Nilan_WWcapacity.rules

// an uninitialized variable where we have to provide the type (as it cannot be inferred from an initial value)
var Number1 x

rule "nilan warm water inital"
when
//	Time cron "0/10 * * * * ?"
	System started
then
	var Number nix = 0
	Nilan_WarmWaterCapacity.postUpdate(nix)
end

rule "nilan warm water capacity"
when
        Item Nilan_T11_Temperature received update or
        Item Nilan_T12_Temperature received update 
//or
//	Time cron "0/10 * * * * ?"
then
	// T11 = top, T12 = bottom of tank
	val Number T11 = Nilan_T11_Temperature.state as DecimalType
	val Number T12 = Nilan_T12_Temperature.state as DecimalType
	var Number oldWWCapacity = Nilan_WarmWaterCapacity.state 
	// Ttarget: target warm water temperature for which the capacity shall be calculated 
	val Number Ttarget = 35.0
	// ratio of tank, which has a water temperature above Ttarget temperature
	var Number ratio  = ( T11 - Ttarget )/ ( T11 - T12 )

//	logInfo ("openhab", "0 ratio " + ratio)

	if (ratio < 0 ) {
	    	Nilan_WarmWaterCapacity.postUpdate(0) 
		return;
	}
	if (ratio > 1) ratio = 1

	// offset (80) and slop (65) extracted from Nilan data sheets
		// return value: liters of above Ttarget temperature that can be provided
        var Number WWCapacity = (80 + 65 * ( T11 + T12 - 40) / 20) * ratio
	logInfo ("openhab", "1 WWCapacity calc " + WWCapacity + ", old " + oldWWCapacity + ", ratio" + ratio + ",T11 " + T11 + ",T12 " + T12)

	var Number change = oldWWCapacity - WWCapacity
	if ( change > 2) Nilan_WarmWaterCapacity.postUpdate(WWCapacity)
	if ( change < -2) Nilan_WarmWaterCapacity.postUpdate(WWCapacity)

end