CSA Certified · Terminating End · Hood + Damper in One Unit
MAC Motorized
MAC Motorized
Fresh Air Damper
24 Vac · Terminating End · CSA Certified · 4"–9"
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Hood and damper combined in one CSA-certified assembly — one wall penetration, one unit
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Seals at the building wall — no passive hood opening, no cold air column between cycles
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Same patented Hoyme 24 Vac spring return drive as the HAC inline damper
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PO or PC — end switch and relay options available
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MAC-L insulated version available for cold climate installations
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Sizes 4"–9" · 2-year electrical / 10-year mechanical warranty
Is this the right product?
✔ Right product if
You need a CSA-certified motorized damper at the exterior wall penetration for fresh air intake or make-up air — hood and damper combined in one unit, one wall penetration.
✗ Not this product if
Damper needs to be in the duct run away from the wall → use HAC inline damper + OOH at exterior
Size above 9" required → HAC inline series covers larger sizes
Cold climate with condensation risk → specify MAC-L insulated version at order
Size above 9" required → HAC inline series covers larger sizes
Cold climate with condensation risk → specify MAC-L insulated version at order
What It Does
One wall penetration. Damper and exterior termination in one unit. No separate hood required.
On a standard fresh air installation, the exterior hood and the motorized inline damper are two separate products at two different locations in the duct run. The MAC eliminates that split. The termination point is the damper, installed right at the wall penetration — you get CSA-certified motorized 2-position open/close control exactly where the duct meets the outside. One unit. One penetration. One certification covering the complete assembly.
When a motorized inline damper is paired with a passive exterior hood, the hood opening is permanently exposed to outdoor air — wind pressure, cold air infiltration, and moisture enter freely through the hood face and sit in the duct run between the hood and the inland damper. The MAC seals at the building wall itself. There is no passive opening between the exterior and the control point, no leakage path around a hood that never closes, and no cold air column sitting in the duct between cycles. In Canadian and northern US climates, that difference is measurable in heating load and building envelope performance.
MAC-L — insulated version for cold climates: The MAC-L is the factory-insulated version of the MAC. Specify when the damper will be exposed to outdoor temperatures and condensation on the damper body is a concern — cold climate residential installs, northern commercial buildings, cold storage applications. The insulation is applied at the factory; no field wrapping required. The MAC-L insulates the damper body only — insulate the interior duct run separately per code.
MAC vs. HAC — Which to Specify
Both provide CSA-certified motorized fresh air control. The question is where the control point belongs.
✔ Choose MAC when…
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Damper at the exterior wall penetration is preferred
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Single unit covering both termination and control
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Tightest possible exterior air seal is a priority
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Retrofit where adding a second interior unit is impractical
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Cold climate — specify MAC-L for factory insulation
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Sizes 4"–9"
→ Choose HAC when…
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Damper needs to be in the duct run, away from the wall
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Control point needs to be accessible indoors for service
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Separate exterior hood already part of the design
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New construction where an interior control point is preferred
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Sizes above 9" required — HAC Belimo series covers larger sizes
Configuration Options
All options factory-set at order. PO/PC, end switch, and relay cannot be changed after manufacture.
| Variant | Action | Relay | End Switch | Part Number (6") |
|---|---|---|---|---|
| OPO | Power Open | No relay | No end switch | MAC-0610-OPO |
| SPO | Power Open | No relay | End switch included | MAC-0610-SPO |
| OPO (relay) | Power Open | Relay included | No end switch | MAC-0611-OPO |
| SPO (relay) | Power Open | Relay included | End switch included | MAC-0611-SPO |
| OPC | Power Close | No relay | No end switch | MAC-0610-OPC |
| SPC | Power Close | No relay | End switch included | MAC-0610-SPC |
| OPC (relay) | Power Close | Relay included | No end switch | MAC-0611-OPC |
| SPC (relay) | Power Close | Relay included | End switch included | MAC-0611-SPC |
PO and PC cannot be changed after installation. The action is set by the motor and spring configuration at the factory. If the wrong action is installed, the fail-safe behaviour is the opposite of what the system requires — a PO unit where PC was needed will spring-close on power loss instead of spring-open. The only correction is replacing the unit. PO is correct for the vast majority of fresh air intake and make-up air applications — confirm before ordering.
