Specifications

2
System 2000 GEN II offers the following additional control features:
1. Set Cooling and Heating capacity cut-out set points
2. Adjustable timing to initiate 2
nd
stage operation
3. Adjustable opposing call changeover timing
4. Priority demand votes on a stat-by-stat basis
5. Provide default occupied and unoccupied set points on every stat
6. Open all dampers for air balancing
System 2000 GEN II components:
• GEN II controller (includes integrated capacity control)
• Zone thermostats
• Power open / power close 24vac supply dampers
• Power open / power close 24vac bypass damper with static pressure control
• Communication cable (Belden 8740) twisted pair
• Time Clock (optional)
• 24vac 40va transformers: 1 to control system and dampers
1 for bypass damper and static pressure control
• Stand-alone thermostat – non-zoned system
GENERAL SEQUENCE OF OPERATION
When the GEN II controllers are powered up, the total number of addressed thermostats (ModStat,
MODS2, DIGICOM, DIGIHP) are determined and verified on the display. This confirms the
controller is communicating with all thermostats in the system. If there are no active heat or cool
calls detected, the supply dampers will modulate to 50% open (ModStat) or full open (MODS2) for
ventilation mode. Additional thermostats may be utilized to control stand-alone rooftop units with
DIGICOM / DIGIHP thermostats. The system blower operation can be configured for constant ON
or intermittent Auto. The controllers are shipped from the factory for Auto fan.
The System 2000 GEN II systems can be field configured for adjustable time based opposite call
changeover, vote based majority changeover, or priority vote changeover by thermostat
assignment. The GEN II controllers are shipped from the factory for 10-minute opposing call
changeover. The GEN II controllers “poll” the thermostats once per minute to determine the
thermostat demand status for heat and cool. The heat and cool changeover functions will operate
by the type of changeover selected on the controller. When the GEN II controllers change modes,
a 5-minute purge cycle is initiated before the changeover is completed.
On active heat or cool calls, the non-calling zones will modulate to the close position, or close 100%
depending on the thermostat being used. When the last calling zone is satisfied in either heat or
cool mode, the GEN II controllers will terminate the HVAC outputs after the next “poll”; and the
blower output will be de-energized (unless controller is configured for constant fan) for a 5-minute
purge cycle. During the purge cycle no heat or cool calls are recognized.
When the system is in the heating mode and calls for cooling are received, an opposing call timer
strategy operates. This timer is adjustable from 5–30 minutes. The factory default is 10 minutes.
At the end of the selected time period, if the opposing call is 3 degrees away from set point, heating
is turned off. After a 5-minute purge cycle, Cooling is turned on until the cool call is satisfied. If
necessary, GEN II will return to the heating mode. If all calls have been satisfied, dampers will
modulate to the 50% open position for ventilation. If the opposing zone strategy is not desired, this
feature may be disabled.
This mode may be enhanced by adding Priority votes to each thermostat in the system, thereby
weighting certain zones more than others. This Priority mode allows you to select 0, 1, or 2
additional votes for a thermostat that has unusual loads, like a conference room.