Specialty Concepts DM3 - Manual (Page 7)

SELECTING WIRE SIZES
Use the following information to determine what wire size you should use for various functions:
TO CONNECT BATTERY POWER CONNECTIONS: You may use any size wire (16 to 20 AWG is best) that
you find convenient. If the DM3 is more than 50 feet from the system’s batteries, use wire greater than 18 gauge. The
larger the wire, the more accurate will be the voltage readings made by the
DM3.
TO CONNECT AUX. INPUT: You may use any size wire for this input.
TO CONNECT CURRENT 1 (INTERNAL SHUNT): Use the following chart to determine wire size:
ROUND-TRIP DISTANCE TO CURRENT TO BE MEASURED RECOMMENDED WIRE SIZE*
LOAD, BATTERY, OR ARRAY
20 FEET UP TO 30 AMPS USE #10 WIRE
50 FEET UP TO 30 AMPS USE #6 WIRE**
100 FEET UP TO 30 AMPS USE #2 WIRE**
* A smaller wire size may be used for lower currents. An external shunt MUST be used if current exceeds 30 amps. It is
suggested that an external shunt be used for wire runs greater than 100 feet round trip.
** The terminal block on the DM3 will not accept wires this large. It is suggested that the wires be terminated with a
suitable spade lug that will fit.
TO CONNECT CURRENT 1 AND OR 2 (EXTERNAL SHUNT): You may use any size wire from the shunt
output to the DM3 for this input.
TERMINOLOGY / GLOSSARY
SHUNT: A small electronic device that will produce a small voltage when a current passes through it. This voltage can then be measured by a
voltage meter. EXAMPLE: You may have 100 amps coming from your solar system; this is VERY difficult to measure. A shunt with 100
amps passing through it will produce 100 mv (millivolts, or thousandth of a volt); this is VERY easy to measure.
SPADE CONNECTOR: A “U” shaped connector that will accept a bare wire in one end and can be fastened under the head of a screw on the
other end. Allows for a very clean method of connecting wires to terminal blocks that are not designed for bare wires.*
LOAD: The device(s) in your solar system that use power. Some examples of loads might be lights, electric refrigerators, inverters, water
pumps, etc.
NEGATIVE LEG(S): The wires that connect the negative sides of the batteries, solar panels, and loads. Usually (but not always) in D.C.
systems, these wires are black. The shunts for the DM3 must be placed in the negative legs for proper operation.
PROGRAMMING JUMPERS: The small black devices used on the DM3 to turn various functions on or off. They consist of a small black
handle that contains a strip of gold-plated metal that shorts adjacent programming pins on the DM3 circuit board.
AMPS: A measure of current, or the AMOUNT of electricity that flows in a circuit. The higher the number of amps delivered from the solar
panels, the faster the batteries will charge.
VOLTS: A measure of the PRESSURE of electricity that flows in a circuit. The higher the voltage, the greater is the amount of electricity that
can be forced through a circuit. Typical voltages for photovoltaic systems are 6, 12, 24, 36, and 48 volts.
WATTS: A measure of the POWER available in a solar system. The larger that this number is, the more work can be done. You can figure out
the watts in your system by multiplying the system voltage by its current rating. For example, a 12 volt system producing 10 amps is a 120
watt system.
REMOTE (or EXTERNAL) SHUNT: A shunt that is not on the DM3. A remote shunt would be used when the current being measured exceeds
30 amps. A remote shunt can also be placed near the batteries in the system allowing small wires to be run to the DM3.
SURFACE MOUNT: An installation method where the DM3 is mounted into a box (4x7 BOX) and the box is then mounted to the surface of the
wall. The unit will protrude from the wall by several inches.
FLUSH MOUNT: An installation method where the DM3 is mounted into a cutout in a wall. This allows the unit to be flush with the wall surface.
ALARM RELAY MODULE: An option for the DM3 that provides for the connection of alarm devices to indicate when battery voltage becomes
too high or low. The relay contacts can drive various alarm devices, such as an audible alarm, a remote warning light, or a radio
transmitter.
ALARM BEEPER MODULE: An option for the DM3 that provides an audible warning should the battery voltage become too high or low.
TRIMPOT: A small screw-adjust device that is used to set the Hi and Lo Alarms.
AWG: American Wire Gauge. Used to identify the size of wire. The smaller the AWG, the bigger the wire size.
D.C. SYSTEM: Direct Current. The kind of power that comes out of batteries and solar panels. Only equipment rated for use with D.C. should
be run directly from the batteries.
A.C. SYSTEM: Alternating current. The kind of power that comes out of standard wall sockets. D.C. can be converted to A.C. by an inverter.
Only equipment rated for use with A.C. should be run from the output of an inverter.
INVERTER: An electronic device that converts D.C. to A.C.
* All of the terminal blocks on SCinc products are designed to accept bare wire. Spade connectors may still be used, if desired.
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