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How to change 120 Volt subpanel to 240 Volt subpanel

Buy indoor 120-240 volt:
100 amp 6 space
100 amp 8-space
125 amp 8-space
125 amp 8-space
125 amp 8-space
200 amp 20 space
Subpanels at Amazon
Main lug
Up to 100 amps

Buy outdoor/ from my affiliate links: 120-240 Volt

70 amp 2-space
60-100-200 amp 2-space
125 amp 8-space

Subpanels at Amazon
Up to 125 amps

120-240 Volt with breakers

Buy main load center:
200 amp 30 space HOM
125 amp 12 space
Intermatic T30000R5
Outdoor subpanels with space for breaker, timer, switches, outlets/ 120-240 Volt. Flush mount, widths vary.
60-125 amp panels w/o timer
60-125 amp with timers
With freeze protection
3-phase subpanel
3-phase subpanel
Not residential
24 space 125 amp
24 space 125 amp
NOT residential
3-pole breakers
3-phase Wiring
single-pole breaker
1" wide Push down breaker
Plug-in breakers
Buy single-pole:
Siemens 15-60 amp

Single-pole tandem breaker
Tandem breakers

Buy QO breaker
20 amp Square D
double-pole breaker
QP type
2" wide Push down breaker
Plug-in breakers
Fits residential panels
Fits subpanels above
Buy double-pole:
Siemens 15-125 amp
Square D 30 amp breaker

Double pole GFCI
breaker base

Breaker base
60 amp 4 breaker
125 amp 8 breaker

124TP2608A 4 breaker spaces
124T2530A 8 breaker spaces
How to install 1" wide push-down breaker
Push-down breaker
Notch on breaker sits against rail or cleat
Rotate breaker down to busbar
Push breaker down over vertical busbar

BR type 1" wide breakers are usually used for residential applications
Available local box store
Buy single-pole:
Siemens 15-60 amp

Buy double-pole:
Siemens 15-60 amp
120 Volt subpanel
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Step 1) Identify basic 120 Volt subpanel

Step 2) Identify if other 120Volt outlets and switches are on that circuit
Identify single pole breaker supplying power to 120V subpanel
Turn breaker OFF, and check which outlets and switches are on that breaker
The change-over to 240Volt will NOT work if other outlets and switches are located between subpanel and main breaker box... unless a dedicated wire is installed from subpanel to main breaker box
120 Volt subpanel Step 3) 120 volt subpanel wiring
By code, White wire is Neutral
Black is Hot

240 Volt subpanel Step 4) Change to 240 volt subpanel
Add black tape to White wire that carries voltage
240 Volt subpanel
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Step 5) Change wiring in main breaker box
Identify single pole breaker supplying power to 120V subpanel
Install 240V breaker
By code, the 240V breaker must be a single connected breaker, and not two 120V breakers.
Move black wire on single-pole breaker to new 240V breaker.
Move white neutral to new 240V breaker
Add black tape to white wire that carries voltage

240V Subpanel will NOT work for 120Volt breakers since ground wire cannot be used as Neutral
120 Volt is NOT available with this diagram
Single-pole 120V breakers can be installed, but it is against code to use Ground wire as Neutral
Wires cannot be over the top of breakers or busbars
Wires cannot lay over the breakers or busbars.
Wires can lay over top of other wires, but not at point where wires connect to busbars.
Lay all wires to sides of box
120 volt and 240 volt subpanelLarger image

120 volt and 240 volt subpanel
3 wires plus ground wire between subpanel and main breaker box

Install subpanel for Tankless electric
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More subpanel wiring

Household NM-B Wires are color-coded so inspectors/ electricians can easily identify which wire is used during construction
Match wire size and breaker amp rating
If your home was wired by professional electrician who pulled permits, then circuit breaker and wire size will match. If manufactured home or travel trailer has not been altered by homeowner then breaker and wire size will match.

If breaker is oversized for wire... fire danger
Breaker can let too much electricity travel through the wire. Wire can overheat and cause fire.
Call electrician if you suspect wiring is not correct,
Absolute electrocution danger when removing cover off main panel. More information below.
Main breaker terminals are still Hot when main breaker is turned off.

Southwire Romex® wire at Amazon

How to replace circuit breaker
How to figure correct size wire and breaker
Use chart on left to select wire and breaker (for short lengths of wire)
Use the 80% rule when calculating Capacity.
wattage shown on chart shows the 80% rule.
When wires and breakers operate at 100%, they get warm.
Warm wires mean amp loss and potential fire hazard.
Warm breaker means that breaker will not last as long, and busbar can be damaged by heat (over period of time)

14 ga wire ++  rated for 120 Volts x 15 Amp = 1800 Watts x 80% = 1440 Watts safe maximum

12 ga wire ++ rated for 120 Volts x 20 Amps = 2400 Watts x 80% = 1920 Watts safe maximum

10 ga wire ++ rated for 240 Volts x 30 Amps = 7200 Watts x 80% = 5760 Watts safe maximum
Square D transformer
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Convert 240Volt to 120Volt without neutral wire from breaker box
Buck-boost transformers buck voltage down, or boost voltage up. This transformer bucks down voltage.
Convert 240Volt to 120Volt without neutral wire from breaker box.
Convert 480Volt to 240Volt or 120Volt
Type 3R outdoor enclosure

480Volt input connects to H1 H4, and then H2 and H3 are connected together
240Volt input connects to H1 H4, and then H3 connects to H1, and H2 connects to H4

240Volt output connects to X1 X4, and then X2 and X3 are connected together
120Volt output connects to X1 X4, and then X3 connects to X1, and X2 connects to X4
Square D transformers at Amazon

Match wire and breaker size
How to wire a subpanel
Read about household single-phase electricity
Read about 3-phase
How to wire 3-phase timers
linesman pliers

front cutting pliers
Utility knife
Electric tools:
Linesman pliers

Wire strippers at Amazon

Crescent-brand end cutting nipper at Amazon
End cutting nippers at Amazon

Utility knife at Amazon
Electricity leaves power plant Resource: Electricity:
The grid is defined by three parts: transmission, distribution and end user. The following links show how it works
Power plant to end user power pole
Power pole to residential breaker box
Power pole to commercial breaker box

How to wire residential electric
How to wire commercial 3-phase

Why you need ground wire
How to wire 3-phase timer
3-phase water heater

Contactors/ relays
Type 1 and type 2 surge protection surge protection
Programmable timers

Woods timers
surge protection
Electronic parts

Industrial supplies

Tools and home improvement

Home and garden

Hayward pool
Pentair pool

Southwire electric

Black and Decker

Irwin Hand tools
Klein hand tools
Fluke electrical testing
Dremel hobby tools

Campbell Hausfeld air powered
Tekton automotive

Powerbuilt automotive
Saws and saw blades
box timers Resource:
Compare box timers
DPDT timers
Control water heater w/ Z-wave
Intermatic control centers Resource:
Intermatic control centers: and parts
Digital control centers and parts
Tork control centers and parts
All control centers and parts
programmable timer Resource:
Programmable timers
Countdown timers
Off delay timers
On delay timers
Timer modules
Din rail
Twin & one-shot
Low voltage power packs Recirculation systems
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