tekmar 667 Snow Detector & Melting Control User Manual

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Section E: Melting Operation

Section E1

General Melting

Operation

Section E1: General Melting Operation

In order for the snow melting system to be started, one of the methods described in section D1 must be used. Once a melting enable
signal is applied and the system is not in WWSD or CWCO, the melting mode begins. When the control is in the melting mode, the
Melting pointer is visible in the View menu. The MELT setting in the Adjust menu sets the slab surface temperature. When the system
is melting and the slab temperature is warming up to the slab target temperature, STRT is displayed in the STATUS item while in the
View menu. The system finishes melting when the slab temperature has been at least the slab target temperature for a period of time.
This period of time is based on whether an automatic or manual melting enable signal starts the snow melting system.

If an automatic melting enable signal starts the snow melting system and the slab temperature reaches the slab target temperature,
DET is displayed in the STATUS item while in the View menu. The system continues to melt until the 090 becomes dry and any addi-
tional running time has expired. Once the melting mode is complete, the system operates in the idling mode.

If a manual melting enable signal starts the snow melting system, the running time is displayed in the STATUS item while in the View
menu and begins counting down once the slab temperature reaches the slab target temperature. The system continues to melt until
the running time counts down to 0:00 and there is no external melt demand. Once the melting mode is complete, the system operates
in the idling mode.

SLAB TEMPERATURE CONTROL

The 667 uses a snow / ice sensor or slab sensor to provide slab tem-
perature control.

Slab Sensor

If a Slab Sensor is used, the control assumes that the sensor is
ap p roximately 1 inch below the surface of the snow melting slab.
Since this point is closer to the source of the heat, this point is
warmer than the surface of the slab. Therefore, the sensor must
be maintained at a higher temperature in order to ensure that the
surface of the slab is maintained at the correct temp erature. The
amount of temperature difference between the surface of the
slab and the slab sensor changes with the outdoor temp erature.
Therefore, the slab core temp erature is increased as the outdoor
air temperature drops. The temperature displayed as SLAB is the
temperature of the slab sensor.

Snow / Ice Sensor 090

The slab temperature is displayed as SLAB in the view menu. This temperature is calculated from the edge and center sensors
built into the 090.

SLAB TARGET TEMPERATURE (SLB TRG)

The SLAB TRG temperature is determined from the melting setting, idle setting and the outdoor air temperature. The control dis-
plays the temperature that it is currently trying to maintain at the slab sensor. If the control does not presently have a requirement
for heat, it displays “---“ in the STATUS item while in the View menu.

ADDITIONAL MELTING TIME (ADD MELT)

In cases where areas of the snow melting system haven’t completely
melted after the melting mode has finished and the 090 is dry, the 667
has a function in which additional time can be added to melt the zone.
This is an adjustable time through the ADD MELT item in the Adjust
menu of the control. The ADD MELT time is calculated into a running
time and is disp layed in the STATUS item while in the View menu.
Once the 090 becomes dry and the slab temperature is at least the
slab target temperature, the running time starts counting down.

Surface temperature = 35˚F

Decreasing Air Temperature

Increasing Slab Core T

per

ature

Slab Surface Temperature is Constant

Slab Outdoor
Reset

Core (sensor)

is warmer

Dry

Snow

Ice Sensor