TS 840 TRANSFER SWITCH
PM057 REV 8 10/01/25 14 Thomson Technology
switch will immediately return to the utility or generator supply if within normal
operating limits.
5.2.4. ADDITIONAL PROCEDURES
If the "Service Disconnected" pilot light is not illuminated, the service will not
have been successfully disconnected and therefore it is not safe to perform
any maintenance until the following additional procedures are performed:
DANGER!!!!
Arc Flash and Shock Hazard. Will cause severe injury or death.
Do not open equipment until ALL power sources are disconnected
This equipment must be installed and serviced only by qualified electrical
personnel utilizing safe work practices and appropriate Personal Protective
Equipment (PPE). Failure to do so may cause personal injury or death
1. Open the door to the transfer switch using a suitable tool and opening the
door lock with the key.
2. Visually inspect the actual position of the transfer switch mechanism. If
the position of the transfer switch mechanism is clearly in the "neutral
position" and the load bus is de-energized on all phases, the service has
been successfully disconnected. Proceed to Step. 4.
If the position of the transfer switch mechanism is not in the neutral position
or the load bus is energized, further procedures are required.
Note: If the position of the transfer switch mechanism is clearly in the
"neutral position, the "service disconnected" pilot light may not have
illuminated due to the following reasons:
a) Utility and generator supply voltages are not present (the pilot light
requires AC supply voltage to be present).
b) The pilot light may be burnt out. The bulb should be immediately
replaced with a suitably rated bulb.
c) Failure of one or more of the sensing/logic contacts. A qualified
service technician is required to trouble shoot this specific condition.
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