Introduction
Once you know what M-Bus is, the practical question follows: which converter should you choose? The wrong choice means either too little capacity (meters drop off the bus) or paying for features you do not need.
Here we compare two of the most requested IWILL serial M-Bus converters – the compact IW-485 and the high-current IW-1000 – and explain when the entry-level IW-CM-M is the better fit.
IW-485 vs IW-1000 at a glance
| Feature | IW-485 | IW-1000 |
|---|---|---|
| Host interface | RS-485 | RS-232 / RS-485 |
| M-Bus channels | 1 | 4 independent |
| Current / loads | Standard | 200 loads @ 300 mA |
| Best for | Small and medium networks | Large-bore meters |
Both support EN 1434-3 and CJ/T188-2004, with a metal enclosure and DIN-rail mounting.
How to choose
Choose the IW-485 if…
you have a standard building with water and heat meters, already have an RS-485 line or Modbus infrastructure, and want an economical, compact converter for transparent reading.
Choose the IW-1000 if…
you work with large-bore meters (industrial heat meters, large water meters), need high bus supply current, or want to split the network into four separate channels for better resilience.
Tip: if you are just starting and want to test reading a few meters, the IW-CM-M series (5 / 100 / 250 loads) is the most accessible starting point.
Do not forget headroom
Always choose a converter with at least 20–30% headroom above the current meter count. Long cables, branches and future extensions all consume extra load. If you plan to grow or have long runs, also consider industrial series with soft start and bus shutdown protection.
Worked examples: sizing for a real site
Scenario A – office building
60 electricity and water sub-meters of standard size, one RS-485 line to an existing Modbus system. 60 meters plus headroom is roughly 80 loads. Choice: IW-485 (or IW-CM-M100) – compact, economical and straight into the RS-485 infrastructure.
Scenario B – heat network substation
Six large-bore (DN100+) industrial heat meters, each drawing significant bus current, spread over long distances. The count is small but the current demand is high. Choice: IW-1000 – four independent channels share the load and the high-current design powers the meters reliably.
The rule: many small meters → look at the number of loads (IW-485). Few but “heavy” meters → look at current and channels (IW-1000).
Conclusion
The IW-485 is the all-round workhorse for most buildings; the IW-1000 is the specialist for heavy, high-current installations. Both give you open access to your metering data – and if you need network or remote reading, look at the Ethernet and GPRS versions.
Not sure which converter fits?
IWILL M-Bus converters are supplied to UK projects on enquiry. Send us your meter list (type, bore size and count), cable lengths and host system, and we will size the converter and headroom for you.