Controlling Inductive Loads with a Contact Closure Output
Contact Closure Outputs (CCOs) have two possible positions, open or closed, which allows them to control low-voltage
equipment or integrate with building management, HVAC, VAV, or other third-party systems. Several Lutron
incorporate CCOs for this purpose. This application note describes the steps required to control inductive loads with the
CCO.
Maintained CCO Control of Low-Voltage Resistive Loads vs. Inductive Loads
The CCO on Lutron
products is designed to switch low-voltage resistive load types, such as contact closure inputs (CCIs),
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LEDs, and low-voltage (e.g., 12 V, 24 V) incandescent lamps. These load types may be switched without concern at the
voltage and current ratings indicated on the Lutron
Inductive loads can damage the CCO due to the voltage spikes they induce during switching. Inductive loads include, but
are not limited to, relays, motors, VAV equipment, and doorbells. Inductive loads can be switched safely by incorporating a
flyback diode (DC voltages) or RC snubber circuit (AC voltages) to suppress the voltage spike created by these loads.
Important Notes
The recommended inductive load-control techniques are detailed on the following page. Before proceeding, please note
the following:
It is best to place the suppressor as close to the load as possible;
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If multiple inductive loads are being controlled by a single CCO, each load should be individually suppressed;
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It is important to identify the type of load being controlled (AC or DC) because the suppression method will differ depending
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upon the load type;
DO NOT use a flyback diode on an AC load because it will not achieve the intended results and can damage the contact
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closure;
While the following circuits and component values are a good starting point, Lutron recommends contacting the
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manufacturer of the inductive load for specific suppression advice.
See individual product instruction sheet for voltage and current ratings.
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product.
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Application Note #434
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Technical Assistance — 800.523.9466 or
+44.(0)20.7680.4481
Revision D
July 2013
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