Lumel ND20

Compatibility

Compatible with EpiSensor Edge over Modbus RTU

Lumel documents Modbus RTU on the ND20's RS-485 port and publishes a register map with addresses, data types, byte order and units for read functions 03 and 04, with worked request and reply frames. This is documented compatibility, without a physical Edge test.

Lumel ND20 standard versions (ordering codes ND20 2211…, ND20 2212…), read with the register map in user's manual ND20-09H. Custom-made versions and the separate ND20CT and ND20LITE products are not covered. Read-only monitoring: no writes to the 4000 to 4070 configuration registers.

Connect it with

• Modbus Interface ZMB-3X From €399 ex VAT Configure
• Gateway ZGW-20 From €899 ex VAT Configure

Models

Specifications

The ND20 suits a switchboard door or panel where a local display of the main electrical values is wanted beside remote readings. It measures single-phase, three-phase 3-wire and three-phase 4-wire networks, balanced or unbalanced, directly or through CTs and VTs, and also keeps a 9000-entry averaged power profile with a real-time clock.^1, 2

Ordering codes

ND20 221100M1 (85 to 253 V AC or 90 to 300 V DC supply) and ND20 221200M1 (20 to 40 V AC or 20 to 60 V DC supply). Both include RS-485, an analogue output and English documentation.^1, 2

Current inputs

External CTs with 1 A or 5 A secondary, range set on the meter; CT ratio 1 to 10000. Measuring range 0.005 to 6.000 A on the 5 A range.¹

Voltage inputs

Programmable 3 × 57.7/100 V, 3 × 69.3/120 V or 3 × 230/400 V; VT ratio 0.1 to 4600.0. Short overload 2 Un, at most 1000 V.^1, 2

Connection modes

3Ph-4 (default), 3Ph-3 and 1Ph-2, set with the conn parameter or register 4057 on software 1.09 and later.¹

RS-485

Terminals 18 (A), 19 (B) and 20 (GND), galvanically separated. Modbus RTU only; address 1 to 247; maximum response time 600 ms.^1, 2

Serial settings

4800, 9600, 19200 or 38400 bit/s; 8N2, 8E1, 8O1 or 8N1. Factory setting address 1, 9600 bit/s, 8N2.^1, 2

Accuracy

The manual gives class 0.2 for current and phase voltage and 0.5 for line voltage, frequency and power (EN 61557-12), and class 0.2S for active energy (EN 62053-22). The datasheet states basic errors of ±0.2% of range for current and phase voltage and ±0.5% of range for energy.^1, 2

Outputs

Relay with normally open contacts, 250 V AC 0.5 A; analogue output 0(4) to 20 mA; passive open-collector energy pulse output, 1000 to 20000 pulses per kWh.¹

Housing

96 × 96 × 77 mm panel housing for a 92.5 × 92.5 mm cut-out; IP65 from the front, IP20 at the terminals; 0.3 kg.^1, 2

Environment

Operating -25 to +70 °C, storage -30 to +70 °C, relative humidity 25 to 95% without condensation.^1, 2

Interface

Documented measurements and integration boundaries for ND20.

