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Old 07-23-2014, 07:44 PM   #15
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It should work, but as mentioned, monitor the cord/plugs for excess heat...
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Old 07-24-2014, 10:17 AM   #16
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Quote:
Originally Posted by RinkersRanch View Post
Fairly easy to tell a 15A outlet from a 20A without removing the wall plate.
Oops, looks like I have a little work to do. And it would have to be on the wall behind my work bench.
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Old 07-27-2014, 08:25 AM   #17
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The 15 amp outlet on the 20 amp circuit wont be the cause of the breaker tripping.
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Old 07-27-2014, 08:49 AM   #18
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I have a dedicated 20 amp outlet in the garage (original wire was there for a water heater - but use gas) put a GFCI in the outlet and run a 50 ft. 12/3 extension to the coach - no problem running one of the 13.5 AC units and the battery charger - I do place the refer on propane. I insure the cord is stretched out and not coiled and try to keep as much in the shade as possible - with air temps this time of year in the 1teens - need all the help I can get to keep things "cool". We live in a master planned community so I can only have the coach home to load and unload (24 hours max) so it sure helps to have one of the AC units running during that time.
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Old 07-28-2014, 05:44 PM   #19
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It's not a question if the A/C will run on 20 amps. If you look in the trailers circuit panel, there will be a 20A breaker for the A/C. This clearly indicates that 20A is sufficient. What you really need to know is if the total load at the trailer exceed approximately 2,400 watts.
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Old 07-28-2014, 06:49 PM   #20
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2400 watts at 120 volts is 20 amps. However, breakers are rated and operate to trip on amperage - not watts.

Watts = Volts x Amps
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Old 07-28-2014, 08:06 PM   #21
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2400 watts at 120 volts is 20 amps. However, breakers are rated and operate to trip on amperage - not watts.

Watts = Volts x Amps
Does your power company bill you for kilowatts used or amps? While breakers are rated in amps, they actually measure watts or volt amps if you prefer. As voltage drops as in a brownout, the amperage will increase.

A breaker has no way of knowing what the serving voltage is.
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Old 07-28-2014, 08:58 PM   #22
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Breakers trip on amps

Amps is unit of measure for current flow

Power meter reads in watts which is unit of measure for power.

Amps by itself means little.

20 amps at 12 volts is only 240 watts...at 240 volts it is 4800 watts...big difference.

Breaker would trip at same point but work done much different.
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Old 07-28-2014, 09:10 PM   #23
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There is some good advice here, but one item that has been overlooked is your actual house wiring. A 15 amp circuit will be fed with 14 gauge solid wire, which would be unacceptable to run your A/C on. A 20 amp circuit must have 12 gauge wire, and if over 100 feet should be 10 gauge wire, but that is usually not done in residential applications. If the breaker panel is at the far end of the house, and you add a 50' cord to it (yes 10 gauge is much better) you still could have significant voltage drop down that 12 gauge wire and through the plugs.

The only real way to know for certain is to run the A/C and check the voltage at both the panel and at the A/C unit, and measure the amperage. That will tell you if you are pushing the limit of capacity of the wiring, or maybe just have a weak breaker that trips occasionally on startup load.
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Old 07-28-2014, 09:22 PM   #24
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Originally Posted by TQ60 View Post
Breakers trip on amps

Amps is unit of measure for current flow

Power meter reads in watts which is unit of measure for power.

Amps by itself means little.

20 amps at 12 volts is only 240 watts...at 240 volts it is 4800 watts...big difference.

