What is the difference between PO and PC action?

PO (Power Open) means the damper opens when 24Vac is applied and spring-closes on power loss — fail-safe closed. PC (Power Close) means the damper closes when 24Vac is applied and spring-opens on power loss — fail-safe open. PO is standard for fresh air intake. PC is used on exhaust applications where the duct must remain open on power loss.

Do I need an end switch?

The end switch is required on any combustion air or fresh air sequencing application where an ADP relay adaptor is used. The ADP uses the end switch signal to confirm the damper blade has physically reached its open position before allowing the appliance to fire. Order the HAC with SPO or SPC action code when an end switch is required.

What sizes does the HAC come in?

The standard HAC is available in 2 inch through 9 inch round duct. Sizes 2 inch and 3 inch use a smaller motor drive. Sizes 4 inch through 9 inch use the standard Hoyme spring motor drive.

Is the HAC CSA certified?

Yes. The HAC inline motorized air damper is CSA certified in Canada and the United States for fresh air, make-up air, and zone control applications.

Can the HAC be used for combustion air?

Yes. The HAC can be used as a combustion air damper when paired with an ADP relay adaptor and ordered with the end switch option. For a combined motorized hood and damper at the wall penetration, consider the HOM or MOH instead.

HAC Inline Motorized Air Damper – CSA, 24Vac, 2

Product image is representative only. Actual product may differ in appearance depending on size, configuration, and options selected at order.

The most specified motorized inline damper in the Hoyme lineup. CSA-certified, 24 Vac, spring return, sizes 2"–9". Handles fresh air intake, make-up air, HRV/ERV duct control, zone control, and ventilation code compliance installs across Canada and the US.

✓ Stall-protected motor — holds against ice and elevated static pressure without tripping or leaving the blade in an unknown position

✓ CSA certified — complete assembly — the damper body, drive, and control hardware together, not just the actuator

✓ PO or PC action — confirm before ordering; changing the action after installation requires full drive disassembly and is not practical once the unit is in a duct run

✓ End switch — confirms blade position; required for ADP relay adaptor interlock sequences

✓ Relay — switched output when damper opens; use to trigger furnace fan or secondary device (not available on 2" and 3")

✓ Replacement parts stocked — motor kits, microswitch kits, spring return kits at your wholesaler; a motor failure does not mean a full damper replacement

Confirm PO vs. PC before ordering. The action is set at the factory. A field conversion procedure exists — it requires removing the motor, reversing the spring plate, and remounting the drive — but this is not practical once the unit is installed in a duct run. The only reliable correction after installation is replacement. PO is correct for the vast majority of fresh air intake and make-up air applications — the duct seals when the system is off. PC is used only when fail-open on power loss is required by the system design.

Sizes

2"–9"

Voltage

24 Vac

Action

PO or PC

Certification

CSA — complete assembly

Drive

Patented Hoyme spring motor

Relay available

4"–9" only

Need an ADP relay adaptor? For ventilation code compliance — fresh air damper interlocked with furnace fan — the ADP relay adaptor sequences the HAC open first, proves position via end switch, then energizes the fan. Order the SPO or SPC variant when using an ADP adaptor. See the ADP series for the correct model for your application.

2-year electrical · 10-year mechanical warranty

Made in Canada · 40+ years field-proven in Canadian climates

HAC Universal Inline Air Control Damper — CSA Certified, 24 Vac, 2"–9", Spring Return

Description

HAC Universal Inline Air Control Damper — CSA Certified, 24 Vac, 2"–9", Spring Return