• Addresses below are the decimal register numbers Lumel prints, and its examples send them unchanged: register 7000 goes out as 1B58h. Read with function 03 (04 is also listed), at most 82 registers per request.
• From 7000 to 7319 each value is a 32-bit IEEE 754 float in two registers, high word first (byte order 3-2-1-0). The 6000 area holds the same values low word first (1-0-3-2) and 7500 holds them as single 32-bit registers. Pick one area for the whole meter.
• Phase voltages L1, L2 and L3 at 7000, 7014 and 7028 (V); phase currents at 7002, 7016 and 7030 (A); phase active power at 7004, 7018 and 7032 (W). Phase voltages are not listed for the 3-wire connection.
• Three-phase active, reactive and apparent power at 7046, 7048 and 7050 (W, var, VA); mean power factor at 7052; calculated neutral current at 7094 (A).
• Frequency at 7056 (Hz); line voltages L1-2, L2-3 and L3-1 at 7058, 7060 and 7062 (V).
• Imported active energy is two floats: an overflow count at 7096 in units of 100 MWh and a counter at 7098 in kWh that rolls over after 99 999.9 kWh. Total kWh = 7096 × 100 000 + 7098. Exported is 7100 and 7102; reactive inductive 7104 and 7106 and capacitive 7108 and 7110 (100 Mvarh and kvarh).
• The same energies as integers: 4038 (high) and 4039 (low), unsigned 16-bit each, (4038 × 65 536 + 4039) ÷ 10 = imported kWh. Exported 4040 and 4041; reactive inductive 4042 and 4043 and capacitive 4044 and 4045 in kvarh.
• Device status at 4050 (one register of bit flags: bit 11 phase sequence error, bit 12 energy error, bit 15 memory damage) and program version × 100 at 4053. A float of 1e20 means an upper overflow or measurement error and -1e20 a lower overflow.

Setup

1. Record the software version

   The start-up screen shows ND20, the rated current and voltage and the program version. Register 4053 returns the same version × 100, and function 17 (report slave ID) returns a string such as ND20-1.09 b-1.04. Registers 4056 to 4061 exist only from version 1.09; record the version with the configuration.

2. Settle ratios and connection first

   Check the current range (rn_I), voltage range (rn_U), CT ratio (tr_I), VT ratio (tr_U) and connection mode (conn) in the PAr menu against the installation. Changing a CT or VT ratio erases the active and reactive energy counters, so settle the ratios before energy readings are collected.

3. Match the serial settings

   Read the address (Addr), transmission mode (trYb) and baud rate (bAUd) from the out menu and enter the same values in Edge. The factory setting is address 1, 9600 bit/s, 8N2. Give every meter on the bus its own address. The menus may be protected by an access code (SEc). A software update returns the meter to its factory settings, so check these again after one.

4. Wire the RS-485 line

   Connect A to terminal 18, B to terminal 19 and the interface ground to terminal 20, as in Lumel's connection diagrams. Keep the cable a single daisy chain and plan termination and any long run with the installer.

5. Start with the frequency read

   Read frequency with the example below and compare it with the display. Then add voltages, currents, power and the energy pairs, checking each new point against the matching display page.

Common questions

Do I send 7056 or 7055 for frequency?

Send 7056. Lumel's examples put the printed register number straight into the request: reading from register 7000 sends address bytes 1B 58, which is 7000. A client that asks for one-based register numbers enters 7057 so that 7056 goes on the wire.¹

Which register area should I read: 6000, 7000 or 7500?

All three hold the same measurements. The 7000 area is two 16-bit registers per float, high word first, which most Modbus clients decode as a standard big-endian float. The 6000 area swaps the words (byte order 1-0-3-2), and the 7500 area gives each float one 32-bit register, so one register there is four bytes. Reading the 6000 area as high word first gives nonsense values, so keep one area for the whole meter.¹

How do I rebuild the energy total from the two float registers?

Each energy is split in two: an overflow count in units of 100 MWh (7096 for imported active energy) and a counter in kWh that rolls over after 99 999.9 kWh (7098). Read both in one request and add them: 7096 × 100 000 + 7098 kWh. For example 2.0 and 34 567.8 give 234 567.8 kWh. The integer pair 4038 and 4039 gives the same total in tenths of a kWh.¹

Why did the energy counters go back to zero?

The manual says the ND20 erases active energy when the voltage or current transformer ratio changes, and reactive energy also when the reactive power method changes. Settle the ratios during commissioning and record a reset in the energy history if they change later.¹

Is the ND20 a billing meter?

The retained manual and datasheet give accuracy classes and EN 61557-12 and EN 62053-22 references but no MID approval. Treat it as a monitoring and power quality meter and use an approved meter where billing is required.^1, 2