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Old 01-30-2015, 02:22 PM   #1
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Default Seemingly phantom breaker tripping

15 amp circuit with a space heater and some lights. Square D QO panel. Breaker never tripped with both the lights and heater on, however it would trip randomly in the night with nothing on. First step was to disconnect the lights and the heater, it still tripped the following night. With the lights and heater disconnected there was no current draw.

Replaced the breaker, and the new breaker tripped almost immediately. Turns out the lights and heater were drawing a combined total of around 22 amps.

Either the lights or heater will be moved to a different circuit.

I post because I'd never seen a breaker behave in this manner before.
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Old 01-30-2015, 02:33 PM   #2
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That's one reason I don't put outlets on a lighting circuit.

That's why I run 20 amp receptacle circuits.


That's why I like every bedroom on their own outlet circuit.
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Old 01-30-2015, 02:39 PM   #3
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In this case, the lights were all plugged in to recepticles.

I do not understand why the circuit wasnt 20 amps. Some of the wiring is #12, for all I know all of it is, but I'm not going to rip into walls to see.
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Old 01-30-2015, 02:49 PM   #4
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Were there more heaters on the circuit? 22 amps sounds like a lotza amps on 1 bedroom. 1 heater shouldn't be more than 1475 watts.
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Old 01-30-2015, 03:09 PM   #5
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Originally Posted by dspiffy View Post
15 amp circuit with a space heater and some lights. Square D QO panel. Breaker never tripped with both the lights and heater on, however it would trip randomly in the night with nothing on. First step was to disconnect the lights and the heater, it still tripped the following night. With the lights and heater disconnected there was no current draw.

Replaced the breaker, and the new breaker tripped almost immediately. Turns out the lights and heater were drawing a combined total of around 22 amps.

Either the lights or heater will be moved to a different circuit.

I post because I'd never seen a breaker behave in this manner before.

(however it would trip randomly in the night with nothing on.)



Nothing on ? Why would it not trip with a load , and trip with no load ?



Or , am I misunderstanding your post ?
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Old 01-30-2015, 03:18 PM   #6
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...............
And was it an afci breaker?

Last edited by guest; 02-01-2015 at 04:03 PM. Reason: Removed snarky remark
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Old 01-30-2015, 03:30 PM   #7
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Originally Posted by bobelectric View Post
That's one reason I don't put outlets on a lighting circuit.

That's why I run 20 amp receptacle circuits.


That's why I like every bedroom on their own outlet circuit.

I don't understand the logic behind any of this.

Care to explain?
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Old 01-30-2015, 03:32 PM   #8
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Originally Posted by dspiffy View Post

I do not understand why the circuit wasnt 20 amps. Some of the wiring is #12, for all I know all of it is, but I'm not going to rip into walls to see.
If this is a residential setting...there are not many locations in the NEC were it is required to run #12/20A ckts.
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Old 01-30-2015, 03:44 PM   #9
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I don't understand the logic behind any of this.

Care to explain?

I wire for the long haul, not code min. If I get he job that's how I bid it. Maybe read my post again.
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Old 01-30-2015, 04:07 PM   #10
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I wire for the long haul, not code min. If I get he job that's how I bid it. Maybe read my post again.
How do you stay competitive doing that though? Where's the line? You can't wire for every future scenario and make any money.
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Old 01-30-2015, 04:29 PM   #11
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Sam. I don't live off of wiring houses. The ones I do are requests from people I do work for and they want a number. Also, the insurance people give a new housing unit a life of 50 years. Look at the electrical changes in the last 50 years. I say 30 years for an electrical service.
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Old 01-30-2015, 04:53 PM   #12
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I wire for the long haul, not code min. If I get he job that's how I bid it.
That doesn't explain anything about what you posted.
All you did was feebly attempt to explain your bid thought process.

That does less than little to support the logic that you:
  • don't put outlets on a lighting circuit.
  • run 20 amp receptacle circuits.
  • like every bedroom on their own outlet circuit

.........
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Last edited by guest; 02-01-2015 at 03:46 PM. Reason: Knock off the smartazz sniping please
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Old 01-30-2015, 06:50 PM   #13
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Not a bedroom, not an AFCI or GFI breaker. The lights alone were around 6 amps.

