Name plate amps-vs- actual amps

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stevewallace

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Moreno Valley, Ca.
I am putting together a design and build for a customer. How, or can I use actual amperages of the equipment instead of name plate amps? This will make a big differance in the wire sizes and overall service size (8000amps -vs- 6000amps). Same question for loadind up pannelboards. Over 250 pieces of equipment.
 
augie47

augie47

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Tennessee
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State Electrical Inspector (Retired)
I'm sorry, but I'm at a loss. Other than equipment being underutilized (such as motors not loaded to their HP rating) what type of equipment has an actual amperage less than it's nameplate amperage ?
 
Buck Parrish

Buck Parrish

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Location
NC & IN
stevewallace said:
I am putting together a design and build for a customer. How, or can I use actual amperages of the equipment instead of name plate amps? This will make a big differance in the wire sizes and overall service size (8000amps -vs- 6000amps). Same question for loadind up pannelboards. Over 250 pieces of equipment.
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Perhaps you can add all 250 pieces of equipment then add deductions?
 
iwire

iwire

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Location
Massachusetts
Steve you do not get to use 'actual amps' you have to use the nameplates.

This is true even with lighting fixtures, you may have a plan that uses fixtures with75 watt lamps but the fixture might be rated 150 watts. In that case you would still have to use the 150 watt figure for calculation purposes.

Gus a lot of equipment draws less than the label, computer equipment is a good example. The tag is based on the max of the units power supply is rated for but the power supply is often oversized for the installed components.
 
bob

bob

Senior Member
Location
Alabama
stevewallace said:
I am putting together a design and build for a customer. How, or can I use actual amperages of the equipment instead of name plate amps? This will make a big differance in the wire sizes and overall service size (8000amps -vs- 6000amps). Same question for loadind up pannelboards. Over 250 pieces of equipment.
Click to expand...

For motors you must use table 230.248 or 230.250 for the design amps.
 
augie47

augie47

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Staff member
Location
Tennessee
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State Electrical Inspector (Retired)
iwire said:
Steve you do not get to use 'actual amps' you have to use the nameplates.

This is true even with lighting fixtures, you may have a plan that uses fixtures with75 watt lamps but the fixture might be rated 150 watts. In that case you would still have to use the 150 watt figure for calculation purposes.

Gus a lot of equipment draws less than the label, computer equipment is a good example. The tag is based on the max of the units power supply is rated for but the power supply is often oversized for the installed components.
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Bob, excellent example. From a Code standpoint aren't we pretty much locked into using nameplate values ?
 
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stevewallace

Member
Location
Moreno Valley, Ca.
They have alot of N.C. punch presses that are rated at 200amps. The actual draw has always been around 75amps. Spot welders are also a prime example. Art 630 does allow for derating of welders.
 
bob

bob

Senior Member
Location
Alabama
stevewallace said:
They have alot of N.C. punch presses that are rated at 200amps. The actual draw has always been around 75amps. Spot welders are also a prime example. Art 630 does allow for derating of welders.
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Isn't a punch press a very short time amp draw?
 
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stevewallace

Member
Location
Moreno Valley, Ca.
If I use name plate I assume I can only load up the 200amp panelboards to 200amps even tho all the equipment never (in reality) runs at the same time. The theory would be it can all be turned on at once?
 
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