tekmar 667 Snow Detector & Melting Control - Manual (Page 4)

© 2002 D 667 - 09/02 4 of 28
Sequence of Operation
Section A
General
Operation
Page 4
Section B
Snow
Melting
Page 5 - 6
Section C
Boiler
Operation
Page 7 - 8
Section D
Melting Enable/
Disable
Page 8 - 10
Section E
Melting
Operation
Page 11
Section F
Idling
Operation
Page 12
POWERING UP THE CONTROL
When the Snow Detector & Melting Control 667 is powered up, the control displays all LCD segments for 2 seconds, then the con-
trol type number in the LCD for 2 seconds. Next, the software version is displayed for 2 seconds. Finally, the control enters into the
normal operating mode and the LCD defaults to displaying the current outdoor air temperature.
MIXING DEVICE
Variable Speed Injection Pump
A standard wet rotor circulator is connected to the 667 on the Var
and Pwr Mix terminals (1 and 2). The 667 increases or decreases the
power output to the circulator based on the system requirements. For
correct sizing and piping of the variable speed injection pump, refer to
Essay E 021. A visual indication of the current variable speed output is
displayed in the LCD in the form of a segmented bar graph.
Section A: General Operation
Mixing
Sensor
Boiler Supply
Sensor
OR
Boiler Return
Sensor
MIXING MAXIMUM (MIX MAX)
The MIX MAX sets the highest fluid temperature that the control is allowed to calculate as the mixing target temperature. If the
control does target the MIX MAX setting, and the MIX SUP temperature is near the MIX MAX, the Maximum pointer is displayed in
the LCD while the MIX SUP temperature is being viewed.
BOILER PROTECTION (Boil MIN)
The 667 is capable of providing boiler protection from cold mixing system
return fluid temperatures. If the boiler sensor temperature is cooler than
the Boil MIN setting while the boiler is firing, the 667 reduces the output
from the mixing device. This limits the amount of cool return water to the
boiler and allows the boiler temperature to recover. This feature can only
be used if the Boil SENS item is set to SUP or RET. The 667 can not
provide boiler protection if the Boil SENS item is set to NONE.
EXERCISING (EXERCISE)
The 667 has a built-in pump and valve exercising function. The exercising period is adjustable and is factory set at 70 hours. If a
pump output has not been operated at least once during every exercising period, the control turns on the output for 10 seconds.
This minimizes the possibility of a pump seizing during a long period of inactivity.
Note: The exercising function does not work if power to the control or pumps is disconnected.