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WattNode Module



Manuals and Technical Documents

Firmware Updates

The WattNode Meter Module production firmware version is periodically updated. In most cases, updating meter firmware is not necessary unless you are experiencing problems or need a new feature. The Meter Module supports both field upgrades and factory firmware updates. There is a nominal charge for factory firmware updates unless they are needed to fix a bug under warranty.

See WND Series WattNode Modbus Firmware Versions page for the full list of versions.

Measurement Specifications

Revenue Grade Accuracy

  • Meets or exceeds the ANSI C12.1-2008 standard when used with class 0.6 or better current transformers
  • Meet or exceeds the ANSI C12.20-2010 standard when used with class 0.3 or better current transformers
  • CT Measurement Range: 1% – 120% of rated current

Current Transformers

All available Current Transformers (CTs) output safe 0.333 Vac at rated current.

  • ACTL-0750 series split core from 5 A to 250 A, accuracy class 1.2 and 0.6 available
  • ACTL-1250 series split core from 250 A to 600 A, accuracy class 1.2, 0.6, and 0.3 available
  • CTBL series large split-core CTs for high currents (standard and custom sizes to 6000A)
  • RCxL series Rogowski coils with build-in integrator
  • CTRC series Rogowski coils for tight spaces with integrator module
  • CTT series solid core CTs are less expensive and prevent tampering

Measurement Types Supported

  • Supports floating-point and integer registers
  • Active (real) power: watts, individual meter elements and sum of elements
  • Reactive power: VARs, individual meter elements and sum of elements
  • Power factor: individual meter elements and sum of elements
  • Active (real) energy: kilowatt-hours (kWh), individual meter elements and sum of elements; net, positive, and negative
  • Reactive energy: kVAR-hours, individual meter elements and sum of elements; net, positive, and negative
  • AC line frequency (Hz)
  • RMS voltage line-to-neutral: VAN, VBN, VCN
  • RMS voltage line-to-line: VAB, VBC, VCA
  • RMS current: CT1, CT2, CT3
  • Demand: individual meter elements and sum of elements
  • Peak demand sum: minimum and maximum
  • Apparent power demand

Diagnostic LEDs

Diagnostic LED lights provide a per-phase indication of line voltage and power (green flashing) and negative power (red flashing) to help troubleshoot connection problems, like reversed CTs. The WattNode Module for Modbus meter also has a red/yellow/green communication LED to indicate RS-485 network traffic, configuration problems, bus contention, and other conditions. See the manual for full descriptions.

Measurement Accuracy Details

The following accuracy specifications do not include errors caused by the current transformer accuracy or phase angle errors. “Rated current” is the current that generates a CT output voltage of 0.33333 Vac or equivalent milliamp output.

Unless otherwise noted, all accuracy specifications assume the following test conditions:

  • Line voltage: 100 to 690 Vac
  • Power factor (PF): 0
  • Frequency: 48 – 62 Hz
  • Ambient Temperature: 23°C ± 5°C
  • CT Current: 1% – 100% of rated current
  • Update Rate: 0.1 second. Internally, all measurements are performed at this rate, except the energy registers, which are updated every 1.0 second.
  • Start-Up Time: Energy measurement starts ~100 milliseconds after the supply voltage is applied. Modbus communication is enabled ~300 milliseconds after the supply is applied; at this time, all the registers will report valid data, such as power, voltage, current, etc.
  • Default CT Phase Angle Correction: 0.0 degrees.
Parameter Test Conditions Typ      Max Unit
EnergySum, Energy1, 2, 3(1) (active energy) elapsed time(2) >= 10 s ±0.2      ±0.5 %
PowerSum, Power1, 2, 3 (active power) averaging >= 1 s ±0.3      ±0.5 %
VoltA, B, C, VoltAB, BC, CA (RMS voltage) averaging >= 1 s ±0.3      ±0.5 %
Current1, 2, 3 (RMS current) averaging >= 1 s ±0.2      ±0.5 %
Freq (frequency) averaging >= 1 s ±0.05     ±0.2 %
PowerFactor1, 2, 3 averaging >= 1 s, PF > 0.5 ±0.5      ±1.0 %
EnergyReacSum, EnergyReac1, 2, 3 (reactive energy) elapsed time(2) >= 10 s, PF < 0.9 ±0.6      ±1.5 %
PowerReacSum, PowerReac1, 2, 3 (reactive power) averaging >= 1 s, PF < 0.9 ±0.6      ±2.0 %
EnergyAppSum, EnergyApp1, 2, 3 (apparent energy) elapsed time(2) >= 10 s ±0.3      ±0.5 %
PowerAppSum, PowerApp1, 2, 3 (apparent power) averaging >= 1 s ±0.3      ±0.5 %

