Hired-Hand Emergency Back-Up and Alarms: Secondary Sensing System - Manual (Page 22)

Manual No. 4801- 2997 Rev 7-08 Secondary Sensing System 22 of 40
8.2 Operation as Stand-Alone System
The S 3 contains an integrated back-up system. This system’s purpose is to back up the master controller in
the case of failure. The back-up system is a stand-alone control system. It contains its own three
temperature sensors which are used to divide the building into zones. These are the same temperature
sensors that are used for the alarming functions described earlier. This allows the user to set High and Low
Back-Up limits, in which the system will use to operate one Heat stage and three Cool stages. The system
is equipped with a fail-safe relay card that is capable of driving four separate 1 h.p. loads. The following
shows the Back-Up System interface.
This setup does not use the Local Network connection that would be present if used in conjunction with the
Evolution 3000/3001. Therefore, its functionality is limited to monitoring the temperature sensors for out
of range conditions but it does still contain some protection against minimum ventilation failure.
8.2.1 Normal S
3
Back-Up Operation
During Normal Operation, the S 3 always maintains the temperature between its high and low limits. It
accomplishes this by using its temperature sensors and its four stage outputs. If the temperature drops
below the Low Limit, the Heat stage will come on. That stage will not turn off until it warms the building
at least 2
°. The same is true if the temperature goes above the High Limit however, there are three levels
of cooling stages on the Back-Up System. The following example explains the operation of the stages in
relationship to the temperature and the limits. In this example the Low Limit is set as 66º F, and the High
Limit is set as 86º F. If the temperature drops to 66º F, then the HEAT stage turns on. The HEAT stage
turns off when the temperature rises to 68º F (2º above the Low Limit). If the temperature rises to 86º F,
then COOL 1 turns on. If the temperature continues to rise to 87º F (1º above the High Limit), then COOL
2 turns on. If the temperature rises to 89º F, then COOL 3 turns on. Stages turn off at temperatures as
indicated by the arrows in Graph 1.
Temperature/Settings
Display
Selection Switch
Back-Up Stages
Indicators
Ventilation Back-Up
Display & Selector
Inlet Overrides
Indicators
Graph 1: Cool 1, 2, 3 and Heat
Temperature (°F)
Heat
Cool 3 - Tunnel
Cool 2
Cool 1 - Vents