Feeder Breaker settings based on 25' Tap Rule

[brian5]

I am upgrading a small portion of a feeder system. I am using 25' tap rule for 3 Loads off of a 1600Amp Breaker. I sized parallel 350 to protect to one third of the 1600A.

Tap one feeds a 400 Amp Disconnect to protect a previously installed 500 running to a distribution panel with a 600 Amp Main Breaker.
Tap Two feeds an auxiliary switchgear with 2 loads 1. 350hp motor 2. 150hp motor. Both Motors are non-Continuous
Tap Three feeds a distribution panel with a 600 Amp Main Breaker.




For the Main Feeder breaker for this circuit 1600A Sensor:

I am looking for help on why the LTPU cannot be set above 620 Amps?

I want to ensure that there are no errand trips on the 1600 Amp Breaker.

Thank you for your help!

Brian

 

[infinity]

For the Main Feeder breaker for this circuit 1600A Sensor:

I am looking for help on why the LTPU cannot be set above 620 Amps?

Where are you getting this information?

 

[smoothops10]

Hard to see but looks like tap 2 is terminating in 800AT. No 'round up rule' allowed for taps. Would need to terminate tap 2 in 600AT maximum for starters.

That will probably not be enough for your 500 HP of motor load. Sorry to say but the whole thing looks hooky to me.

 

[infinity]

Hard to see but looks like tap 2 is terminating in 800AT. No 'round up rule' allowed for taps. Would need to terminate tap 2 in 600AT maximum for starters.

Looks like 800 to me too. If he wanted to keep 2 sets he would need a minimum of 600 kcmil.

 

[brian5]

Answers

Answers

Infinity, I am supplying the information to upgrade.

Smoothops10, What is Hooky?

How can I attach a better picture?

I will try to explain better......

Main Breaker (2B) is a 1600 Amp Breaker. I am looking for setting for this breaker based on the 25' Tap Rule.

I based the 3 taps on parallel 350 to be greater than 1/3 of the 1600 Amp breaker. 350 Kcmil THHN I am using 350 amps per parallel feed. Giving me 700 Amps capacity per load.

TAP 1 : I am installing a 400 Amp Fused Disconnect to supply the Control Room I- Line to Protect the 500 Kcmil THHN.

TAP 2: Auxillary Switchgear 2B-1A feeds breakers 2B-1B, 2B-1C. 350HP & 150HP Non continuous Motors.

TAP 3: SouthEast I-Line Panel has a 600 Amp Main Breaker


I am looking for help in setting the main breaker. I feel the main breaker should be set at 1600 Amps. Based on the following

Tap 1: 400 Amps
Tap 2: 685 Amps
Tap 3: 600 Amps

 

[infinity]

The 1600 amp 2B is fine if your load calculation says that 1600 amps is enough. The problem is the 800 amp OCPD at 2B-1A, it needs to be no more than 620 amps {310*2=620} to protect your parallel 350's or they need to be changed to 600 kcmil {420*2=840} to get you enough conductor for the 800 amp OCPD.

 

[brian5]

The 1600 amp 2B is fine if your load calculation says that 1600 amps is enough. The problem is the 800 amp OCPD at 2B-1A, it needs to be no more than 620 amps {310*2=620} to protect your parallel 350's or they need to be changed to 600 kcmil {420*2=840} to get you enough conductor for the 800 amp OCPD.

Thank You

Brian