NIBE S1256

Compatibility

Compatible for read-only monitoring over Modbus TCP

NIBE's S-Series technical information explicitly covers S1256, names built-in Modbus TCP/IP from software 2.2.1, and lists read-only FC04 input registers for this model family.

S1256-8, S1256-13 or S1256-18 with S-Series software 2.2.1 or later and the local TCP/IP interface enabled. Confirm the exact product, activated accessories, firmware, exported register list, IP access and reading-only mode. S2125 with a separate indoor controller is a different topology.

Connect it with

• 
  Gateway ZGW-20
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Models

Specifications

NIBE identifies the S1256 as a ground-source heat pump with an integrated water heater, offered in 8, 13 and 18 kW classes in its European range. This is a smaller building unit; the guide does not imply that it is the right capacity for every commercial plant.²

Product scope

S1256-8, S1256-13 and S1256-18 ground-source heat-pump variants²

Minimum interface software

S-Series version 2.2.1 or later for Modbus TCP/IP¹

Local connection

Modbus TCP/IP on port 502, restricted to a local private address and a trusted client IP¹

Polling boundary

At most 100 registers per second and 20 registers per query¹

Temperature example

Outdoor temperature BT1: input-register ID 1, FC04, signed 16-bit, °C with factor 10¹

Operating example

Compressor status: input-register ID 1100, FC04, 0 off or 1 on¹

Performance boundary

Internal readings are operating telemetry; external electricity and heat meters establish site COP/SPF^1, 2

Interface

Documented measurements and integration boundaries for S1256.

• Read-only input registers cover outdoor, flow, return and brine temperatures, compressor status and current compressor frequency, subject to installed configuration.
• NIBE's common-register table includes alarm state, run time and internal energy or power-related values. Their measurement boundary and availability must be checked before use.
• For site COP or seasonal performance, meter the complete heat-pump electrical boundary and delivered heat separately, at matching intervals.

Setup

1. Identify the exact S1256 variant and installed S-Series software.

   Confirm version 2.2.1 or later, the active accessories and the existing building controller before selecting registers.

2. Configure the site's protected Ethernet or Wi-Fi connection in menu 5.2, activate Modbus TCP/IP in menu 7.5.9, restrict the trusted IP and enable reading-only mode.

   Do not expose port 502 to the public internet.

3. Export the register list from the installed unit to USB in menu 7.5.9.

   Select only the values actually available for that variant and accessory set. Keep the manufacturer's 20-register-per-query and 100-registers-per-second limits.

4. Start with a single FC04 input such as outdoor temperature BT1, published ID 1 and signed 16-bit degrees Celsius with factor 10.

   Confirm the client library's register-address convention against the exported CSV and the controller's operating-info display; do not assume an unverified offset.

5. Compare compressor status and temperature trends against local observations.

   Record source device, unit, scale, timestamp and mode for every accepted point.

6. Keep all holding-register writes, AUX control, compressor blocking and hot-water changes outside this monitoring setup.

   Add independent electricity and heat meters before reporting COP, SPF or delivered flexibility.

Common questions

Does the S1256 need a separate Modbus accessory?

NIBE documents built-in Modbus TCP/IP for the S-Series from software 2.2.1. Check the exact installed controller and firmware; the older Modbus 40 accessory belongs to different product arrangements.¹

Can Edge read the outdoor temperature without changing heating control?

The S1256 table identifies outdoor temperature BT1 as a read-only FC04 input. Enable the controller's reading-only mode and trusted-IP restriction, then verify the installed register export and display value.¹

Can internal energy values be used as measured COP?

Do not equate an internal operating value with delivered heat divided by the complete electrical input. A defensible COP or SPF boundary needs a heat meter and electricity metering for the relevant compressor, pumps and backup heat circuits.^1, 2

Can the same setup be used on an S2125?

The S2125 is an outdoor unit used with a separate indoor module or controller. Select that controller's exact register list and connection design; the S1256's integrated-controller assumptions do not transfer automatically.¹