Motorized Dampers — MUD Series

Name: Motorized Dampers — MUD Series
Brand: ACE FORGE HVAC

Round motorized dampers for balancing fresh air against exhaust, with a silent 24 VAC hysteresis motor and spring return to closed.

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Specifications

Motorized Dampers — MUD Series — key specifications
Parameter	Value
Available sizes	4", 5", 6", 8", 10"
Motor	24 VAC, 6W hysteresis — silent operation
Failure mode	Spring returns to closed when de-energized
Status indication	Red rod shows open / closed
Flow adjustment	Integrated flow-control adjustment screw

Values as published in the 2026 product catalogue. Ask us for the model-level submittal sheet before specifying.

Features

✓Balances exhaust air by introducing make-up fresh air
✓Spring-return-to-closed keeps the duct sealed on power loss

Overview

MUD series round motorized dampers balance an exhaust system by letting make-up fresh air in as the exhaust runs. They are available in 4", 5", 6", 8" and 10" round sizes and use a 24 VAC, 6W hysteresis motor, which is why the catalogue describes them as silent. Spring return drives the blade closed when the damper is de-energized, so the duct is sealed on power loss rather than left open.

In a system the damper is energized with the exhaust fan, and the integrated flow-control adjustment screw sets how much air passes when it is open. That is the whole job: match the make-up airflow to the exhaust so the house is not depressurized. Selection is mostly a duct-size and control-voltage decision, so the damper is normally quoted together with the exhaust fan and a control that can supply 24 VAC.

Where it is used

Make-up air for a residential exhaust system so the house is not depressurized
Range hood and bathroom exhaust balancing
Homes with mechanical exhaust and no passive make-up path
Multi-unit residential exhaust balancing
Light-commercial exhaust make-up on a 24 VAC control circuit

Selection & installation notes

01
Match the damper to the round duct: 4", 5", 6", 8" and 10" are the listed sizes.
02
Check the transformer capacity against the motor draw — 24 VAC, 6W — plus the other 24 VAC loads on the same circuit.
03
Use the integrated flow-control adjustment screw to set make-up airflow against the measured exhaust airflow at commissioning.
04
The red rod shows open or closed. Confirm it stays visible after installation so the position can be checked without opening the duct.

Common questions

What does the damper do when the power fails?

The spring returns it to the closed position when de-energized, so the duct is sealed. Check that this is the behaviour your design wants, since the exhaust side may also stop and the two should be considered together.

Which size do I need?

Match the round duct: 4", 5", 6", 8" and 10" are available. If your duct is a different size, tell us the airflow you need and the factory will confirm the options.

How is it controlled?

It runs on 24 VAC and is normally energized with the exhaust fan. Confirm the control and the transformer capacity for the circuit before quoting.

Is it quiet?

The catalogue describes the 24 VAC, 6W hysteresis motor as silent. A sound rating is not published for it — if sound level matters to the project, ask us to confirm it for the model you are quoting.