Guest Post: Steve Mesh on Writing the Sequence of Operations

Whether you use traditional lighting control devices or newer systems such as networked lighting controls (NLCs), you have to communicate and document how you want those devices or systems to behave. This documentation should include a Control Intent Narrative and Sequence of Operations.

Intended to be read and easily understood by the owner and other project team members, the Control Intent Narrative (CIN) is a document that explains in plain language what the lighting control system is expected to do in general terms. Listing specific settings and behaviors essentially converts the CIN into a Sequence of Operations (SOO), which is therefore actionable and measurable. These are explained in detail in ANSI/IES LP-16-22 and in this three-part article series by the LCA.

Why is this important? Prevailing commercial building energy codes require a “written controls narrative (see Section C408.3.2.2 in the latest version of the IECC) including recommended settings.” And it’s simple best practice, ensuring that the design intent for the proposed lighting control system satisfies the owner project requirements (OPR) and that the final design satisfies the design intent. After installation, these documents support commissioning and long-term maintenance and use of the system. As lighting control systems become more inherently sophisticated to satisfy energy codes and deliver extended capabilities, this best practice has significantly grown in importance.

The trick is writing that first one, which requires some effort, though one might consider this an investment, as it will be replicable (via editing) for the next project. LP-16 can help get past any writers block with its side-by-side CIN and SOO examples for 11 discrete lighting control strategies and 14 examples for specific space types.

As an educator working with utilities to teach NLCs, I developed a CIN/SOO as an illustrative model for a hypothetical small office space I use to teach students how to wire and commission a lighting control system. This 1,200-sq.ft. space contains a reception area, open office area, enclosed conference room, lavatory, and kitchen. Here’s the plan:

Click here to view/download the image full size.

You can click on the plan to download a larger version you can view for legibility. For this lighting control solution, I create a CIN/SOO in spreadsheet form that spells out the intent of the system and then the specific triggers/behaviors:

Click here to see the SOO matrix full size (PDF). Click here to download it as an XLS spreadsheet.

Again, you can click on either image to download a file you can view that offers greater legibility than what’s possible on a webpage. The matrix format is inherently elegant, though there’s quite a bit of information to unpack.

Here’s what this means as a narrative:

Zone Information

• Control zone designation (indicated by a lower-case letter on the plan such as “a”).
• Control zone name (such as “Open Office”).
• Control subzone information (such as “Primary Daylight” zone – zone “aa”).
• Fixture type (such as TYPE A).
• Fixture descriptions (such as “2’x4’ LED troffer”).
• Unique fixture identification/location numbers – since I assign unique numbers for each fixture on the plan (something I never did in the past before the advent of NLCs).
• Fixture quantity.
• Watts each.
• Total zone wattage.
• Total zone amperage at either 120 or 277 volts (depending on the project; note that load controllers in NLC systems are typically rated in amperage).
• Load type – in this sample project, most fixtures employ 0-10V dimming drivers; however, some are fixtures with medium-screw base sockets for use with LED replacement lamps and, therefore, must be connected to phase-control dimming controllers.

I established this essential information for all five zones (actually seven, as there are three subzones for the Open Office area).

Control Strategies, Devices, and Settings

Let’s take this one control strategy at a time:

Manual Control

• Manual control device – Catalog numbers are listed for specific device(s) used in the zone.
• “Favorite” (preset) button settings – e.g., set to “50%” output (since students pair single-gang dimmers to most of the zones, and those dimmers all have a “Favorite” button).
• In “Scene 1,” … “Scene 2,” … and “Scene 3,” in the Conference Room zone, I ask attendees to commission a single-gang, multi-scene preset selector device.

Note that the preset device has four buttons—three for different programmable scenes and a “full Off” button. Therefore, I must specify the levels I want them to program for each preset button.

It might be logical for someone to commission such a preset selector panel using the following output levels: Scene 1 – 100%, Scene 2 – 66%, Scene 3 – 33% (remember that the bottom button is reserved for “full Off”). However, I asked them to program the buttons as follows: Scene 1 – 50%, Scene 2 – 10%, Scene 3 – 75%. Why? Because it is human nature to hit the top button upon entering the room. Since this room is at a window wall, 50% of the output is probably more than adequate light when people are having a meeting, especially during the day. 10% output is adequate for when the room is used for an A/V presentation. The third button will provide 75% power if higher output is desired. Of course, if the owner wants to adjust those settings after the initial commissioning, that’s their prerogative.

