**Device Type:** Analog Input - Current Sensor

**Signal:** 0-10VDC / 4-20mA output

**Power:** 24VAC/VDC (self-powered or loop-powered)

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

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**Common Models:**

- Veris H8000 Series, CR Magnetics CR4395/CR5395, Functional Devices RIBX, Ohio Semitronics GW5, Wattnode WNC

**Used For:**

Motor current monitoring, proof of operation, energy monitoring, fault detection, load verification, kW demand tracking

- **Measurement:** AC current (amperage)

- **Ranges:** Common ranges:

* 0-5A, 0-10A, 0-20A, 0-50A, 0-100A, 0-200A, 0-500A

* Select range for 150% of maximum expected load

- **Technology:** Split-core CT (current transformer) - most common

- **Output:** 0-10VDC or 4-20mA proportional to current

- **Power:** 24VAC/VDC (externally powered) or loop-powered (4-20mA only)

- **Wire Type:** 18AWG for signal output

- **Accuracy:** ±1-2% of reading typical

**Environment:** 32-140°F, 0-95% RH non-condensing (indoor electrical rooms)

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- ☑ Safety glasses (ANSI Z87.1)

- ☑ **Insulated gloves (Class 0 minimum for <1000V)**

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

- ☑ Hard hat

- ☑ Face shield (if working near exposed bus bars)

- ⚠️ **HIGH VOLTAGE - LETHAL** - Line voltage present (120V-480V typical)

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

- ⚠️ **ENERGIZED CONDUCTORS** - Do not touch wires with CT installed

- ⚠️ **MAGNETIC FIELDS** - Strong fields near high-current conductors

- ⚠️ **NEVER open CT secondary while CT installed on energized conductor** - Can generate lethal voltage

- ⚠️ **NEVER install CT on energized conductor unless qualified** - Only qualified electricians

- ⚠️ **CT must be closed before energizing** - Open CT can arc and fail

- [ ] **REQUIRED if installing on existing energized system**

- [ ] **RECOMMENDED for all installations** - Safer to install with power off

- [ ] Only qualified electricians should work on energized equipment

- [ ] Arc flash hazard assessment required per NFPA 70E

- [ ] If must work energized: Follow company arc flash procedures

- Licensed electrician (check local codes)

- Arc flash training and PPE

- Electrical safety certification

- Authorization to work on energized equipment

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- Insulated tools (if working energized)

- Wire strippers (18AWG)

- Screwdrivers (insulated handles)

- Multimeter (DMM)

- Clamp meter (for verification)

- Label maker

- Voltage tester (non-contact)

- Current transducer (CT) - correct range for load

- Control wiring (18AWG)

- Wire nuts or terminal blocks

- Cable ties (for CT support)

- Labels (CT location and phase)

- [ ] **CRITICAL:** Verify CT range ≥150% of maximum load current

- [ ] **Confirm CT output type matches controller input (0-10V vs 4-20mA)**

- [ ] Identify correct phase/conductor to monitor

- [ ] Review electrical single-line diagram

- [ ] Verify power locked out (if de-energized install)

- [ ] Confirm qualified personnel available (if energized install)

1. **Lock out power:**

- Coordinate with building operator

- Lock circuit breaker in OFF position

- Apply personal lock and tag

- Verify zero voltage with meter

- Wait for motor to stop completely

2. **Select conductor:**

- **Single phase:** Install CT on hot leg (L1) - NOT neutral

- **Three phase:** Install CT on one phase (typically L1)

- **For all three phases:** Need three CTs

- **Verify conductor size** fits through CT opening

3. **Install split-core CT:**

- Open CT hinge (split-core opens like clamshell)

- Position CT around conductor (centered)

- **IMPORTANT: Arrow on CT points toward load** (away from source)

- Close CT firmly until it clicks (secure latch)

- **Do NOT force** - if won't close, verify no obstruction

- Support CT with cable tie to prevent stress on conductor

4. **Connect CT output wiring:**

* Red: +Power (24VAC/VDC from controller)

* Black: Common

* White/Green: Signal output (0-10V)

* Connect to controller 4-20mA input (polarity matters)

* No external power required

- Tighten terminals: 7-9 in-lbs

- Route wiring away from high-voltage conductors

5. **Label CT and wiring:**

- CT label: "MOTOR-1-L1" (motor name and phase)

- Arrow direction verified (toward load)

