Amperage for mixed use circuit?

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  #1  
Old 10-27-06, 10:50 AM
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Question Amperage for mixed use circuit?

Our garage will be on one circuit with lights, garage door openers and outlets all connected. I thought outlets have to be on 20A circuits. Does this circuit need to be 20A or can it be 15A by code?

Thanks guys!
 
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Old 10-27-06, 10:52 AM
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You need to tell us where you live. Either add that to your profile or at least tell us.
 
  #3  
Old 10-27-06, 10:52 AM
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Depends. How many total watts of lights and how many door openers and what horsepower are they? Even if a 15A would be legal, I think a 20A circuit is well advised.
 
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Old 10-27-06, 11:02 AM
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I'm in NJ. I know 20A would be a better choice, the issue is this:

Currently a 15A breaker. Circuit box to GFI is wired 12-2. Everything else branches from there and is all 14 gauge. Depending on code, the question comes down to: is it harder to pull out the 14 gauge or live with the 15A circuit?

Thanks!
 
  #5  
Old 10-27-06, 11:11 AM
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The NEC does not mandate that a garage circuit be 20 amps. Nor does it prohibit this circuit from having both lights and receptacles on it.

If it were my garage, I would probably run a 15 amp circuit in for the lights and openers (using the existing 15 amp breaker), to use the existing 14 gage wire already in place, and leave the receptacles on the 12 gage wire (buy a 20 amp circuit breaker).

If you leave this as it is, the recetpacles MUST be 15 amp receptacles.
 
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Old 10-27-06, 06:51 PM
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Can you clarify "MUST be 15 amp receptacles"?

Is there a problem with a 20A receptacle on a 15A circuit? If so, why?

Thanks.
 
  #7  
Old 10-28-06, 05:44 AM
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Originally Posted by syakoban
Can you clarify "MUST be 15 amp receptacles"?

Is there a problem with a 20A receptacle on a 15A circuit? If so, why?

Thanks.
The code does not allow a 20 rec on a 15 amp circuit. The reason has to do with the trip curve of a breaker, or fuse.

Appliances that Require more than 15 amps have a different configuration on the cord preventing you from plugging them into a 15 amp rec.

If you plugged an appliance in that was drawing say 16 amps on a 15 amp circuit, the breaker would not trip immediatly. This is because of the trip curve on an inverse time delay fuse or breaker. The higher the amperage the faster the trip.

In my example it could take several minutes for the breaker to trip, causing unsafe wear on the 15 amp wiring system.

When this type of overload happens occasionally a fire is not likely to happen, and the breaker will eventually do it's job.

In my example above, a user is likely to keep reseting the breaker, or if the tool is say a drill or saw, the breaker may not ever actually trip, causing the circuit to keep experiencing the fault condition. This would eventually over heat the wires and cause them to become weaker. A snow ball effect would begin, and could result in a fire.
 
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Old 10-28-06, 10:58 AM
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OK... now what I thought I knew, I might not. As part of our home renovation, I submitted some electrical schematics which were aproved, showing 20A circuits for the dedicated receptacle circuits in the living areas of the house (den, bedrooms, etc.). Should they have 20A receptacles or 15A?

Checking out the existing dedicated washing machine/gas dryer circuit, there's a 20A breaker (12 gauge wire) and typical 15A receptacle. What should that be?


As an aside, is there any functional difference between a standard receptacle and a decora? I've told my wife that the decora is functionally the same, just better looking.

Thanks!
 
  #9  
Old 10-28-06, 11:12 AM
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In the US you are allowed to put 15 amp receptacles on a 20 amp circuit. The key in that sentence is the 's' at the end of receptacles. To do this there must be more than on receptacle on the circuit. A duplex receptacles counts as more than one receptacle.

You are fine anywhere in your house using 15 amp receptacles on a 20 amp circuit unless for some reason there is a single simplex receptacle on the circuit and nothing else.

Remember that the bedrooms must be on an AFCI protected circuit, meaning that the circuit breaker for the bedrooms must ba an AFCI circuit breaker (unless your area does not require them).

There is no functional difference between the various receptacles. There are differences in the way they are hooked up, but that is it. However, usually (but perhaps not always) cheaper receptacles (like the bulk $.39 ones) MAY wear out sooner.
 
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Old 10-28-06, 11:48 AM
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Am I right to believe that the same applies to switches? For example, the new bathroom will have a single GFI outlet, exhaust fan, and lights all on the same 20A (hairdryer you know...) circuit.

Can the 2 switches be 15A or should they be 20A?

Thanks again!
 
  #11  
Old 10-28-06, 12:33 PM
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Yes, the switches can be 15 amp switches.
 
  #12  
Old 10-28-06, 04:30 PM
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So when do you use a 20A switch?
 
  #13  
Old 10-28-06, 04:41 PM
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Originally Posted by syakoban
So when do you use a 20A switch?

When the actual load down line from the switch is over 15 amps.
 
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Old 10-28-06, 09:46 PM
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Wink

Thanks guys! The info was VERY helpful.
 
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