tekmar 667 Snow Detector & Melting Control Installation - Manual (Page 6)

6 of 32 © 2009 D 667 - 03/09
COLD WEATHER CUT OUT (CWCO)
Maintaining the system at either the melting or idling temperature during extremely cold temperatures can be expensive or impossible.
The control turns the snow melting system off when the outdoor air temperature drops below the Cold Weather Cut Out (CWCO)
temperature. While the control is in CWCO, the word CWCO is displayed in the Status item in the VIEW menu. The heater in the
sensor is kept on during CWCO until the control detects moisture. If water is detected, the heater is turned off but the control retains
the moisture detected information. When the outdoor temperature rises above the CWCO temperature, the control exits CWCO and
if the Snow / Ice Sensor 090 detected moisture during CWCO, the control initiates Melting mode. If the control has been started prior
to the CWCO, it resumes the Melting mode once the outdoor air temperature rises above the CWCO temperature.
STATUS (STATUS)
While in the VIEW menu there are a number of items available to determine the current status of zone 1. To view the current status
of zone 1, select the Status 1 item in the VIEW menu.
• STRT The word STRT is displayed after the snow melting system has been manually enabled. It is displayed until the
zone reaches its slab target temperature. If the zone is at its slab target temperature, STRT is displayed for fi ve
seconds after the snow melting system has started operation. This is to verify that the control has entered into the
Melting mode.
• STOP The word STOP is displayed for fi ve seconds after the snow melting system has been manually disabled. The
word STOP is also displayed if either a Remote Start / Stop Module 039, Remote Display Module 040 or the Stop
on the control stops the snow melting system and an external melt demand is still present.
• IDLE The word IDLE is displayed as long as the zone is operating at its idling temperature.
•“IDLE” The word IDLE is fl ashed on the display as long as the zone is operating in temporary idle.
• EXT The word EXT is displayed when the Run Time has reached 0:00 and the control still has an external melt demand.
In this situation, the zone continues melting until the melt demand is removed or the control is stopped.
• DET The word DET is displayed after the snow melting system has been automatically enabled by the
Snow / Ice Sensor 090 and the zone is at its slab target temperature. DET is also displayed once the control is
manually enabled after automatic detection by the 090 and the running time has counted down to 0:00.
• 0:00 to 23:59 hr While the zone is up to temperature and melting, the remaining Run Time is displayed.
• INF If an infi nite RUN TIME is selected and the zone is melting, INF is displayed.
• WWSD When the zone is in Warm Weather Shut Down, WWSD is displayed.
• CWCO When the control is in Cold Weather Cut Out, CWCO is displayed.
SNOW MELTING OVERRIDE
If the Away setting is selected in the SCHEDULE menu, the snow melting system is shut
down. Both the Melting and Idling temperatures are ignored as long as the control remains
in the Away mode.
SYSTEM PUMP OPERATION (Sys P1 and System Pmp 2)
The system pump contacts close and remain closed as long as the system is either in
the Melting or Idling mode. The system pump contacts shut off if the control is in CWCO,
WWSD, or if there is no call for Melting or Idling.
MELTING CONTACT OPERATION
The Melting contact (terminals 21 and 22) closes and remains closed as long as the system is in Melting mode. This contact can be
used as an external signal to indicate that the system is currently in Melting mode. This contact can also be used as a means of
prioritizing or enabling multiple snow melting controls.
PURGE
The system pumps continue to operate for up to 2 minutes after the last demand is removed. This purges the residual heat from the
boiler into the snow melting slab. If the boiler temperature drops below the Boil Min setting after 20 seconds, the purge is aborted
and the system pumps are turned off.