The Siemens 7KT1663 is the non-MID M-Bus variant of the PAC1600 series for CT-connected 5 A measurement. It brings M-Bus networked energy monitoring to installations where loads exceed 80 A and operational visibility is the goal — without the cost of MID billing certification.

When does the M-Bus + CT combination make sense without MID?

This combination fits three common scenarios: (1) Industrial facilities monitoring large loads through existing CTs where the network is already M-Bus based — the 7KT1663 drops into the existing infrastructure without paying for unneeded billing certification. (2) Data centres tracking energy usage by rack row or PDU segment through CTs, reporting to a DCIM system via M-Bus — operational data, not billing data. (3) University campuses and hospital estates with centralized BMS on M-Bus, metering individual buildings or departments for energy management and sustainability reporting — accountability without legal metrology.

How does CT sizing work with the 7KT1663?

Select current transformers with a /5 A secondary and a primary rating matching the maximum expected load. For a 400 A feeder, use 400/5 A CTs. The meter adds negligible burden (~0.3 VA) to the CT secondary. Since this is non-MID, there is more flexibility in CT selection — you can use existing CTs already installed in the switchgear if they have a /5 A secondary, even if they are not metering-class accuracy. The overall measurement accuracy will be limited by the CT class.

Frequently Asked Questions

What is the practical cable distance for M-Bus with the 7KT1663?

At the standard 2400 baud rate, M-Bus cable runs can reach several kilometres using standard telephone-grade twisted pair (JYStY 2×0.8 mm² or similar). The limiting factor is typically the voltage drop on the bus supply and the total cable capacitance, not the data signal itself. For very long runs or large numbers of meters, a higher-powered M-Bus master or repeaters may be required.

Can I convert an existing Modbus system to use M-Bus meters?

Modbus and M-Bus are different protocols at the physical and data link layers. You cannot directly connect an M-Bus meter to a Modbus RS-485 bus. However, protocol gateways that convert M-Bus to Modbus TCP or Modbus RTU are widely available from building automation suppliers, allowing M-Bus meters to feed data into a Modbus-based SCADA or BMS.