Breaker would trip at same point but work done much different.
From one of the NEMA papers I receive:

In order to debunk the myths it is important to understand the basic operation and design of the trip mechanisms in a circuit breaker. The thermal portion of the circuit breaker works by use of a bi-metallic strip which causes a spring-loaded latch to release and trip the breaker. The deflection of the bi-metallic strip depends on the temperature, thus the breaker has a trip temperature and it is the heat generated within the breaker that causes the temperature to rise, the faster the heat rise, the faster the breaker reaches temperature and trips. Heat is directly proportional to the power (watts), which is proportional to the square of the current (P=I2 x R)

The first (and most common) misconception is that a breaker trips when its nameplate rating is exceeded. A circuit breaker will trip in several minutes with a small increase in current over its rating. Actually, a 20 amp breaker must trip at a sustained current of 27 amperes (135 percent) at less than one hour, and at 40 amperes (200 percent of wire rating) in less than 120 seconds. These two trip points (135 percent and 200 percent) are defined in NEMA Standard AB-1, MCCBs and Molded Case Switches.

A circuit breaker is designed to open (trip) before the energy passing through it creates enough heat in the branch circuit wiring to cause damage to the wiring.

While breakers are labeled in amps as a convenient measurement, they are tripped by watts.
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Old 07-29-2014, 07:24 AM   #25
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LOL! This is more schooling than I ever anticipated when I started the thread. Thanks, folks! I should think about replacing that outlet with a 20A GFCI and can check the wiring then. It is only about 30' from the panel.
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Old 07-29-2014, 08:21 AM   #26
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Originally Posted by joshuajim View Post
From one of the NEMA papers I receive:

In order to debunk the myths it is important to understand the basic operation and design of the trip mechanisms in a circuit breaker. The thermal portion of the circuit breaker works by use of a bi-metallic strip which causes a spring-loaded latch to release and trip the breaker. The deflection of the bi-metallic strip depends on the temperature, thus the breaker has a trip temperature and it is the heat generated within the breaker that causes the temperature to rise, the faster the heat rise, the faster the breaker reaches temperature and trips. Heat is directly proportional to the power (watts), which is proportional to the square of the current (P=I2 x R)

The first (and most common) misconception is that a breaker trips when its nameplate rating is exceeded. A circuit breaker will trip in several minutes with a small increase in current over its rating. Actually, a 20 amp breaker must trip at a sustained current of 27 amperes (135 percent) at less than one hour, and at 40 amperes (200 percent of wire rating) in less than 120 seconds. These two trip points (135 percent and 200 percent) are defined in NEMA Standard AB-1, MCCBs and Molded Case Switches.

A circuit breaker is designed to open (trip) before the energy passing through it creates enough heat in the branch circuit wiring to cause damage to the wiring.

While breakers are labeled in amps as a convenient measurement, they are tripped by watts.
This is good stuff, I learned a lot and it brought back some of my electrical/electronic training. All was good until the last sentence, where the NEMA paper kinda contradicts itself, or at best confuses the reader (I'm grinning, not criticizing) " . . . they are tripped by watts" when earlier the paper cites they are tripped by temperature/heat . . .
Now don't get upset, I know there is a correlation between watts/current/voltage/temperature, I'm just jerking your chain, it is a very good explanation of how/why a breaker trips!
But let's face it, we all know that Watts is a derived unit of measure.
None of this, of course, goes to the OP's original question, DOH!
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Old 07-29-2014, 08:48 AM   #27
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Engineers - ask them what time it is and they tell you how to build a watch...
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Old 07-29-2014, 09:12 AM   #28
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" . . . they are tripped by watts" when earlier the paper cites they are tripped by temperature/heat . . .
Now don't get upset, I know there is a correlation between watts/current/voltage/temperature, I'm just jerking your chain, it is a very good explanation of how/why a breaker trips!
But let's face it, we all know that Watts is a derived unit of measure.
None of this, of course, goes to the OP's original question, DOH!
OK, chain properly jerked.

The paper was 6 pages long and I only pulled one short section ...and the final sentence you quoted. There is further explanation that is not relevant including graphs showing relevance between the volt/amp/time/ambient temperature correlation. What they were trying to say is that the "heater" in the breaker reacts to the power going through it. Power is measured in watts as voltage and amperage are variables but watts is the final measurement.

Wanna get into the magnetic portion of the breaker.
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