3 phase service load

[Sahib]

430.24 is what it is.

125% largest motor
100% other motors
125% non-motor continuous
100% non-motor noncontinuous

See Exceptions 1 and 3, which permits reducing load demand and feeder size.

 

[Smart $]

See Exceptions 1 and 3, which permits reducing load demand and feeder size.

Exceptions may provide some relief, but odds are most if not all the motors going in that shop are continuous duty rated... and I doubt there will be any interlocking of machinery to reduce the load. Not saying otherwise is impossible, just quite unlikely.

 

[Sahib]

So the OP may apply 1.25 to FLA of largest motor and demand factor to the sum of FLA of other non continuous rated motors with special permission of AHJ per code. Add the two to arrive at load demand and feeder size.

 

[Smart $]

So the OP may apply 1.25 to FLA of largest motor and demand factor to the sum of FLA of other non continuous rated motors with special permission of AHJ per code. Add the two to arrive at load demand and feeder size.

That's just it. All motors will likely be rated "Continuous Duty". This rating is with respect to the motor's design and so marked on the motor nameplate. Where one uses a continuous-duty rated motor in an intermittent manner, they are required to factor the motor in at 140% or 200%. If you are looking to decrease the demand, this is not the way to do it... :slaphead:

 

[Sahib]

The OP should consult AHJ anyway to ensure characteristics of motors and conditions for reduced feeder size.

 

[iwire]

The OP should consult AHJ anyway to ensure characteristics of motors and conditions for reduced feeder size.

Or the OP could have you contact the AHJ and straighten it all out.

 

[kwired]

So the OP may apply 1.25 to FLA of largest motor and demand factor to the sum of FLA of other non continuous rated motors with special permission of AHJ per code. Add the two to arrive at load demand and feeder size.

OP is asking about the service, all the motors will be on the service regardless of how many feeders it gets split into.

 

[oldsparky52]

Why does nameplate KVA come into play in service calculation? Aren't you required to use Table 430.250 ratings for service calculations?

 

[kwired]

Why does nameplate KVA come into play in service calculation? Aren't you required to use Table 430.250 ratings for service calculations?

Some of the equipment mentioned may not be simple single motor operated appliances and may be a little more complex then that, but otherwise yes.

 

[Smart $]

Why does nameplate KVA come into play in service calculation? Aren't you required to use Table 430.250 ratings for service calculations?

Technically no such thing as nameplate kVA.

Other than that you are correct. One is [typically] required to use the 430.xxx tables for the FLA for motors.

 

[Sahib]

OP is asking about the service, all the motors will be on the service regardless of how many feeders it gets split into.

Are you saying 430.24 not applicable to service feeders?

 

[kwired]

Are you saying 430.24 not applicable to service feeders?

What is a service feeder?

If anything 430.26 could apply. 430.24 alone is not going to allow any kind of "demand factor" to be applied.

Once again, if no usage pattern is established then it is hard to give much allowances, making it difficult to reduce the load on a new installation unless you have some other very similar application to establish a pattern from.

 

[Sahib]

What is a service feeder?

Service entrance conductors.

 

[iwire]

Service entrance conductors.

And now that you cleared that up what does 430.24 have to do with demand?

 

[Sahib]

And now that you cleared that up what does 430.24 have to do with demand?

If you reproduce 430.24 and give your comments here, we may discuss further. Okay?

 

[iwire]

If you reproduce 430.24 and give your comments here, we may discuss further. Okay?

That's what I thought, more games.