Gossen Metrawatt ENERGYMID EM2289/EM2389

Compatibility

Compatible with EpiSensor Edge over Modbus RTU

ENERGYMID meters with feature W7 are compatible with EpiSensor Edge over Modbus RTU on their RS-485 bus terminals, read through a ZMB-31 Modbus Interface or a Gateway serial port. Gossen Metrawatt publishes interface description 3-349-910-03 with zero-based addresses, function codes, format types and units.

EM2281, EM2289, EM2381, EM2387 and EM2389 with feature W7 (Modbus RTU), read with interface description 3-349-910-03. The TCP/IP (W4), M-Bus (W2), LON (W1) and LPWAN (W8) variants have their own interface descriptions and are outside this guide. Site check: read frequency at register 11 and compare it with the display. Read-only monitoring: no writes to the parameter registers from 10000.

Connect it with

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

Models

Specifications

Models

EM2281 (U2281) and EM2289 (U2289) direct connection; EM2381 (U2381), EM2387 (U2387) and EM2389 (U2389) transformer connection. Modbus RTU is feature W7.²

Current

Direct: Iref 5 A, Imax 80 A, starting current 20 mA. Transformer: Iref 1 A, Imax 6 A (includes 5(6) A), starting current 2 mA.²

Voltage

Reference voltage U5 230 V L-N, U6 400 V L-L or U3 100 to 110 V L-L, allowable deviation -20% to +15%; nominal frequency 50 Hz.²

Accuracy

Active energy class B (EN 50470-3), reactive energy class 2 (EN 62053-23); MID approval, modules B and D. Multifunctional values: voltage and current 0.5%, power 1%, frequency 0.05%.²

Modbus RTU

RS-485, address 1 to 247, 300 to 115,200 baud, frame 8E1 (factory), 8O1, 8N2 or 8N1; response delay 10 to 100 ms; ready 5 s after power-up.¹

Bus

Unit load 1/8, up to 256 meters per bus; up to 1000 m of shielded twisted pair, at least 0.22 mm², 100 to 150 ohm termination at both ends.^1, 2

Housing

4 module widths, approx. 72 x 90 x 70 mm, on a 35 mm top-hat rail; front IP 51, terminals IP 20; weight below 0.3 kg.²

Environment

Operating -25 to +55 °C, storage -25 to +70 °C, at most 95% humidity without condensation, indoor use up to 2000 m.²

Interface

Documented measurements and integration boundaries for ENERGYMID EM2289/EM2389.

• All register addresses in the interface description are zero-based and are sent exactly as printed: frequency at register 11 goes on the wire as 0x000B. Measured values are read with function 04; parameters with function 03.
• Voltage, current and power use format type 1: a SINT16 mantissa and a shared exponent in the low byte of its exponent register, value = mantissa x 10^exponent. A mantissa of 8000h means the variable is undefined.
• Primary voltages L1-L2, L2-L3 and L3-L1 at 0, 1 and 2, their mean at 3, phase voltages L1-N, L2-N and L3-N at 4, 5 and 6 and their mean at 7, in V with the voltage exponent at register 12.
• Primary phase currents L1, L2 and L3 at 100, 101 and 102, their mean at 103 and neutral current at 104, in A with the current exponent at 108.
• Primary active power P1, P2, P3 and Ptot at 200 to 203 (W) and reactive power Q1, Q2, Q3 and Qtot at 204 to 207 (var), with the power exponent at 212. Power factor per phase at 208 to 210 and total at 211: SINT16, divide by 1000.
• Frequency at register 11: UINT16, multiply by 0.01 for Hz. Voltage THD at 8 to 10 and current THD at 105 to 107: UINT16, divide by 1000.
• Total energy, all tariffs, as UINT32 mantissas in two registers: active import at 300 (OBIS 1.8.0), active export at 302 (2.8.0), reactive import at 304 (3.8.0) and reactive export at 306 (4.8.0). Primary energy in Wh or varh = mantissa x the primary energy factor at 308 (UINT32), or mantissa x 10^exponent from register 310.
• Gossen Metrawatt notes that up to and including Modbus RTU firmware V1.20 the primary energy factor is not to be used; on those meters scale with the exponent at 310. The interface hardware and firmware versions are in the fixed block at 3700 (two registers).
• The interface description does not state the word order of a UINT32. Read register 300 as two registers and compare the result with the main display; if it only matches with the words swapped, set the Edge point to low word first.
• Energy of the active tariff at 400 to 406 with its factor at 408 and the active tariff (1 to 8) at 412. Each of tariffs 1 to 8 has its own block from 600 to 1313, with cutoff-date and resettable copies from 1400 and 2200.
• Operating hours at 500 (UINT32). Error status flags 1 and 2 are repeated in each block (13 and 14 for voltage): bits mark voltages below 75% or above 120% of Un, currents below start-up, frequency faults and an incorrect direction of rotation.
• Registers from 3000 to 10800 can only be read and written as whole fixed-length blocks. Parameters from 10000 (CT ratio, VT ratio, Modbus address, baud rate, tariff selection, clock, reset and cutoff dates) are written with function 16; keep them out of a monitoring poll.

Setup

1. Confirm feature W7

   Check the type plate or order number for W7 (for example U2289-V018 or U2389-V028). W4 meters use Ethernet with a different description, and W1, W2 and W8 meters have no Modbus RTU port.

2. Set address, baud rate and frame on the meter

   In the Modbus menu set a unique address from 1 to 247, the baud rate and the frame format (8E1 from the factory). The frame format can only be changed at the meter, and every device on the bus must use the same settings.

3. Wire and terminate the bus

   Use the top bus terminals marked for the W7 interface, with A as the positive and B as the negative line. Terminate both cable ends with 100 to 150 ohm and connect the shield to protective earth at one point only.

4. Read frequency and one voltage

   Read frequency at register 11 with the example below, then the phase voltage at 4 with its exponent at 12. Compare both with the display. On a standard M0 meter, which the datasheet lists without voltage, current and power on its display, start with the energy registers instead.

5. Add energy with its factor

   Read active energy import at 300 (two registers) and the primary energy factor at 308, multiply them in Edge and compare the result in kWh with the main display. On Modbus RTU firmware V1.20 or earlier use the exponent at 310 instead of the factor.

Common questions

Do I subtract one from the ENERGYMID register numbers?

No. The interface description states that all register addresses are zero-based and are transmitted directly as listed, with no conversion. Its own example reads current THD at registers 105 to 107 by sending 00 69.¹

How do I turn the energy registers into kWh?

Each energy value is a UINT32 mantissa in two registers. Multiply it by the UINT32 primary energy factor in the same block (308 for the totals) to get Wh or varh, then divide by 1000 for kWh. Gossen Metrawatt says the factor is not to be used up to and including Modbus RTU firmware V1.20; on those meters use mantissa x 10^exponent with the exponent at 310.¹

Why do voltage and current read 8000h?

A mantissa of 8000h means the variable is undefined. The datasheet lists voltage, current, power, power factor, frequency and THD as display values of the multifunctional M1 and M3 variants only; a standard M0 meter shows energy. On an M0 meter start with the energy registers.^1, 2

Can I read the logbook or load profile with Edge?

The operating logbook from 3100 and the meter reading profile from 3400 must be read as whole blocks of exactly 16 or 32 words and stepped through entry by entry. They are structured records, not single measurements, so keep Edge on the measured values and energy registers.¹

Is the ENERGYMID a billing meter?

Yes. The datasheet gives MID approval (conformity assessment modules B and D) with accuracy class B for active energy, so the meter suits sites where an MID meter is required.²