Installation Manual

13
ElectroMelt System
Design Guide
Design Steps
Controls
Three control methods are commonly used with snow-melting and anti-icing
systems. All three methods require a contactor as shown in the diagram on the
next page. The contactor must be sized to carry the load. Each method offers a
tradeoff of initial cost against energy efficiency. Choose the one the best meets
the project performance and requirements.
Automatic snow controller
An automatic snow controller offers the highest system reliability and the lowest
operating cost. Raychem's SD-CIT-1 automatic snow controller detects both
precipitation and low temperature and automatically energizes the ElectroMelt
snow-melting system. When precipitation stops or the temperature rises above
freezing, the controller de-energizes the snow-melting system. However, the
pole-mounted sensor cannot detect runoff from adjacent areas, snow which is
tracked into the heated area, or freezing dew.
Ambient thermostat
An ambient thermostat can be used to energize the system whenever the ambi-
ent temperature is below freezing. Raychem's AMC-1A ambient thermostat
should be used whenever the design objective is to prevent surface icing under
all conditions (anti-icing). Since the number of hours of freezing temperatures is
two to ten times the number of snowfall hours, the energy usage of a system
under control of an ambient thermostat is two to ten times that of a system con-
trolled by an automatic snow controller.
Manual control
Under manual control the system is operated by a manual switch controlling the
system power contactor. In some small installations, the system may be con-
trolled directly by operating the circuit breakers.