I have a wired MBUS reader IWM-MB3 which is attached to a B Meters water meter along with a USB MBUS adapter all purchased from the shop.
All data fetched over a period of several days since install using an emonHP has had a value for volume of 0.0 m3 although the dials on the water meter can be seen to be increasing.
B Meters provide an app for Android and one for Windows which may be used to access the unit but as I don’t have access to an Android device I am trying to connect via the Windows app.
The MBUS USB converter is recognised by windows and set up as COM3. The B Meters MBUS windows app is configured to use COM3 at 2400 baud (same as emonHP).
So far no response to any command has been displayed including scanning the MBUS by the B Meters app.
Has anyone been able to access an IWM-MB3 from Windows using the B Meters app and if so how was this achieved?
Any other thoughts etc considered.
Ultimately of course I want to determine why all values read to date have been 0.0.
You’re seeing emonHP read 0.00 m3 from the M-Bus module even though the clockwork dials are moving.
Q1: Is the module installed / oriented correctly? If it isn’t perfectly aligned then it won’t pick up the moving dials. Even in its “default” configuration it ought to increment the volume register - you’re just setting the “starting value” and mbus primary address when using the BMeters software
Q2: Can you read the module using MBSheet and the MBUS USB converter? (independent check that the converter is working correctly in windows)
Q3: What do you get using an independent parser for the volume? Paste the MBsheet output into this to rule out the 0.0 being an emonHP parsing issue rather than a module issue:
I initially wrote the below assuming that it was a T230 heat meter. It isn’t relevant but seeing as I’ve written it now and maybe it helps somebody finding it via search at a later date.
I should think that if the meter display shows volume/energy etc but emonHP shows 0.00 then emonHP is looking at the wrong “register” or failing to “parse” the BMeters telegram.
Meter Configuration?
Is this an eBay special heat meter of unknown provenance?
Landis&Gyr T230 heat meters (the BMeters / Ista variants are a rebrand) have an unhelpful “rolling frame” option that can sometimes be configured accidentally:
Deactivating the rolling frame function (default setting): You can switch off the rolling frame function by performing an application reset with CI = 50h (see section 4.2.5) without sub-code (see Table 2). In this functional state, an REQ_UD2 data request triggers only the first frame of normal operation mode.
This is often the reason that they are ripped out and replaced on heat networks.
Readout interval?
How often are you trying to rad this meter and is it battery powered? If it’s got 3x lithium cells in it then it can be read once per minute maximum. Read more often and the meter my not respond / the m-bus might respond but themeter hasn’t passed any values to it to include within the telegram.
The reader is snuggly fitted to the top of the meter and the securing screw is fitted. So yes it is installed/orientated correctly.
This is what I was trying to achieve with the B Meters software without success. Using MBSheet as you suggested I have been able to connect to the meter and read data as shown here:
Both MBSheet and the M-Bus Parser decode the response with a volume of 0.0 m^3. Here is the M-Bus Parser output
ID: 25743672 MAN:BMT MED:WATER GEN:22
Identification
Readout time 01.07.2026 19:13
Product name BMT_22
Serial number 8BMT1625743672
Medium Water
Generation 22
Values
01.07.2026 17:13 Volume 0 m³
The same as emonHP.
Both the reader and meter were purchased from the Openenergymonitor shop.
The emonHP was pre-provisioned by openenergymonitor and the emonHUB MBUS config section has a read_interval = 10.
I have been in contact with Glyn via [email protected] and it looks likely that a replacement reader will be shipped.
The good thing with your suggestion to use MBSheet is that I now have been able to connect to the meter reader using my PC and verify that MBSheet and emonHP produce the same result.
I’ve had a look at your data and I can see the water meter is working, reporting data with 0.01m3 (1L) resolution
It took 5.5 days for the meter to start reporting. It seems it take a while for the battery in the IWM-MB3 reader to charge up, according to the datasheet this rechargeable battery is charged from the USB MBUS reader. The was actually a sticker on the box which said to allow 6 days of recharging before use, however since the reader started reporting immediately I assume the battery was already pre-charged. I guess it’s the hall-effect part of the reader which reads the water meter rotation, which take a while to charge.
Apologies for being aware of this, nobody has mentioned it in the past! I’ve just installed the same meter on my home system, it’s currently reporting 0m3, I guess I’ll need to wait 5-6 days for it to start reporting
The packaging for the meter as well as the flow meter purchased at the same time was disposed of by the plumber installing a replacement ASHP and I hadn’t noticed any sticker when it was delivered.
The morning after my last post I saw that the meter had started reporting non-zero values and thought it was something to do with using the MBus Sheet app that had caused this.
That looks to be a coincidence given your more more plausible explanation that the internal battery was now sufficiently charged.
I had been meaning to update this post but hadn’t got around to it - my bad!
Actually the sticker says 6hrs, but it seems to take longer than this. My water meter has been connected for 3 days now, no data yet. I’m expecting it to start reporting in a day or two. Will keep you posted
I’m considering if we should pre-charge them before shipping.
