Damper Actuator (Modulating) - Quick Reference SSO

Device Type: Analog Output - Actuator
Signal: 0-10VDC / 2-10VDC / 4-20mA input
Power: 24VAC (most common) / 24VDC
Version: 1.0 | Date: Dec 2025

DEVICE OVERVIEW

Common Models:

Belimo LMB24-SR, LRB24, NMB24, Johnson Controls M9000, Honeywell MS7505/MS8105, Siemens GCA/GMA

Used For:
OA/RA/EA damper control (economizer), mixing box dampers, VAV box dampers, bypass dampers

Specifications:

Torque: 35-150 in-lbs (match to damper size)
Stroke Time: 60-90 seconds typical
Rotation: 90° (spring return “SR” or non-spring “NSR”)
Wire Type: 18AWG minimum for control, 16AWG for power
Wiring: 3-wire (power, common, control) or 4-wire (+ position feedback)

Environment: -40°F to 120°F, NEMA 2 (indoor) / NEMA 4 (outdoor)

SAFETY - PPE REQUIRED

☑ Safety glasses (ANSI Z87.1)
☑ Cut-resistant gloves
☑ Hard hat (required in mechanical rooms/rooftops)
☑ Fall protection (if working >6 feet)

HAZARDS

⚠ ROTATING EQUIPMENT - Air handler fans, belts, pulleys (LOCKOUT REQUIRED)
⚠ PINCH POINTS - Damper blades close with force, keep hands clear
⚠ SHARP EDGES - Sheet metal ductwork and damper frames
⚠ WORKING AT HEIGHTS - Rooftop units, catwalks, ladders
⚠ HOT/COLD SURFACES - Near heating coils or chilled water

LOCKOUT/TAGOUT

MANDATORY: Lock out air handler/RTU before working on dampers
Notify building operator
Switch unit to OFF or manual mode
Lock breaker/disconnect with personal lock
Test that fan will not start
Keep key with you at all times
Remove lock only after work complete and area safe

INSTALLATION CHECKLIST

TOOLS NEEDED

Cordless drill + bits
Socket set (for coupling)
Allen wrenches (actuator mounting)
Wire strippers (18-16 AWG)
Adjustable wrench
Multimeter (DMM)
Label maker
Thread sealant (outdoor apps)

MATERIALS

Coupling hardware (included with actuator)
Sheet metal screws
Wire nuts or terminal blocks
Cable ties
Mounting bracket (if needed)
Damper linkage (if replacing)

PRE-INSTALL

LOCKOUT air handler/RTU before starting
Verify actuator torque rating matches damper size
Confirm actuator rotation matches damper (CW/CCW)
Check control signal type matches actuator input (0-10V / 2-10V / 4-20mA)
Verify fail-safe requirement (spring return vs non-spring)
Damper accessible and safe to work on

INSTALL STEPS

Remove old actuator (if replacement):
- Disconnect wiring, label if reusing
- Remove coupling from damper shaft
- Remove actuator from mounting bracket
Prepare damper shaft:
- Clean shaft of rust, paint, debris
- Verify shaft rotates freely by hand
- Check damper blades not bent or binding
- Lubricate shaft bushings if needed
Mount actuator:
- Position actuator on mounting bracket
- Align actuator shaft with damper shaft
- Install coupling per manufacturer instructions
- Tighten coupling set screws (do not overtighten)
- Verify actuator cannot slip on shaft
Set mechanical stops (if adjustable):
- Manually position damper to full closed
- Adjust actuator closed stop to match
- Manually position damper to full open
- Adjust actuator open stop to match
- Verify 90° rotation matches damper travel
Route and terminate wiring:
- 3-Wire Standard:
  - Red: +24VAC/VDC power
  - Black/Blue: Common
  - White/Green: Control signal (0-10V / 2-10V / 4-20mA)
- 4-Wire with Feedback:
  - Add Yellow/Orange: Position feedback signal
- Tighten terminals: 7-9 in-lbs
- Support wire with cable ties
- Leave 12” service loop
Label wiring:
- Example: “AHU-1-OAD” (AHU-1 Outside Air Damper)
- Label both ends clearly
Restore system:
- Remove lockout device
- Notify operator
- Verify fan starts normally

POST-INSTALL

EXPECTED READINGS

PRE-POWER (Power OFF, Actuator Disconnected)

Continuity: Each wire <5 ohms end-to-end
Isolation: >10K ohms to ground (all wires)
Damper Movement: Rotates freely by hand, no binding
Spring Return Test: If SR model, damper returns to fail-safe position when power removed

POWER-UP

Supply Voltage: 24VAC/VDC ±10% (21.6-26.4V acceptable)
Power Consumption: 3-8 VA typical
Control Signal Range:
- 0-10VDC: 0V = closed, 10V = open
- 2-10VDC: 2V = closed, 10V = open
- 4-20mA: 4mA = closed, 20mA = open

POSITION VERIFICATION

Control Signal	Expected Position	Feedback Signal (if equipped)
0V / 2V / 4mA	0% (Closed)	0V / 2V
5V / 6V / 12mA	50% (Mid)	5V / 6V
10V / 10V / 20mA	100% (Open)	10V / 10V

Stroke Time: 60-90 seconds full travel (0-100%)

PROOF OUT TESTS

TEST 1: Manual Override Test (if equipped)

Do: Engage manual override switch/button on actuator
Expect: Actuator can be manually positioned, motor disengaged
Pass If: Manual override works, returns to auto when released

TEST 2: Full Stroke Test

Do: Command actuator from controller: 0% → 100% → 0%
Expect:
- Smooth, continuous rotation (no jerking or binding)
- 60-90 second stroke time each direction
- Position indicator moves smoothly
- Damper blades visible moving through full range
Pass If: Completes full stroke both directions within spec time

