VFD Control Integration - Quick Reference SSO

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

DEVICE OVERVIEW

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

Control Methods:

Analog Speed Command: 0-10VDC (most common for HVAC)
Start/Stop: Binary output (relay or digital output)
Communication: Modbus RTU/TCP or BACnet (advanced)

Specifications:

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

SAFETY - PPE REQUIRED

☑ 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)

HAZARDS

⚠️ 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

CRITICAL SAFETY RULES

⚠️ 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

LOCKOUT/TAGOUT

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

QUALIFIED PERSONNEL ONLY

VFD installation/service requires:

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

INSTALLATION CHECKLIST

TOOLS NEEDED

Wire strippers (18AWG)
Screwdrivers (insulated)
Multimeter (DMM)
Megohmmeter (for motor insulation test)
Allen wrenches (VFD parameter access)
Label maker
Laptop/tablet (for VFD programming)

MATERIALS

Control wiring (18AWG, shielded recommended)
Wire nuts or terminal blocks
VFD programming cable/adapter (manufacturer specific)
Labels (clearly mark all control wiring)

PRE-INSTALL

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

CONTROL WIRING STEPS

TERMINAL IDENTIFICATION (varies by manufacturer):

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)

STEP 1: Wire Analog Speed Command (0-10VDC)

Locate VFD analog input terminals:
- Typically labeled: AI+, AI-, or AIN+, AIN-
- Check VFD manual for exact terminal numbers
Connect from controller:
- Controller AO+ (0-10V output) → VFD AI+ terminal
- Controller COM → VFD AI- terminal
- Tighten terminals: 7-9 in-lbs
- Use shielded cable if run >50 feet
- Ground shield at controller end only (not both ends)
Verify voltage range:
- Most VFDs default to 0-10V input
- Some can be configured for 4-20mA - verify setting

STEP 2: Wire Digital Run Command (Start/Stop)

Locate VFD digital input terminals:
- Typically labeled: DI1, Run, or Start
- May require jumper removal (VFD ships with local control enabled)
Connect from controller:
- Option A: Dry contact (relay):
  - Controller relay NO contact → VFD DI1 and COM
  - When relay closes = VFD runs
- Option B: Digital output (24VDC):
  - Controller DO+ → VFD DI1
  - Controller COM → VFD COM
  - When DO energized = VFD runs
Verify input voltage:
- Most VFDs accept 24VDC digital inputs
- Some require configuration for voltage vs contact

STEP 3: Wire Status Feedback (Optional but Recommended)

Locate VFD relay output terminals:
- Typically: RO1-COM-NO-NC (relay output 1)
- Check VFD manual for terminal assignment
Connect to controller binary input:
- VFD RO1-NO → Controller BI (binary input)
- VFD RO1-COM → Controller COM
- When VFD running, contact closes = BI TRUE
Configure VFD relay output:
- Program RO1 for “Running” status
- Or “Fault” status (opens when fault)
- Or “At Speed” status (closes when >90% speed)

STEP 4: Label All Wiring

Speed command: “VFD-AHU1-SPEED”
Run command: “VFD-AHU1-RUN”
Status feedback: “VFD-AHU1-STATUS”
Label at both controller and VFD ends

STEP 5: VFD Parameter Programming

CRITICAL PARAMETERS TO CONFIGURE:

Control Mode:
- Set to “External” or “Terminal Control”
- Disable keypad/local control
Speed Reference:
- Set to “AI1” or “Analog Input 1”
- Verify 0-10VDC range selected
Run Command:
- Set to “DI1” or “Digital Input 1”
- Verify contact or voltage input type
Min/Max Speed Limits:
- Minimum speed: 20-30% typical (prevents motor stalling)
- Maximum speed: 100% or less (may limit for noise/safety)
Acceleration/Deceleration Ramps:
- Accel time: 10-30 seconds typical (prevents high inrush)
- Decel time: 10-30 seconds typical (prevents water hammer)
Motor Nameplate Data:
- Enter motor voltage, FLA, RPM, Hz from motor nameplate
- VFD uses for protection and efficiency
Status Relay Configuration:
- Program RO1 for “Running” or “Fault”
- Set NO or NC operation

TYPICAL PARAMETER EXAMPLES (varies by manufacturer):

P001 = Control Mode → External Control
P002 = Speed Reference → AI1 (0-10V)
P003 = Run Command → DI1 (Digital Input)
P004 = Min Speed → 30%
P005 = Max Speed → 100%
P006 = Accel Time → 20 seconds
P007 = Decel Time → 20 seconds
P010 = Motor Voltage → 460V
P011 = Motor FLA → 27A
P012 = Motor RPM → 1750

STEP 6: Restore Power and Test

Remove lockout device
Restore VFD power
Verify VFD display shows “Ready”
Do NOT command run until motor verified safe

POST-INSTALL

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

EXPECTED READINGS

PRE-POWER (Controller Commands VFD Off)

