I’ve installed all parts of my new EmonHP level3 and am awaiting the HP installers to connect the Axioma to their new HP pipework.
Data from the heat meter, the electricity meter and the emonTH is arriving at emoncms.org just fine, so thanks to the team for making this such a smooth installation process. I’ve hardly done any setup and everything has just worked -)
My 2 queries are:-
In the Axioma manual it says that “it is forbidden” to run the MBus cable within 5cm of any electrical cables. Why is this? Is it something to do with potential interference, or perhaps electrical safety?
The heat meter runs on an internal battery in the absence of external power. I have connected the Axioma mains cable to a spur, but I don’t see any indication that the unit is receiving external power. Is there a display for this?
Nothing to do with safety, it’s just to avoid electromagnetic interference interfering with the MBUS signal, in reality it will probably be fine if the MBUS cable does come a bit closer to a mains cable, especially it’s a relatively short run.
That’s perfect. Correct, there’s no indication that the meter is receiving power but assuming your FCU is outputting power you can assume the meter is getting a supply.
Drop us a message once your heat meter is connected and we’ll get your system approved on heatpumpmonitor
My MBUS extension is about 6 metres and uses one twisted pair of cat5 cable and is pinned closer than 5cm to some twin and earth cables used for ring mains and lighting. This is the neatest route to run the cat5.
At this stage of my installation I’m only getting flow and return temps from the heat meter and these seem to be reported reliably to the emonPi.
Is this a valid test of bus data reliability, or will the data become more susceptible to interference when more parameters are being transmitted when the HP is completely commissioned?
M-Bus is usually run for large distances within apartment buildings. It’s not unusual to have 250 devices and 5 km of cable on a single network.
If you start running this, in untwisted pair, in cable trays next to high power elevator supplies etc you can have issues with noise.
For single domestic property installations don’t sweat it. It’s slow (2400 baud) and relatively high current so pretty much immune to noise. Only when there’s loads of cable in the network must one care.
Presence of any readings indicate successful reception of the packets/telegrams from the meter and passing of the checksum.
Yes, that’s a valid test. If there were any mbus drops outs, the flow and return readings will be affected. I would be very surprised if there was a problem. Most installers don’t pay any attention to this, and it’s almost never a problem. But it’s best practice to separate mains AC and low voltage signal cabling if possible.
Just spotted on the shop page for this heat meter:
" Glycol: By default, these heat meters DO NOT support the use of glycol. If you’re using glycol, please contact us."
I don’t know what Octopus are planning to fill my system with, but what difference does this make?
Is there a setup parameter that must be set in the Axioma before first use?
The ultrasonic heat meters like the Axioma don’t support glycol, so make sure Octopus fill your system with water. Glycol reduces system efficiency, so using water is a good thing. The Octopus installs I’ve seen all use water, I pretty sure this is the standard procedure for them.
There’s no config require on the Axioma, just make sure it’s plumbed in correctly as per our user guide and the all air is removed from the system. Getting all the air out of the system is very important for heat meter operation. The air removal process will take a few hours to properly undertake.
Hi, My heat pump is now installed and last night it ran a disinfectant cycle. The water heated just fine so I guess the heat pump is working . However, the Axioma heat meter is not reporting any flow or heat.
I’ve read your doc about clearing air from the pipework and the installers have at least begun to do this. So I’m surprised that the heat meter is showing absolutely zero readings (rather than some partial readings as shown in your doc).
Any thoughts on what I can do to trace whether the Axioma is registering some heat and if this is arriving at the emonPi2 (I don’t think data is arriving at the emonPi)?
Many thanks, David.
There was no flow rate reported during the initial DHW run, due to the meter reporting an error due to air in the system. Having air in a new system is very common and unavoidable. The installer should run a purging process to ensure all the air is removed, see: https://docs.openenergymonitor.org/heatpumps/removing_air.html
The other issue is that it looks like the DHW detection CT has been clipped in the wrong place, it should be clipped around the Live conductors(s) supplying the diverter valve. If there’s more than one live cable i.e permanent Live and switched Live, the CT should be around both Live cables, but not the neutral. What made and model of diverter valve do you have, could you post a photo?
Here’s photos of the 3-way valve and the ct clamp. I have extended the ct cable with about 10 metres of cat5 UTP. I used one of the twisted pairs. If you think this may be the problem, I could use more than one of the twisted pairs?
Approximately what voltages should I measure on the jack plug at the emonPi for the valve when it is energised and non-energised?
Thanks for the photo. Ah it’s an ESBE we’ve had mixed experiences with these, there’s a chance the CT approach won’t work with this valve. However, I can see the CT is only clipped around the permanent live Brown cable, could you also clip it around the switched live Black cable?
How long is the extension?
The voltage on the CT will be very low, 1mV or less. You won’t be able to measure it with a multimeter.
I’ve adjusted that ct clamp and now both the brown and black wires are running through it - in the same direction The cat5 extension is less than 10 metres. At the emonPi inputs page, input P1 reads around 30.
I’ve set the system to do some CH and it looks like my graph is still classifying as DHW.
Presently the cylinder is too hot (59 degrees) to run a HW cycle. I’ll force a HW cycle tomorrow and see what happens.
In the meantime, I think I’ll rewire the cat5 extension so that all 8 cores are in use (+ and - ct legs in each of the 4 twisted pairs.)
Thanks again.
ESBE actuators are MoMo valves (motor on/motor off) rather than spring return valves like Honeywell’s etc. There are two types of ESBE actuators, either 3-point or 2-point controlled (ignoring the proportional option). 3-point have a two switched lives - one for each direction and you would put the CT on which ever switched live moved the valve to the DHW position. 2-point is essentially the same with the addition of a relay inside and have a permanent live and a switched live - the permanent live will move/hold the valve in one direction/position and the switched live switches the internal relay to move/hold the valve in other direction/position, so generally the CT would work on switched live. Although I’ve not personally used the OEM DHW CT with a ESBE 2-point actuator, it seems odd that it would need to be on both the permanent and switched lives - unless as the switched live is only powering the internal relay coil, rather than the actuator motor, then maybe it’s doesn’t draw enough to trigger OEM ?
Also make sure the the actuator is set correctly with the valve shoe position and that the white valve shaft adapter is around the correct way (one end is for the new style ESBE valves with a splined shaft and the other for the older style valves with tapered shaft) - I’ve been to a lot of jobs where this is done incorrectly, RTFM.
With a 3 point ESBE valve, CT clamp on switched live to move to DHW position, how ill it know when the DHW cycle is finished if another switched live moves the valve back to the heating position?
Wouldn’t you need a different system with two CT clamps?
As mentioned, the 3-point actuator has two switched lives, one moves the valve in one direction (for DHW) and the other to move the valve in the other direction (for HTG), so if wired/controlled correctly, only one will be live at a time, so put the CT on the the wire that is live for DHW - obviously a 3-point controlled actuator will not work if you only have a single switched live control output, unless you use it to switch a external relay to then control the actuator (the 2-point has this relay built in). Hope that make sense.
So, on the 3 point actuator the DHW switched live is live all of the time the DHW is in operation?
I had assumed that it would only be live whilst the valve was in motion and then the second switched live would only be live to move the valve back to the heating position?
The switched live(s) is coming from the heat pump controls and will be live for the duration of the DHW cycle and then switch off (and switch on the HTG live if using 3-point control). The actuator has a micro switch to stop the actuator motor once its reached its end position.