(1) Note: when parameters are written like Energy1, 2, 3, this means Energy1, Energy2, and Energy3.

(2) Note: This indicates that energy accuracy should be evaluated over a period of 10 seconds or longer.


Power Supply

  • Nominal Power Supply Voltage: 6 to 24 Vdc power supply or isolated 12 to 24 Vac control transformer
  • Power Supply Minimum Operating Voltage: 6 Vdc or 10 Vac
  • Power Supply Absolute Maximum Voltage: 40 Vdc or 30 Vac
  • Power Supply Watts: typical 0.6 W, maximum 1.0 W
  • Power Supply Current (milliamps):
DC Supply Volts Typical (mA) Maximum (mA)
6 90 130
12 50 70
18 35 50
24 30 45
30 27 40

General Electrical

  • Line Frequency: 45 to 65 Hz
  • Nominal Line-to-Neutral Vac: 90 to 347 Vac
  • Nominal Line-to-Line Vac: 120 to 600 Vac
  • Measurement Over-Voltage Limit: 720 Vac
  • Over-Current Limit: 200% of rated current. Exceeding 200% of rated current will not harm the meter, but the current and power will not be measured accurately.
  • Maximum Surge: EN 61000-4-5: 2kV, ANSI C12.1 combination wave: 6kV, 1.2/50 μs – 8/20 μs
  • Line Voltage Power Consumption: The line voltage sensing circuitry draws 0.006 watts per phase at 120 Vac, increasing to 0.150 watts per phase at 600 Vac.
    • Real Power (50-60 Hz): <= 0.2 watts
    • Power Factor: ~1.0
    • Rated VA: 25 VA at 720 Vac, 50 Hz. The Rated VA is the maximum at 115% of nominal Vac at 50 Hz.
  • Measurement Category: The line voltage measurement terminals on the meter are rated for CAT III, 600 Vac. Measurement Category III is for measurements performed in the building installation. Examples are measurements on distribution boards, bus-bars, branch circuits, plug loads, and permanently connected equipment such as motors, boilers and heaters.

Current Transformer Inputs:

  • Voltage Mode:
    • Nominal Input Voltage (At CT Rated Current): 0.33333 Vac RMS
    • Absolute Maximum Input Voltage: 5.0 Vac RMS
    • Input Impedance at 50-60 Hz: 23 kΩ
  • Current Mode:
    • Nominal Input Current (At CT Rated Current): 40 mA RMS
    • Absolute Maximum Input Current: 200 mA RMS
    • Input Impedance at 50-60 Hz: 10 Ω

EIA RS-485 Interface

  • RS-485 Output Isolation: 4500 Vac RMS
  • Driver Output:
    • Voltage (Open Circuit): ±6 Vdc maximum
    • Voltage (54 Ω load): ±1.5 Vdc minimum
    • Current (54 Ω load): ±60 mA typical
    • Rise Time (54 Ω || 50 pF load): 900 nS typical
  • Receiver:
    • Common-Mode Range: -7 Vdc to +12 Vdc max
    • Sensitivity: ±200 mV
    • Bus Load: 1/8 unit load (up to 64 meters)
    • Failsafe Modes: bus open, shorted, and idle


