Service Entrance Automatic Transfer Switch - Marathon TS 870 Installation, Operating & Service Manual

The generator will continue to supply the load until the utility supply has returned.
The retransfer sequence is completed as follows: when the utility supply voltage is
restored to above the preset values (adjustable from 70% to 95% of nominal) on all
phases, a transfer return delay circuit will be initiated. Following expiry of the Utility
Return Timer (adjustable from 0 to 60 min.), the Transfer to Generator Supply signal
will be removed (contact opening), then the Transfer to Utility Supply signal (contact
closure) will be given to the transfer switch mechanism. The load will then retransfer
the load from the generator supply back to the utility supply.
timer circuit will delay the transfer sequence in the neutral position (i.e. both power
switching devices open) until the neutral delay time period expires (adjustable from 0
to 60 seconds).
An engine cooldown timer circuit will be initiated once the load is transferred from the
generator supply. Following expiry of the cooldown delay period (adjustable from 0 to
60 minutes), the engine start signal will be removed (contact opening) to initiate
stopping of the generator set.
5.2.

SERVICE ENTRANCE AUTOMATIC TRANSFER SWITCH

Note: This applies only to service entrance transfer switches
5.2.1. NORMAL OPERATION
Under normal conditions, the load is energized from the utility supply through the
closed utility transfer power switching device. If the utility power fails, the generator
will start and the load will be re-energized via the closed generator transfer power
switching device.
In the normal operating mode, the Service Disconnect switch shall be in the
"energized" position.
5.2.2. OVER CURRENT TRIP
Should the utility power switching device trip open due to an over current condition,
TSC 900 transfer controller will initiate an engine start signal and will permit transfer
of the load to the generator supply. The utility source will be locked out and the load
will remain on the generator supply until the TSC 900 alarm signal is manually reset.
Refer to the TSC 900 Instruction Manual for further details on Transfer Fail operation.
PM062 REV 10 15/04/07
TS 870 TRANSFER SWITCH
12
Note: A neutral delay
Thomson Power Systems