Samsung MIM-B19N (EHS)

Modbus RTU

Submitted by

Last updated: 03. 2026

Requires external gateway
Samsung MIM-B19N

The Samsung MIM-B19N is a Modbus RTU gateway that connects Samsung HE, HT and EHS heat pump units to TapHome via RS-485. The gateway translates between the Samsung R1/R2 internal bus protocol and standard Modbus RTU, exposing water temperature sensors, hot water control, operation modes and comfort functions as holding registers.

Each MIM-B19N can manage up to 1 outdoor unit (4 including sub-units for modular installations) and 48 indoor units. The gateway address is set using a combination of DIP switches and a rotary switch (range 1–247).

Hardware connection

Specifications

Power supply: DC 12 V from CN12 on outdoor unit main board
Operating temperature: -10 °C to +50 °C
Protocol: Modbus RTU Slave, RS-485
Baud rate: 9600, even parity, 1 stop bit, 8 data bits
Max units: 48 indoor units + 1 outdoor unit per gateway
Max bus length: 1000 m (RS-485)

RS-485 wiring

Connect the MIM-B19N to TapHome using a 2-wire RS-485 connection:

A (R1) –> A+/D+ on TapHome RS-485
B (R2) –> B-/D- on TapHome RS-485

The MIM-B19N draws power from the outdoor unit via the DC 12 V connector (CN12). The Samsung internal communication uses the F1-F2 bus to reach indoor and outdoor units.

Important – RS-485 polarity
Match the RS-485 polarity between the MIM-B19N and TapHome. Swapped A/B wires will prevent communication. The RED LED on the module blinks when Modbus communication is active – if it stays off, check the wiring.

Wiring topology

1
2
3
4
5
Outdoor unit ──── F1/F2 ──── MIM-B19N ──── RS-485 (A/B) ──── TapHome Core
  │                              │
  └── 12V/GND (CN12) ───────────┘
  │
  └── F1/F2 ──── Indoor units (up to 48)

Configuration

DIP and rotary switch addressing

The MIM-B19N address is calculated as the sum of DIP switch values plus the rotary switch value.

Switch	Location	ON value
SW4-1	DIP	128
SW4-2	DIP	64
SW5-1	DIP	32
SW5-2	DIP	16
SW1	Rotary	0–15 (hex)

Address examples:

SW4 (1,2)	SW5 (1,2)	SW1 (rotary)	Address
OFF, OFF	OFF, OFF	1	1
OFF, OFF	OFF, OFF	2	2
OFF, OFF	OFF, ON	3	19
OFF, OFF	ON, ON	5	53

Recommended: Address 1 for a single gateway (all DIP switches OFF, rotary switch set to 1).

Address 0 is invalid. Valid range is 1–247.

Indoor unit prerequisite

Before the MIM-B19N can control indoor units, the “Use of central control” (SEG5) setting on each indoor unit must be set to “Use (1)”. Without this setting, the gateway can read status but cannot send control commands.

Multi-unit addressing

For systems with multiple indoor units, register addresses shift by 50 per unit:

Indoor unit	Base register	ON/OFF register
Unit 0 (first)	50	H:52
Unit 1	100	H:102
Unit 2	150	H:152

The TapHome template is configured for the first indoor unit (IU=0). For additional units, duplicate the template and adjust the register offsets by adding 50 × unit_index.

Device capabilities

Water temperature monitoring

The template provides two water temperature sensors for the hydronic circuit:

Water Inlet Temperature (H:65) – water return temperature, read-only, °C x 10 conversion
Water Outlet Temperature (H:66 read / H:68 write) – water flow temperature with setpoint control. The setpoint ranges depend on the unit type:
- HE: Cool 5–25 °C / Heat 15–50 °C
- HT: Heat 25–80 °C (no cooling)
- EHS: Cool 5–25 °C / Heat 15–55 °C

Hot water (DHW) control

Domestic hot water is managed through three devices:

Hot Water ON/OFF (H:72) – enables or disables DHW production
Hot Water Mode (H:73) – selects the DHW mode: ECO, Standard, Power, Force (EHS only), or Cool
Hot Water Temperature (H:75 read / H:74 write) – current DHW tank temperature and setpoint. Setpoint ranges:
- HE: 30–75 °C
- HT: 35–75 °C
- EHS: 30–70 °C

