NBC™ Flat Belt - IOM
P/N: 1118140 Rev: 07/29/2020 Page 75 of 129
1.39: USE OF 115 VAC CONTROLS
Important information regarding the use of 115 VAC controls:
These Function Modules will accept 115 VAC level control inputs. There are some cautions that must
be observed to avoid Function Module hardware failure.
Function Module signal inputs are protected against 500 volt spikes. 115 VAC control signal wiring run
in conduit along with higher voltage motor wiring could experience voltage spikes that exceed the 500
volt limit. This can be prevented by running control wiring in separate conduit from motor wiring.
Additional protection for the Function Module inputs can be achieved by using an MOV (metal oxide
varistor) placed across the input terminals within the Function Module. Suggestions of suitable MOV’s
would include Panasonic ERZV07D241 or Little fuse V250LA2.
Long conduit runs with motor wiring for multiple motors, and the use of variable frequency drives, all
contribute to electrical noise, with a good potential for high voltage spikes. If there is any doubt, the
control signals to the Function Modules should be run in conduits separate from motor wiring.
The Function Module signal inputs have high impedance. When connected to some output devices,
such as some PLC triac outputs, the inputs could sense an “on” state even if the output connected to
it is not on. This can be corrected by adding additional loading to the output. This can be done by
adding a loading resistor, placed across the output terminals.
Do not put this resistor inside of the Function Module. The size and wattage rating of the resistor
would depend on the output characteristics of the PLC card. A typical value would be 10,000 ohms
(10K ohms) and 2 watts. The resistor must be able to dissipate 1.32 watts at 115 VAC, so it will get
warm.
Do not put this resistor inside of the Function Module. The size and wattage rating of the
resistor would depend on the output characteristics of the PLC card. A typical value would be
10,000 ohms (10K ohms) and 2 watts. The resistor must be able to dissipate 1.32 watts at 115
VAC, so it will get warm.
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