max capacity

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Timboe

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I have a 200amp motor control panel and there are motors running out of it. If i put a amp meter on the incoming legs 480volts i get 43 amps on each leg. How many more amps can i get out of this panel with the addition of motors? A simple answer needed for a simple guy.
Timboe
 
A lot of the ?ifs? and such depend on whether all the motors were running when you took your readings, what size wire was used to feed power to this Motor Control Center from upstream, and what the rating is for the upstream overcurrent protection device. But I would agree that the number of amps available should be no higher than Tom?s stated 117. By the way, that number is based on trying to keep the load below 80%, or below 160 amps.
 
Would it be 80% of the 200 amps, or 125% of the largest motor plus 100% of all the other motors?
 
infinity said:
Would it be 80% of the 200 amps, or 125% of the largest motor plus 100% of all the other motors?
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Part of the what ifs. What about if the largest single motor starts after all the others are running? The 200 amp CB may not big enough to handle the inrush. Maybe all of them have to start at the same time.

Simple anwers just don't work sometimes and by the looks of some of these threads, what I always thought was straight forward and clear, just ain't.
 
ptonsparky said:
Simple answers just don't work sometimes
Click to expand...

I agree and this is one of those times.

His amp clamp measurement is basically meaningless.

You would need to start with an NEC load calculation and work from that point.
 
Ok here`s somemore info. I don`t have the prints in front of me but heres what i know. All the motors are 2hp and start at the same time except that I have one 20hp that I start off of a VFD drive which ramps up over about a 8 second period. Cool stuff ain`t it
 
Ask the Neurosurgeon

Ask the Neurosurgeon

Really basic, what you're measuring is the running load and not the starting load. Starters protect motors and breakers protect wires. Get a Master Electrician to calculate your needs (starting, running, overload, and fault) before you go further.
 
There are so many unknowns in this equation that there is no answer that can be given to you with any certainty.

The answer depends on such things as:

- the size and type of the BC OCPD feeding the MCC
- the size of the conductors feeding the MCC
- whether you intend to follow NEC rules on such things
- how many motors you have, their HP rating (and the VFD rating) and how long they run

It is entirely possible that by code rules it is already maxed out.
 
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