Help, Wiring Questions 240v AC

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  #1  
Old 12-01-13, 09:57 PM
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Help, Wiring Questions 240v AC

Hello,
Looking for anyone that can help me with a few ?'s I have.


First Off:

I have a detached garage with a 40amp breaker from house to 100amp breaker box in the garage ran with 8awg (looks to be aluminum wire).

Then in the garage I have 20amp breaker for lights, 20amp breaker for outlets, 15amp for outside gfi outlet & motioin light, and then a 2-pole 20amp breaker for 240v.

My questions are:

1: can I switch out the 20amp breaker for the lights to a 10amp breaker as there is nowhere near 20amps being used for the few small cfl lights I have.

2: So then I could upgrade the 2-pole 20amp breaker to a 2-pole 30amp breaker? I already have 10-3 wire ran.


3: Just wondering, If Adding all the breakers up would equal 75amps, I understand im not using all of them nore using all them at one time either. But is that bad seeing as there is only 40amps coming from the house?


4. I was looking at putting a electric heater in garage for the winter, along with air compressor. But would like to use a single plug & outlet for both items (not being used at the same time of course). But I see some heaters at 230v 240v & 250v & same with the air compressors. Is there a difference in wiring for different volts? Or should my air compressor & heater both be the same volts to use on one type of outlet?

Any Help would be greatly appreciated.
 
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  #2  
Old 12-01-13, 10:22 PM
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Welcome to the forums.

1) If the wiring is currently #12 then leave the 20A breaker there. The smallest breaker made is 15A anyway.

2) You can upgrade without making any changes to the other breakers. You have #10 which is ok on a 30A breaker.

3) It is very common for the breakers to add up to more than the service can provide. You need to be aware of what you are using so as not to trip the 40A breaker supplying the sub-panel.

4) A single receptacle to serve both items is ok. We have 120v/240v service. Many devices list anywhere from 220v-240v but all will run fine on the 240v power you have. The compressor and the heater do not have to be the same exact voltage.
 
  #3  
Old 12-02-13, 06:38 AM
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Wink

Thanks a bunch pjmax for clearing it up for me.
If the items I use are rated for 20amps, I read there start up amps would be more than regular running amps. Will 30amps be good?
 
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Old 12-02-13, 06:41 AM
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Breaker trip curves allow for the high startup current so motors can start. What are you trying to put on the 30 amp circuit? What is the nameplate data on the motor?
 
  #5  
Old 12-02-13, 06:43 AM
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Also I would like to have a outlet and plugs on the heater & air compressor. Do I just use a 30amp dryer outlet and plug? Or is there somthing diffrent and smaller style 30amp than dryer stuff? Thanks again
 
  #6  
Old 12-02-13, 06:47 AM
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Didnt get items yet.

60gal compressor 3.7hp
5000watt electric heater.

Both are single phase motors.
Both say use 20 amps
 
  #7  
Old 12-02-13, 08:52 AM
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can I switch out the 20amp breaker for the lights to a 10amp breaker as there is nowhere near 20amps being used for the few small cfl lights I have.
10 amp circuit breakers are a rarity, but can be found if you really need one.

Circuit Breaker: SQD: QO110

I'd just leave the circuit on the 20 amp breaker.

I have a detached garage with a 40amp breaker from house to 100amp breaker box in the garage ran with 8awg (looks to be aluminum wire).
Is your garage service wiring overhead or underground?
 
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Old 12-02-13, 10:06 AM
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Ran underground.
Ill just leave the lights to the 20amp.
Any chance know what outlet and plugs would use for the 30amp 240v
As stated in above question dry outlet & plug or is a smaller style plug & outlet rated for 30a 240v.?

Thanks for everyones input so far!
 
  #9  
Old 12-02-13, 10:26 AM
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Any chance know what outlet and plugs would use for the 30amp 240v
As stated in above question dry outlet & plug or is a smaller style plug & outlet rated for 30a 240v.?
Dryer cords/plugs and receptacles are 30 amp rated. All 30 amp rated devices will be very similar in size.
 
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