Red Lion TCU - Manual (Page 88)

Output Leakage Current
The AL1 and AL2/OP2 outputs of the TCU have an RC Network (Snubber)
on the Normally Open contacts. High energy noise spikes are generated
whenever current through an inductive load (such as motors, solenoids or
relay coils) is interrupted. This noise may interfere with the unit doing the
switching and other nearby equipment causing erratic operation and
accelerate relay contact wear.
The Snubber Network is specifically designed with a capacitor and resistor
connected in series and installed across relay contacts. The network will have
a small amount of AC leakage current even when the TCU’s Relay Module is
“off”. The leakage current is 2.1 mA nominal at a line voltage of 120 VAC,
and 4.3 mA nominal at 240 VAC respectively. Leakage current may cause
some loads to stay on or to turn on when the Relay Module is turned off. This
would only occur in unusual applications (such as with a relay with unusually
low holding current or an LED). The leakage current may be eliminated by
disabling the snubber, however, doing so will degrade the EMC performance
of the unit.
First determine which output is associated with the leakage current: either
AL1 or AL2/OP2. Remove the Bezel Assembly from the case (see Removing
Bezel Assembly, page 5). The snubbers are located on the Option PCB (on the
right side of the unit when viewed from the front). The snubbers consist of a
capacitor and a resistor. The two resistors are located along the upper rear
edge of the Option PCB. They are green in color and have color code stripes of
yellow, violet, black and gold. There will be markings on the PCB close to the
r e s i s t o r s t h a t s a y “ S N U B 1 ” a n d “ S N U B 2 ” f o r A L 1 a n d A L 2 / O P 2
respectively. Using a pair of diagonal cutters, cut both leads of the
appropriate resistor and remove it from the unit. Be sure to remove the resistor
for only the problem alarm channel; leave the other channel’s snubber
functional in case it is needed.
The above stated leakage currents are valid when using the Relay Module
(OMD00000). The Triac Module (OMD00001) has its own built in snubber
and will introduce additional leakage current into the circuit. The Triac
Module has leakage current of 2.1 mA nominal at a line voltage of 120 VAC,
and 4.3 mA nominal at 240 VAC.
Note: The Snubber Network will be in one of the two configurations shown
above, depending on model ordered.
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