RT-SVD03G-EN 137
Snubber Circuits
ReliaTel controls utilize relays to energize alternating current (AC) loads. Because of the
characteristics of AC loads dealing with inrush current, snubber circuits are used.
The purpose of a snubber circuit is to act as a filter to help dampen the voltage peaks associated
with the opening and closing of the relay contacts. The snubber circuit is a resistive/capacitive
circuit, with a resistor and capacitor wired in series across the on-board relay contacts.
Snubber circuits may cause confusion because 24 vac will be present if the output wire is
disconnected from the load; such as a relay or contactor coil, and the contacts of the board relay
are open. The voltage potential between the disconnected wire and ground will be 24 vac, but no
current will be present. When the wire is placed back on the contactor coil, the 24 vac potential will
disappear. To properly verify whether voltage is present to energize a relay and contactor, the
circuit must be complete and in tact.
Figure 80. Snubber Circuits
Resistor
Capacitor
Relay Contacts
24VAC Power Supply (On Board)
24VAC Output to Load Being
Controlled.
(Off Board)
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