**Device Type:** Output Device - Variable Frequency Drive Control

**Signal:** 0-10VDC speed command + Binary start/stop

**Power:** VFD powered separately (208V-480V typical)

**Version:** 1.0 | **Date:** Dec 2025

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**Common VFD Brands:**

- ABB, Siemens, Allen-Bradley/Rockwell, Schneider Electric (Altivar), Danfoss, Yaskawa, Delta, Eaton

**Used For:**

Fan speed control (supply, return, exhaust), pump speed control (chilled water, condenser water, hot water), precise motor speed regulation, energy savings

- **Analog Speed Command:** 0-10VDC (most common for HVAC)

- **Start/Stop:** Binary output (relay or digital output)

- **Communication:** Modbus RTU/TCP or BACnet (advanced)

- **Speed Command:** 0-10VDC (0V = 0%, 10V = 100% speed)

- **Alternative:** 4-20mA (4mA = 0%, 20mA = 100%)

- **Start Command:** Dry contact closure or 24VDC signal

- **Status Feedback:** Auxiliary relay contacts (running, fault, at speed)

- **Wire Type:** 18AWG for control signals, shielded recommended

**Environment:** Indoor electrical room, 32-104°F typical

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- ☑ Safety glasses (ANSI Z87.1)

- ☑ **Insulated gloves (Class 0 minimum)**

- ☑ **Arc-rated clothing (if working on energized equipment)**

- ☑ Hard hat

- ☑ Face shield (if near bus bars)

- ⚠️ **HIGH VOLTAGE - LETHAL** - VFD power terminals (208V-480V)

- ⚠️ **ARC FLASH HAZARD** - Can cause severe burns or death

- ⚠️ **STORED ENERGY** - VFD capacitors stay charged after power off (wait 5+ minutes)

- ⚠️ **ROTATING EQUIPMENT** - Motor/fan controlled by VFD

- ⚠️ **REMOTE START HAZARD** - Motor can start unexpectedly from BAS command

- ⚠️ **VFD can restart motor remotely** - Lock out power before servicing motor

- ⚠️ **Capacitors remain charged** - Wait 5-10 minutes after power off, verify 0V

- ⚠️ **DC bus voltage >400V** - Lethal voltage inside VFD even when motor off

- [ ] **REQUIRED for VFD power wiring** - Lock out main disconnect

- [ ] **Required for motor service** - Even if only working on BAS control

- [ ] NOT required for low-voltage control wiring (if VFD already installed and powered down)

- [ ] Wait 5-10 minutes after lockout for capacitor discharge

- [ ] Verify 0V with meter before touching terminals

- Licensed electrician for power wiring

- Arc flash training and PPE

- VFD-specific training (manufacturer recommended)

- BAS technician can wire control signals if power side locked out

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- Wire strippers (18AWG)

- Screwdrivers (insulated)

- Multimeter (DMM)

- Megohmmeter (for motor insulation test)

- Allen wrenches (VFD parameter access)

- Label maker

- Laptop/tablet (for VFD programming)

- Control wiring (18AWG, shielded recommended)

- Wire nuts or terminal blocks

- VFD programming cable/adapter (manufacturer specific)

- Labels (clearly mark all control wiring)

- [ ] **Verify VFD sized correctly:** HP, voltage, amperage match motor

- [ ] Confirm control voltage available (24VDC from controller typical)

- [ ] Verify VFD has 0-10VDC analog input

- [ ] Confirm VFD has digital run input

- [ ] Review VFD installation manual

- [ ] **Lock out VFD power** before wiring control terminals

- **Analog Speed Input:** AI+, AI-, or 0-10V+, 0-10V-

- **Digital Run Input:** DI1, Run, Start/Stop

- **Common:** COM, GND, Digital Common

- **Status Outputs:** RO1, RO2 (relay outputs for status)

1. **Locate VFD analog input terminals:**

- Typically labeled: AI+, AI-, or AIN+, AIN-

- Check VFD manual for exact terminal numbers

2. **Connect from controller:**

- Controller AO+ (0-10V output) → VFD AI+ terminal

- Controller COM → VFD AI- terminal

- Tighten terminals: 7-9 in-lbs

- Ground shield at controller end only (not both ends)

