards and Engagement, CSA Group, the Electrical Safety Authority, any authority having jurisdiction, or any manufacturer. Always work from the edition of any standard adopted by your authority having jurisdiction.