- Wire labels at both ends

6. **Restore power:**

- Verify CT fully closed

- Verify wiring secure

- Remove personal lockout

- Restore breaker to ON position

- Follow company arc flash procedures

- Wear required arc-rated PPE

- Use insulated tools only

- Install CT while maintaining safe distance from exposed conductors

- [ ] CT fully closed and latched

- [ ] Arrow pointing toward load (verified)

- [ ] CT positioned on correct phase

- [ ] Wiring routed safely away from high-voltage

- [ ] All terminals tight

- [ ] Labels applied to CT and wiring

- [ ] Power restored

- [ ] Photos taken

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- **CT Output:** Should read 0V or 4mA (no current flowing)

- **CT Closed:** Verify CT fully latched (no gap)

- **Wiring Continuity:** <5 ohms end-to-end

| Motor Current | Typical Output (0-50A CT) |

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

| 0A (motor off) | 0V |

| 10A | 2V |

| 25A (mid-load) | 5V |

| 50A (full load) | 10V |

| Motor Current | Typical Output (0-50A CT) |

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

| 0A (motor off) | 4mA |

| 10A | 7.2mA |

| 25A (mid-load) | 12mA |

| 50A (full load) | 20mA |

- **FLA (Full Load Amps):** On motor nameplate

- **Starting current:** 5-8× FLA typical (brief inrush)

- **Running current:** 70-100% FLA normal load

- **No-load current:** 20-40% FLA typical

- **Overcurrent:** >100% FLA indicates overload

- Clamp actual conductor with clamp meter

- Compare clamp meter reading to CT output

- Calculate expected CT output: (Actual Current / CT Range) × Output Range

- **Example:** 25A actual, 0-50A CT, 0-10V output: (25/50) × 10V = 5V expected

- **Acceptable:** Within ±5% of calculated value

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- **Do:** Motor off, measure CT output

- **Expect:**

* 0-10V output: 0-0.2V

* 4-20mA output: 4-4.2mA

- **Pass If:** Reading near zero (no current)

- **Do:** Start motor, observe CT output change

* Reading increases from 0 to running current within 1-2 seconds

* Brief spike during startup (5-8× normal)

* Stabilizes at normal running current

- **Pass If:** CT responds to motor starting

- **Do:** With motor running, compare CT to clamp meter

- **Expect:** CT reading within ±5% of clamp meter

- **Pass If:** Acceptable accuracy confirmed

- **Do:** If load varies (VFD, dampers, valves), vary motor load

- **Expect:** CT reading tracks load changes

- **Pass If:** Output proportional to current

- **Do:** Compare current on L1, L2, L3

- **Expect:** All three phases within ±10% of each other

- **Pass If:** Balanced load (no phase loss)

- **If unbalanced >10%:** Potential motor or wiring problem

- [ ] CT appears in controller AI list

- [ ] Reading displays in Amps

- [ ] Graphics show live current reading

- [ ] Used for proof of operation or alarms

- [ ] No faults or errors

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1. Verify motor is running (listen/observe)

2. Measure actual current with clamp meter - is there current?

- **If no current:** Motor not running or power issue

3. Check CT closed and latched properly

4. Verify CT on correct conductor (not neutral)

5. Check CT arrow pointing toward load

6. For powered CT: Verify 24VAC/VDC supply voltage

7. Test CT output wiring continuity: <5 ohms

8. **If motor running with current but CT reads zero:** CT failed - replace

1. Verify CT range adequate (not oversized)

- Example: 10A load with 0-500A CT gives low resolution

2. Check CT fully closed (gap causes low reading)

3. Verify conductor centered in CT opening

4. Compare to clamp meter reading

5. Check for loose CT output wiring

6. **If consistently low by same %:** CT may need calibration

1. Verify CT range matches spec (not undersized)

2. Check CT arrow direction (reversed gives false reading)

3. Verify only ONE conductor through CT

- **Common error:** Both hot and neutral = double reading

4. Compare to clamp meter

5. **If consistently high:** CT may be wrong ratio or failing

1. Check CT securely mounted (vibration can cause fluctuation)

2. Verify CT fully closed and latched

3. Check output wiring for loose connections

4. Look for EMI/RFI interference (route wiring away from power cables)

5. Verify good connection at controller input

6. **If motor has VFD:** Some fluctuation normal (PWM switching)

