Consumption To Demand (BConsumptionToDemandBlock)

This block converts consumption values into demand values for both value and trend requests. This block supports both trend and value requests.

Value requests require access to trend data as their consumption data source. Even though the value request does not include a time range, this block requests the previous one (1) hour of trend data from the input source and searches for the last trend record prior to the current time. It calculates demand by taking the real time value and using the time delta from the last record in the underlying trend.

Figure 111. Consumption to Demand properties

To view these properties, double-click the block on the Wire Sheet or the block name in the Nav tree.

Property	Value	Description
Out	read-only value slot	Outputs the demand value calculated from the `Trend In` consumption value.
Trend In	required value slot	Links from the output of other logic blocks or data sources to supply trend data to the current logic block.

Example

Consider an energy point (KWH) with a 15-minute-interval history. The current value of the point is 240 at 1:28:49 PM and the last record in the applicable history is from 1:15:00 PM.

Inputs: there are 3,600,000 milliseconds in one hour and the time difference is 13 minutes 49 seconds.

Calculations: (13 minutes * 60,000 milliseconds/minute) + (49 seconds * 1,000 milliseconds/second) = 829,000 milliseconds

demand = consumption * (milliseconds in one hour / time difference milliseconds) = 240 KWH * (3,600,000 / 829,000) = 1042 KW

Figure 112. Consumption To Demand algorithm

The screen capture shows the blocks used in the algorithm. The following Property Sheet shows how the Proxy Ext properties are configured.

Figure 113. Consumption To Demand properties

For a trend request, if the history data are logged as delta values (delta consumption per interval instead of a totalized, ever increasing value), the totalize property in the request must be true. Otherwise the block calculates the delta of the values, which are already delta-logged. Note, the default totalize property value might be true for the binding but the DataSourceBlock’s Use Request Totalize and Totalize properties are false by default. You must either set the Totalize property on the DataSourceBlock or change the Use Request Totalize property to true and also ensure the binding’s Totalize property is true.

Figure 114. Consumption To Demand algorithm configuration

Now, consider another example in which an energy consumption history logs at 15-minute intervals with delta values as follows:

Figure 115. Energy consumption history example

The algorithm processes a consumption value of 75.0 KW-hr at 12:15:00 AM and returns a demand value of 300.0 KW at 12:00 AM. The demand value is offset backwards one 15-minute interval indicating what would have been the demand from 12:00 AM - 12:15 AM. This offset results in the 75.0 KW-hr consumption recorded at 12:15 AM.

Figure 116. Calculated demand values offset

NOTE: For the specific use case above where consumption is delta logged at 15-minute intervals, the calculated demand should be four times the consumption value because the calculation is consumption * (60 minutes / 15 minutes) or simplified as consumption * 4.