TSC 800 TRANSFER SWITCH CONTROLLER
PM 049 REV 10 08/09/25 Thomson Technology
79
Symptom Possible Causes
TSC 800 Display is Blank (cont’d)
mounted transformer or internal power supply failed (one or
both sources).
-
Isolation Plug is pulled. Confirm correct voltage
configuration and/or levels prior to installing the Isolation
Plug.
-
Utility power is failed and generator running but its local
breaker is open.
*
Transfer Switch Cycles between
sources
-
Limit Switch is not being fully actuated to break the motor
circuit during transfer. Limit switch adjustment incorrect
(Limit Switch Struck Late or not at all on 100A-1200A
molded case switch style ATS).
-
TSC 800 generator under voltage and/or under frequency
time delays set to short. Time delays are exceeded on load
application causing recycling to Utility supply (happens only
during an on load test and utility available).
*
Transfer Switch controller
indicates the mechanism has made
position but does not conduct to
the load bus and the PSD is not
tripped
-
Limit switch adjusted to close to yoke arm causing the ATS
mechanism to stop before PSD closes (Limit Switch Struck
Early on 100A-1200A molded case switch style ATS).
*
Less than programmed Neutral
Delay Time (NDT) or none at all
administered during transfer
between powered sources.
-
Neutral Delay Bypass feature enabled. Effectively cancels
NDT if not required (canceled if load bus voltage for all
phases drops below 20% of nominal system voltage).
Normal Operation.
-
Transfer Switch incorporates a Bypass configuration
(currently is bypassing the ATS mechanism) and the test
cable connected. No neutral positioning will be detected
and no NDT applied as a result (normal condition).
-
High residual voltage from the connected loads (neutral
position can not be determined). Contact Thomson
Technology for possible corrective solutions.
*
Engine runs for no apparent reason
-
Verify the TSC 800 has not been set for a manual or auto off
load test operation. If yes, select “Auto” (“None” in firmware
versions 1.7 and earlier).
-
Verify the TSC 800 engine start LED is lit on the rear of the
controller. If not lit isolate one of the remote start wires to
confirm the start is from the TSC 800 (contact closes to
start, open wire should cause generator to stop). Engine
start relay coil on TSC 800 failed (drops to issue start,
energized to inhibit start).
-
Local Generator Engine controller has built in cool down
function or test features separate from the TSC 800.
-
Local generator controls are in Manual Run.
*
Oscillating/unstable voltage
readings displayed for one or more
sources when measured voltage
with an independent meter
confirms stable voltage
-
System neutral conductor has not been solidly bonded to
ground for one or more of the sources or a 3-phase 3-wire
system has been applied to an ATS designed for a 3-phase
4-wire configuration. Isolation transformers will need to be
added to create the ground reference to correct the
problem. Contact Thomson Technology for corrective
solutions.
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