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2
Hot wires and 1 neutral wire arrive from meter box.
Blue color added to 1 hot wire for illustration <> in real breaker box, the 2 hot wires are black
The 2 hot wires connect to the Main Breaker <> a lug is
tightened very tight to hold wire in place. Neutral is connect to
neutral busbar.
Each hot wire connects to different busbar through the main breaker
> here the busbars are named A and B > the 'blue' hot
wire provides power to blue busbar <> remember, blue color added for illustration only
Hot busbars are 120 Volts each > they never touch each other
> they are suspended away from
the main box by insulators
240 Volt potential exists between busbar A and busbar B
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 See basic 120V and 240V water heater circuits | What
is difference between 120Volt and 240Volt? Inside
main breaker box are Three busbars.
One busbar is Neutral busbar.
Two busbars are Hot busbars.
Each Hot busbar is 'out of phase' with the other.
Bare ground wires connects to Neutral busbar as redundant safety.
| All residential circuits require Two wires to complete circuit. **120Volt circuit requires 1 Neutral wire and 1 Hot wire. Hot wire can come from either Hot busbar. By Code, these wires are Black-Hot and White-Neutral. If either wire is interrupted, the circuit turns OFF. By code the Black Hot wire is switched ON-and-OFF.
**240Volt circuit also requires 2 wires to complete circuit. In the case of 240V, the circuit requires 2 Hot wires. One Hot wire from each 'out of phase' busbar is required to complete 240Volt circuit. These
wires can be Black and White or Black and Red, and with heavier
gauge wires, like 6 gauge and 4 gauge, the wires are Black and Black. If either wire in 240V circuit is interrupted, the circuit turns OFF. See 30 amp switch turning off water heater
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 | How to install electric meter on water heater |

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How to replace circuit breaker Breakers
are held in place at both ends <> one end locks into a
cleat -or- snaps onto a bar <> other end of breaker rotates to busbar and then 'stabs'
onto the busbar
Push firmly to make sure breaker is stabbed all the way down
When
replacing a breaker, check busbar for damage or burning from previous
breaker <> busbars are frequently damaged by aging
breakers that
arc and burn <> arcing will damage busbar so new breaker
will no
longer work in the same slot. Read steps 32-37:
When lights flicker,
check breaker immediately before sparking causes damage in breaker box. Check
breaker and listen
for fizzing or crackling sound. Check if the breaker screw is tight
against wire. Flickering lights are usually a loose wire at a
plug, but it pays to check breaker first to avoid busbar damage.
Always put cover back on breaker box to prevent sparks from leaving
breaker panel.
Read how to replace circuit breaker |
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