Slant/Fin SC-3 - Manual (Page 18)

19 SC-3 Controller
Setpoint operation is only available when DHW MODE is set to OFF. Since DHW MODE
is only available if BOILER 3 is set to OFF, DHW will default to OFF if BOILER 3 is set to
AU.
SETPOINT
The control can operate to satisfy the requirements of a setpoint load in addition to a space heating load. A setpoint load overrides the
current outdoor reset temperature and WWSD setting in order to provide heat to the setpoint load.
SETPOINT DEMAND
A setpoint demand is required in order for the control to provide heat to the setpoint load.
The control registers a setpoint demand when a voltage between 24 and 230 V (ac) is
applied across the Setp / DHW and Com Dem terminals (7 and 6). Once voltage is applied,
the Setpoint Demand pointer turns on in the LCD. The control operates the boiler(s) to
maintain at least the SETPOINT setting.
BOILER TARGET DURING SETPOINT
The boiler target temperature during a setpoint demand is increased to at least the SETPOINT
setting. This temperature is maintained as long as the control has a setpoint demand.
SETPOINT MODE
A setpoint demand is required in order for the control to provide heat to the setpoint load. The control registers a setpoint demand when a
voltage between 24 and 230 V (ac) is applied across the Setp / DHW and Com Dem terminals (7 and 6). Once voltage is applied, the
Setpoint Demand pointer turns on in the LCD. The control operates the boiler(s) to maintain at least the SETPOINT setting.
Setpoint MODE 1 - Setpoint in Parallel
Whenever a setpoint demand is present, the boiler(s) is operated to maintain the setpoint target. The primary pump (Prim Pmp) does not
turn on, but may operate based on a Boiler Demand.
It is assumed that the Setpoint pump will provide adequate flow through the heat exchanger and the boiler.
Setpoint MODE 2 - Setpoint in Parallel with Priority
Whenever a setpoint demand is present, the boiler(s) is operated to
maintain the setpoint target and the primary pump (Prim Pmp) contact
is opened.
It is assumed that the Setpoint pump will provide adequate flow
through the heat exchanger and the boiler.
Setpoint MODE 3 - Primary Pump during Setpoint
Whenever a setpoint demand is present, the primary pump (Prim Pmp) is turned on and the boiler(s) is operated to maintain the setpoint
target. Setpoint MODE 3 is the most common application to Slant/Fin setpoint operation. MODE 3 is used in this manual.
SETPOINT PRIORITY OVERRIDE
The setpoint has a Priority Override while in SETP MODE 2. In order to prevent the building from cooling off too much or the possibility of
a potential freeze up during setpoint priority, the control limits the amount of time for setpoint priority. The length of Setpoint priority is
determined by the PRIORITY OVERRIDE setting. Once the allowed time for priority has elapsed, the control overrides the setpoint
priority and operates setpoint and heating simultaneously by turning on the primary pump (Prim Pmp).
CONDITIONAL SETPOINT PRIORITY
If the boiler(s) supply temperature is maintained at or above the required temperature during setpoint generation, this indicates that the
boiler(s) has enough capacity for setpoint and possibly heating as well. As long as the boiler target temperature is maintained and the
heating and setpoint targets are similar, setpoint and heating occur at the same time.
SPACE HEATING ONLY WITH SETPOINT CONTROL