8.3  Separation of Electrical Circuits for Electrical Energy Monitoring 

§130.5(b)

The separation of electrical circuits requirement allows monitoring the specific contributions of separate loads to the overall energy use of a building. By designing the electrical distribution system with separation of electrical loads in mind, energy monitoring can be readily set up and implemented without significant physical changes to the electrical installations. The goal is to be able to monitor the electrical energy usage of each load type specified in Table 130.5-B of the Energy Code. Building owners, facility management, and others can make use of such energy usage information to better understand how much energy has been used by each building system during a certain period. Further analysis of such energy information can help facilitate energy efficiency and related measures to improve building energy performance for building owners and operators.

Table 130.5-B specifies the load types that must be separated. These requirements vary depending on the kVA rating of the electrical service.

Healthcare facilities are exempt from the separation of electrical circuits requirement.

 

Example 8-6: Separation of Electrical Loads – Service Rated Less Than 50 kVA

Question:

My new nonresidential building is served by a single panel with a service less than 50 kVA.

What is the required separation of electrical circuits for this building?

Answer:

Renewable power sources and electric vehicle charging stations must be separated from other electrical load types and from each other, in accordance with the “Electrical Service rated 50kVA or less” column of Table 130.5-B and §130.5(b). The renewable power sources must be separated by group. All electric charging vehicle loads can be in aggregate.

If there are no renewable power sources or electric vehicle charging stations in this building, it is not required to separate the electrical circuits for electrical energy monitoring.  

8.3.1      Compliance Methods

Electrical power distribution systems must be designed so that measurement devices can monitor the electrical energy usage of load types according to Table 130.5-B. However, for each separate load type, up to 10 percent of the connected load may be of another load type. The Energy Code allows any approach that provides the ability to measure the loads of the building separately.  

The separation of electrical circuits requirement of §130.5(b) may be satisfied by any method that accomplishes this goal, including any of the following example methods:

A.    Example Method 1 (See Example 8-7)

Switchboards, motor control centers, or panelboards may be separated by load type, allowing energy measurement of each load type independently and readily. This method must allow measurement and determination of the actual interval demand load value for each disaggregated load in the system.

This is a straightforward approach for measurement of each load type, as each switchboard, motor control center, or panelboard serves a single load type. Summation of the load measurement of the distribution equipment in accordance with the respective load type can result in the energy usage of each load type. This method is simple and straightforward in terms of the effort required in compiling the measurement data.

B.    Example Method 2 (See Example 8-8)

Switchboards, motor control centers, or panelboards may supply other distribution equipment with the associated loads separated for each load type. The measured load for each piece of distribution equipment must be able to be added or subtracted from other distribution equipment supplying them. This method must allow measurement for each disaggregated load in the system.

This method allows distribution equipment to serve more than one load type while allowing the separate energy use of each load to be determined. More effort may be required in obtaining the energy usage of each load type.

C.    Example Method 3 (See Example 8-9)

Switchboards, motor control centers, or panelboards may supply more than one load type as long as each branch circuit serves a single load type, and the equipment includes provisions for measuring individual branch circuits. For example, neighboring branch circuits in a panelboard may serve receptacles and fans, respectively, but the branch circuits cannot serve mixed load types.

D.    Example Method 4

Buildings for which a complete metering and measurement system is provided so each load type can be measured separately.

This method allows a complete metering system to be used to meet the requirements of §130.5(b), provided that, at a minimum, the system measures and reports the loads called for in Table 130.5-B of the Energy Code. Such an installation goes beyond the requirement of the Energy Code as it meters and measures the power and energy usage of each load type. It provides benefits for building owners and operators by giving them a readily available tool for assessing the building energy usage as soon as the facility is turned over to them.

 

Example 8-7: Separation of Electrical Circuits by Panelboard

Question:

I am working on a new nonresidential building project with a service more than 50 kVA and less than 250 kVA. Following is the proposed separation of circuits for connecting different load types to the service equipment. Does this concept meet the requirements of the Energy Code?