Occupancy Sensing

• Occupancy sensing device – as with the manual controls, specific catalog numbers are provided.
• “Occupied” light level – e.g., “50%” (meaning that lights will turn On to 50% upon people entering the space, not to full output, which would consume more energy than is probably required).
• “Vacant” light level – e.g., “10%”. Why would I suggest that lights remain on but at 10% output during vacancy periods? Because there’s a big difference in perception between all lights being Off in a space versus having lights On even at a very low level. Dimming lights to 10% still saves a huge amount of energy. Note that NLC systems allow you to set “Occupied” and “Vacant” levels between 1-99% because they are now just variables you set in the software. They are not based on pre-programmed options in the device, burned into the integral circuitry.
• Sensitivity – e.g., “Medium.” This will usually provide the best opportunity for energy savings. This defines the amount of motion needed to trigger the lighting On.
• Timeout delay – e.g., “10 minutes.” Most energy codes prohibit delays longer than 20 minutes. However, I typically suggest shorter delays to save the maximum energy. Again, remember that the owner can still ask to change this variable after initial commissioning. Typically, if someone leaves their space for a quick break, it is less than 5 minutes. If they are gone longer than 10 minutes, the lights will turn Off. It is essential to help save energy but also be aware of the occupant’s comfort (i.e., lights not constantly turning Off).
• Fade rate – e.g., “2 seconds.” Many NLC systems allow you to program specific fade rates, but some do not. This may also be true for fade rates based on changes in photosensor input. The moral of the story – if there’s a function that is absolutely essential for your project (such as the ability to reprogram the fade rate from a sensor), then make sure you inquire about that before you purchase the system.
  • Occupancy sensor notes – an example in my spreadsheet is “parallel operation of all occupancy sensors in conference room troffers.” Why did I include this note? With traditional wired control devices, occupancy sensors could be parallel-wired so that all fixtures in a space turned On and Off based on input from any of the sensors within this space. The fixtures used in the Conference Room are TYPE A fixtures (same as those in the Open Office space). These are luminaire-level lighting control (LLLC) fixtures, which contain pre-installed, fixture-integrated dimming, occupancy sensors and photosensors. Those allow each individual fixture to turn on and off independently, thereby generating as much energy savings as possible. However, in some spaces, such as the Conference Room, it may be preferable for all of them to turn On or Off simultaneously based on input from any of the fixture-integrated sensors. Hence: “parallel operation of all occupancy sensors in conference room troffers.”

Daylight Harvesting

• Daylight harvesting device – as with other strategies, specific catalog numbers are provided for photosensors.
  • Target light level – e.g., “30 footcandles” (horizontal, on desk surfaces @ 30” AFF). Typically, photosensors must be calibrated on-site and then commissioned to achieve the desired target level. However, some NLC system manufacturers make photosensors that have been “pre-programmed” in the factory to send a signal to fixtures that (hopefully) will provide the approximate target light level – such as 30 horizontal footcandles on the desk. They should also allow a commissioning agent to refine the calibration and programming of the photosensors on-site if the target isn’t achieved to the agent’s or owner’s satisfaction.
  • Daylight harvesting notes – an example is “disable sensor in software.” When and why would you need to say that? In this project, I’ve used the TYPE A 2’x4’ LED troffers in the Restroom . As mentioned, these meet the definition of “LLLC” controls. Since there are no windows or skylights in this Restroom, there’s no reason to use the “Daylight Harvesting” function. Therefore, I ask attendees to “disable” this function in the software. As before, this is now a software-based function. To do this, there’s no need to get on a ladder and manually adjust DIP switches in the fixture.

Scheduling

• Event 1 – e.g., “turn lights on at 8:00 am, Monday-Friday.”
• Event 2 – e.g., “turn lights off at 8:00 pm, Monday-Friday.”
• Note that I’ve only scheduled the “turn lights On at 8:00 am” event for the Open Office and Reception areas but not for the Conference Room, Restroom, or Kitchen area. Those are rooms/spaces where either lights will turn On automatically based on signals from occupancy sensors (in the Reception area or Restroom), or where you have to manually turn them On from a wallbox switch/dimmer (such as in the Kitchen area).
• Also note that in some of these spaces – such as the Kitchen area – there is an occupancy sensor paired to the line of wallwashers illuminating that area. However, there is a note to program that as a “vacancy” sensor. There will probably be more than adequate light from the nearby Open Office area 2’x4’ troffers to illuminate that area anyway. If someone still wants/needs more light, they can always go to the wall switch and turn On the wallwashers. Therefore, the logic of only assigning the “Event 2” programming is the same – by requiring someone to manually turn On the lights if they think they need them. As mentioned before, the reason to include these types of variables in the SOO is to try to save as much energy as possible. Remember that may help to reduce the payback for the initial system cost.
• Finally, note that some NLC systems allow you to create “events” in the schedule. This means that something happens in the system at distinct points in time. That could mean that lights turn On, or they turn Off, or go to a set lighting level. Or – maybe it means that occupancy sensors become active, or inactive for that matter. Or photosensors. Other systems allow you to program behaviors for blocks of time. You may have specific reasons to want a system that uses one or the other of these methods. There are many such nuances in how vendors write software for their user interfaces. The onus is to ask for a demonstration so you know exactly how a vendor’s software works – and whether that will provide all of the required functions.

