WarmlyYours SCV-DUAL - Manual (Page 10)

Snow Switch ® Model LCD–8 Aerial Snow Controller, 100 – 240 VAC
24782 Rev. A 03/13 (800) 234-4239 http://www.networketi.com 9 of 14 Environmental Technology, Inc.
Special Case: Hold-On Time is 0
For the special case that only occurs with a manual swipe when the hold-on
time is set to zero (0), the heater operates for at least one hour, even if there is a
snow condition. In terms of a strict state description in this one case, a snow condi-
tion does not cause the system to enter the snow state, but rather to stay in the
hold-on state. If the snow remains after the one hour, the heater remains energized.
In the “enabled” Lockout state, the heater is not on. When snow is detected,
the system enters the Snow state if the ambient air temperature is above 17°F, but
it enters the Lockout state instead if the temperature is below 17°F. Additionally, this
Lockout state is entered if the temperature falls below 17°F during an automatic
hold-on cycle. If the temperature rises above 17°F in the Lockout state but with no
moisture detected (not snowing), the hold-on timer is restarted. In the Lockout state,
the heater is not on.
If in the Idle state and the temperature is below 17°F when a magnet swipes
the magnetic switch, the system initiates its manual cycle as usual. If the tempera-
ture falls below 17°F during the cycle, it is ignored. If the unit is in the Lockout state
and the user swipes the magnetic switch, the temperature reading is ignored. This
will be maintained until the end of the snow event (that is, until a return to the Idle
state).
The override ends when the heaters turn off. However, if a manual cycle is
initiated while when the environment is frigid, and then snow starts, the heaters
remain energized until the snow stops and for the hold-on time thereafter.
Note: Avoid selecting both low-temperature lockout and a hold-on time of zero
(0) hours, as the heaters may not energize.
Alarms
When the LCD-8 operates normally, its green LED is lit continuously. Under an
alarm condition, this LED will flash rapidly—on and off twice a second. The alarm
may or may not inhibit operation, depending on circumstances.
Three possible conditions exist which initiates an alarm:
• Bad cup thermistor. If the cup thermistor is bad, the unit will not do
automatic snow melting. The rationale is that we can’t turn on the cup
heater without risking damage to the unit; and if snow or freezing rain
falls with the cup cold, it may stay there for weeks, and the unit would
never shut off. The manual hold-on cycle will work.
• Bad ambient thermistor. If the ambient thermistor is bad, the unit will
operate normally if it is configured as a precipitation sensor; if it is config-
ured as a snow sensor, it will not do automatic snow melting. The manual
hold-on cycle will work.
• Corrupted configuration. If the configuration is corrupted, the unit will
operate under its default configuration.
The bad thermistor alarms will clear if the thermistor repairs itself. The cor-
rupted configuration alarm will clear if the unit is reconfigured: in that case the user
is advised to cycle power, confirming reconfiguration.