I.C.E. HTDM Food Process Unit - Manual (Page 17)

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III. AVAILABLE OPTIONS (Software controlled)
1) Space Override
Units equipped with this option will modulate normally in one of
the above heat modes until continuity is sensed between terminals
J19 and J21. Upon sensing continuity unit will de-energize the
auto indicator LED and ramp to full fire until the contacts are
opened. Regular heat mode operation will be resumed once the
contacts between J19 and J21 are opened.
2) Low Limit
The unit will shut down the supply fan if the duct temperature
falls below the factory set point.
3) System Preheat
The unit can use a built in time delay before the contacts to the
main supply fan are energized. This will allow a preheating of
the heat exchanger to insure that only warm air will be supplied
to the space.
Preheat operation begins with a normal trial for ignition. Once
flame has proven the unit will modulate to the midpoint of the
firing range. The heat mode led will indicate the preheat cycle
by flashing. The unit will remain at the midpoint until the
preheat cycle is ended. Once ended the main supply fan contacts
will energize and normal heat mode operation will begin.
4) Standby mode
Standby mode is to be used in conjunction with an on/off
thermostat or when periodic heating is required. In Standby mode
the ICECON2 is continually powered. The unit will indicate
standby mode by flashing the power LED. In this mode the heat
cycle will remain powered down until there is a call for heat from
indicated by a 24VAC signal on terminal J22. Upon a call for heat
a normal start up sequence is ran and the unit will then enter
heat mode. Once the call for heat is satisfied and the 24VAC
signal is lost on terminal J22 the ICECON2 controller will exit
heat. The unit will enter a post heat purge. During this time
the combustion blower and firing valve are ramped to full fire.
Upon completion of the post heat purge the burner and combustion
blower are shut down. The main supply fan will remain in