Schneider ElectricMTN684064KNX Bus Power Supply, 30 V / 640 mA, Integrated Choke, Up to 64 Bus Devices, 4-Module DIN Rail, 110-230 V AC

Product Description

What this part is

A Schneider Electric (Merten) KNX power supply REG-K/640 mA — the device that generates the 30 V bus voltage a KNX installation runs on. It feeds one KNX line with up to 640 mA, enough for a maximum of 64 bus devices, and the line choke that the bus needs for signal transmission is integrated, so no separate choke is required. Four modules wide on a TH35 DIN rail.

Correcting the source data

Earlier copy on this listing named Omron as the manufacturer. MTN is the Merten article prefix, now part of Schneider Electric and catalogued under SpaceLogic KNX — Omron has never used this numbering. The correct manufacturer is Schneider Electric / Merten, and MTN684064 is the article number to search on.

Decoding the designation

MTN – Merten article number prefix (Schneider Electric)REG-K – Reiheneinbaugerät Komfort, Merten’s designation for a DIN-rail-mounted device640 mA – maximum bus output current, which is what sets the device count for the line

What these specs mean in practice

Two limits govern a KNX line and both apply at once. The 640 mA figure is the current budget: add up the bus current draw of every device on the line and stay under it. The 64-device figure is the topology limit for a line segment, and you can hit that ceiling well before the current one, or the other way round with hungry devices — whichever comes first is the binding constraint. Because the choke is integrated there is no separate coil to buy or wire, and no data rail is needed: the bus lands on a standard KNX bus connecting terminal. The output is short-circuit proof, so a shorted bus pair will not destroy the supply. The front disconnect button separates the supply from the bus, and because KNX devices hold their configuration but reinitialise on power-up, that button is the standard way to reset every device on the line during commissioning without pulling terminals.

Published specifications

Function: KNX bus power supply with integrated choke, one lineBus output: 30 V secondary, 640 mA maximumBus devices supported: up to 64 on the lineNominal supply voltage: 110 to 230 V AC ±10%Operating voltage range: 92 V AC minimum to 253 V AC maximumMains frequency: 50 to 60 Hz ±10%Output protection: short-circuit proofIndication: LEDControls: disconnect button for the bus supply, used to reset connected bus devicesConnection: KNX bus connecting terminal; no data rail requiredMounting: DIN rail TH35 per EN 60715Width: 4 modules, approx. 72 mmColour: light grey

Quantity and configuration

Sold as 1 piece — the power supply only. No KNX bus connecting terminal, bus cable, DIN rail or data rail is included; a data rail is not needed for this device.

Installation and setup notes

One supply serves one line. Where a line needs more than 640 mA or more than 64 devices, split it with a line coupler and give the new segment its own supply — do not parallel two supplies onto the same segment unless the manufacturer’s documentation for the specific units permits it. Position the supply with an eye to cable lengths: KNX limits the distance between a power supply and the furthest device, and between two supplies on the same line. Use the disconnect button rather than switching the mains when you want a clean reinitialisation of the bus devices during commissioning, and watch the LED to confirm the bus is actually being fed before you start chasing addressing faults.

Interchange guidance

The output current is the part. Merten and Schneider also supply 160 mA, 320 mA and 1280 mA KNX supplies in the same REG-K format, and none of those is a substitute where the line’s current budget has been calculated around 640 mA. Supplies without an integrated choke need a separate coil and are not drop-in. KNX supplies from other manufacturers are electrically compatible with the bus by definition of the standard, but the module width, terminal layout and reset behaviour differ, so a like-for-like panel swap needs the same article number or a deliberate re-layout. This is a KNX bus supply, not a general-purpose 24 V DC panel supply, and it must not be used to power auxiliary loads.