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about chiller feeder

about chiller feeder

about chiller feeder

(OP)
hi, i was informed that hospital's chiller manufacturer wants a feeder size for feeding of about( its load is 100 KVA))  120 mm2 (underground cable which has a capacity of 170  ampere,) İ calculate that a 120 mm2 cable has a capacity of 320 Amp and it is too much and i guess a cable of 50 mm2 is enough roughly, pls tell me why this chiller feeder is asked too compared to a simple calculation.is it about starting current? if so i know thay NEC wants minimum %125 size cable on the basis of the load value.but why this chiller feeder  needs  ABOUT 5/2 of the load ampacity?...

RE: about chiller feeder

Hi bulancak,

More data please -- voltage, phase, length of feeder, is the chiller reciprocating or centrifugal, etc...

Thanks and good on ya,

Goober Dave

RE: about chiller feeder

How long is this feeder?  Perhaps it's size requirement is for voltage drop reasons.  What is the feeder length?  Also, what environment will it be in?  Higher temperatures and runs inside conduit ect, will have a derating of the cable.

------------------------------------------------------------------------
If it is broken, fix it.  If it isn't broken, I'll soon fix that.

RE: about chiller feeder

Please don't mix NEC and conductor size in mm2.  People that know NEC requirements generally think in AWG/kcmil wire sizes while people that think in mm2 wire sizes generally aren't conversant with NEC requirements.

RE: about chiller feeder

(OP)
no no just 140 meter:) but i calculated that a 50 or maximum 70 mm2 cable is enough.İt is just a 4-compressor chiller.lets take it 90 KW if it is a 100 kVA load. look 0,0124x140x90/50=3,12 % so a 50 cable carry about 170 A.SO how can it be?? why he ask for a 120 mm2? he says according to the chart of the manufacturer firm, it is obligatory but i cant understand how can it be??

RE: about chiller feeder

You said. "120 mm2 (underground cable which has a capacity of 170  ampere)." so what is the issue?

How did you "calculate" 320A ampacity?
What does manufacturer of the cable say about the ampacity?
What type of cable? Cu or AL? 3-conductor with armor and PVC jacket? Singel conductors?

NEC or not you need to size 125% of the continuous current. Do you know your local codes?

RE: about chiller feeder

(OP)
it is NYY cu cable. İf we lay a cable of 120 mm2 it has a current carrying capacity and i think it is too much for a 100 kVA chiller.it is pvc isolated cable also, it is nyy in DİN codes.pls help me

RE: about chiller feeder

(OP)
EXCUSE ME a 50 mm =170 A and 120 mm2 =320 A capacity from A NYY cable laid underground.

RE: about chiller feeder

You should derate the current carrying capacity of your cable when laying underground:
  • There are more cables in proximity
  • You also derate your cable when the temperature it is expected to be laid in is higher than its temperature rating.
  • the kind of laying used (duct or tray; direct burial)
I don't know how it is with IEC but see NEC 310 for the recommended derating factor.

RE: about chiller feeder

Can you check the FLA on the nameplate of the chiller? I normally used this in getting the size of the conductor for chiller.

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