Unit power and operation mode

Central Heating ON/OFF (H:52) – turns the heat pump unit on or off
Operation Mode (H:53) – selects Auto, Cool, Dry, Fan, or Heat mode

Quiet mode and away function

Quiet Mode (H:78) – enables or disables outdoor unit noise reduction (Silence On/Off)
Away Function – exposed as a service attribute (read H:79) and service action (write H:79) on the Quiet Mode device. Activates the outing/away mode for energy saving when nobody is home

Service diagnostics

The module exposes three service attributes for system monitoring:

Communication Status (H:50) – bitfield showing: Exist, Type OK, Ready, Communication error
Unit Type (H:51) – identifies the connected unit type (HE, HT, EHS, FCU, ERV, AHU, Chiller)
Remote Control Restriction (H:64) – shows whether the remote controller is locked

Two service actions are available:

Buzzer (H:3) – turns the outdoor unit buzzer on or off
Remote Control Restriction (H:64) – locks or unlocks the wired remote controller (write 0x6363 for restriction, 0x0000 for no restriction)

The module ReadScript monitors the MIM-B19N error register (H:0) for address errors, R1/R2 communication errors and tracking errors, and reports the outdoor unit error code (H:1) in TapHome.

Additional capabilities

The MIM-B19N register map also exposes registers for indoor set temperature (H:58, range 16–30 °C heating / 18–30 °C cooling), discharge temperature (H:60), cooling and heating discharge setpoints (H:61, H:62), indoor unit error codes (H:63), outdoor temperature (community-discovered, H:5), room temperature (H:59), and defrost status (H:2). These can be added in a future template update.

The indoor set temperature register (H:58) is not included in the current template. To control the room setpoint, it can be added as a custom Modbus device in TapHome using holding register 58 with a range of 16–30 and a x10 multiplier.

LED and 7-segment indicators

Indicator	Function
Y-GRN LED	Blinks during MIM-B19N to outdoor unit communication
RED LED	Blinks during Modbus RS-485 communication with BMS/TapHome

7-segment error codes:

Display	Condition
E6 / 16	All indoor/outdoor communication stopped for >3 minutes
E6 / 15	Specific indoor unit communication stopped for >3 minutes
E6 / 04	Tracking not completed within 10 minutes after power on
E6 / 54	EEPROM error
E6 / 34	Address error

Troubleshooting

No Modbus communication (RED LED not blinking)

Check RS-485 cables:
- A wire correctly connected to A+/D+ on TapHome
- B wire correctly connected to B-/D- on TapHome
- Verify polarity is not swapped
Verify the gateway address using DIP and rotary switches
Confirm TapHome is set to: 9600 baud, even parity, 1 stop bit, 8 data bits
Check that the RS-485 bus length does not exceed 1000 m

Unit not tracked (Communication Status bits 0–2 not all = 1)

Verify indoor unit is powered on and connected to the Samsung F1/F2 bus
Check that “Use of central control” (SEG5) is set to “Use (1)” on the indoor unit
Wait up to 10 minutes for tracking to complete after power-on
If 7-segment shows E6/04, reset the MIM-B19N module

Control commands not taking effect

Confirm Communication Status register (H:50) shows bits 0–2 all set to 1 (Exist + Type OK + Ready)
Check that Remote Control Restriction is not active (H:64 = 0x0000)
Verify the indoor unit address is within range (0–47)
Allow at least 10 ms between consecutive Modbus read/write commands

Temperature readings showing 0 or incorrect values

Ensure the unit has completed tracking (Communication Status = Ready)
Verify the correct unit type – some registers are only available for HE/HT/EHS
Check the service attribute “Unit Type” in TapHome to confirm the detected model

Available devices

Samsung MIM-B19N Module

Service Attributes

Communication Status	reads H:50 (UInt16); bitfield: b0=Exist, b1=Type OK, b2=Ready, b3=Communication error
Unit Type	reads H:51 (UInt16); decodes lower/upper byte to identify unit type: HE (0x6E), HT (0x78), EHS (0x73–0x75), FCU, ERV, AHU, Chiller
Remote Control Restriction	reads H:64 (UInt16); 0x0000=No restriction, other=Restriction active

