tekmar 356 Mixing Control - Manual (Page 7)

Copyright © D 356 -0
9/08
7 of 16
Section C: Boiler Operation
Section C1
General Operation
Section C2
Boiler Sensor
Placement
Section C1: General Operation
BOILER OPERATION
When the 356 determines that boiler operation is required, the Boiler contact terminals (5 and 6) close. While the Boiler contact is
closed, the burner segment in the LCD is displayed.
BOILER MINIMUM (BOIL MIN)
Most boilers require a minimum water temperature in order to prevent flue gas condensation. The BOIL MIN adjustment is set to the
boiler manufacturer’s minimum recommended operating temperature. Only when the boiler temperature is measured by a boiler
sensor can the 356 provide boiler protection. In this case, when the boiler is firing and the boiler temperature is below the BOIL MIN
setting, the 356 turns on the MIN segment and reduces the heating load on the boiler by limiting the output of the variable speed
injection pump. If the installed boiler is designed for low temperature operation, set the BOIL MIN adjustment to OFF.
BOILER PROTECTION
Refer to section A for a description of boiler protection.
Section C2: Boiler Sensor Placement
BOILER SENSOR ON THE SUPPLY (BOIL = Supply)
The boiler sensor can be located on the boiler supply if the 356 is the only control that is
operating the boiler. When in the supply mode, the 356 determines the required operating
temperature of the boiler using
Boiler Load Reset. With Boiler Load Reset, the 356 operates
the boiler at the lowest possible supply temperature that is sufficient to satisfy the
requirements of the variable speed injection pump. If this mode of operation is selected,
the boiler pump should operate continuously.
Note: The boiler pump should not be operated by the boiler’s aquastat, as this may lead to
improper cycling of the boiler because of inconsistent flow past the boiler supply sensor.
BOILER SENSOR ON THE RETURN (BOIL = Return)
The boiler sensor should be located on the boiler return if the 356 is one of many controls
that can call for boiler operation. When in the return mode, the 356 provides a boiler
enable. The 356 no longer tries to control the boiler supply water temperature directly, but
allows the boiler to operate at its operating aquastat setting when required. If this mode of
operation is selected, the boiler pump should operate continuously.
Note: The boiler pump should not be operated by the boiler’s aquastat, as this may lead to
improper cycling of the boiler because of inconsistent flow past the boiler return sensor.
NO BOILER SENSOR
The 356 is capable of operating without a boiler sensor if desired. Without a boiler sensor
the 356 provides a boiler enable, and is unable to provide boiler protection. This type of
application is typical if the 356 is drawing heat from a heat source that already incorpo-
rates some form of boiler protection.
Boiler return
sensor
No boiler
sensor
Boiler supply
sensor