DIY Manual

42 | P a g e 10-543-1 REV A
DIY Manual
Our panel mount breakers, the MNEDC series, are NOT polarity sensitive; you can wire either
terminal without regard to current flow. Figure 10 shows the terminal lugs of an MNEDC breaker.
With this type of connection, ensure you use terminal lugs or ring terminals crimped to the wire.
Torquing Circuit Breaker Setscrews
Bare copper wire inserted into the setscrew terminal of a circuit breaker will loosen due to a
reaction called cold flow, or creep, which is the tendency of a solid material to move slowly under
the influence of mechanical stresses, such as the setscrew snugged up tight against the bare wire.
This may happen within an hour of installation. Therefore, it is important to properly torque the
set screws per the breaker specifications (found on our website). Professional installers will tell
you to torque it 2-3 times! Good practice is to 1) Torque the setscrew; 2) Wiggle the wire; 3) Re-
torque setscrew. Figure 11 shows the setscrew terminal of an MNEPV circuit breaker.
Sizing Breakers
The National Electrical Code states that an overcurrent protection device (circuit breaker or fuse)
can be loaded to only 80% of its rating for continuous loads. Since 80% is the inverse of 125%,
the multiplication factor of 125% is used when sizing a circuit breaker or fuse. This “80 derate”
rule does not apply if the circuit breaker or fuse is rated at 100% continuous duty, such as the
MidNite series of DC breakers.
Figure 9
Figure 10
Figure 11