Chiller Breaker sizing

[david]

View attachment 2572287

(180,180,150,150)=660

660 +(58.8 total fans)=
718.8 + (4.2 control) =
723 +(900 rpm 50 hp motor)
723+ 40.9= 763.9

Not sure about the 50 hp motor but the closes I could get to 763 total

 

[david]

View attachment 2572287

The table note on top says min Circuit ampacity 1000 amps

The highlighted section in the lower table says min Circuit ampacity 763

Why is the lower table using the rla as the min. Circuit ampacity?

Just trying to follow what your doing here

 

[david]

Never mind I see what your doing the Asterix * means 763 without the pump motor or control kva so
(180+180+150+150) +25% largest
660 +45=705
705 +fans 58.8= 763.8
764 total RLA

 

[david]

Never mind I see what your doing the Asterix * means 763 without the pump motor or control kva so
(180+180+150+150) +25% largest
660 +45=705
705 +fans 58.8= 763.8
764 total RLA

705 ×175%= 1233.75
705 ×225% max = 1586.25

For just the chiller
705 + 58.8 (21 fans )=763.8 min Circuit ampacity

 

[david]

I get a maximum OCPD size of 943A (= MCA + 100% largest RLA) if 440.22 applies,
Cheers, Wayne

180 x225% = 405
405 + (180 +150+150+58.8)
405 + 53.8 = 943.8

MCA (763) + 180 =943

Where did you get that formula from?

So min. Circuit ampacity plus the largest compressor RLA = maximum over current protection.
That formula seems simpler.

 

[wwhitney]

Where did you get that formula from?

Algebra:

A = 1.25 * x1 + x2 + x3 + etc
B = 2.25 * x1 + x2 + x3 + etc

Therefore

B - A = x1, or
B = A + x1
MOCP = MCA + (largest RLA/FLA) for HVAC equipment

For motors, the difference in coefficients is 1.25, so MOCP = MCA + 1.25*(largest motor FLA).

Cheers, Wayne

 

[david]

Algebra:

A = 1.25 * x1 + x2 + x3 + etc
B = 2.25 * x1 + x2 + x3 + etc

Therefore

B - A = x1, or
B = A + x1
MOCP = MCA + (largest RLA/FLA) for HVAC equipment

For motors, the difference in coefficients is 1.25, so MOCP = MCA + 1.25*(largest motor FLA).

Cheers, Wayne

In other words 225% -125%=100%

Since the formula for max overcurrent protection includes the formula for min Circuit ampacity

And the difference being in this example an addition of 100% of 180