tekmar 268 Boiler Control - Manual (Page 9)

9 of 32 © 2010 D 268 - 11/10
Primary Pump Purge
After a demand is removed, the control continues to operate the primary pump for a period of time. The maximum length of time
that the primary pump continues to run is adjustable using the Purge setting. The primary pump continues to run until either the
purging time has elapsed or the boiler supply temperature drops more than a differential below the boiler minimum setting.
Section D1
Boiler Reset
(Stand Alone)
BOILER DEMAND
When operating in the stand-alone mode, a boiler demand is required in order for the
control to provide heat to the heating system. A boiler demand is generated by applying
a voltage between 24 and 230 V (ac) across the Boiler Demand and Common Demand
terminals (6 and 7). Once voltage is applied, the Boiler Demand pointer is displayed in
the LCD. If the control is not in WWSD, the control closes the primary pump contact. The
control calculates a boiler target supply temperature based on the outdoor air temperature
and the characterized heating curve settings. The control then fires the boiler(s), if
required, to maintain the target supply temperature. To use the stand alone mode, the
External Input / Stand Alone DIP switch must be set to Stand Alone.
OR
6 7
Boil
Dem
Com
Dem
24 to 230 V (ac)
Section D: Boiler Reset Operation
Section D1: Boiler Reset (Stand Alone)
BOILER PUMP OPERATION
In certain modes of operation, the control can operate the individual boiler pumps on each boiler in addition to the primary pump.
The boiler pump turns on prior to the boiler firing and continues to run after the boiler is turned off. The amount of time that the boiler
pump turns on prior to the boiler firing is determined by the BOIL MASS setting. If a BOIL MASS of Lo is selected, the boiler pump
turns on 15 seconds prior to the boiler. If a BOIL MASS of Medium is selected, the boiler pump turns on 22 seconds prior to the
boiler. If a BOIL MASS of Hi is selected, the boiler pump turns on 30 seconds prior to the boiler. However, if the control is operating
based on a setpoint demand, the boiler pump turns on 5 seconds prior to the boiler.
Boiler Pump Purge
The amount of time that the boiler pump continues to run after the boiler turns off is adjustable using the boiler pump purge setting
(PURG Boil Pmp).
BOILER TARGET TEMPERATURE
The boiler target temperature is determined from the characterized heating curve settings and the outdoor air temperature. The
control displays the temperature that it is currently trying to maintain as the boiler supply temperature. If the control does not
presently have a requirement for heat, it does not show a boiler target temperature. Instead, “– – –” is displayed in the LCD.