1. **CT arrow reversed** - pointing toward source instead of load

2. Open CT (if can be done safely) and reinstall with arrow toward load

3. **Or:** Some controllers allow signal reversal in software

1. Normal motor startup is 5-8× FLA for 1-2 seconds

2. Adjust controller alarm time delay (3-5 seconds typical)

3. Or set alarm threshold higher (125% FLA instead of 110%)

1. Conductor too large for CT opening - need larger CT

2. Multiple conductors trying to fit through CT

3. CT hinge damaged - replace CT

4. Verify CT rated for conductor size

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- [ ] Verified motor is running (visual/audible confirmation)

- [ ] Measured actual current with clamp meter

- [ ] Verified CT fully closed and latched

- [ ] Checked CT arrow pointing toward load

- [ ] Verified only ONE conductor through CT

- [ ] Verified correct conductor (not neutral)

- [ ] Checked supply voltage for powered CT (24V ±10%)

- [ ] Compared CT reading to clamp meter reading

- [ ] Documented motor nameplate FLA

- [ ] Taken photos of CT installation

- **CT:** [Mfg / Model / Range / Location]

- **Motor:** [HP / Voltage / FLA from nameplate]

- **CT Output Type:** 0-10V / 4-20mA

- **CT Reading:** _____ A (from controller)

- **Clamp Meter Reading:** _____ A (actual current)

- **Motor Status:** Running / Off / Variable load

- **CT Arrow Direction:** Toward load / Reversed / Unknown

- **Supply Voltage (if powered):** _____ VAC/VDC

- **Conductor:** L1 / L2 / L3 / Single phase

- **Symptoms:** [Zero, low, high, erratic, negative]

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

- **Field Specialist:** [Phone]

- **Electrician:** [Phone] (if CT reinstall needed)

- **Programmer:** [Phone] (if alarm/threshold issue)

- **Dispatch:** [Phone]

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- Rarely required - CTs are typically factory calibrated

- If reading consistently off by >5%

- After CT replacement

1. Measure actual current with calibrated clamp meter

2. Record CT output from controller

3. Calculate expected output: (Actual Current / CT Range) × Output Range

4. Compare actual to expected

5. **If within ±5%:** No calibration needed

6. **If outside ±5%:** Apply controller offset or replace CT

- Most controllers allow calibration offset

- Calculate correction factor

- Apply in controller configuration

- Retest with clamp meter

- CT Range: 0-50A, Output: 0-10V

- Clamp meter: 25A actual

- Expected output: (25/50) × 10V = 5.0V

- CT reads: 4.5V

- Error: -0.5V (-10%)

- Apply +0.5V offset in controller

**Acceptable Tolerance:** ±5% of reading

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✓ **CT sizing:** Select range for 150% of maximum expected current (allows for motor startup)

✓ **Arrow direction:** MUST point toward load (away from breaker) - reversed gives false readings

✓ **One conductor only:** Common error is running supply AND return through CT = 0 reading

✓ **Not on neutral:** Always install on hot leg, never neutral (neutral current should equal hot)

✓ **Three-phase motors:** Need three CTs for full monitoring (one per phase)

✓ **Single-phase motors:** One CT on hot leg sufficient

✓ **VFD applications:** CT must be rated for PWM waveforms (most modern CTs are)

✓ **Proof of operation:** Set alarm at 20-30% FLA (below normal running current)

✓ **Energy monitoring:** Sum all three phases for total power calculation (requires kW transducer)

✓ **Split-core advantage:** Can install without de-energizing (but only if qualified)

✓ **Solid-core CTs:** More accurate but require conductor disconnection for install

✓ **Startup inrush:** Normal 5-8× FLA spike for 1-2 seconds - don't set alarms too sensitive

- 1 HP: 1.1A

- 2 HP: 2.2A

- 3 HP: 3.3A

- 5 HP: 5.5A

- 7.5 HP: 9A

- 10 HP: 11A

- 15 HP: 17A

- 20 HP: 22A

- 25 HP: 27A

- 30 HP: 32A

- 40 HP: 43A

- 50 HP: 54A

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**Document ID:** SSO-CURRENT-001

**Revision:** 1.0

**Next Review:** Dec 2026

**SAFETY WARNING:** Installation of current transducers involves work on or near energized electrical equipment. Only qualified personnel should perform this work. Always follow lockout/tagout procedures when possible.