Conduit
sizing
The conduit fill is the amount of areas in square inches, of
conductors inside section of conduit. Conduits fill is necessary for
dissipation of heat, pulling of wires, potential high cost change orders when
the conductors that you specified do not fit inside the conduit. We require
conduit fill when we installing new conduit & conductors or adding new conductors
to existing conduit run. The maximum allowable fill for new conduit is 26% & for old 40%. Some necessary
instructions are remember:
·
Always
put extra conduit in crossing roads.
·
If
the conduit crossing is for illumination or power supply, put in a spare 2”
conduit.
·
If
the conduit crossing is for signal conduits at an intersection put in a spare
3” conduit. If the crossing is not at the intersection put in a spare 2”
conduit.
·
A
2” conduit should be the minimum size used for all crossings.
·
Install
a spare 2” conduit into a service cabinet.
·
Install
a spare 2” conduit between all transformers and the improvement the transformer
is serving. (ITS cabinet, VMS cabinet,
etc.)
·
Always
best try to not use too many different sizes of conduits. Stick with even sizes
of conduits. (1”, 2”, 3” or 4”).
·
Leave
room for future conductors. Running 2” conduit nears the service or where there
is potential for future expansion usually provides plenty of future room.
·
The
conduit from the luminaries pole to the adjacent junction box 5’–10’
away shall be 1”. This is usually the only place you would ever run a 1”
conduit in grade (except the grounded
electrode conductor)
Here two
types of conduits are designed with illustrations.
1.
Rigid
Metal Conduit: Type RMC
2.
Rigid
Nonmetallic Conduit: Type RNC ( PVC schedule 40, PVC schedule 80 & HDPE
schedule 40)
