Which function code does the DTSU666 use?

Function code 03 (read holding registers) for every value, and function code 16 (10h) to write settings. Each value is two registers.

What are the default communication settings?

Modbus RTU at address 1, 9600 bit/s, 8 data bits, no parity and 1 stop bit. The meter also supports DL/T 645, so check the protocol setting if it does not answer Modbus.

What is the programming code?

701 by default. It unlocks the address, baud rate, parity, wiring mode and CT and PT ratio settings on the front buttons.

Can the DTSU666 measure exported energy?

Yes. Reverse active energy is kept in total at 1028h (4136) and per phase at 102Ah to 102Eh, alongside forward energy at 101Eh (4126) onwards. Combined active energy on the display is forward plus reverse.

Does it work on a three-wire supply?

Set net to n.33 for three-phase three-wire, or use the DSSU666. Phase voltages, phase B power and the phase power factors are then not valid.

Chint DTSU666 Modbus register map with EpiSensor Edge

Compatibility

Compatible with EpiSensor Edge over Modbus RTU.

Connect its RS-485 port to a Modbus Interface or to a serial interface on the Gateway. Edge polls it with its Modbus client.

Edge reads 30 values from it, listed under Interface.

Connect it with

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

Specifications

The DTSU666 is a three-phase, four-wire energy meter in a 4-module DIN-rail housing, made by Chint for energy monitoring in industrial sites, hotels, schools and large buildings. It measures line and phase voltage, phase current, active and reactive power per phase and in total, power factor and frequency, and keeps forward and reverse active energy for each phase and in total.¹

Power: Self-powered from the measured supply. Powered through its voltage inputs, terminals 3, 6, 9 and 10; it has no separate supply terminals.¹
Nominal voltage: 3 × 230/400 V AC¹
Current input: Through current transformers, 100 A/40 mA or 250 A/50 mA¹
Active energy accuracy: Class 1¹
Operating voltage range: 0.9 to 1.1 Un specified, 0.8 to 1.15 Un extended¹
Wiring: 3-phase 4-wire (n.34) or 3-phase 3-wire (n.33)¹
Pulse constant: 400 imp/kWh¹
RS-485 port: Modbus RTU or DL/T 645, 1200 to 9600 bit/s, terminals 24 (A) and 25 (B)¹
Dimensions: 100 × 72 × 65 mm, 4 DIN modules¹
Protection: IP51 front panel, for use in an IP51 enclosure¹
Working temperature limits: -40 to 70 °C¹
Standards: IEC 61010-1, IEC 61326-1¹

Where it is used

Grid-connection metering on three-phase solar PV and battery systems, from the forward and reverse energy on each phase.
Solar PV monitoring
Distribution board and feeder monitoring through current transformers in commercial and public buildings.
Transformer and distribution board monitoring
Bringing DTSU666 meters already on an RS-485 bus into a BMS or SCADA system through Edge.
Modbus meter integration for a BMS or SCADA system

Interface

This register map is for the DTSU666.

Communication settings

Protocol: Modbus RTU over RS-485 (DL/T 645 selectable)
Unit address: 1 to 247, default 1
Baud rate: 1200, 2400, 4800 or 9600 bit/s, default 9600
Parity and stop bits: n.1 (no parity, 1 stop bit) by default; n.2, E.1 or O.1
Functions: FC03 reads, FC16 (10h) writes
Float order: IEEE 754, high word first (ABCD)
Read with: FC03 (holding registers)
Word order: High word first on every value
Addresses: Zero-based PDU addresses, as sent on the bus

From DTSU666.001 and DSSU666.001 series electronic energy meter user manual (ZTW0.464.0104)¹.

Register map

Download

Point	Address	Hex	Format	Scale	Unit
Voltage L1-L2	8192	`0x2000`	FLOAT32	×0.1	V
Voltage L2-L3	8194	`0x2002`	FLOAT32	×0.1	V
Voltage L3-L1	8196	`0x2004`	FLOAT32	×0.1	V
Voltage L1-N	8198	`0x2006`	FLOAT32	×0.1	V
Voltage L2-N	8200	`0x2008`	FLOAT32	×0.1	V
Voltage L3-N	8202	`0x200A`	FLOAT32	×0.1	V
Current L1	8204	`0x200C`	FLOAT32	×0.001	A
Current L2	8206	`0x200E`	FLOAT32	×0.001	A
Current L3	8208	`0x2010`	FLOAT32	×0.001	A
Total Active Power	8210	`0x2012`	FLOAT32	×0.1	W
Active Power L1	8212	`0x2014`	FLOAT32	×0.1	W
Active Power L2	8214	`0x2016`	FLOAT32	×0.1	W
Active Power L3	8216	`0x2018`	FLOAT32	×0.1	W
Total Reactive Power	8218	`0x201A`	FLOAT32	×0.1	VAr
Reactive Power L1	8220	`0x201C`	FLOAT32	×0.1	VAr
Reactive Power L2	8222	`0x201E`	FLOAT32	×0.1	VAr
Reactive Power L3	8224	`0x2020`	FLOAT32	×0.1	VAr
Total Power Factor	8234	`0x202A`	FLOAT32	×0.001	-
Power Factor L1	8236	`0x202C`	FLOAT32	×0.001	-
Power Factor L2	8238	`0x202E`	FLOAT32	×0.001	-
Power Factor L3	8240	`0x2030`	FLOAT32	×0.001	-
Frequency	8260	`0x2044`	FLOAT32	×0.01	Hz
Import Active Energy	4126	`0x101E`	FLOAT32	×1	kWh
Import Active Energy L1	4128	`0x1020`	FLOAT32	×1	kWh
Import Active Energy L2	4130	`0x1022`	FLOAT32	×1	kWh
Import Active Energy L3	4132	`0x1024`	FLOAT32	×1	kWh
Export Active Energy	4136	`0x1028`	FLOAT32	×1	kWh
Export Active Energy L1	4138	`0x102A`	FLOAT32	×1	kWh
Export Active Energy L2	4140	`0x102C`	FLOAT32	×1	kWh
Export Active Energy L3	4142	`0x102E`	FLOAT32	×1	kWh

