Did you know? Plug loads account for nearly half of all energy usage, even in green, high-efficiency buildings! 

The number of plugged-in gadgets seems to grow every year in modern facilities. These devices are often unnoticed and consume a considerable amount of energy even when on standby. Managing these plug loads creates one of the best energy-saving opportunities for specifying engineers, building owners, and facility managers!  

Simply put, plug load control is turning off plug load devices when they are not in action. The same strategy can be applied for automatic control of lighting loads either at the receptacle or circuit level. This article explains everything you need to know about plug load control and integrated designs for lighting and plug load controls. 

Before we get to that, a bit of basics: 

What are Plug Loads? 

Plug loads are the energy used by any device or equipment plugged into a standard AC outlet (120V/15A). These products typically draw power even when they are not in use. Examples include computers, task lighting, coffee makers, and vending machines that can be switched off at night without causing harmful consequences. In office buildings, plug load accounts for more than 25% of the total energy consumed. Even in ultra-efficient buildings, plug loads and lighting account for nearly half of all energy usage. If left unchecked, it can cause wastage of huge amounts of energy and money.  

Interpreting the Codes 

Due to the substantial energy savings potential, commercial building energy codes such as ASHRAE 90.1, Title 24, and IECC now mandate controlled receptacles via occupancy sensing or schedule-based control.  

ASHRAE 90.1 

ASHRAE energy efficiency standard requires plug load controls are mandatory in all commercial buildings.  

Section 8.4.2 requires at least 50% of all receptacles in private offices, open office areas (including those installed in modular partitions) and computer classrooms must be controlled by an automatic control device like: 

1. An occupancy sensor that will shut off receptacles within 20-30 minutes of all individuals vacating a space 
2. A schedule based / timer-based control device that turns receptacles off at specific programmed times  

Plug-in devices cannot be used to meet this requirement.

Exceptions: 

1. Equipment designated for 24-hour continuous operation 
2. Space where an automatic shutoff would put occupants’ safety at risk 

Title 24 

The California energy code Title 24 has brought significant changes in its 2019 version as follows.  

1. Requires both controlled and uncontrolled 120V receptacles in private and open offices, office kitchenettes, conference rooms, reception lobby and other spaces. 
2. There must be at least one controlled receptacle within 6 feet for each uncontrolled receptacle. Or duplex receptacles with one controlled and one uncontrolled shall be installed.  
3. There must be at least one controlled receptacle per workstation in open offices. 
4. The electric circuits feeding controlled receptacles must be automatically shut off within 30 minutes after the guest room has been vacated.

The latest Title 24 updates contain significant changes regarding demand responsive controls. Click here to read

Want to learn more about Title 24 lighting requirements? Click here

IECC

The updated version of IECC also has similar receptacle control requirements.  

In specific applications (such as enclosed offices, workstations, and classrooms), at least 50% of all permanently installed 15A and 20A receptacles must be controlled. Additionally, at least 25% of branch circuit feeders installed for modular furniture not shown on the plans must be controlled. 

The control function may be split-controlled receptacles (with the top controlled) or separate controlled receptacles (within a foot of each uncontrolled receptacle). 

The receptacles may be controlled via an occupancy sensor, scheduled basis using a time-switch control function or signal from another system. 

Want to learn more about IECC lighting requirement? Click here

How to Achieve Plug Load Controls? 

Now that we are aware of what we need to control, the question is how do we do it? Majorly, there are three plug load control strategies: occupancy-based control, time-based control, and system-based control. 

Occupancy Sensing Based Receptacle Control 

This approach saves a great deal of energy and money by being responsive to occupancy. The equipment connected to the receptacle will turn off with an occupancy-based plug load control when a space is vacant. Occupancy sensors are ideal for high usage areas with irregular schedules, such as private offices, classrooms, conference rooms, pantries, and restrooms.  

For simple retrofits where ceiling sensors already exist for lighting control, one can wire a device to the sensor, which transmits a wireless signal to a receptacle in the space. This receptacle can switch a 15-or 20-amp load on or off based on occupancy. 

Alternatively, facility managers can control the power pack that controls the receptacles connected to the building control system via category cables.

Plug load control can also be done at an individual receptacle. For example, an occupancy sensor can be connected to an outlet or mounted underneath a desk

Time-based Receptacle Control 

An automated, time-scheduled controlling system is the best fit for workspaces with predictable occupancy patterns, such as factories and lobbies. It is also considered as the simplest way to comply with plug load control requirements. In this case, one can make half of the receptacles time-based to meet the ASHRAE 90.1 criteria for 50% control. 

Schedule-based/timer-based method turns receptacles off at specific programmed times. 

For example, a workspace during the day can be programmed differently than at night.  

The control devices can be programmed to shut off equipment from 6 p.m. to 6 a.m. or after a set amount of time, such as 8 hours. Timers with astronomic and Daylight Saving Time (DST) functionality automatically adjust to the sunset, sunrise and day light.  

ASHRAE 90.1 mandates that the occupants be able to override shutoff for up to two hours via a manual switch located in the space or on the receptacle itself. 

System-based receptacle control 

For larger building systems, an automatic signal from an external control system (for e.g., alarm system) will turn off the receptacles within 20 minutes of all occupants leaving space.   

How to Choose the Right Plug Control Method? 

There is no one-size-fits-all for plug load controls! Start by considering the loads, building, occupants, how the space is used and applicable codes and standards. Then decide which strategy is best: hardwiring or wireless, networked or not, receptacles or power strips, scheduling or occupancy sensing. 

Another thing to keep in mind is the type of building- existing or new. In an existing building, wireless controls and portable advanced power strips with personal occupancy sensors can be simple and cost-effective. Extending the automatic lighting control system required by energy code to control plug loads can be simply accomplished in a new building. For private offices time-based control is the best option but in one or two rooms, they could choose stand-alone, occupancy-based plug load control.  

Not all commercial building outlets need plug load control. Some devices, like security systems and refrigerators, shouldn’t be left off. 

Be in Control of Your Plug Load! 

As plug load represents a relatively untapped energy savings resource in enterprise buildings, architects and designers clearly must focus on strategies to reduce this critical area of energy consumption. Upgrading lighting control system to include plug load control can limit energy usage, support an organization’s sustainability efforts, and save money on utility bills.   

What plug load control measures are you considering to reduce energy consumption?

For more information on Plug Load Controls, feel free to contact our team of experts.