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ADDING
ON SUBPANELS:
If your main service panel is full and you wish to add circuits,
you may want to install a subpanel. Before you begin, check local
codes. Then proceed as follows:
- Switch
all main circuit breakers to OFF or remove all main fuses. Remember,
incoming power cables and connections to main breakers or switches
are still "live" even though the mains have been turned off. Remove
the font cover.
- The
supply wires coming into the subpanel must be protected at their
point of supply by installing a properly sized circuit breaker
or fuse. The ampere rating of the protecting breaker or fuse cannot
exceed the rating of the subpanel being installed. Branch circuit
wire sizes and breaker ratings must also conform to code requirements.
- Remove
the front cover of the subpanel.
- Select
the cable clamps approved for the wire or cable sizes used.
- Before
removing any knockouts, determine where the wiring must enter
and exit the sub panel box and also determine the size knock out
required based on the diameter of conduit hub or cable clamp being
used. Remove only those knockouts needed for wiring.
To remove the 1/2" knockouts, place a nail set on either side
and give the tool a sharp rap with a hammer to the edges inward.
From inside the main service panel, grip the bent edges of the
knockout with pliers and work them back and forth until the knockout
comes off.
Some panels have multisection knockouts for 6 and 8 gauge 240-volt
lines. In such a panel, remove the center, like you did for the
1/2" knockout, then pry up the next ring using a heavy screwdriver
levered on a pair of pliers. Grip the pried-up edges of the ring
with the pliers from outside the panel and pull off the ring.
To complete the opening, tap the last ring inward and remove it
with the pliers from inside the panel.
According to code regulations, all unused, open knockout holes
must be closed. Filler plugs are available from your electrical
supplier for this purpose.
- The
subpanel may be flush or surface mounted on a wall as you desire.
To flush mount a subpanel in a recess within a wall, remove the
small oval knockouts in the box sidewalls. Position the box between
the wall studs so the front edge of the box will be even with
the wall surface. Fasten the box to studs with nails or screws
through the small knockouts.
To surface mount a panel on a wall, fasten it with screws or nails
(or other mounting devices appropriate for the type of wall construction)
through the mounting holes in the back of the subpanel.
- Once
the wiring for the new branch circuit is completed, cut the wire
allowing sufficient length for panel installation. (Remember that
excess wire can easily be cut away, but adding on to it is prohibited
by code). Install the cable clamps or conduit and bushings in
knockouts to protect the wire insulation. Tighten the locknut.
Pull the wire in the subpanel far enough to allow for the longest
connection. Working in the panel, pass the inner connector ring
over the wires and screw the connector together, allowing only
enough cable sheathing to enter the panel to give purchase to
the connector. Tighten the connector's toothed inner ring using
a screw driver and hammer, then tighten the screws on the connector
outside the panel.
- To
prepare copper supply wire or feeder cable, cut it into individually
required lengths. Carefully strip off only enough insulation to
allow the wire to be fully inserted in the terminal.
To prepare aluminum supply wire, once it has been stripped, wire-brush
the exposed ends and immediately coat them with a UL-listed conductor
termination compound. This compound, available from your electrical
supplier, is an oxide inhibitor.
CAUTION: Do not connect aluminum wires to the subpanel
or breaker unless they are marked CU/AL. Some subpanels and breaker
terminals are suitable for copper wire only.
- The
wires supplying the panel must be protected at the point of supply
by a properly sized breaker in accordance with code requirements.
To connect the supply lines, loosen the terminal screws, connect
the bare copper or aluminum or green equipment wire to the equipment
ground bar. Do not attach the equipment ground wires to the neutral
bar in the subpanel. (A ground bar accessory kit can be purchased
from your local electrical supplier. The proper ground bar kit
series number can be obtained from the label on the inside of
the subpanel door). Connect the white neutral sup ply to the neutral
supply wire to the neutral bar.
Connect the black and/or red supply wires to the power supply
terminals. Tighten all terminal screws securely. If a torque is
specified on the subpanel label, use a torque wrench to tighten
the terminal screws.
- To
install the breakers, switch it to the OFF position. Loosen the
breaker terminal screws. Tilt the breaker. Slide the breaker onto
the hook strip and firmly press it onto the load center tab. Make
sure the newly installed breaker is pushed inward until fully
seated.
- To
prepare the branch circuit wires, cut wires to individually required
lengths. Carefully strip off only enough insulation to allow the
wire to be fully inserted into the terminal.
- To
connect the branch circuit wires, follow the same procedure as
given in step 10.
- Remove
only as many knockouts from the subpanel cover as required to
create openings for the breaker. If any are inadvertently removed,
fill the unused openings in the cover with filler plates that
are available from your local electrical supplier.
- Replace
the subpanel front cover.
- Identify
all branch circuits. Attach the directory label to the inside
of the cover or door.
- Have
your local electrical inspector check a new installation before
it is energized. Be sure the new branch breakers are in the OFF
position. Restore power to the circuit supplying the subpanel.
One at a time, switch the new breakers or fuses to the ON position.
If the breaker trips or the fuse blows, do not reset or replace
it until the condition causing the problem is fixed. Turn the
power off and recheck. If you can't find the problem, consult
an electrician.
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