measure voltage drop and current draw

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goodoboy

Senior Member
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Houston
Hello,

Is it good engineering practice to measure voltage drop and current draw of a unit to see if the design as done correctly? We design for 3% voltage drop.

Thanks,
 
I have done it many times in the Telecom and data sectors. It is actually pretty easy to do and can be done with simple tables. By doing it that way you only have to do it one time. After that it is cookie cutter. All you have to do is base it on length, breaker size, and wire gauge. Don't make it more complicated than you need to.

For example with the formula don't get hung on on ambient temps and just use a fixed K value of 11.1 or 22.2. But here is how it works for say a single-phase 20 OCPD using 16 amps of current. Use to low of a current or short distance and you might not meet NEC minimum requirement.

0 to 22 feet = 12 AWG
23 to 35 feet = 10 AWG
36 to 55 feet = 8 AWG

Just remember to increase the EGC size as you increase the load conductor wire gauge. After you have done it a few times you will not even need to look at tables.
 
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I have done it many times in the Telecom and data sectors. It is actually pretty easy to do and can be done with simple tables. By doing it that way you only have to do it one time. After that it is cookie cutter. All you have to do is base it on length, breaker size, and wire gauge. Don't make it more complicated than you need to.

For example with the formula don't get hung on on ambient temps and just use a fixed K value of 11.1 or 22.2. But here is how it works for say a single-phase 20 OCPD using 16 amps of current. Use to low of a current or short distance and you might not meet NEC minimum requirement.

0 to 22 feet = 12 AWG
23 to 35 feet = 10 AWG
36 to 55 feet = 8 AWG

Just remember to increase the EGC size as you increase the load conductor wire gauge. After you have done it a few times you will not even need to look at tables.

Thank you kindly

Thanks to everyone for the help
 
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