System Design Considerations: Zonal vs. Granular Control

Networked Lighting Control 101

Smart buildings, smart cities, smart everything. At every turn, it seems that more and more “things” are becoming smarter at an ever-quickening pace – including buildings and their lighting systems. While lighting controls have been around for decades – at least in their simplest form (i.e. relay control) – it’s the latest advancements in LED technology, coupled with the plummeting price of sensors, that will prove the biggest boon to this smart building workhorse.

What was once rudimentary on/off control with a hefty price tag, is now a cornucopia of efficiency options. Looking to task-tune your lighting with 0-10 step dimming? Now you can. Want to take advantage of daylight harvesting? Now you can. Temperature and humidity control? You guessed it, now you can. What’s more,  you now have the capability to take advantage of each of these control strategies on a single networked platform – allowing for control from any device, in any location, from any location. Now that's an improvement over legacy on/off control.

Today’s networked lighting control system benefits are easy to tout. And while nice to hear, simply recounting the bells and whistles of a given system leaves many end-uses at a loss in understanding how the system would work in their specific facility. Moreover, they're at a loss in understanding how a networked lighting control system should be designed for the desired outcomes they're shooting for. This alone is critical information that one must fully absorb if looking to upgrade a building's entire lighting infrastructure. I mean, we're talking about some serious investment dollars.

Whether you’re considering an advanced lighting control system to harvest data to improve operational efficiencies, or looking to reduce energy expenses through aggressive lighting control strategies, let’s explore the role system design will play in achieving your goals.

System Design Considerations

When it comes to a networked lighting control system there are really two system designs to consider:

1) Zonal Control System Design
2) Granular Control System Design

While each has their own unique benefits – of which we’ll cover in more depth below – the important thing to understand at this point is how each design controls fixtures. By understanding this first, we’ll then have a much better grasp of each design’s capabilities and whether it would fit your desired lighting control goals.

As a side note, these system designs are applicable to either a wired control system or a wireless control system. The important thing to note here is the desired outcome you’re looking to achieve and which design best fits. We’ll cover the differences between wired and wireless control systems in a future post.

So, what’s the difference between the two system designs? In a nutshell, a system that’s designed for zonal control can only control lights at the circuit level and a granular system design controls lighting at the fixture itself.

Let’s take a deeper look at why this is important and what role it plays in achieving your specific lighting control goals.

Zonal Lighting Control Design

As we mentioned, a zonal system design controls lighting at the circuit level. Thus, the flexibility of individual fixture control is limited. While this may be the case and seem like a major downfall, there are many benefits of a zonal system design. First, let’s look at what we mean when we say that lights are controlled at the circuit level.

Zonal Lighting Control Example

 

zonal-system-design

As pictured above a zonal system design relies heavily on the existing circuitry of the facility. Here, in this example, each of the colored areas above would indicate a wiring circuit. A zonal system design would place the control devices at the circuit level – usually at the electrical panel – and would control that given shaded area. The problem? Let's look at an example.

Example of Zonal Control Setback

For example, say for some areas of the building you’d like to develop a lighting control strategy that is different from the other areas of the building. Here, you’d be bound by the lighting circuit and some circuits may bleed over into another area of the building that you don’t necessarily want to apply that specific control strategy too. This is a very common setback when dealing with a zonal control design.

There are benefits of a zonal system design, though. Let’s take a look.

Benefits of Zonal System Design

As with any construction project, budgets are the be-all and end-all of what is, and is not, possible. This is where a zonal system design provides the most value. Due to the sheer fact that controlling lights at the circuit level automatically reduces the number of parts and pieces you’d need. You'd thereby find direct savings from lower material and installation labor costs.

But more than pure material and labor savings, a zonal system design may just be the best fit for your desired lighting control outcome. Let me explain.

Let’s say your end goal for a new lighting control system is to reduce energy expenses. Let’s also assume that you already have legacy sensors installed in your office spaces and work floor areas, but these are your traditional relay, on/off, sensors. The benefit of migrating to a more advanced networked lighting control solution can be found in the new capabilities gained. Namely, the ability to establish predefined, flexible, and comprehensive control strategies, that can be applied across your entire facility. Think step dimming (i.e. keeping lights at a lower level of burn), or facility-wide time schedules.

Even though you’re only controlling lights at the circuit level, with a networked communication path to all fixtures running back to a central control center you can now tell your lights to do far more things than in the past. Again, think in terms of dimming control, occupancy based control, and automatic time schedules (i.e. turn lights down to 30% at 5 PM, 15% at 8 PM, and then off after 10 PM) as mentioned above. These more advanced strategies will aid greatly in meeting your original end goal by squeezing the efficiency sponge a bit more.

So, what about granular control? How does this system design differ?

Granular Lighting Control Design

In a granular system design, the control capabilities go far beyond circuit level. In fact, the control capabilities of a granular design go down to the individual fixture itself. This granular control gives you far more flexibility in not only developing your lighting control strategies but in your data-harvesting capabilities as well.

Let’s look at what a granular control system design would look like.

Granular Lighting Control Example

granular-system-design

As pictured above a granular system design considers each individual fixture in the overall system infrastructure versus existing circuit runs as in a zonal design (as indicated by the blue squares above). By mapping out each individual fixture and enhancing it with an individual controls device, end-users now have the power to create zones and control strategies as they wish – no longer bound by the existing wiring of the facility. Let's take a deeper look at some other benefits of a granular system design.

Let's take a deeper look at some other benefits of a granular system design.

Benefits of a Granular System Design

With deeper control capabilities, a granular system design fits the bill for most folks. Ideal for those who are looking to reduce energy usage and harvest meaningful operational data to drive productivity.

Through induvial fixture control, a granular system design provides end-users the power to develop extremely specific lighting control strategies centered around task-tuning. Task-tuning is the process of controlling light levels as they correspond to a specific task or job responsibility (i.e. lighting conditions for an open office space with hundreds of computers requires different lighting levels than an electronics manufacturing bench where highly detailed work is completed).

Going beyond task-tuning, a granular system design provides end-users with the flexibility for adapting their lighting control strategies. For example, to better align their control strategy with how building occupants use the building. Take for example a building with normal operating hours of 6 AM – 5 PM. While your facility is open at 6 AM, most employees won’t arrive until 9 AM. Moreover, various areas of your building may be under or over utilized throughout a given day. (i.e. The period between 5 PM and 9 PM when only cleaning personnel in the building. During this timeframe, there's no need to light 50,000 square feet of space when only 500 square feet is utilized).

A granular system design data-gathering capabilities needed to determine exactly which areas and “hot-spots” and “cold-spots”. In fact, these hot and cold spots can be tracked throughout the day, even down to the hour. Thereby, providing you with actionable data for matching your control strategies with your building occupant's habits.

Determining the Right System Design

Your specific needs, wants, and overall goals determine the system design that yields the greatest return on investment.  You'll be poised to design a system that is right for your facility, once these parameters are defined; along with a proposed project budget. At the end of the day, a one-size fits all approach will easily lead you astray. Key points to consider here are:

  1. How do your end goals correspond with a zonal design versus a granular design;
  2. Is there an opportunity to create a hybrid approach? Where some areas of your facility are zonal while others are granular.

By starting here you'll build the technical understanding required to ensure a smooth networked lighting control project.