26 | uponorpro.com
A Snow-free Area Ratio of 0 is defined as
a system that allows snow accumulation.
These systems operate the snow melting
system from a cold start resulting in the
lowest energy consumption costs and the
longest times to start melting snow.
In this case, set the Idle to off. This
is recommended for most residential
applications:
• Flat residential driveways
• Patios
• Residential sidewalks
Some systems are designed for keeping
a slab surface free of ice rather than free
of snow. The most common applications
include:
• Car wash bays and aprons
• Aircraft hanger aprons
• Turf conditioning on golf course greens
These systems require the use of idling at
or near freezing throughout the winter and
may result in high energy consumption.
Warm weather shut down
During warm weather, the slab is warm
enough to naturally melt snow or ice. The
control has a Warm Weather Shut Down
(WWSD) setting in the Set Temp menu that
prevents the control from entering Melt or
Idle operation in order to conserve energy.
The control shows WWSD on the display
when WWSD is in effect.
Automatic (Auto)
The control enters WWSD when both
the slab temperature of the zone and the
outdoor temperature exceed the Melt
temperature setting by more than 2ºF (1ºC).
Manual WWSD
The control enters WWSD when the
outdoor air temperature exceeds the
WWSD setting by 1ºF (0.5ºC) and when
the slab temperature exceeds 34ºF (1ºC).
The control exits WWSD when the outdoor
air temperature falls 1ºF (0.5ºC) below the
WWSD setting or if the slab temperature
falls below 34ºF (1ºC). This allows the Melt
temperature setting to be set higher than
the WWSD. This is useful when high slab
temperatures are required to melt the snow
or ice. An example of this are installations
using paving bricks on top of sand and
concrete layers.
Cold weather cut out
Maintaining the melting or idling
temperature during extremely cold
temperatures is not only expensive but may
be impossible if the heat loss of the slab
exceeds the input capacity of the heating
plant or electric cable. The control turns the
snow melting system off when the outdoor
air temperature drops below the Cold
Weather Cut Out (CWCO) temperature
and the slab is below freezing. This is a
safety and energy-saving measure. The
control shows CWCO on the display when
CWCO is in effect. When the temperature
reaches the CWCO setting in an actively
melting system with a Pavement Snow and
Ice Sensor, melting is suspended until the
outdoor temperature rises above the CWCO
setting. If a Pavement Snow and Ice Sensor
is not installed, melting is permanently
stopped when CWCO is in effect. Melting
does not resume when the temperature
rises above the CWCO setting.