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)

POWER-UP (Controller Commands VFD to 50% Speed)

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

TYPICAL VFD DISPLAY VALUES (Running at 60Hz = 100% 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)

PROOF OUT TESTS

TEST 1: Speed Command Verification

Do: Command VFD to 0%, 25%, 50%, 75%, 100% from controller
Measure: Voltage at VFD AI+ terminal with multimeter
Expect:
- 0% = 0V
- 25% = 2.5V
- 50% = 5V
- 75% = 7.5V
- 100% = 10V
Pass If: Voltage proportional to command (±0.2V)

TEST 2: Run Command Verification

Do: Command VFD to run from controller
Expect:
- 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

TEST 3: Motor Rotation Direction (CRITICAL SAFETY TEST)

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
Expect:
- Fan: Rotation matches directional arrow on housing
- Pump: Rotation matches arrow on pump body
- Correct direction: Airflow/water flow in expected direction
If WRONG 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

TEST 4: Speed Ramp Test

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

TEST 5: Status Feedback Verification

Do: Command VFD on and off
Expect:
- 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

TEST 6: Minimum Speed Test

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

TEST 7: Full Speed Load Test

Do: Command VFD to 100% speed
Measure: Motor current with clamp meter
Expect:
- 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

TEST 8: Emergency Stop Test

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

TEST 9: Controller Integration

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

TROUBLESHOOTING

VFD WON’T START (Display Shows “Ready” but No Run)

Check run command:
- Measure at VFD DI1: Should see closed contact or 24V
- If no signal: Controller not commanding run
Check VFD parameters:
- Verify run command set to DI1 (external control)
- Check if keypad/local control still enabled (disable it)
Check VFD faults:
- Display shows fault code?
- Reset fault and retry
Check interlocks:
- Some VFDs require multiple inputs to run
- Verify all required interlocks satisfied

VFD RUNS BUT WRONG SPEED

Measure speed command voltage:
- Should be 0-10V at VFD AI+ terminal
- If wrong voltage: Controller output problem
Check VFD parameter:
- Verify AI1 set for 0-10VDC (not 4-20mA)
- Check min/max speed limits
Check wiring:
- Verify AI+ and AI- not reversed
- Check for voltage drop in long wire runs
Calibrate: Some VFDs allow analog input calibration

MOTOR ROTATION WRONG DIRECTION

STOP immediately - Wrong rotation can damage equipment
Lock out VFD power
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
Restore power and retest
Verify: Rotation now correct

VFD SHOWS FAULT / TRIPS

Common VFD Faults:

Overcurrent (OC):

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

Overvoltage (OV):

Decel time too short (increase to 20-30 sec)
Regenerative load (fan coasting = backfeeds VFD)
Add braking resistor if frequent overvoltage

Undervoltage (UV):

Incoming power voltage too low
Check supply voltage at VFD input terminals
Voltage sag during motor start

Ground Fault:

Motor insulation failure
Test motor with megohmmeter (should be >1 megohm to ground)
Check motor cable for damage

Overtemperature:

VFD overheating (check cooling fans)
Ambient temperature too high (>104°F)
Blocked ventilation (clean filters)

Phase Loss:

Missing input phase (L1, L2, or L3)
Check fuses, breakers, contactors
Measure voltage at VFD input (all 3 phases present?)

VFD RUNS BUT MOTOR DOESN’T

Check VFD output:
- Measure voltage at T1, T2, T3 (VFD motor terminals)
- Should see voltage when VFD running
- If no voltage: VFD output problem
Check motor connections:
- Verify motor cable connected
- Check for loose or broken wires
Check motor contactor (if present):
- Some installations have contactor between VFD and motor
- Verify contactor energized when VFD runs
Test motor:
- May be motor problem (bearing seizure, winding failure)
- Megohmmeter test motor insulation

STATUS FEEDBACK NOT WORKING

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
Check wiring: Verify connections at controller BI
Check controller config: BI configured as NO or NC?

MOTOR STALLS AT LOW SPEED

Increase minimum speed: Typical 20-30%
Check V/Hz curve: May need boost voltage at low Hz
Check load: Motor may be oversized for load

EXCESSIVE NOISE OR VIBRATION

Check motor mounts: Loose or damaged
Fan unbalanced: Check fan blades and wheel
VFD switching frequency: Increase carrier frequency (reduces audible noise)
Mechanical resonance: Avoid certain speed ranges

ESCALATION - COMPLETE BEFORE CALLING

PRE-ESCALATION CHECKLIST

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

PROVIDE THIS INFO

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]

CONTACTS

Field Specialist: [Phone]
Electrician: [Phone] (motor wiring issues)
VFD Technician: [Phone] (manufacturer support)
Programmer: [Phone] (control logic issues)
Dispatch: [Phone]

COMMON ISSUES & TIPS

✓ 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

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.

Quartz 4

Explorer

SSO Vfd Control