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PO. Box 726 n TULSA, OK 74101 n TEL 918-627-5530 n FAX 918-641-7336 n www.nelsonheaters.com
GA-2318, R1
Sheet 3 of 15
May 2008
GENERAL INFORMATION
The SMMC-3 Control Panel manages snow and ice melting equipment for sidewalks, driveways, gutters, downspouts,
etc. Suitable for controlling all types of heating cable systems, the SMMC-3 can monitor snow and ice accumulation in
three separate zones. The SMMC-3 programming allows each zone to be controlled independently or on a priority mode
basis. In the priority mode, one zone can be given priority and the other zones cannot be energized until the melting/de-
icing in that zone is complete. This can reduce the loading on the system by ensuring that multiple zones are not
energized simultaneously. The SMMC-3’s program allows customization of the key elements necessary for intelligent
and efficient snow melting control.
The SMMC-3 can access information from three different types of moisture sensors – surface (SMPS-1), aerial (SMAS-
1) and gutter (SMGS-1) and one temperature sensor (SMTS-1). The surface, aerial and gutter sensors detect moisture
from snow, ice, sleet, etc. and send appropriate signals to the SMMC-3. Similarly, the temperature sensor sends
temperature data back to the SMMC-3. Independent temperature and moisture information is processed by the SMMC-3
to ensure that heating equipment will only be energized when precipitation occurs during freezing conditions. For each of
the SMMC-3 control zones, up to two individual moisture sensors can be connected. However, for each zone only one of
these may be a surface sensor. Each SMMC-3 must have a temperature sensor, SMTS-1, in order to function. A SMTS-
1 is included with each SMMC-3.
The SMMC-3 is housed in an enclosure suitable for commercial/industrial applications (NEMA 12) and features an LCD
display, programming and associated indicator lights for operation of each zone.
The SMMC-3 is powered by 120VAC; control relays provide a 120VAC output to operate external contactors.
See Fig. 1 & 2.
PRE-PROGRAMMED CONFIGURATION
The SMMC-3 Control Panel is delivered preprogrammed for a single zone system, for use with either an aerial (SMAS-1)
or gutter (SMGS-1) sensor. (Note that the SMMC-3 does not distinguish between the gutter and aerial sensors). The de-
energize temperature (the SMMC-3 will not energize the heating equipment when the ambient temperature is warmer
than this) is pre-set to 37°F (3°C), and relay hold time (the length of time that the heating equipment will stay energized
after it no longer senses the presence of ice/snow in the zone) is 3.0 hours. If the snow/ice melting system has been
designed to operate in this manner, then no programming is required: simply wire as per the following instructions.
Fig.1
Control PanelSMMC-3
LCD
Programming
Buttons
Sensor Status
Lights
(on when ZONE
sensor is energized)
Manual Override
Buttons
Output Relay
Status Lights
(on when ZONE
heating is energized)
ON
/
OFF
Switch
Access Cover
SMMC-3