3. **Verify voltage range:**

- Most VFDs default to 0-10V input

- Some can be configured for 4-20mA - verify setting

1. **Locate VFD digital input terminals:**

- Typically labeled: DI1, Run, or Start

- May require jumper removal (VFD ships with local control enabled)

2. **Connect from controller:**

* Controller relay NO contact → VFD DI1 and COM

* When relay closes = VFD runs

* Controller DO+ → VFD DI1

* Controller COM → VFD COM

* When DO energized = VFD runs

3. **Verify input voltage:**

- Most VFDs accept 24VDC digital inputs

- Some require configuration for voltage vs contact

1. **Locate VFD relay output terminals:**

- Typically: RO1-COM-NO-NC (relay output 1)

- Check VFD manual for terminal assignment

2. **Connect to controller binary input:**

- VFD RO1-NO → Controller BI (binary input)

- VFD RO1-COM → Controller COM

- When VFD running, contact closes = BI TRUE

3. **Configure VFD relay output:**

- Program RO1 for "Running" status

- Or "Fault" status (opens when fault)

- Or "At Speed" status (closes when >90% speed)

- Speed command: "VFD-AHU1-SPEED"

- Run command: "VFD-AHU1-RUN"

- Status feedback: "VFD-AHU1-STATUS"

- Label at both controller and VFD ends

1. **Control Mode:**

- Set to "External" or "Terminal Control"

- Disable keypad/local control

2. **Speed Reference:**

- Set to "AI1" or "Analog Input 1"

- Verify 0-10VDC range selected

3. **Run Command:**

- Set to "DI1" or "Digital Input 1"

- Verify contact or voltage input type

4. **Min/Max Speed Limits:**

- Minimum speed: 20-30% typical (prevents motor stalling)

- Maximum speed: 100% or less (may limit for noise/safety)

5. **Acceleration/Deceleration Ramps:**

- Accel time: 10-30 seconds typical (prevents high inrush)

- Decel time: 10-30 seconds typical (prevents water hammer)

6. **Motor Nameplate Data:**

- Enter motor voltage, FLA, RPM, Hz from motor nameplate

- VFD uses for protection and efficiency

7. **Status Relay Configuration:**

- Program RO1 for "Running" or "Fault"

- Set NO or NC operation

1. Remove lockout device

2. Restore VFD power

3. Verify VFD display shows "Ready"

4. Do NOT command run until motor verified safe

- [ ] All control wiring terminated tight

- [ ] VFD parameters programmed correctly

- [ ] Labels applied to all control wiring

- [ ] VFD display shows "Ready" (no faults)

- [ ] Motor rotation verified (see proof out tests)

- [ ] Photos taken of wiring and parameter settings

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- **Speed Command:** 0V at VFD AI+ terminal

- **Run Command:** Open (relay) or 0V (digital output)

- **VFD Display:** "Ready" or "Stop"

- **Status Feedback:** FALSE/0 (not running)

- **Speed Command:** 5V at VFD AI+ terminal (50% of 0-10V)

- **Run Command:** Closed (relay) or 24V (digital output)

- **VFD Display:** Shows % speed, Hz, RPM, amps

- **Status Feedback:** TRUE/1 (running)

- **Motor Operation:** Running at ~50% of full speed

| Command | Speed | Frequency | Motor RPM | Current |

|---------|-------|-----------|-----------|---------|

| 0V / 0% | 0% | 0 Hz | 0 | 0A |

| 2V / 20% | 20% | 12 Hz | 350 RPM | 3-5A |

| 5V / 50% | 50% | 30 Hz | 875 RPM | 8-12A |

| 10V / 100% | 100% | 60 Hz | 1750 RPM | 20-27A |

**Note:** Current values depend on motor load (fan/pump affinity laws)

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- **Do:** Command VFD to 0%, 25%, 50%, 75%, 100% from controller

- **Measure:** Voltage at VFD AI+ terminal with multimeter

* 0% = 0V

* 25% = 2.5V

* 50% = 5V

* 75% = 7.5V

* 100% = 10V

- **Pass If:** Voltage proportional to command (±0.2V)

- **Do:** Command VFD to run from controller

* Relay closes (continuity) or digital output energizes (24V)