Samsung_MIM_B19N HE/HT/EHS

Read (module)

var err := MODBUSR(H, 0, Uint16);
IF(GETBIT(err, 0) = 1, ADDERROR("${adress_error}"));
IF(GETBIT(err, 1) = 1, ADDERROR("${comm_error_R1/R2}"));
IF(GETBIT(err, 2) = 1, ADDERROR("${tracking_error}"));
var reg := MODBUSR(H, 1, Uint16);
IF(reg = 0, "", ADDERROR("${integ_od_unit_err}, reg)");

Service Attributes

Communication Status

var com := MODBUSR(H, 50, Uint16);
var b0 := IF(getbit(com, 0) = 1, "Exist ", "");
var b1 := IF(getbit(com, 1) = 1, "- Type OK ", "");
var b2 := IF(getbit(com, 2) = 1, "- Ready ", "");
var b3 := IF(getbit(com, 3) = 1, "Communication error ", "");
RETURN(b0 + b1 + b2 + b3);

Unit Type

var type := GETBITS(MODBUSR(H, 51, Uint16),8, 8);
var lower := GETBITS(MODBUSR(H, 51, Uint16),0, 8);


IF(type = 10, RETURN("FCU"));
IF(lower = 108, RETURN("ERV+")); 
IF(lower = 110, RETURN("HE")); 
IF(lower = 120, RETURN("HT")); 
IF( 90 <= lower AND lower <=99 , RETURN("AHU"));
IF( 100 <= lower AND lower <= 102 , RETURN("ERV"));
IF( 115 <= lower AND lower <= 117 , RETURN("EHS"));
IF( 140 <= lower AND lower <= 149 , RETURN("Module Chiller"));
IF( 160 <= lower AND lower <= 169 , RETURN("FCU kit"));
RETURN("Indoor Unit");

Remote Control Restriction

var r := MODBUSR(H, 64, Uint16);
IF(r = 0, "No restriction", "Restriction " + r);

Central Heating ON/OFF Switch

Turns the heat pump unit on or off

Hot Water Mode Multi-value Switch

Selects DHW mode — ECO, Standard, Power, Force (EHS only), or Cool

Values / States: ECO · Standart · Power · Force(EHS) · Cool

Hot Water ON/OFF Switch

Enables or disables domestic hot water production

Hot Water Temperature Thermostat

Current DHW tank temperature and setpoint control

Operation Mode Multi-value Switch

Selects the heat pump operation mode

Values / States: Auto · Cool · Dry · Fan · Heat

Quiet Mode Switch

Enables outdoor unit noise reduction (Silence On/Off)

Values / States: Silence on · Silence Off

Water Inlet Temperature Temperature Sensor Read-only

Water return temperature sensor (read-only)

Water Outlet Temperature Thermostat

Water flow temperature with setpoint control

Connection: Modbus RTU • 9600 baud• 8E1 • Slave ID: $[SlaveId]

Possible improvements (8)

H:2 Defrost Status — 0 or 0xFF=Defrost off, Others=Defrost on. Read via module readscript as MODBUSR but not exposed as device
H:58 Set Temperature (Indoor) — Indoor/room temperature setpoint, °C × 10. Heating: 16–30°C, Cooling: 18–30°C. Missing from template despite being R/W for HE/HT/EHS
H:60 Discharge Temperature — Discharge temperature °C × 10 — available for HE/HT/EHS. Read-only
H:61 Cooling Discharge Set Temperature — Cooling discharge setpoint 8–18°C (°C × 10). R/W for HE/HT/EHS
H:62 Heating Discharge Set Temperature — Heating discharge setpoint 30–43°C (°C × 10). R/W for HE/HT/EHS
H:63 Indoor Unit Error Code — 0=No error, 100–999=Error code. Partially covered by module readscript (H:1 outdoor error) but per-unit indoor error not exposed
H:5 Outdoor Temperature — Outdoor ambient temperature °C × 10. Community-discovered, not in official register table
H:59 Room Temperature — Current indoor/room temperature °C × 10. Listed as read-only for Indoor/FCU, community confirms availability for HE/HT/EHS on some firmware

Download Template

Sources

MIM-B19N Installation Manual — Modbus register table, wiring, DIP switch addressing
midsummerwholesale.co.uk
Extended register map with MessageSet IDs for outdoor/indoor hidden registers
github.com
Samsung Modbus community integration reference
github.com