End switch required with ADP relay adaptor. If using an ADP-0241-S5A for furnace fan sequencing or ventilation code interlock, order the SPO or SPC variant. The ADP uses the end switch signal to confirm the MAC has physically opened before energizing the furnace fan — without the end switch, the interlock cannot function correctly.
Part Number Decoder
MAC-0611-SPO
MAC
Product family: motorized terminating-end fresh air damper
06
Size (2-digit): 04=4", 05=5", 06=6", 07=7", 08=8", 09=9"
10 / 11
Relay: 10 = no relay | 11 = relay included
O / S
End switch: O = no end switch | S = end switch included
PO / PC
Action: PO = Power Open (spring-close fail-safe) | PC = Power Close (spring-open fail-safe)
No suffix
Standard MAC. Add −L suffix at order for factory-insulated MAC-L version.
Key Specs
Sizes
4", 5", 6", 7", 8", 9"
Voltage
24 Vac
Drive
Patented Hoyme spring motor — stall-protected, nylon bearings
Action
PO or PC — specify at order
End Switch
Optional — required for ADP interlock
Relay
Optional — factory-installed
Insulation
Standard MAC or factory-insulated MAC-L
Certification
CSA certified — Canadian & US
Warranty
2-yr electrical / 10-yr mechanical
Common Questions from the Counter
Answers to what comes up most when specifying the MAC.
What's the difference between the MAC and the HAC for a fresh air intake?
The MAC is a terminating-end unit — it installs at the wall penetration and serves as both the exterior hood and the motorized damper in one CSA-certified assembly. The HAC is an inline damper that installs in the duct run and needs a separate exterior OOH hood at the wall. Use the MAC when you want one unit at the wall doing both jobs. Use the HAC when the damper needs to be positioned in the duct run — for example, when the control point needs to be accessible indoors, when a separate exterior hood is already part of the design, or when sizes above 9" are required.
Why does the MAC seal better than a separate hood and inline damper?
A passive exterior hood is always open — outdoor air, wind pressure, and moisture enter freely through the hood face and sit in the duct between the hood and the inland damper. The MAC seals at the wall itself. There is no open hood on the exterior, no cold air column in the duct between cycles, and no passive infiltration path between the building exterior and the damper blade. In cold climates, that wall-level seal is the difference between a fresh air system that performs as designed and one that leaks continuously between ventilation cycles.
What happens if I order the wrong action — PO vs. PC?
The action is set by the motor and spring configuration at the factory and cannot be changed after manufacture. If the wrong action is installed, the fail-safe behaviour is the opposite of what the system requires — a PO unit where PC was needed will spring-close on power loss instead of spring-open. The only correction is replacing the unit. Confirm the action requirement before placing the order. PO is correct for the vast majority of fresh air intake and make-up air applications.
Do I need the end switch if I'm using an ADP relay adaptor?
Yes — for ADP relay adaptor interlock sequences, the end switch is required. The ADP uses the end switch signal to confirm the MAC has physically opened before allowing the next step in the sequence — energizing the furnace fan, releasing the appliance safety circuit, or sending a status signal to the controller. Without the end switch the ADP has no position confirmation and the interlock cannot function correctly. Order the SPO or SPC variant when using an ADP adaptor.
Is the MAC available in sizes larger than 9"?
The standard MAC is available in 4"–9". For larger motorized fresh air intake applications, use the HAC inline damper series with the appropriate Belimo actuator — available up to 20" and larger in round duct. See the HAC product page for the full size range.
Ready to Order
MAC — Motorized Fresh Air Damper
Select your size, action (PO/PC), end switch, and relay option — then add to cart. ADP interlock requires end switch (SPO/SPC). Cold climate: specify MAC-L at order.
Configure & Order →
Size · Action · End Switch · Relay
Need help specifying the MAC?
Technical support available through your Hoyme wholesaler or direct.