What to look for in the breaker box
Unless your home is very old and has never had its electrical
service updated, it has 240-volt service from the
street and into the main service panel as well.
Nearly every service panel has two 120-volt wires and
one neutral wire running to it from the utility company. Each wire powers one “bus” (copper vertical leg) inside
the main service panel. That’s why you usually see two
columns of breakers (or fuses) when you open your
service panel door. The common 120-volt circuits that
power everything from your lava lamp to your vacuum
cleaner are powered from one of those two buses. The
standard 15- or 20-amp circuit breakers work by clipping
onto one of the buses. Then the circuit’s hot (red
or black) feed wire is clamped to the circuit breaker,
while the neutral (white) wire and bare copper ground
wire are clamped to the common neutral bar.
The way you get a 240-volt circuit is simple. A
“double-pole” circuit breaker is clipped into both 120
buses at the same time, so the voltage to the circuit is
doubled. That’s why 240-volt circuits
need two hot wires and a neutral to carry the electricity
to the appliance, plus a ground wire.
Do you have enough amperage capacity
in the service panel for a new
Service panels are rated for the maximum amps they can
provide. A 60-amp panel found in an older home, for
example, can handle up to 60 amps of current to the
house. The panel has to be large enough to handle the
existing electrical demand of the house plus the new
appliance without exceeding the panel’s amperage rating.
(A standard, no-frills electric range needs 40 amps.)
Figuring this out is more complicated than simply calculating
the total amperage of the circuit breakers already
in the panel. The electrician you hire to install the new
circuit will help you decide if the panel is up to the task.
Most panels have plenty of power for extra appliances,
but if you have to increase the capacity, there are solutions.
Most likely, if you have enough circuit spaces,
you’ll have no problem adding the range circuit, especially
if you don’t have any 240-volt power-hungry
appliances like air conditioners, electric water heaters
Is there physical space in the service
panel for another double-pole
Last, there have to be two spaces left in the panel for two
additional circuit breakers. If the available
spaces aren’t stacked directly above each other, existing
breakers can be pulled and reinserted in new positions
to provide that arrangement.
If you have an older panel that has fuses instead of breakers, or if the circuit breaker panel is already full, an
electrician can add a subpanel to handle the extra
240-volt circuit. A subpanel is a mini electrical panel
that is fed from the main panel to create spaces for more
circuits. Adding a subpanel is relatively inexpensive,
depending on how much work needs to be done and the
condition of your service panel.
A subpanel probably isn’t worth the investment if you have a fused panel. It would be better to have the main
panel upgraded to a modern circuit breaker–based one
with plenty of room for extra circuits. Putting in a larger
panel with higher amperage capacity may be several times the cost of a subpanel. It also might entail improving the
home’s electrical system to bring it in line with local code requirements, a substantial additional expense.
Circuit Breaker Panel
A 120-volt circuit breaker occupies one slot on one of the two legs (buses). A 240-volt breaker occupies two adjoining slots on one bus, but draws power from both buses.
Panel cover removed for instruction only. Do not remove yours. Bare wires can easily shock and kill you. Hire a licensed electrician for work on the main panel.