Tariff Targets - Metasys - LIT-12011288 - Software Application - Metasys Building Automation System - 6

DLLR Technical Bulletin

Product
Building Automation Systems > Building Automation Systems > Metasys Building Automation System
Document type
Technical Bulletin
Document number
LIT-12011288
Version
6
Revision date
2013-10-15

Utility rates are often higher during certain hours of the day and during certain times of the year. For example, some utilities add a demand surcharge for energy used during peak times but may offer cheaper rates at night. To address these different rates, DLLR supports the use of tariff targets. For DL, the tariff target indicates the maximum allowed average power during the current interval. DL sheds loads to keep the demand (energy usage) below the current DL target. For LR, the tariff target indicates the amount of power by which the demand has to be reduced. The Active DL Target and Active LR Target attributes in the DLLR object Focus view indicate which target currently is active (Figure 1).

Note: The Focus tab is called the Configuration tab in the SCT or in a wizard.
Figure 1. Active Tariff Targets on DLLR Object Focus View

You can define up to 12 tariff targets for Demand Limiting and 12 tariff targets for Load Rolling. At least one tariff target must be set for each configured energy strategy (DL, LR, or both), and only one tariff target for each can be active at one time. You can define targets with the Set Target command or by editing the DL Tariff Targets and LR Tariff Targets attributes. You can select which target is active via the Set Target command or by editing the Active DL Target and Active LR Target attributes. You also can alter the value of the current target by editing the Current Demand Limit and Current LR Target attributes. These two attributes are useful for changing the target on a real-time basis using a control process or Signal Select object.

Each target consists of a target value, such as kilowatts (kW) for electricity, and a text string that identifies the type of target. Examples include On-Peak, Off-Peak, Summer On-Peak, and Summer Off-Peak. Table 1 is an example of several DL tariff targets.

Table 1. Tariff Target Example

Tariff Target

Description

850 kW

On-Peak

1100 kW

Off-Peak

750 kW

Summer On-Peak

1000 kW

Summer Off-Peak

The currently active tariff target can be set on the DLLR Focus view or by operator command, scheduling, or through a control process. For example, you can schedule a Set Target command to the DLLR object to switch among the various targets. Any change in the target becomes effective in the next demand interval. You also can set a control process to change a target by writing a value to the Current Demand Limit or Current LR Target attributes.

Note: Use one particular tariff target description in the tariff array only once. For example, if the facility uses On-Peak and Off-Peak targets during the summer, then switches to a different set for the winter, the Summer On-Peak/Summer Off-Peak selections and the Winter On-Peak/Winter Off-Peak selections can be used. You should not specify two On-Peak entries and two Off-Peak entries. Instead, always use one of the more meaningful description pairs that are available.