Flowline LU78 EchoSwitch - Manual (Page 23)

Rev A MN300282 23 of 34
ELECTRICAL Step Six
Input Power and Relay Connections: The EchoSwitch® is powered from 95 to 250 VAC power. Power is
applied to the L1 and L2 terminals. Typically, Hot is applied to L1 and Neutral to L2. The Gnd terminal should
be connected to a solid earth ground to help shield the sensor from external EMI/RFI interference.
The EchoSwitch® features three 60 VA, 2A max relays. Relay 1 has both the Normally Open and Normally
Closed contacts available. Relays 2 and 3 have the Normally Open contacts available. All three relays have
their commons connected and are isolated. The example below shows Relay 2 wired NO. Make sure to select
a relay state that is fail‐safe and takes into account when power is lost to the EchoSwitch®.
The switching of heavy inductive loads such as pump motors can create voltage spikes in the many thousands
of volts. It is recommended that the power to the EchoSwitch® and to the coils of the isolation relays be
sourced from a main that is not switching inductive loads as shown below.
 Note #1 – Isolate power to instrument from power to load (pumps, etc.) as much as possible by running
power to the sensor directly from main power source.
Relay Configuration:
All three (3) EchoSwitch® relays share the common relay terminal.
 Relay #1 is a Form “C” SPDT contact.
o It is useful for controlling a valve which requires a contact to open
and a contact to close.
 Relays #2 & #3 are Form “A” SPST contacts.
o These two relays (#2 & #3), in addition to relay #1, can be used for
controlling valves, pumps or alarms.
Note: Because all three (3) relays share the common relay terminal, the
relays must all switch the same power.