This figure shows an electrical single line diagram with a utility connection, an electrical service equipment and a number of connected electrical loads - including lighting, HVAC, plug loads, water system loads, renewable power sources, elevators, loads associated with renewable power and EV charging stations. The service equipment includes a service metering, and all the loads are noted for future metering for electrical power and energy.

Answer:

The proposed design meets the separation of electrical circuit requirement of §130.5(b) as there are separations of circuits for connecting different load types to the service equipment. There should be provisions including physical spaces for future setup of measurement devices for energy monitoring at each electrical installation location.

Example 8-8: Separation of Electrical Circuits by Panelboards and Subpanels

Question:

Part of my proposed design is to use a distribution panel serving HVAC loads, with the panel also feeding a lighting subpanel. There is a separate panelboard serving plug loads only.

Does this design meet the requirements of the Energy Code?

This figure shows an electrical single diagram with a utility connection and a service equipment, A number of locations are noted with future metering of electrical power and energy in this example electrical distribution system. One location is at the load side of the feeder breaker serving the panel with plug loads only. Another location is at the load side of the feeder breaker serving the distribution panel which serves HVAC loads and a panel board with lighting loads only. For this panel board with lighting loads only, there is yet another future metering planned at its feeder breaker. Lastly there is a service metering located at the service equipment.

Answer:

The proposed design meets the separation of electrical circuit requirement of §130.5(b) as each load type in the building can be accounted for by addition and subtraction of the measured loads, as indicated in Method 2.  

Example 8-9: Separation of Electrical Circuits by Branch Circuits

Question:

Can a panelboard with provisions allowing branch circuit energy monitoring be used to meet the separation of electrical circuits requirement? Each circuit would serve no more than one load type.

This figure shows future metering planned for each branch circuit at the load side of the panel circuit breakers. Each branch circuit feeds one load type only.

Answer:

The proposed design allows each load type to be separately measured at the branch circuit, so it meets the requirements of §130.5(b).

8.3.2      Application Considerations

The Energy Code allows the use of conventional panelboards, motor control centers, and other standard wiring methods for meeting the separation requirement. The requirement may also be met by a well-planned wiring approach, such as connecting all HVAC units to a single feeder from the service using a combination of through feeds and taps. The regulations are intentionally written to specify the “what” without prescribing the “how,” providing flexibility.

In a “typical” small building with a service size of 50 kVA or less, separation of electrical loads is not required for the building loads, except for any renewable power sources (solar PV systems) and electric vehicle charging stations installed at the building.

In buildings with a service size between 50 kVA and 250 kVA, separate risers for lighting, receptacles/equipment, and HVAC are allowed to be used for meeting the separation of electrical circuits requirement. Large loads or groups of loads, such as an elevator machine room or a commercial kitchen, may be connected to panelboards or motor control centers served by a dedicated feeder, and the electrical power and energy of the entire group of loads can be measured by metering the feeder.

For buildings with a service size more than 250 kVA, lighting and plug loads are required to be separated by floor, type, or area. In a single-story building, all the lighting loads could be fed from a single panel, and all the plug loads could be fed from another panel (or, alternatively, both types of loads could be fed from one panel with provision to allow for future metering for each load type – metering data further be further organized, compiled, and viewed with software or mobile applications for each load type). 

In a multistory building, a simple way to comply would be to install a separate lighting panel and a separate plug-load panel for each floor of the building. However, it would also be acceptable (and may be more useful) to divide the load according to which area of the building it serves (such as office, warehouse, and corridors) or by the type of light fixture (for example, metal-halide, fluorescent, dimmable, and fixed-output). For example, the first- and second-floor office lights could be fed from the same panel, while the warehouse lights are fed from a second panel. Dividing the load by area or type instead of by floor is more likely to yield useful information when the loads are analyzed in an energy audit. All the above approaches are acceptable methods of complying with the Energy Code.