TEST 3: Position Accuracy Test

Do: Command 0%, 25%, 50%, 75%, 100%
Expect: Actuator stops at each position, feedback (if equipped) matches command
Pass If: Position within ±5% of commanded (±4.5° for 90° rotation)

TEST 4: Linkage & Blade Test

Do: Stroke actuator full range while observing damper blades
Expect:
- All blades move together (parallel operation)
- Blades seal tight at closed position
- No binding or interference at any position
- Linkage does not slip or flex excessively
Pass If: All blades operate correctly through full range

TEST 5: Fail-Safe Test (Spring Return models)

Do: Remove power while actuator at mid-position
Expect: Actuator returns to fail-safe position (typically closed for OA dampers)
Pass If: Returns to fail-safe within 15 seconds, stays in position

TEST 6: Controller Integration

Actuator appears in controller output list
Controller can command actuator (0-100%)
Position feedback reads correctly (if equipped)
Graphics show live position
Actuator responds to automatic control sequences
No faults or errors

TROUBLESHOOTING

NO POWER / ACTUATOR DEAD

Measure supply voltage at actuator terminals: 24VAC/VDC ±10%
- If no voltage: Check controller output, circuit breaker, wiring
Test continuity of power wiring end-to-end: <5 ohms
Check terminal connections tight
Verify polarity (DC circuits)
Listen for motor sound when power applied (should hear humming)
If voltage present but no sound: Replace actuator (motor failed)

ACTUATOR RUNS BUT DAMPER DOESN’T MOVE

Check coupling: Tighten set screws (may have loosened)
Manually rotate actuator: Should feel resistance (motor engaged)
Check damper shaft: May be disconnected from blades inside duct
Check linkage: Rods or arms may be disconnected or broken
If coupling slipping: Reposition and tighten, may need new coupling
If shaft broken: Requires damper disassembly/replacement

ACTUATOR MOVES BUT INCORRECT POSITION

Verify control signal at actuator terminals:
- 0V/2V/4mA = Closed
- 10V/10V/20mA = Open
- If signal correct but position wrong: Check mechanical stops
Adjust mechanical stops to match damper travel
Verify coupling aligned correctly (0° = closed, 90° = open)
Check position feedback wiring (if equipped)
If position feedback wrong: Verify feedback wire connected, check at controller
If mechanical stops maxed out: May need larger torque actuator

ACTUATOR STALLS OR BINDS

Check damper blades for physical obstruction
Verify linkage not bent or binding
Check shaft bushings not seized
Measure current draw: >300mA indicates overload
If overcurrent: Damper too large for actuator torque rating
If binding at certain position: Adjust linkage or repair damper
If generally binding: Lubricate shaft bushings, check alignment

SLOW OR ERRATIC MOVEMENT

Measure supply voltage under load: Should stay within ±10%
Check for voltage drop in long wire runs
Verify control signal stable (not fluctuating)
Listen for unusual motor sounds (grinding, clicking)
Check gearbox for wear or damage
If voltage drops: Increase wire gauge or add local power supply
If motor sounds bad: Replace actuator (gearbox failing)

ACTUATOR WON’T RETURN TO FAIL-SAFE (SR models)

Remove power and manually feel spring tension
If no spring tension: Spring broken - replace actuator
If spring weak: May be old actuator, replace
Check for mechanical binding preventing spring return
Verify damper not too large for spring force

POSITION FEEDBACK INCORRECT

Verify feedback wire connected properly
Measure feedback signal at actuator: Should match position (0-10V or 2-10V)
Measure feedback signal at controller: Should match actuator reading
If different at controller: Wiring issue, check for shorts or high resistance
If same but wrong: Feedback potentiometer may be misaligned
If no feedback signal: Replace actuator (feedback pot failed)

ESCALATION - COMPLETE BEFORE CALLING

PRE-ESCALATION CHECKLIST

PROVIDE THIS INFO

Device: [Mfg / Model / Torque Rating / Location]
Damper: [Type: OA/RA/EA / Size / Blade count]
Supply Voltage: _____ VAC/VDC
Control Signal Range: 0-10V / 2-10V / 4-20mA
Commanded Position: _____ %
Actual Position: _____ % (visual or feedback)
Stroke Time: _____ seconds (0-100%)
Symptoms: [Specific problem - not moving, slow, binding, etc.]
Current Draw: _____ mA (if measurable)
Steps Taken: [Troubleshooting completed]
Photos: Attached to Service Fusion ticket

CONTACTS

Field Specialist: [Phone]
Programmer: [Phone] (if control sequence issue)
Project Manager: [Phone] (if wrong actuator size/type)
Dispatch: [Phone] (parts/resources)

COMMON ISSUES & TIPS

✓ Coupling slipping: Use Loctite on set screws, tighten to spec (don’t overtighten)
✓ Actuator too small: Check damper size vs torque rating (35 in-lbs per ft² of damper area)
✓ Spring return vs non-spring: SR for fail-safe applications (OA dampers close on power loss)
✓ 2-10V vs 0-10V: 2-10V provides feedback if wire breaks (will read 0V = alarm)
✓ Mechanical stops: Set stops to match damper travel (prevents over-rotation)
✓ Outdoor applications: Use NEMA 4 rated actuator, apply thread sealant
✓ Linkage alignment: Ensure damper blades parallel to each other through full stroke
✓ Feedback wiring: If 4-wire, feedback goes to AI input on controller (separate from command AO)
✓ Stroke time adjustment: Some models have adjustable stroke time (check manual)
✓ Cold weather: Actuators may be slower in extreme cold (-40°F), allow extra time

Document ID: SSO-DAMPER-001
Revision: 1.0
Next Review: Dec 2026

Quartz 4

Explorer

SSO Damper Actuator