Download the DTSU666 register map as CSV

Edge template

This JSON file supplies the register map. Applying it to an existing meter replaces its sensor list while retaining the site connection, unit ID and enable state.

Model	Connection	Points	Version	Updated	Download
DTSU666	Modbus RTU over RS-485 (DL/T 645 selectable)	30	1.0.0	23 Sep 2026	Download

Downloads need a signed-in account with Edge download access.

Use the template in Edge

Import the JSON file
On the target Gateway in Edge, open Settings, then Device Templates. Choose Import and select the downloaded JSON file. Confirm that the model and template name match your device.
Load the map for your meter
In the Modbus device wizard, choose the site connection and unit ID, then use Load Template to select the imported map. For an existing device, apply the template to that exact model. Its connection, unit ID and enable state are retained.
Test a reading
Use Test in the wizard and compare a known reading with the meter display. Check its unit, sign and scale, then confirm that timestamps keep advancing. These starter maps are read-only and leave exports off until you configure them.

Setup

Wire voltage and current
Connect phase A, B and C voltage to terminals 3, 6 and 9 and neutral to 10. Wire the current transformers to 13 and 14 for phase A, 16 and 17 for phase B, and 19 and 21 for phase C; the first terminal of each pair, marked *, is the current input.¹
Wire the bus
Connect RS-485 A to terminal 24 and B to terminal 25, with 0.25 to 1 mm² conductors, from a ZMB-31 or the Gateway's serial interface.¹
Set address and speed
Press SET and enter the programming code (701 by default), then set Addr, bAud and the parity and stop bits. The factory setting is address 1, 9600 bit/s, no parity and 1 stop bit (n.1).¹
Set wiring and ratios
Set net to n.34 for three-phase four-wire, and set the current ratio (Ct) and voltage ratio (Pt). For directly connected voltage, Pt is 1.0.¹
Read one register
Import the Edge template and read Voltage L1-N at holding register 8198 (2006h) with function code 03. A raw float of 2200 is 220.0 V; compare it with the Ua page on the display.¹

Before you rely on the decode

The addresses are the manual's hexadecimal addresses as zero-based decimal, so Uab at 2000h is 8192 and total import energy at 101Eh is 4126. Read them with function code 03.

Each value is an IEEE 754 float in two registers, high word first (ABCD). The template sets Edge to big-endian bytes with no word or byte swap.

The floats carry the manual's units: voltage in 0.1 V, current in 0.001 A, power in 0.1 W or var, power factor in 0.001 and frequency in 0.01 Hz. The template applies those multipliers; energy is already in kWh.

In three-phase three-wire mode (DSSU666, or net = 1) the phase voltages, phase B power and phase power factors are not valid.

The display always shows primary values, multiplied by the CT and PT ratios. Chint's manual lists these as the regular addresses and refers to its detailed protocol for primary-side data, so with a CT ratio set, compare current and power with the display before you rely on them.

Common questions

Why are my DTSU666 readings ten or a thousand times too large?: The floats carry Chint's scale. Voltage is in 0.1 V, current in 0.001 A, power in 0.1 W or var, power factor in 0.001 and frequency in 0.01 Hz, so a voltage of 2300 is 230.0 V. Energy registers are already in kWh.¹
Which function code does the DTSU666 use?: Function code 03 (read holding registers) for every value, and function code 16 (10h) to write settings. Each value is two registers.¹
What are the default communication settings?: Modbus RTU at address 1, 9600 bit/s, 8 data bits, no parity and 1 stop bit. The meter also supports DL/T 645, so check the protocol setting if it does not answer Modbus.¹
What is the programming code?: 701 by default. It unlocks the address, baud rate, parity, wiring mode and CT and PT ratio settings on the front buttons.¹
Can the DTSU666 measure exported energy?: Yes. Reverse active energy is kept in total at 1028h (4136) and per phase at 102Ah to 102Eh, alongside forward energy at 101Eh (4126) onwards. Combined active energy on the display is forward plus reverse.¹
Does it work on a three-wire supply?: Set net to n.33 for three-phase three-wire, or use the DSSU666. Phase voltages, phase B power and the phase power factors are then not valid.¹

Chint DTSU666