OVER LOAD WIRE

Status
Not open for further replies.
D

domnic

Senior Member
Occupation
Electrical Contractor
I have a # 12 thhn wire 120 volts 1500 watts . can that wire be over loaded with the numbers i stated. ( 80 f temp )
 
If you mean will the current cause it to heat up and exceed it's temperature rating the answer is no.
 
domnic said:
what if the device hade a 54% power factor ?
Click to expand...
what has a .54 PF without being basically unloaded? In other words, if this were an induction motor RATED for 1500W, that rating would be the full load rating, in which case the PF would be somewhere around .80, maybe better. If the PF were .54, that would only happen if the motor was unloaded, in which case it would not be pulling 1500W.

Or conversely it is was still pulling 1500W at a .54 PF, then that means the full load rating was something higher, likely 2200W, in which case the FLC would be around 18.5A. Still OK on a 20A circuit, so long as it is not continuous.
 
Last edited:
Even if so, the 75C rating of #12 copper is 25 amps. So no it wont overheat. Whether you can fuse it at 25A is a separate question and depends on where the wire is and what it is powering.
 
Jraef said:
what has a .54 PF without being basically unloaded? In other words, if this were an induction motor RATED for 1500W, that rating would be the full load rating, in which case the PF would be somewhere around .80, maybe better. If the PF were .54, that would only happen if the motor was unloaded, in which case it would not be pulling 1500W.

Or conversely it is was still pulling 1500W at a .54 PF, then that means the full load rating was something higher, likely 2200W, in which case the FLC would be around 18.5A. Still OK on a 20A circuit, so long as it is not continuous.
Click to expand...
There is an ongoing confusion for some people between the Efficiency of a motor (effective output power divided by the real part of input power) and the Power Factor of that motor. Both vary with motor load, but the efficiency number (if specified) will generally refer to full load conditions.
Right up there with to confusion between the mechanical output power of a motor (as measured by the actual work done by the motor shaft) and the electrical input power in Watts (or sometimes in terms of the heat equivalent of Horsepower.)

Side question: We have seen a steady tendency for electrical units, and scientific units in general) to be named or renamed after a prominent scientist or inventor in the associated field. Why no proper name for horsepower? Any candidates? :)
 
GoldDigger said:
Side question: We have seen a steady tendency for electrical units, and scientific units in general) to be named or renamed after a prominent scientist or inventor in the associated field. Why no proper name for horsepower? Any candidates? :)
Click to expand...
Probably because horses were used for centuries before theoretical values and mathematical equations.
 
The term “horsepower” was first used by none other than James Watt, comparing the power of a steam engine to that of a draught horse. The SI unit “Watt” came along after his death as a way of honoring his work.
 
Jraef said:
The term “horsepower” was first used by none other than James Watt, comparing the power of a steam engine to that of a draught horse. The SI unit “Watt” came along after his death as a way of honoring his work.
Click to expand...
Do you happen to know the standard horse he based his calculations on? Being a little facetious, but we watched some Draft horse pulls last year and those are not all created equal. Is that where the efficiency comes in to play?
 
One HP = Ability to lift 33,000 pounds one foot per minute. Or the ability to lift one pound 33,000 feet per minute.

Unless you are talking about boiler HP.

One boiler horsepower is equal to the thermal energy rate required to evaporate 34.5 pounds (15.6 kg) of fresh water at 212 °F (100 °C) in one hour.
 
Last edited:
GoldDigger said:
Side question: We have seen a steady tendency for electrical units, and scientific units in general) to be named or renamed after a prominent scientist or inventor in the associated field. Why no proper name for horsepower? Any candidates? :)
Click to expand...
I have a name that relates to a long eared animal, similar to a horse, for a few people!
 
I wonder how they came up with those numbers. Did they test a bunch of horses and then come up with an average? Were they fresh horses doing a one minute pull? Or is that what a horse can do all day long? Is there a capacity factor for horses? Are horses tested at a pressure of 29.92 and 59 degrees?
 
Status
Not open for further replies.
Top