Trim

• High-end trim – e.g., “80%.”
  • This is also called “Task Tuning” or “Institutional Tuning.” Currently, there isn’t an overwhelming consensus in the industry about terminology.
  • High-end trim is a variable you set so that lights do not exceed that level regardless of what control strategy is being used. For example, let’s say you set a high-end trim level of 80%.  Even if you raised a manual slide dimmer to the maximum level, the lights would only be at 80% output.
• Low-end trim – e.g., “5%.”
  • In some cases, especially depending on the quality of the LED drivers, light drops out (turns Off) at very low dimmed levels. Programming a low-end trim variable ensures that lights remain on at low levels until you command the lights to “turn Off.”
  • As an example, let’s say that the LEDs turned off at a level of 3%. If you set a low-end trim at 5% and then turn a manual slide dimmer to its lowest setting, the LEDs will still be on.
  • Where might this be important? Let’s say you have a conference or multipurpose room often used for a/v presentations. Let’s assume the room has a wall-mounted dimmer with raise and lower buttons. If an occupant wants to turn lights down to the minimum level (but not full Off) and they use the “lower” button to achieve that, will the lights actually remain on at a very low level? Setting the “low-end trim” variable will ensure they can only turn lights Off using the actual Off button.

Load Shedding

• Load Shedding reduction – e.g., “50%.”
  • Some state energy codes (such as California Title 24) require that most buildings have equipment that is Automated Demand Response (ADR) capable. This means there is some method to bring an external signal – from a Demand Response Automation Server (DRAS) – into the NLC system and force certain behaviors. The Title 24 requirement in any project is as follows: “For compliance testing, the lighting controls shall demonstrate a lighting power reduction in controlled spaces of a minimum of 15 percent below the total installed lighting power as described in NA7.6.3. The controls may provide additional demand responsive functions or abilities.” <paragraph 110.12(c)1>.

If this project was in California, then programming a value of a 50% reduction in output would certainly meet the code requirement. Note that a light output reduction of only 15% is below the threshold of anyone’s ability to discern that lights have dimmed!

Also note the following:

• Even if there’s no state energy code requirement for demand response capability, some utilities offer incentives that require you to use demand response-capable controls. If so, then you would still need to program them and demonstrate that the system can at least potentially take input from a DRAS and force lights to reduce their output. This is why some manufacturers are incorporating ADR functions in their NLC systems.
• In certain zones, I’ve asked for the lights to be turned “full Off” during a demand response event – including the Reception area wallwashers, Conference Room 2’x4’ LED troffers, and Kitchen area wallwashers. However, in the restroom I’ve asked that lights are “Unaffected” during an ADR event. Since the restroom cannot “see” any other lights since it’s an enclosed space, I wouldn’t want anyone in the restroom to suffer any disruption during an ADR event.
• The verbiage I used in this spreadsheet for demand response was to program certain zones for a “50% reduction” in output during an ADR event. It’s important to ensure that whoever is reading and using this SOO spreadsheet understands the difference between programming lights for a “50% reduction” (from whatever the current levels are) versus dimming lights to an absolute value of 50% of full output. You might decide to expand on this to ensure there is no misunderstanding about how you want the system to be programmed. That may be true with other variables as well.

Emergency Lighting

I did not include Emergency Lighting descriptions and desired behaviors in this spreadsheet. I don’t usually have the time in introductory-level classes to discuss Emergency Lighting in detail. However, in a typical CIN, it should be covered as a matter of basic intent.  Because of new methodologies for how NLC systems can operate in emergency conditions, an SOO will ultimately need to cover specific variables and behaviors.  Since this is a life safety issue, such details are typically created by a licensed professional such as an electrical engineer.

Writing the SOO

While there is no gold standard for developing a CIN and SOO, the Illuminating Engineering Society describes best practices in ANSI/IES LP-16-22, which are also covered in the Lighting Controls Association’s course on lighting control system design, part of Education Express. In this article, I showed how I personally approached it as an NLC educator to provide what I hope is a useful illustration of the importance and construction of this documentation.