tekmar 356 Mixing Control - Manual (Page 4)

Copyright © D 356 -0
9/08
4 of 16
OPERATION
The 356 uses a variable speed injection pump to control the supply water temperature to
a hydronic system. The supply water temperature is based on either the current outdoor
temperature, or a fixed setpoint.
Outdoor Reset
When the outdoor design (OUTDR DSGN) setting is not set to OFF, the 356 calculates
a mixing supply temperature based on the current outdoor air temperature and the
Char-
acterized Heating Curve settings.
Setpoint Control
When the outdoor design (OUTDR DSGN) setting is set to OFF, the 356 supplies a fixed
mixing supply temperature equal to the MIX TARGET setting. An outdoor sensor is not
required during this mode of operation.
VARIABLE SPEED INJECTION
A standard wet rotor circulator is connected to the 356 at the back of the control. The 356
increases or decreases the power output to the circulator when there is a mixing demand.
The circulator speed varies to maintain the correct mixed supply water temperature at the
mix sensor. For correct sizing and piping of the variable speed injection driven circulator,
refer to essay E 021. A visual indication of the current variable speed output is displayed in
the LCD in the form of a horizontal bar graph.
BOILER PROTECTION (BOIL MIN)
The 356 is capable of providing boiler protection from cold mixing sys-
tem return water temperatures. If the boiler sensor temperature is cooler
than the BOIL MIN setting while the boiler is firing, the 356 reduces the
output to the variable speed injection pump. This limits the amount of
cool return water to the boiler, and allows the boiler temperature to re-
cover. This feature can only be used if a boiler sensor is installed.
EXERCISING
The 356 has a built-in exercising function. If the pump has not been operated at least once every 3 days, the control turns on the
output for 10 seconds. This minimizes the possibility of the pump seizing during a long period of inactivity.
Note: The exercising function does not work if power to the control or pump is disconnected.
FACTORY DEFAULTS
The control comes preset with several factory defaults. These defaults are based on the terminal unit selection (see section B2). To
fine-tune building requirements, these defaults may be changed. If a factory default value for a terminal unit is changed, the terminal
unit number will flash when selected in the ADJUST menu.
To reload the factory defaults listed in section B2, power down the control and wait for 10 seconds. Power up the control while
simultaneously holding the
Item and buttons. The terminal unit number should now be displayed constantly in the LCD rather
than flashing.
Section B: Mixing
Section B1
General
Section B2
Installer
Section B3
Advanced
Section B1: General
MIXING DEMAND
A mixing demand is required in order for the 356 to provide heat. A mixing demand is
generated by connecting terminal
T(7) to terminal C-(9) through a switching device. Once
the switching device closes, the Mixing Demand pointer is displayed in the LCD. The 356
calculates a MIX TARGET supply temperature based on the outdoor air temperature and
settings. If required, the 356 operates the boiler in order to provide heat to the variable
speed injection pump.
% Out
Current output of
variable
speed injection pump
30 10 70 50 90
Zone Valve Motor
End Switches
M
M
To control
C
R
Mixing
sensor
Boiler return
sensor
Boiler supply
sensor
or
Outdoor Design
Increasing W
ater
T
emperature
Design Supply
Decreasing Outdoor Temperature
Terminal Unit
Indoor Design