Wire size.

[mike7330]

I’m look at a chiller replacement job.
Existing chiller is using (3) 500kmcl 385amp 75c
New chiller MCA 388.5
Anyway around this ? Or pull 3 new 600kmcl
My thoughts are new 600kmcl
Just seeing if there’s a way to save owner some money
Thanks


Sent from my iPad using Tapatalk

 

[Ingenieur]

can you apply any ambient temp adjustment?

 

[infinity]

Splice a larger conductor on each end with a 90° C connector.

 

[Ingenieur]

Splice a larger conductor on each end with a 90° C connector.

lol
clever

 

[mike7330]

Thanks!
There’s room in the switchgear at the bottom to splice and I will need to extended wires on roof, so I’ll will just add
WP pull/splice box on roof

Happy Veterans Day to our men and women and for your service to our great country

 

[Ingenieur]

Thanks!
There’s room in the switchgear at the bottom to splice and I will need to extended wires on roof, so I’ll will just add
WP pull/splice box on roof

Happy Veterans Day to our men and women and for your service to our great country

is the ckt run on the roof top or interior clg?

 

[mike7330]

is the ckt run on the roof top or interior clg?

Circuit runs inside building, through roof to existing disconnect
I’m planing on running additional conduit on elevated mechanical structure

 

[kwired]

Reality is that unit probably never draws full rated load, yet code says you need higher ampacity conductors. If you can save some $$ with the method suggested I think it is OK. Make sure whoever pays the bills knows what kind of $$ you had saved them, or if they are really high on conforming with what is usual or are afraid of insurance, OSHA, etc. then change the conductors anyway.

 

[Ingenieur]

Reality is that unit probably never draws full rated load, yet code says you need higher ampacity conductors. If you can save some $$ with the method suggested I think it is OK. Make sure whoever pays the bills knows what kind of $$ you had saved them, or if they are really high on conforming with what is usual or are afraid of insurance, OSHA, etc. then change the conductors anyway.

doesn't the mfg's mca have 25% headroom?
and he's only 1% shy

if in an temp conditioned/controlled space <77 F take the 5%

can he use the eq to calc ampacity vs table?
will it be higher?

 

[kwired]

doesn't the mfg's mca have 25% headroom?
and he's only 1% shy

Sure it does, but unless a 100% rated device he still needs 125%

if in an temp conditioned/controlled space <77 F take the 5%

That is certainly possible to do also, if routed through space that is that temperature. Some portions of the circuit could be subject to higher temps, some lower temps.

can he use the eq to calc ampacity vs table?
will it be higher?

Lost me, what is eq?

Still have seldom if ever seen a compressor unit that draws RLA unless it has something wrong with it or was improperly selected for the application. Modern chiller is likely variable speed or multi-stage and won't even have much of a chance to draw RLA except when hottest design temp of the system is reached, which is maybe just a day or two every few years.

 

[mike7330]

No name plate

No name plate

I wish I had the name plate to unit, all I have is the spec sheet from manufacture
This unit is 208/ 230 3p
Building is 208 volt so I would error on the side of the higher ampacity rating and especially
On a hot summer day.
Yes the chiller is staged with 4 compressors and 6 cooling fans, but load has been calculated for full load
And 450 amp feeder breaker
I can’t use any temp derating because of some of the rooms the conduit is installed in

I would like to thank everyone, I plan on giving them 2 quotes for new 600kmcl and 90 c
Splices with explanations