Temperature measurement on electric Water Heater

Is there Velbus “approved” solution? I searched the forum and I see some solutions were developed over the years. All I need is a point measurement, 0 to 90 deg C. The sensor will be build into the water heater. I plan to use openHAB, so currently I consider something like ESP-8266 chip with a temp sensor DS1820 (info from openHAB forum), but I’d prefer to have a 100% velbus solution as it seems to be much more reliable that openHAB.

I have fairly complicated control plan, but even having part of it in the velus part of the control woud be great.

The full plan: Electric boiler - what brand for integration with openHAB? - Home Automation - openHAB Community


The pure Velbus way would be a 2Kohm bead and an input of a VMB4AN

which gives you full profiling, with 4 modes, each with a trigger point.

(I’m happy for you to remotely connect to a live system if you want to experiment).

The easiest.

Look for something with a simple volt free or 24V trigger and pull that into a Velbus relay.
A VMB1RYS would be easy.

Have you looked at pages 13 and 14 of this manual?
Specifically connection A , programmable function input (0V)

(Corrected link)

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Thank you! I need to find some other use for VMB4AN - otherwise the price of the module would be higher than the price of the water heater :slight_smile: I’m not yet ready to play with a live system :- someone could get burned :smiley:

Can you check the link? I tried 3 browsers - no go.

Sorry, yes, I’m not sure what happened there.

The link should be working now

(Corrected link)

That very much depends on the granularity of control that you are looking for.


you could wait until the NEW " VMB8IN " becomes available, which I’m told will have 8 sensor compatible inputs, all with threshold options and multi alarm triggers. (TBC)
update, No, unfortunately the next VMB8IN will only support pulse inputs

When I say a “Live” system, I do mean a fully isolated demo rig.

I wouldn’t want you setting my heating targets to 32ºC in every zone :laughing:


This openHAB thread has also been updated with extra comments and product links

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I posted a graph on the openHAB community forum, but I thought it might be interesting for anyone to find when scrolling through this topic.

This shows a PIR triggering a light and under cabinet water heater.
Which had been off overnight for 9 hours.

Note the energy spike as the water heater recovers to it’s 63ºc target, further spikes are important things like the coffee machine :coffee: , bringing the highest peak to 4KWh.

I was surprised at how little energy it uses.

But not as surprised as I was to see that 90 minutes later, when the PIR is triggered again, it doesn’t use any energy as the water is still within its target window.

(On below 56ºc and off at 63ºc)

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Thank you for sharing! That looks class - I’ll definitely consider that solution as energy might be “environmentally cheaper” for me than water. With under-sink heater the hot water is instant. With a water tank 10 m away some water is always wasted unless I go for well insulated pipes and constant circulation.

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