How
to install a subpanel
Example installation does not require meter pull How to pull meter
2) Two Hot wires connect to 60-150 Amp breaker in main breaker box. Either hot wire can connect to either hot busbar inside subpanel.
3) Neutral connects to Neutral busbar so subpanel can power 120 and 240 breakers.
4) Ground wire connects to Ground busbar. Ground busbar can be purchased separately.
If Subpanel located at another structure, for example garage several hundred feet away, might be cheaper to use ground rod located outside other structure. If structure is farther than 140', then wire gauge increases from #6 to #4. Consult local electrician for correct gauge.
See chart
Electrical formulas
How to wire Tankless water heater
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Replace any 240V breaker with new 60 Amp breaker
Or remove two 120V breakers to make room for new 60 Amp breaker.
Normally, each 240V breaker serves 1 appliance.
For example stove has 240V breaker. Water heater has separate 240V breaker. Air conditioner another 240V breaker.
240V appliances cannot be 'doubled-up' on a single 240 breaker. Each needs separate breaker.
If there are no extra slots in breaker box, add a Tandem breaker. Also you can double-up two lightly used 120Volt circuits.
How to replace circuit breaker
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Subpanel with 6 slots.
This panel accomodates three 240Volt breakers
-or- six 120Volt breakers
Same plan applies to larger gauge wires.
2 Hot wires, 1 Neutral wire and 1 bare ground wire.
Larger gauge wires are usually black, but each wire has mark
Look for markings on each wire.
Subpanel located farther than 150', use #4 wire
Check with local electrician for correct wire size
Local code may require conduit for wire entering box
Tighten screws very tight against copper wire
http://waterheatertimer.org/images/sub-2-048-wires-connect-600.jpg
Remove two 120Volt single breakers to make room for 240V subpanel breaker
Move 120V lines to tandem. Important: 14 gauge wire connects to 15Amp breaker. 12 gauge wire to 20 amp breaker. 10 gauge wire to 30 amp breaker. Unsafe to connect a 14 gauge wire to 20 or 30Amp breaker: See wire size chart
Also possible to double up less-used 120V lines on single breaker. For example attic light and hallway breaker doubled-up on spare bedroom breaker as long as 14 gauge wire goes to 15Amp breaker and 12 gauge wire goes to 20Amp breaker etc.
Tighten screws very tight against copper wire
Tandem breakers at Lowes
Photo shows typical residential breaker-types
When white wire is used to carry voltage, add black tape to notify next electrician that voltage is present and white wire is not Neutral
This is safe electrical practice.
Read more: How to replace circuit breaker
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Square
D breaker installed in subpanel Breaker snapped onto rail, and then pushed down onto hot busbars |
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Inside
main breaker box Blue color is added for illustration purpose only. 240Volt potential exists between both hot busbars. So 240Volt breaker pushes down onto both hot busbars. 120Volt breaker pushes down onto one hot busbar. |
One busbar is Neutral busbar.
Two busbars are Hot busbars.
Each Hot busbar is 'out of phase' with the other.
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
Bare ground wire connects to Neutral busbar as redundant safety.