* VFD display changes to "Run" or shows Hz/RPM

* Motor does NOT start yet (speed = 0)

- **Pass If:** Run command received by VFD

- **WARNING:** Have qualified person ready to hit E-stop

- **Do:**

1. Command VFD to run at 10-20% speed (slow start)

2. Observe motor/fan rotation direction

* **Fan:** Rotation matches directional arrow on housing

* **Pump:** Rotation matches arrow on pump body

* **Correct direction:** Airflow/water flow in expected direction

* STOP immediately

* Lock out VFD

* Swap any two motor leads (L1-L2, L2-L3, or L1-L3)

* Restore power and retest

- **Pass If:** Correct rotation confirmed

- **Do:** Command VFD from 0% to 100% over 30 seconds

* Smooth acceleration (no jerking or surging)

* Current gradually increases

* No overcurrent faults

* Motor reaches full speed within accel time

- **Pass If:** Smooth ramp to full speed

- **Do:** Command VFD on and off

* Status BI changes from FALSE to TRUE when VFD runs

* Status BI changes from TRUE to FALSE when VFD stops

* Controller graphics show VFD running

- **Pass If:** Status feedback matches actual operation

- **Do:** Command VFD to minimum speed (20-30%)

* Motor runs smoothly without stalling

* No vibration or unusual noise

* Current stable

- **Pass If:** Motor operates stably at minimum speed

- **If motor stalls:** Increase minimum speed parameter

- **Do:** Command VFD to 100% speed

- **Measure:** Motor current with clamp meter

* Current <100% of motor FLA

* VFD shows Hz, RPM, amps

* No overcurrent or overload faults

* Normal motor sound (no grinding or vibration)

- **Pass If:** Motor operates correctly at full load

- **Do:** Press VFD emergency stop button (E-stop)

* Motor stops immediately (coast stop) or within decel time

* VFD shows "E-stop" or "Fault"

* Status feedback changes to FALSE

* Controller shows fault or alarm

- **Pass If:** E-stop functions correctly

- **Reset:** Clear E-stop and VFD fault before resuming

- [ ] VFD speed command appears in controller AO list

- [ ] VFD run command appears in controller BO list

- [ ] Status feedback appears in controller BI list

- [ ] Graphics show VFD speed, status, and control

- [ ] Control sequences operate VFD correctly

- [ ] No communication errors or faults

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1. **Check run command:**

- Measure at VFD DI1: Should see closed contact or 24V

- **If no signal:** Controller not commanding run

2. **Check VFD parameters:**

- Verify run command set to DI1 (external control)

- Check if keypad/local control still enabled (disable it)

3. **Check VFD faults:**

- Display shows fault code?

- Reset fault and retry

4. **Check interlocks:**

- Some VFDs require multiple inputs to run

- Verify all required interlocks satisfied

1. **Measure speed command voltage:**

- Should be 0-10V at VFD AI+ terminal

- **If wrong voltage:** Controller output problem

2. **Check VFD parameter:**

- Verify AI1 set for 0-10VDC (not 4-20mA)

- Check min/max speed limits

3. **Check wiring:**

- Verify AI+ and AI- not reversed

- Check for voltage drop in long wire runs

4. **Calibrate:** Some VFDs allow analog input calibration

1. **STOP immediately** - Wrong rotation can damage equipment

2. **Lock out VFD power**

3. **Swap two motor leads:**

- Have electrician swap any two of the three motor leads

- Example: Swap L1 and L2 at VFD output or motor terminals

4. **Restore power and retest**

5. **Verify:** Rotation now correct

- Motor overloaded or mechanical binding

- Accel time too short (increase to 20-30 sec)

- Check motor current vs FLA rating

- **If current >FLA:** Motor or load problem

- Decel time too short (increase to 20-30 sec)

- Regenerative load (fan coasting = backfeeds VFD)

- Add braking resistor if frequent overvoltage

- Incoming power voltage too low

- Check supply voltage at VFD input terminals

- Voltage sag during motor start

- Motor insulation failure

- Test motor with megohmmeter (should be >1 megohm to ground)

- Check motor cable for damage

- VFD overheating (check cooling fans)

- Ambient temperature too high (>104°F)

- Blocked ventilation (clean filters)

- Missing input phase (L1, L2, or L3)

- Check fuses, breakers, contactors

- Measure voltage at VFD input (all 3 phases present?)

