the exhaust temperature spread monitor is enabled automatically in the logic.
during startup,acceleration and load selection the exhaust temperature spread monitor has a bias added to allow for transients.
if there is high spread at full speed (for instance if a can flames out) the unit will trip on high spread.
thermal stabilization of the unit has nothing to do with the spreads.
thermal stabilization of the unit is defined by the rate of change of the interstage temperatures (wheelspace thermocouples), usually: less than 2degF in 15min
high exhaust spread is related to combustion or exhaust thermocouple problems.
the unit could be in transient thermal state (wheelspace temperature changing) and still have a high spread condition and trip.
conversely... the unit could have high wheelspace temperatures (in alarm) due to damaged sealing and no spread.
saludos.
a.