Description
Product image is representative only. Actual product may differ in appearance depending on size, configuration, and options selected at order.
Motorized all-weather hood damper that mounts at the wall penetration — hood, damper, and flashing in one unit. Seals at the building exterior when the system is off. Same patented Hoyme 24 Vac spring return drive as the HAC and HOM lineup. CSA certified. Sizes 4"–8".
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Seals at the wall — not in the duct — when the MOH closes, the air path is sealed at the building exterior; no cold air column sitting in the duct between the damper and outside between ventilation cycles
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One unit replaces two — eliminates the separate all-weather hood and inline damper that a standard HAC + OOH installation requires at two different points in the system
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Same patented Hoyme spring motor drive — stall-protected Synchron motor, nylon bearings; holds against ice load without tripping, clears the obstruction when conditions change
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Base "L" dimension 7½" — extension sleeve available for deeper walls — standard unit fits typical 2×4 wall assemblies (7½"); optional extension sleeve extends reach up to 14" for 2×6, stucco, and thicker wall assemblies; specify at order; flashing included
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CSA certified — complete assembly — motor, blade, and housing; covers fresh air intake and combustion air applications for Canadian and US installations
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PO or PC action, end switch available — all factory-set; confirm PO vs. PC before ordering — cannot be changed after installation; end switch required for combustion air appliance interlock
Not for dryer ventilation. The dryer exhaust environment — high humidity, lint, elevated temperature — is outside the MOH's listed application. Use the BDH Back Draft Hood for dryer exhaust termination. Also confirm wall depth at the installation point: the standard "L" dimension is 7½". If wall depth exceeds 7½", specify the extension sleeve at order — it extends reach to 14". Walls exceeding 14" require factory confirmation.
Use MOH when…
✓Wall penetration is the natural control point
✓Sealing at the building exterior is the priority
✓One unit instead of separate hood + inline damper
✓Retrofit where replacing the existing hood is the cleaner solution
Use HAC + OOH when…
→Damper needs to be in the duct run — not at the wall
→Existing all-weather hood already in place
→Insulated damper body needed — see HAC-L
→Heat bypass needed for zone control — see HAC-H
Seals at
Building exterior — not in duct
Sizes
4"–8"
Voltage
24 Vac, 5W
Action
PO or PC
Wall Depth ("L")
7½" standard; 14" with optional extension sleeve
Certification
CSA — complete assembly
Not Suitable For
Dryer ventilation — use BDH
Confirm Before Ordering
Wall depth; extension sleeve if wall > 7½"
Combustion air interlock? Order the MOH with end switch (SPO or SPC variant). The end switch proves the blade has physically reached the open position before the appliance fires. Select the correct ADP adaptor by appliance type: ADP-0MV2-S5A (millivolt), ADP-1102-S5A (110 Vac boiler/tankless), or see the ADP series for 24 Vac furnace applications.
2-year electrical · 10-year mechanical warranty
Made in Canada · Same Hoyme spring motor drive as HAC and HOM lineup