Lighting Load

[Matt Mckenzie]

If I have a lighting panel board with 804 amps of load what is the MINIMUM size over current protection device needed to feed it.

 

[Matt Mckenzie]

question

question

I am back and forth between 800 and 1000 amp OCP. Something is telling me that the minimum is 800.....

 

[Matt Mckenzie]

can somebody help?

can somebody help?

Can someone help answer the above question please

 

[mopowr steve]

I would say at least 125% of the 804 Amp if it's a continuous load =1005A So I guess you should go with a 1200amp just to give you a little wiggle room.

You may have to be a little more specific about that load, is that on all phases or is that to be spread across phases.

 

[iceworm]

If I have a lighting panel board with 804 amps of load what is the MINIMUM size over current protection device needed to feed it.

I am back and forth between 800 and 1000 amp OCP. Something is telling me that the minimum is 800.....

Matt -
Look at 215.2.A.1.a and 215.3

The load is 100% of the non-continuous plus 125% of the continuous. Does your 804A take that in to account.

Next is 240.6. Standard CB ratings are 800A, 1000A So, if the calculated load is over 800A, then you are stuck with a 1000A CB.

You didn't ask, but look at 240.4.C. If the CB is over 800A, there is no "round-up". The conductor ampacity has to be greater than the CB rating.

However, if 240.6.C applies, (restricted Access), then one can pick a CB with an adjustable trip and set it just above the 804A. The conductors can now be smaller as long as they are over the trip setting.

Look up the references. See if this helps.

ice

 

[Smart $]

The OCPD rating cannot be less than the calculated load after the application of demand factors, if any. And if any part of that load is continuous, that portion needs to be factored by 125% for conductor and OCPD sizing.

FWIW, you can only round the fractional part of an ampere calculation result.