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Auto-Dim Explained

Bodine’s patented Auto-Dim is a feature unique to our ELI series inverters which allows for a lighting load to be much greater than the inverter’s ratings when in the normal AC mode. Auto-Dim allows for your fixtures to be on, off, switched, or dimmed, all without affecting emergency operation.

When normal power is present, the inverter simply passes AC power to the connected luminaires. When power fails, the inverter’s internal circuitry draws power from the battery to supply 120 or 277 VAC. If this power draw exceeds the inverter’s output ratings, lesser inverters may not reach their rated runtime or, worse still, not function at all. A Bodine ELI series inverter with Auto-Dim monitors its output voltage and current to detect the power draw of the connected luminaires and controls the 0-10V lines to optimize their power draw.

Wiring diagram showing a Bodine ELI-S-250 inverter connected to normal luminaires (95 VA) and Normal+EM luminaires

Auto-Dim means that one small inverter can provide backup power for a large bank of luminaires. In this example, five 95 VA luminaires from a circuit of many are designated to be emergency lighting. A single ELI-S-250 is used to power 475 VA of luminaires. When in the emergency mode, the dimming signal reduces the power needs of all connected luminaires and drives them at 50 VA each, or 250 VA total.

Auto-Dim can also be used with a single luminaire that would normally require more power than a small inverter can supply. The example below shows the Bodine ELI-S-10 installed inside of a 40 VA luminaire. As this luminaire has 0-10V dimming, the ELI-S-10 can take over the dimming controls while in the emergency mode and limits the power needs of the luminaire to 10VA.

Diagram comparing emergency lighting inverter configurations with and without Bodine's Auto-Dim

Finally, the example below demonstrates this value of Auto-Dim. In it, five 95 VA luminaire require emergency backup power. Auto-Dim saves money by allowing the inverter to be sized appropriately to meet life safety code requirements and nothing more. (See the section below discussing code requirements for more details.) Without Auto-Dim, the inverter required is much larger and more expensive. All luminaires will be driven at full light output in the emergency mode, which is typically not required to meet emergency egress code requirements.

Wiring diagram showing how the Bodine ELI-S-10 inverter connects to a room dimmer and AC driver in a combined normal and emergency luminaire

Notice, in this example, normal dimming is not used. To take advantage of Auto-Dimming, normal dimming controls is not required. Only the dimming connections from the inverter to the luminaires are required.

NOTE: These examples present an ideal case of dimming level versus driver input power. Many things directly affect the input power requirements of AC drivers/ballasts. Particularly, AC Driver/ballasts become less efficient at low dimming levels, which will impact the max level of dimming achievable in the emergency mode and must be considered in the end system.

Auto-Dim and code requirements:

Lighting connected to an Auto-Dimming inverter can meet the code required emergency lighting illumination levels. As mentioned above, full power from the designated emergency luminaires is not necessary for virtually all applications. Applications vary, and the reduced light levels and illumination requirements of the environment must be considered though either the use of lighting design tools or direct measurement. Illumination requirements are generally an average of 1 foot-candle across the path of egress. Chicago requires a minimum of 1 foot-candle. Because local code can further vary, be sure to find your specific requirements. And, as always, call Bodine if you need assistance.

See all Bodine inverters with Auto-Dim

Good to know:

The connected luminaires must be capable of dimming by use of a 0-10V dimming signal.
You do not need to use dimming controls in the normal mode to take advantage of Auto-Dim. You need only connect the Inverter's dimming out connections to the luminaires dimming lines.
If you do use dimming in the normal mode, normal operation is unaffected by the inverter. The inverter will pass through to the luminaires whatever signals your dimming switch provides.
Rarely is full light output of a luminaire required to meet the NFPA 101 code requirements of 1.0 foot candle average on the floor. In fact, one very bright luminaire surrounding by darkness may actually violate the same code, which requires a level of uniformity across the egress path during an emergency.
Auto-Dimming is just that, automatic. There is no setup required to take advantage of Auto-Dim in your application.

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