Snow Melting
Control 650
Pulse Width Modulation
On
Time
PRGM
F C
Item
Date
S/N
Power supply:
24V 60Hz 3VA
Relay capacities:
120V 10A 1/3hp
5
System
Melt at power up
On
Off
6
3
4
Heat
No Power
7
8
9
Com
Sen
Slab
Sen
Out
Sen
24 V Only
2
1
C
R
Power
Outdoor
Slab Sensor
Target Slab
Start
Stop
CWCO
Idling
Melting
Warm Weather Cut Off (WWCO)
If the control is in melting or idling mode and the “Slab” and “Outdoor” temperatures rise above the “Melting” temperature, the control
shuts down the melting system and enters Warm Weather Cut Off mode. During WWCO, the WWCO pointer flashes slowly. The
timer continues to run and normal operation is resumed when the “Outdoor” temperature drops below the “Melting” temperature.
Cold Weather Cut Off (CWCO)
Maintaining the slab at a “Melting” or “Idling” temperature in extremely cold conditions can be expensive and may even be
impossible. When it does snow at these colder temperatures, the snow is usually dry, light and less slippery. The control therefore
turns the melting system off when the “Outdoor” temperature drops below the “CWCO” setting. While the control is in CWCO, the
CWCO pointer flashes slowly. The timer continues to run until the slab temperature drops below the “Target Slab” temperature.
When the outdoor temperature rises above the “CWCO“ temperature, the control exits CWCO and continues with normal operation.
On Time
The control has a built in timer which is used to set the length of time the control operates the system in melting mode. The timer begins
counting down when the snow melt system is turned on and the slab has reached the “Melting” temperature.
Powering up the Control
After the Snow Melting Control 650 is powered-up, the LCD
screen segments are turned on for 3 seconds. The control
then monitors and displays the outdoor temperature.
Melting Mode
The Snow Melting Control 650 is a manual control; in order to
start the melting system with the control powered up, the
“Start” button is pushed. The melt system can also be started
by setting the “Melt at power up” DIP switch to “On” and
powering up the control. When the control is in melting mode,
the melting pointer flashes slowly and the system relay is
turned on. The heat relay is cycled on and off to maintain the
slab at the “Melting” temperature. The method used to cycle
the heat relay is called Pulse Width Modulation (PWM). For
more information on PWM, see Essay 000. Once the slab has
reached the “Melting” temperature, a timer starts. The control
remains in melting mode until the timer “On Time” reaches
zero, the “Stop” button is pushed, or the remote switch is
turned off.
Note: If the remote switch is turned off and on again to restart
the system, the switch must be kept off for at least 1
second for the control to fully power down.
Idling Mode
When the snow melting system starts from a cold temperature,
the time required for the slab to reach “Melting” temperature
can be excessive. To decrease this start up time, the slab can
be maintained at an “Idling” temperature. The Idle feature is
also useful for preventing frost and light ice formation. When
the control is in idling mode, the idling pointer flashes slowly
and the system relay is turned on. The heat relay is cycled on
and off to maintain the slab at the “Idling” temperature.
- Data Brochure
Snow Melting Control 650
06/94
D 650
Sequence of Operation
°
C or
°
F
indicators
Programming
mode
indicator
Item
identifiers
Wiring
Chamber
and
Terminals
Programming
and Melt
Start/Stop
buttons
Item
selection
and display
button
Hole for mounting screw
Hole for mounting screw
Temperatures
and On Time
display
The tekmar Snow Melting Control 650 is a microprocessor-based control that uses a Slab Sensor 072 and an
Outdoor Sensor 070 (both supplied with the control) to maintain a snow melt slab at a set surface temperature
during snow melting. When melting is not required, the melting system is either shut down or the slab is
maintained at an idling temperature for faster response and improved safety. The melting mode is initiated
manually by a button on the control or by an optional remote switch. Built in energy saving features include warm
and cold weather cut offs that automatically shut the melting system down in warm weather or extremely cold
conditions. The timer included in the control can be programmed to operate the snow melt system for a set time
period. Viewing and programming the operating parameters in either
°
C or
°
F is accomplished through a digital
LCD. The display indicates an error message whenever a sensor or its wiring develops a fault.
F
Snow Melting
Control 650
Pulse Width Modulation
On
Time
Item
Outdoor
Slab Sensor
Target Slab
Start
Stop
CWCO
Idling
Melting
