Contrec 515 BR03, Operation Manual

Page: 27 / 110

Installation & Maintenance
515 BR03 - 15 August 2021 17
RC Network for Interference Suppression
When driving inductive loads with the relay outputs, it is recommended to
use RC suppression networks (often called “Snubbers”), fitted at the load
end, for the following reasons:
•
To limit the amount of electrical noise caused by arcing across the
contacts, which may, in extreme cases, cause the microprocessor to act
erratically or cause other unwanted interference with connected signals.
•
To protect the relay contacts against premature wear through pitting or
SSR (where specified) against premature failure.
RC suppression networks consist of a capacitor and series resistor and are
commonly available in the electrical industry. The values of R and C are
dependent entirely on the load. However, if the user is unsure of the type of
snubber to use, values of 0.25

F and 100

will usually suffice. Note that
only UL and mains approved RC suppression networks should be used.
The basic principle of the operation is that the capacitor prevents a series of
sparks arcing across the contact as the contact breaks. The series resistor
limits the current through the contact when the contact first makes.