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Night and security led
Mar 15 2021

LED and Fluorescent Emergency Ballast

As we continue to replace older lighting to LED, it is important to understand building and life safety code as we retrofit old lights to more modern systems.

Emergency ballasts are one of the most complicated systems to maintain, as well as retrofit to LED.  First, let us get some basic terminology down.

Security and Night Lights

Night lights, often called Security Lights, are those that stay on 24 hours per day.  They remain on even when you turn a switch off – and typically there is one per large room.   This fixture has a separate wiring to it, bypassing the switch.  Whether the light switch is controlled by occupancy or a manual switch, the light will stay on as the wiring bypasses the switch for that one light.

Common Issues on night lights with LED conversion:  When converting to LED, watch out for these lights.  Any fixture based occupancy sensor should be addressed separately from the group.  While it can dim when not occupied, it should not turn all the way off unless local code ordinance allows.

Emergency Ballasts and Drivers

Emergency Ballasts are designed to keep lights on during the event of a power outage.  Often, these lights are mounted to an exit sign and look like a pair of bug eyes.  However, just as common is to find these in a 2×4 light fixture, warehouse high bay, or strip fixture.  

EM ballasts are similar to traditional fluorescent ballasts, but they have a battery internal that can allow a certain amount of time that the light can stay on, usually one light in the fixture.  These ballasts require their own dedicated wiring (a normal hot switched lead and an unswitched hot lead) as the unswitched lead bypasses any switch.  This dedicated wiring charges the battery, but also signals to the ballast when to start providing power from the battery when A/C power fails.  If the fixture is wired to a switch and lacks a dedicated unswitched hot lead, this fixture will simply turn on emergency power mode each time you turn the lights off – discharging the battery.  As these batteries only have so many charge/discharge cycles (enough to safely leave a building in a power interruption) – they are not designed to be energized each time lights are switched off.  

Additionally, battery life is shortened each time a battery is discharged.  Typical emergency ballasts might last 5 to 10 years, but much shorter if used frequently at night when lights are turned off.  EM ballasts can be tested individually with a button test system, and they will illuminate when pressed if they are working properly. 

Common Issues on EM Ballasts and LEDs:  Most commonly we find that fixtures might have been originally wired incorrectly, often without the separate unswitched hot lead to the EM ballast.  This leads to expensive replacement of the EM ballast, which is being too frequently discharged.  In this situation, a unswitched hot lead needs to be provided to signal when power is truly cut to a space.

em ballast and LED conversion
Safely converted an EM Ballast

Converting Existing EM Ballasts to LED

There are several approaches that work when converting EM fixtures to LED.

The preferred and easiest approach is to install a new fixture, with an EM ballast or driver.  Often, this can provide DC to the LED diodes and power them for a longer period of time in a power interruption.  This fixture will need two sources of wires, unless it is wired directly from the breaker and can then be optimized with sensors and control systems.  

Type C LED retrofits can also be applied, by replacing the existing ballast with an EM ballast that is compatible with a Type C tube.  This approach works well when the existing system is older and in need of replacement.

Type A retrofits are also an option, where the existing EM ballast is still functioning.  In this type of retrofit, all ballasts remain and LED tubes replace the existing fluorescent lighting.  This has the advantage of being incredibly low cost and minimal labor – but compatibility with existing ballasts and EM ballasts takes careful consideration and sampling.  

Unfortunately, if the existing EM ballasts are T12s or HIDS, replacing them is the best course.  T8 EM ballasts that have good life can be retrofitted if the existing ballast and battery system has life left in it.  

While local utility energy efficiency rebates may be slightly lower due to the complexity of EM ballasts, they typically are found in less than 10% of fixtures and do not measurably change the overall project incentives. While they do add to project costs, we find that a comprehensive replacement will lead to lower overall maintenance costs and avoid unexpected issues during inspections.


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