My theory is that the old breaker should have tripped when the heater and lights were on, but instead tripped hours later after they had been turned off/disconnected. Basically a very long time delay. As I said, I'd never seen a breaker fail in that way, and found it interesting, especially for future troubleshooting.
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Old 01-30-2015, 07:13 PM   #14
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Originally Posted by dspiffy View Post
Not a bedroom, not an AFCI or GFI breaker. The lights alone were around 6 amps.

My theory is that the old breaker should have tripped when the heater and lights were on, but instead tripped hours later after they had been turned off/disconnected. Basically a very long time delay. As I said, I'd never seen a breaker fail in that way, and found it interesting, especially for future troubleshooting.
Maybe the breaker isn't failing. Maybe there's a load, or an intermittent load that you're unaware of.

Quote:
Replaced the breaker, and the new breaker tripped almost immediately. Turns out the lights and heater were drawing a combined total of around 22 amps.

Either the lights or heater will be moved to a different circuit.

I post because I'd never seen a breaker behave in this manner before.
Why wouldn't a 15a breaker trip at 22 amps?
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Old 01-30-2015, 07:56 PM   #15
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That's exactly the point. The old breaker should have tripped immediately, but didnt.
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Old 01-30-2015, 08:03 PM   #16
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or an intermittent load that you're unaware of.



?
or an intermittent short

worked on a circuit with similar symptoms, the short was in the crawl space where a nail was bent over NM instead of staple, burned or melted about 4' of outer insulation and inner insulation in places, sometimes the bare hot would touch the bare ground. breaker had occasionally tripped for months or years.
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Old 01-30-2015, 10:14 PM   #17
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I ask the client if they use space heaters: if yes, BR's get 20amp circuits, otherwise they're getting 15's; lights and recep's are on separate circuits always; and yeah, every room has it's own circuit.
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Old 02-01-2015, 02:34 AM   #18
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There has been no phantom tripping since the breaker was replaced. There has been no tripping at all once the lights were moved to a different circuit.
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Old 02-01-2015, 04:02 PM   #19
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Quote:
Originally Posted by Celtic View Post
I don't understand the logic behind any of this.

Care to explain?
Quote:
Originally Posted by bobelectric View Post
I wire for the long haul, not code min. If I get he job that's how I bid it. Maybe read my post again.
Quote:
Originally Posted by Celtic View Post
That doesn't explain anything about what you posted.
All you did was feebly attempt to explain your bid thought process.

That does less than little to support the logic that you:
  • don't put outlets on a lighting circuit.
  • run 20 amp receptacle circuits.
  • like every bedroom on their own outlet circuit

.........
Celtic, no need to be antagonistic about this. The logic is crystal clear to most everyone on here.

Code minimum does not require any of the bullet points...but common sense, especially with today's glut of electronics and appliances makes what Bob does a good value and IMHO enhances safety.

I don't put receptacles on lighting circuits....I don't want an overload on the recepts to kill the lighting in a room.

I always run 20 amp receptacle circuits, as have every EC I have ever worked with. One space heater can often max out a 15 amp circuit, so why provoke nuisance tripping? The increased cost of copper is minimal compared to the enhanced safety and value added.

As for each bedroom on it's own circuit, again not required but a very good idea. My master suite I am wiring up here actually has THREE 20 amp circuits. (one of which is fed from my subpanel and backup generator.) Why? Because I want it that way, I do use space heaters here in the winter and because the added cost is a whopping $24.00 in breakers and wire.

Finally, I do what the client wants, as long as they are willing to pay and it does not compromise safety. If they want Code Minimum, that's what they get. If they want every receptacle on it's own circuit that's what they get.

Last edited by guest; 02-01-2015 at 04:05 PM.
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Old 02-01-2015, 04:22 PM   #20
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Originally Posted by bobelectric View Post
That's one reason I don't put outlets on a lighting circuit.

That's why I run 20 amp receptacle circuits.


That's why I like every bedroom on their own outlet circuit.
I don't do many houses, but around here, 1500 watt space heaters are very common.

I would also put all recpt's on 20s; 15s would be perfectly fine for lights, but not recepts.
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