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Old 04-25-2011, 04:26 PM   #1
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switch from 120v to 240v new breaker


Hello folks,
My idea is to switch a currently 120v 20amp breaker to a 240v 20amp breaker. Before I embark deeper i have a few Questions:
  • some of the fronts of the current breaks say 120v/240v 20a on it? i know my house is using 120v for most all outlets so whats the 240 mean?
  • Gauge wiring for 240v 20a vs. 120v 20a? are they both 12 gauge or is it better to use 10?
  • I could not find a gauge for the wiring currently in my house can anyone help with this by look at the picture? 600v?
  • Where is my master breaker switch. Does my pannel not have one? or does this indicate that its a sub panel, which im pretty sure its not.?
thanks for time!
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switch from 120v to 240v new breaker-snc00668.jpg   switch from 120v to 240v new breaker-snc00667.jpg   switch from 120v to 240v new breaker-snc00666.jpg   switch from 120v to 240v new breaker-snc00665.jpg   switch from 120v to 240v new breaker-snc00663.jpg  


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Old 04-25-2011, 04:35 PM   #2
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switch from 120v to 240v new breaker


Quote:
My idea is to switch a currently 120v 20amp breaker to a 240v 20amp breaker
Why make the change?

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Old 04-25-2011, 05:45 PM   #3
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switch from 120v to 240v new breaker


For what purpose are you planning on switching from 120 to 240?

You do not have a main breaker in this panel, I suspect that the main breaker (disconnect) is at the meter location. Therefore this is a sub panel.

#12 wiring is good for 120 or 240 volts at 20 amps.

240 is(usually) for high power application- dryer, water heater, kitchen range, central air etc.
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Old 04-25-2011, 07:30 PM   #4
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switch from 120v to 240v new breaker


A breaker marked 240 volts is allowed to be used for either 120 volt or 240 volt circuits. A breaker marked 120 volts only may not be used on a 240 volt circuit.

The same wire sizes used for 120 volt circuits (14 gauge for 15 amps, 12 gauge for 20 amps, etc.) apply to 240 volt circuits. Note that sustained (continuous) loads such as heaters or air conditioners should not more more than 80% of the breaker rating; use the next size up if needed.
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Old 04-25-2011, 07:47 PM   #5
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switch from 120v to 240v new breaker


awsome thank you for the replies. i plan on installing a air conditioning unit, i wil make sure the 20a will be over 80%.

can anyone tell what guage wire i have? white means 15?
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Old 04-25-2011, 09:30 PM   #6
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switch from 120v to 240v new breaker


well taking a look at my outside meter there is one box with two sections. It says on the box im only permitted to open door 2, door 1 has a lock. Inside door 2 there isn't much just a wire the comes from outside threw 2 and into 1. So without a main cutoff switch does this mean i have to call my electric company and shut off everything?? to change a breaker???
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Old 04-25-2011, 09:54 PM   #7
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switch from 120v to 240v new breaker


First of all, the color of the wire has nothing to do with its amperage rating. The size of the wire is listed on the cable you post in your picture, however not visible in the picture. In addition to that, you need to install a two pole breaker of the proper amperage, and proper wire size to make your installation work. You just can't add a 240v 2 pole breaker to existing wiring unlees the wiring is for a 240v circuit.
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Old 04-26-2011, 02:13 AM   #8
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switch from 120v to 240v new breaker


That is a main lug panel the main breaker or disconnect switch should be directely behind that panel otherwise you will have to follow the conduit where it goes { typically found below the meter socket }

Second thing if you going to use one of the exsting conductor or cable for 240 volt circuit you double check make sure there is nothing else on that circuit otherwise you will see magic smoke real quick.

The safest and wisest methold is run a new circuit and be done with it.

As far for breaker size for your A/C unit it will depending on what type of unit you will install that will affect the rating.

