tekmar 654 Snow Melting Control Installation - Manual (Page 25)

25 of 44 © 2013 654_D - 06/13
Sequence of Operation
Snow Melting Overview
A snow melting system can offer a safe, convenient, and cost
effective way of removing snow and ice from the snow melting
slab and similar surfaces. Safety is increased by activating
the snow melting system as soon as the snow falls rather
than waiting for mechanical snow removal after snow has
accumulated. This eliminates slip hazards and reduces the
risk of injury by mechanized snow melting equipment, thereby
reducing potential liability costs. The elimination of snow plow
equipment and corrosive salts also reduces damage to the
slab surface and to the environment. Snow melting systems
when controlled correctly can be cost competitive compared
to mechanical snow removal. The snow melting control can operate in one of four
different ways:
Melt Heats the slab to melt snow or ice
Idle Pre-heats the slab just below freezing to shorten the
time required to melt snow
Storm Temporarily pre-heats the slab just below freezing to
shorten the time required to melt snow
Off Snow melting system is off
The control display shows the control operation in the home
screen.
Melt Operation
The snow melting system operates the heating equipment
to heat the slab from a cold start or from the idle or storm
temperature to reach the melt temperature setting to melt
snow or ice. Melt operation can be triggered automati-
cally using a snow / ice sensor, by tracking the run time
of another zone, manually by pressing a button, or by a programmable schedule. The melt temperature setting
affects calculated targets such as the slab target, boiler
target and mix target.
Slab Temperature Control
Controlling the slab temperature is critical to minimizing the
cost of snow melting. This requires that either a Snow / Ice
Sensor 090 or 094 or a Slab Sensor 072 or 073 is installed.
The Snow / Ice Sensor contains a built-in slab temperature
sensor. While the control will continue to operate without a
slab sensor installed, operating costs will be much higher.
The slab is operated using slab outdoor reset. As the outdoor
temperature gets colder, the heat loss of the slab increases.
In order to keep the slab surface at a constant temperature
while operating, the inner core of the slab must be heated
above the melt, idle or storm temperature setting. The amount
that the slab inner core temperature is above the melt, idle
or storm setting is proportional to the outdoor temperature.
Since the slab sensor is installed below the surface of the
slab, it is not measuring the true slab surface temperature but
rather the inner core temperature. The control automatically
compensates for this temperature difference. However, the Slab item in the View menu displays the actual measured
temperature, so it is normal to view slab temperatures that
exceed the melt, idle, or storm temperature settings.
Surface temperature = 35 F
Decreasing Air Temperature
Increasing Slab Core T
e
mperature
Slab Surface Temperature is Constant
Slab Outdoor Reset Slab Outdoor Reset
Core (sensor)
is warmer