  • UL: UL Listed 2808
    • UL / IEC 61010-1, 3rd Edition
    • CAN/CSA-C22.2 No. 61010-1-12, 3rd Edition
  • FCC: Class B, FCC Part 15, radiated and conducted emissions
  • CE: EN 61326-1: 2013, industrial locations
    • Radiated Emissions: CISPR / EN 55011, Class B
    • Conducted Emissions: CISPR / EN 55011, Class B
    • Electrostatic Discharge: EN/IEC 61000-4-2: (B) Self-Recovering
    • Radiated RF Immunity: EN/IEC 61000-4-3: (A) No Degradation
    • Electrical Fast Transient / Burst: EN/IEC 61000-4-4: (A) No Degradation
    • Surge Immunity: EN/IEC 61000-4-5: (A) No Degradation
    • Conducted RF Immunity: EN/IEC 61000-4-6: (A) No Degradation
    • Power Frequency H-field Immunity: EN/IEC 61000-4-8: (A) No Degradation
    • Voltage Dips, Interrupts: EN/IEC 61000-4-11: (B) Self-Recovering
  • RoHS Compliant


  • Operating Temperature: –40°F to +176°F  (–40°C to +80°C)
  • Operating Humidity: non-condensing, 5 to 90% relative humidity (RH) up to 104°F (40°C), decreasing linearly to 50% RH at 131°F (55°C)
  • Operating Altitude: Up to 9842 ft (3000 m)
  • Pollution: POLLUTION DEGREE 2 – Normally only non-conductive pollution; occasionally, a temporary conductivity caused by condensation must be expected
  • Indoor Use: Suitable for indoor use
  • Outdoor Use: Suitable for outdoor use if mounted inside an electrical enclosure (Hammond Mfg., Type EJ Series) rated NEMA 3R or 4 (IP 66)


  • Enclosure: High impact, ABS/PC plastic
    • Flame Resistance Rating: UL 94V-0, IEC FV-0
    • Size: 19 in. × 3.68 in. × 1.15 in. (106.4 mm × 93.4 mm × 29.1 mm)
  • Connectors: Euroblock pluggable terminal blocks
    • Green: up to 12 AWG (2.5 mm2), 600 V
    • Black: up to 12 AWG (2.5 mm2), 300 V
    • Screw torque 4.4 lbf·in (0.5 N·m)
  • Weight: 4.7 oz (134 gm)
WND-M1-MB Dimensional Drawing
WattNode Module Modbus Dimensional Drawing

WattNode® Module for Modbus – Options

The WattNode® Module Modbus® and WattNode Revenue Module Modbus meter is available with several factory options at an additional charge. See the manual for more information and details about the registers mentioned below. To specify options, add the option codes you want as a string to the base part number. For example: WND-M1-MB Opt 19K,AD=1,EP specifies a meter configured for 19.2 kB, address 1, and even parity.

Meter Element Configuration Options

These are used to configure the ConnectionType or MeterConfig registers.

Only one of the following two options may be specified for a particular meter.

  • Option CTR=x – Set the ConnnectionType register to x (the default is 1). See the WND Meter Module Reference Guide for more information.
Connection Type Name Meter Element Mapping Service Types Notes Meter Config1 Meter Config2 Meter Config3
0 Custom Custom Any May not be used with the CTR=x option
1 Wye CT1-VAN CT2-VBN CT3-VCN 3-phase 4-wire wye May also be used for 4-wire delta service 10 20 30
2 Delta CT1-VAC



3-phase 3-wire delta CT3 is not used. Works for grounded delta with any phase grounded. 90 50 0
3 Branch circuits CT1-VAN CT2-VAN CT3-VAN 1-phase, 2-wire with neutral Use for monitoring 1-3 neutral connected branch circuits 10 10 10
4 House and Inverter CT1-VAN CT2-VBN CT3-VAB See notes 1-phase, 3-wire with neutral for CT1 and CT2; 1-phase, 2-wire without neutral for CT3 10 20 40
5 Line to Line CT1-VAB 1-phase, 2-wire (no neutral) CT2 and CT3 are not used 40 0 0
  • Option MCR=xx/yy/zz – Set MeterConfig1 to xx, MeterConfig2 to yy, and MeterConfig3 to zz. See the WND Meter Module Reference Guide for more information