1. **Check VFD output:**

- Measure voltage at T1, T2, T3 (VFD motor terminals)

- Should see voltage when VFD running

- **If no voltage:** VFD output problem

2. **Check motor connections:**

- Verify motor cable connected

- Check for loose or broken wires

3. **Check motor contactor** (if present):

- Some installations have contactor between VFD and motor

- Verify contactor energized when VFD runs

4. **Test motor:**

- May be motor problem (bearing seizure, winding failure)

- Megohmmeter test motor insulation

1. **Check VFD relay output:**

- Verify RO1 configured for "Running" status

- Test continuity across relay contacts when running

- **If open when should be closed:** VFD relay not operating

2. **Check wiring:** Verify connections at controller BI

3. **Check controller config:** BI configured as NO or NC?

1. **Increase minimum speed:** Typical 20-30%

2. **Check V/Hz curve:** May need boost voltage at low Hz

3. **Check load:** Motor may be oversized for load

1. **Check motor mounts:** Loose or damaged

2. **Fan unbalanced:** Check fan blades and wheel

3. **VFD switching frequency:** Increase carrier frequency (reduces audible noise)

4. **Mechanical resonance:** Avoid certain speed ranges

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- [ ] Verified speed command voltage at VFD (0-10V)

- [ ] Verified run command at VFD (closed contact or 24V)

- [ ] Checked VFD display for fault codes

- [ ] Reviewed VFD parameters (control mode, speed ref, run cmd)

- [ ] Measured motor current (compare to FLA)

- [ ] Verified correct motor rotation direction

- [ ] Tested status feedback operation

- [ ] Documented all VFD parameter settings

- [ ] Taken photos of VFD display and wiring

- **VFD:** [Mfg / Model / HP Rating / Voltage]

- **Motor:** [HP / Voltage / FLA / Application]

- **Speed Command Measured:** _____ VDC at VFD AI+

- **Run Command Status:** Closed/Open or _____ VDC

- **VFD Display:** [Fault code / Ready / Running / Hz / Amps]

- **Motor Current:** _____ A (measured with clamp meter)

- **Motor FLA:** _____ A (from nameplate)

- **Rotation Direction:** Correct / Wrong / Not tested

- **Symptoms:** [Won't start, wrong speed, trips, noise, etc.]

- **Parameter Settings:** [Control mode, speed ref, run cmd]

- **Steps Taken:** [Troubleshooting completed]

- **Field Specialist:** [Phone]

- **Electrician:** [Phone] (motor wiring issues)

- **VFD Technician:** [Phone] (manufacturer support)

- **Programmer:** [Phone] (control logic issues)

- **Dispatch:** [Phone]

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✓ **Motor rotation:** ALWAYS verify correct rotation on first startup - wrong direction damages equipment

✓ **Accel/decel times:** 10-30 seconds typical - prevents overcurrent and water hammer

✓ **Minimum speed:** 20-30% prevents motor stalling and unstable operation

✓ **Shielded cable:** Use for analog speed command if >50 feet - prevents interference

✓ **Ground shield once:** At controller end only, never both ends (prevents ground loops)

✓ **Control mode:** Must be set to "External" or "Terminal" control

✓ **Parameter backup:** Save VFD parameters to file after programming

✓ **VFD sizing:** Must match motor HP and voltage - undersized VFD trips on overcurrent

✓ **Motor cable:** VFD-rated cable required - standard motor wire may not be adequate

✓ **Bypass contactor:** Allows manual operation if VFD fails (emergency backup)

✓ **Energy savings:** VFD reduces fan/pump energy by 50-70% at part load (affinity laws)

✓ **Soft start:** VFD eliminates need for separate soft starter

✓ **Remote monitoring:** Enable Modbus/BACnet for advanced diagnostics

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**Document ID:** SSO-VFD-001

**Revision:** 1.0

**Next Review:** Dec 2026

**SAFETY WARNING:** VFDs contain lethal voltages and can restart motors remotely. Always lock out power before servicing motor or VFD. Capacitors remain charged after power off - wait 5-10 minutes and verify 0V before touching terminals.