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sticking out from one end that is bolted to the busbar with a
machine screw (bolt type fine threads and not sheet metal screw
type steep pitch threads).
When replacing these types of breakers, the retaining bolts or
machine screws will have power on them unless power to the
entire panelboard has been removed.
It is not uncommon for some individuals to initially determine
that it is necessary to replace these types of breakers with power
still applied to the busbars. One engineer said, “I am not a big fan
of working anything above 12 volts hot, for I have witnessed too
many good folks get hurt doing what was initially anticipated as
being a quick and simple task.”
When this type of breaker must be replaced with power still
applied to the busbars, it should be done only under strict safety
procedures, using proper personnel protective equipment and
double insulated tools (every day plastic handle screwdrivers must
not be used). A detailed job safety analysis should be conducted
before any hot work is undertaken.
On more than one occasion the engineer has witnessed some
truly professionals conducting rehearsals of this type of activity
several times until each safety step was done correctly. Take the
time you need to be safe.

Stab Lock Type Breakers
This type of breaker employs a male-female type of plug &
receptacle connection to a metal busbar on one end. The opposite
end of the breaker is mated to the enclosure housing and does not
make electrical contact with the busbar.
These types of breakers are found in homes and light
commercial applications installed in loadcenters. With this method
of mounting some movement of the breaker is normal.
This small amount of breaker case movement is typically 1/8 of
an inch or less on the busbar end. The circuit conductor
termination lug may also exhibit some minor movement of the
termination lug; again normally this movement is less than about
1/8 of an inch.

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