tekmar 268 Boiler Control User Manual
Page 15
15 of 32
© 2010
D 268 - 11/10
Section F1
Setpoint
Section F: Setpoint Operation
Section F1: Setpoint
7
Com
Dem
8
Setp/
DHW
24 to 230 V (ac)
Setpoint operation is only available when DHW MODE is set to OFF.
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.
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
SETP MODE 1 - Setpoint in Parallel
Whenever a setpoint demand is present, the boiler(s) is operated to maintain the setpoint target. The primary pump does not turn
on, but may operate based on a Boiler Demand or an External Input Signal.
It is assumed that the Setpoint pump will provide adequate flow through the heat exchanger and the boiler.
SETP 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 P1) contact
is opened.
It is assumed that the Setpoint pump will provide adequate flow
through the heat exchanger and the boiler.
SETP MODE 3 – Primary Pump during Setpoint
Whenever a setpoint demand is present, the primary pump (Prim P1) is
turned on and the boiler(s) is operated to maintain the setpoint target.
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 over-
rides the setpoint priority and operates setpoint and heating simultaneously by turning on the primary pump (Prim P1).
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 main-
tained and the heating and setpoint targets are similar, setpoint and heating occur at the same time.
Boiler
Pumps
Primary
Pump
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 (8 and 7). 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.