4160V Chiller

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faresos

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I havn't delt much with equipment that are rated more than 600V. My question is; How do I size conductors, conduits and overcurrent devices (fuses or breakers) for 4160V Chiller? here are the info I have from the cut sheets:
Motor LRA= 223A
Primary RLA=42.5A
MCA=55A
MOCP=70A

I know the cut sheets indicate all those info but I just need to know if the math is done as the same as the 600V equipment. Also, what table do I need to use to figure out the conductor size (will be run overhead in conduit) for the Chiller. (this is an existing Chiller, 250ton, and will be replaced with a new one, 500ton). The existing cable is 3#2(5kv, EPR,insulated, 1/c.

your response is really appreciated
 
#2 5 kv EPR is going to be rated about 130 amps so it is well within the required rating. What is the OC rated and what type OC?
 
Bob, thanks for your respond..

The only OC I see is inside the unit-mounted meduim voltage starter, which will be fuse type. Not sure of size that will be used. This unit is tapped from meduim voltage cable going to a meduim voltage disconnect switch then will be going to the unit (which that's the cable that I will need to provide). What Ampacity table do I need to use and what Temp. rating I need to be looking at to detrmine the size of the conductor? Does the LRA have anything to do with sizing the conductor?

Thanks gain...
 
faresos said:
Bob, thanks for your respond..

The only OC I see is inside the unit-mounted meduim voltage starter, which will be fuse type. Not sure of size that will be used. This unit is tapped from meduim voltage cable going to a meduim voltage disconnect switch then will be going to the unit (which that's the cable that I will need to provide). What Ampacity table do I need to use and what Temp. rating I need to be looking at to detrmine the size of the conductor? Does the LRA have anything to do with sizing the conductor?

Thanks gain...
Click to expand...

A medium voltage starter is very similar to a low voltage starter. The fuses provide short circuit protection and there is an overload relay of some type (electronic is common on 5kV) to provide the running current protection.

The 5kV conductor is sized based on running amps just like at 480V.

So just like the circuits you are familar with:
LRA is locked rotor amps and is typically used in coordination studies as well asto determine the voltage drop during starting.
RLA is the Running Load Amps and is used to size the overload protection
MCA is the Minimum Circuit Amps and is used for sizing the circuit conductors.
MOCP is the Maximum Overcurrent Protection which is used to "size" the fuses. 5kV is a bit different than 480V equipment so check with your fuse manufacturer.
 
faresos said:
here are the info I have from the cut sheets:
Motor LRA= 223A
Primary RLA=42.5A
MCA=55A
MOCP=70A

The existing cable is 3#2(5kv, EPR,insulated, 1/c.

your response is really appreciated
Click to expand...
Your post sounded as if you were going to use the existing cable. If you
are installing new cable it must be shielded Don says but you could use a smaller size. #8 is listed at 55 amps and #6 is rated at 75 amps.
 
faresos said:
What Ampacity table do I need to use and what Temp. rating I need to be looking at to detrmine the size of the conductor? Does the LRA have anything to do with sizing the conductor?

Thanks gain...
Click to expand...

For your information, ampacities for cables rated over 2,000 V are listed in the NEC Tables 310.67 through Table 310.86. I believe you would have to use the Type MV-90 column under the 2,001 V - 5,000 V heading and would need to choose what type of conductor and configuration you would use for the new conductors.
 
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