Dimmer for heater to set temp


I´ve set up openhab2 with Homematic devices. I added a dimmer item to remotely set the temperature of my heater. Unfortunately it does not work the way I wanted, actually it does not work at all.

In my openhab events.log I saw this:

2018-02-16 18:09:19.997 [ome.event.ItemCommandEvent] - Item 'HzSetTempBad' received command 42
2018-02-16 18:09:20.011 [vent.ItemStateChangedEvent] - HzSetTempBad changed from 0 to 42
2018-02-16 18:09:23.277 [vent.ItemStateChangedEvent] - HzSetTempBad changed from 42 to 41
2018-02-16 18:09:23.299 [vent.ItemStateChangedEvent] - HzTempBad changed from 25.30 to 25.40

So the dimmer sets a percentage value, but the heater obviously is working with °C values. I thought I could get the dimmer and the heat talk to each other using a rule which converts my percentage values into °C values.

Do you think taht would work? If so, could you help me to set up the rule, e.g. if you have an example or sth.!?

Thanks in advance!

Why a Dimmer and not a simple Number item? Can you please explain?

because you cannot set a number item / change it´s value. Also it is discovered as a dimmer item…

Well, my hmip-etrv devices do have SET_POINT_TEMPERATURE channels that are recognised as Number. I setup the items as follows

Number aBathRadiator_1_SET_POINT_TEMPERATURE { channel="homematic:...:1#SET_POINT_TEMPERATURE" }

and in the sitemap I use them like this

Setpoint item=aBathRadiator_1_SET_POINT_TEMPERATURE minValue=4.5 maxValue=30.5 step=1.0

mmh, cool, I didn´t know it works this way, thanks for that!

But now my problem is I need this setpoint in my home.items. How could I implement it there? My sitemap looks like this, there are only my rooms grouped.

sitemap home label="Homecontrol"

	Frame {
		Group item=gFF label="Wohnung" icon="firstfloor"
		Frame {
		Group item=gBM label="Keller" icon="cellar"
		Frame {
		Group item=gAL label="Alarmanlage" icon="shield"
	Group item=gVac {
		Switch item=actionControl mappings=[vacuum="Vacuum", pause="Pause",spot="Spot", dock="Dock"]
 		Switch item=actionFan mappings=[38="Silent", 60="Normal", 77="Power",90="Full", -1="Custom"]
		Default item=statusBat 
		Default item=statusArea 
		Default item=statusTime 
		Group  item=gVacStat
		Group  item=gVacCons
		Group  item=gVacDND
		Group  item=gVacHist
		Group  item=gVacNetwork
/*	Group item=TvWz {
		Switch item=TvCommand mappings=[power="Aus", mute="Stumm"]
		Default item=TvDimmer
/*	Frame label="Date" {
		Text item=Date
		Frame label="Charts" icon="line"{
			Webview item=ChartKz url="" height=7
	Setpoint item=HzTargetTempBad minValue=4.5 maxValue=30.5 step=1.0

I actually want this setpoint item in my Bath group which is grouped in the gFF “Wohnung” group…