The mapping from current transformer inputs to line voltage inputs is controlled with the MeterConfig registers. There are one meter element and one configuration register for each current transformer. For each meter element (CT), you can select the line voltage to be associated with that CT from the following list:

  • 0 = Disable meter element
  • 10 = VAN (also called VA)
  • 20 = VBN (also called VB)
  • 30 = VCN (also called VC)
  • 40 = VAB
  • 50 = VBC
  • 60 = VCA
  • 70 = VBA (equal to -VAB)
  • 80 = VCB (equal to -VBC)
  • 90 = VAC (equal to -VCA)

The default settings for the MeterConfig registers follow. These match the behavior of the older WNB and WNC meters:

  • MeterConfig1 = 10
  • MeterConfig2 = 20
  • MeterConfig3 = 30

Current Transformer Options

The following options are only for use with non-standard current transformers (CTs), such as milliamp output CTs or CTs with a full-scale output voltage other than 0.333 Vac. Most CCS CTs, including standard Accu-CTs, do not require any of the following options.

  • R=xxx or R=xxx/yyy/zzz – Specify the burden resistance for all three phases or for each phase individually. This means a burden resistor is installed in the meter to allow use of a milliamp output CT. If this option is not specified or the value is 0, then there is no burden resistor installed in the meter and the meter must be used with 0.333 Vac CTs (internally burdened millivolt output CTs).
  • V=xxx or V=xxx/yyy/zzz – Specify the full-scale CT output voltage for all three phases or for each phase individually. If this option is not specified, then 0.33333 Vac is the default value.
  • MA – Specify that the meter is designed for 40mA output CTs. Equivalent to “Opt R=10,V=0.4”

Communications Options

The communications options are used to configure the Modbus address, baud rate, and other communications parameters.

Defaults: AD=1, BAUD=19200, 8 (eight data bits), N (no parity), 1 (one stop bit)

  • Option AD=xxx – This is the Modbus slave address. If not specified, the default address is 1.
  • 9.6K – Set the baud rate to 9,600. This is a shorter version of “BAUD=9600”.
  • 19K – Set the baud rate to 19,200. This is a shorter version of “BAUD=19200”.
  • 38K – Set the baud rate to 38,400. This is a shorter version of “BAUD=38400”.
  • BAUD=xxxxxx – Set the baud rate to xxxxxx, where xxxxxx may be 1200, 2400, 4800, 9600, 19200, 38400, 57600, 76800, or 115200. The default baud rate is 19200.
  • EP – Enable even parity (the default is no parity)
  • 8N2 – Select two stop bits. The default is one stop bit.
  • T1 – Install a fixed (non-switchable) 120Ω burden resistor and two 1.2k Ω bias resistors (to Modbus common and 3.3V). By default, the meter module does not provide termination or biasing.

Cost Reduction Options

These options are normally only available if the Meter Module is ordered in high volume for OEM applications.

  • NDL – No LEDs and no light pipes.
  • 1PD – (Single-phase delta) Only populate components for one CT channel (CT1). On the voltage inputs, do not populate or use low-cost/low-accuracy components for the N and L3 (phase C) inputs. Use normal connectors.
  • 1PY – (Single-phase wye) Only populate components for one CT channel (CT1). On the voltage inputs, do not populate or use low-cost/low-accuracy components for the L2 and L3 inputs. Use normal connectors.
  • 1P – (Single-phase) Only populate components for one CT channel (CT1). On the voltage inputs, do not populate or use low-cost/low-accuracy components for the L3 inputs. Use normal connectors.
  • WND-M0-MB – No enclosure (for embedded use)

Warning: Hazardous Voltages – Only qualified personnel or licensed electricians should install the WattNode meter and current transformers.

Modbus is a registered trademark of Schneider Electric USA, Inc.