Merci,
Marc
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Old 04-26-2011, 03:11 AM   #9
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switch from 120v to 240v new breaker


Quote:
Originally Posted by AllanJ
Note that sustained (continuous) loads such as heaters or air conditioners should not more more than 80% of the breaker rating; use the next size up if needed.
I dont understand what you said there. let me give an example:

The condensing unit needs 50 amps. I install a 60 amp disconnect with 2 25 amp fuses in it. at the panel, the circut feeding the a/c is connected to a 60 amp breaker?
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Old 04-26-2011, 06:47 AM   #10
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switch from 120v to 240v new breaker


On the ac unit there will be a label. This will give you the min and max amps required. You size your conductor based on the min amp listing.
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Old 04-26-2011, 06:54 AM   #11
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switch from 120v to 240v new breaker


Quote:
Originally Posted by thehvacguy View Post
I dont understand what you said there. let me give an example:
He is saying that a load such as this should be more than 80% of a circuit.


Quote:
Originally Posted by thehvacguy View Post
The condensing unit needs 50 amps. I install a 60 amp disconnect with 2 25 amp fuses in it. at the panel, the circut feeding the a/c is connected to a 60 amp breaker?
Your logic is completely wrong. Two 25A fuses do NOT make a 50A circuit.
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Old 04-26-2011, 08:24 AM   #12
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switch from 120v to 240v new breaker


Large appliances and also most air conditioners may have several amperes ratings published:

1. Running amperes
2. Startup amperes
3. Suggested or minimum amperage for the circuit feeding it
4. Maximum amperage for the circuit feeding it

Running amperes for heaters and air conditioners should be no more than 80% of the wire or cable rating for example if the circuit is 30 amps then running amps should be no more than 24.

Maximum amperage means that, if the appliance has 20 as max amps, you may not hook it up to a 30 amp circuit. Small plug in appliances and also lights have a max amp circuit rating of 20 amps unless otherwise noted.

Occasionally startup amperes is greater than suggested circuit amperes as published. If this is the case then the manufacturer recommends a "slow blow" breaker or fuse.
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Last edited by AllanJ; 04-26-2011 at 08:32 AM.
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Old 04-26-2011, 01:06 PM   #13
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switch from 120v to 240v new breaker


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Originally Posted by frenchelectrican View Post
That is a main lug panel the main breaker or disconnect switch should be directely behind that panel otherwise you will have to follow the conduit where it goes { typically found below the meter socket }

Second thing if you going to use one of the exsting conductor or cable for 240 volt circuit you double check make sure there is nothing else on that circuit otherwise you will see magic smoke real quick.

The safest and wisest methold is run a new circuit and be done with it.

As far for breaker size for your A/C unit it will depending on what type of unit you will install that will affect the rating.

Merci,
Marc
Ah, and there she is. I found what appears to be the main breaker box outside directly behind what i though was the main. First glance inside the box leaves me wondering where the actual main switch is? Is it the giant leaver seen on the right that seems to disconnect the two one time fuses? any thoughts?

As far as the existing conductor goes, I'm really, really, not a fan of "magic smoke" so I'll just plan to lay down a new circuit entirly and keep the 120v 20a as itself.

Thanks for the swift responses!
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Last edited by popwarfour; 04-26-2011 at 02:31 PM.
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Old 04-26-2011, 09:47 PM   #14
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switch from 120v to 240v new breaker


bump please
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Old 04-26-2011, 10:32 PM   #15
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switch from 120v to 240v new breaker


Oui you got it there that is the main fuse disconnect switch.

When you hit the lever on the right side it will shut the power off to inside however some fuse box may not always the case some did have stay on at one side of the fuse while the other side is off.

It good to flip the handle from time to time to make sure they are not binded up. { I know many peoples hate to reset the clocks or reboot the computer and whatever else .,, }

But one major warning when you turn the main fuse lever off the top lugs will stay hot all the time so don't poke around that area either you will get electrique shock or a serious short circuit due the that lug from the meter to the upper lugs are unfused.

I am glad you make a wise move to run a new circuit for that useage again verify that equiment to make sure you have proper size conductor to support that equiment.

Merci,
Marc

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