Controlling the Light

Today’s lighting control systems (LCS) are more elaborate and high-tech than ever. The once-simple systems consisting of a few low-voltage switches, a small lighting control panel (LCP) and a time clock now involve special ballasts and relays, motion and daylight sensors, photocells, dimmers, scene controllers, and more than one panel. Those complex components are connected and integrated and operate in concert with each other. And yes, they still have a few of those low-voltage switches.

For estimators, it’s not a matter of just counting what is shown. You have to know whether what is shown is complete. If not, you need to know how to complete it.

Spec check: conduit or open cabling?

Conduit can be a material and labor-heavy item. You don’t want to carry it if you don’t have to, but you don’t want to leave it out if you need it.

Most devices in an LCS are connected with Category 6 or similar low-voltage cables. The actual requirement for running these cables in conduit is not always clearly specified or detailed. If they are unclear, write a request for information (RFI). Much depends on your ceiling types (accessible or not). Check the specifications, sheet notes and any wiring schematics or details provided.

How many neutrals does it take to turn on a lamp?

Engineers don’t always completely (or correctly) circuit their designs. This requires estimators to know how the LCS works and how it needs to be wired into the lighting circuitry.

It is important to note with most LCS designs, switch legs (neutrals) are fed directly from the LCP and/or power panel—not from local switches. This can affect your homerun configurations.

Engineers usually provide subscript letters telling you which devices control which fixtures (or lamps). Each subscript letter requires a dedicated switch leg. Example: A common office design uses the half-on/half-off or a/b switching configuration, requiring two switch legs.

However, in open offices, conference rooms and many common-use areas, you could find much more complex switching scenarios symbolized with multiple subscripts such as “a, b, c, d, e, f, g and h.” So you would need eight switch legs. That’s three times more wire! Depending on how many areas are configured like this, you could need several more wires in homeruns and possibly larger conduits.

I once estimated a museum where the subscripts ran up to z, and then continued with aa, bb, all the way to zz. There were a lot of crazy homeruns. Of course, none of them were shown.

Engineers don’t always tell you how things work

An example of engineer neglect is how the fixtures on emergency circuits work with and integrate into the LCS. In most scenarios, emergency lighting fixtures don’t get controlled. Also, per the National Electrical Code, emergency circuits must be separated from normal power circuits and feed the fixtures independently from the normal power.

Yet we often see “emergency fixtures” integrated into the array of “normal fixtures” and controlled by the LCS under “normal power.” If you see that terminology, you will likely need some sort of special relay at each emergency fixture.

I once estimated a project where each emergency fixture required a special $375 relay. There were more than 200 emergency fixtures (200 $375 = $75,000). Now, that was just the additional cost for the relays. Labor and hardware also were required to mount the relays and connect them to the fixtures: about $25 in materials ($5,000) and one hour each to install (200 hrs. $50/hr. labor = $10,000). That’s $90,000, and I haven’t factored in overhead, profit or taxes. Ouch!

Review each spec, detail and sheet note

Those special relays were not shown on the lighting plans. They were simply noted in the lighting control diagram by a symbol of a J-Box with the letters “EM” and an asterisk next to it. At the bottom of the diagram, the asterisk was noted: “Emergency fixtures controlled by daylight harvesting system. EC to confirm all requirements.”

It took two RFIs to find out about the required relay, and we never got a revised schematic showing us how it all was wired. At least we got the $375-plus relay covered.

It’s not just about controlling lighting fixtures

Today’s higher end LCS can be integrated into the building energy management system and can do a lot more than just control lighting fixtures. There are several other electrically powered and controlled systems that could potentially require integration. Motorized shades; projector screens; heating, ventilating and air conditioning systems; and even power outlets can all be part of a LCS, so ensure you know what these systems require.

Estimating today’s LCS requires serious study and takeoff time. It is important to plan for this time in your estimate’s schedule. You should never rush this part of your takeoff. If you do, you could easily miss some very costly installations.

SHOOK is the president and chief estimator for his estimating company, TakeOff 16 Inc. He has worked in the electrical construction industry for more than 18 years. Reach him at 707.776.0800 and

About the Author

Stan Shook

Stan Shook was ELECTRICAL CONTRACTOR's estimating columnist from 2005 to 2012. He works as an electrical estimator in California. Read his blog at or contact him directly

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