500 Amp Wire Size

Status
Not open for further replies.
I have a chiller that needs 500 Amps. It is actually drawing 474 amps. I think i need 750 MCM. IS that right? Also if i was to parallel this would i need 250 MCM?
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
sullyelectric said:
I have a chiller that needs 500 Amps. It is actually drawing 474 amps. I think i need 750 MCM. IS that right? Also if i was to parallel this would i need 250 MCM?

Got a link to the chiller specs?
 

charlie

Senior Member
Location
Indianapolis
:)
sullyelectric said:
. . . I need 750 MCM, IS that right? Also if I was to parallel this would I need 250 MCM?
Correct unless it is a continuous load and if you had two runs of 250 kcmil in separate conduits. This is all contingent on what the manufacturer's instructions require.
 
i havent even seen it yet. i just got the call this afternoon and im going by to look at it tomorrow morning, i will check the specs.
 

charlie

Senior Member
Location
Indianapolis
chris kennedy said:
Got a link to the chiller specs?
It is interesting how many times one person is typing while another is posting. One of these days, I will start checking before I pull the trigger on my own posts. :rolleyes: Looking at the bright side, Chris and I ended up saying about the same thing. :)
 

benaround

Senior Member
Location
Arizona
sullyelectric said:
I have a chiller that needs 500 Amps. It is actually drawing 474 amps. I think i need 750 MCM. IS that right? Also if i was to parallel this would i need 250 MCM?

sully, a chiller would be a contious load 474 x 125% = 592.5 amps, that the

conductors would need to be rated for. Paralell 350mcm in seperate conduits

with a #1 in each conduit for the EGC, all copper. I don't think it can be

done with just 1 conductor per phase, unless cable tray is used.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
You really need to complete nameplate information. A chiller could have an MCA rating which would be used to size the conductors without the need to add 25%.
 
the min cir ampacity is 474 amps on the nameplate. i think i will be running paralell 4/0 thhn. that should give me 520 amps. does the breaker i am using need to be rated for 90 degree wire?
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
sullyelectric said:
the min cir ampacity is 474 amps on the nameplate. i think i will be running paralell 4/0 thhn. that should give me 520 amps. does the breaker i am using need to be rated for 90 degree wire?
Yes it does. Let me know where you find one. If you do the terminations on the other end will most likely be 75C rated so your wire is good for 460 amps.
 

iwire

Moderator
Staff member
Location
Massachusetts
I agree with Chris, parallel 4/0s will not make it as there are no 90 C breakers.

There are some workarounds but why re-invent the wheel?

With an MCA of 474 in my opinion these are the minimum size copper conductors forgetting any ambient temperature adjustments.

One run of 750 copper

Two runs of 250 copper in separate raceways

Two runs of 300 copper in one raceway
 

iwire

Moderator
Staff member
Location
Massachusetts
Jraef said:
If you buy a 100% rated breaker (extra cost), they typically come with 90C lugs. Sometimes that is the only difference.

But the breaker instructions will tell us to size based on 75C. Correct?
 

iwire

Moderator
Staff member
Location
Massachusetts
electricalperson said:
a lot of lugs i buy now come 90c. maybe someday in the future breakers with 90c lugs will be common

My understanding is it is not just a matter slapping on 90 C lugs. The breaker itself would have to be designed to operate within specification with conductors approaching 194 F hanging off of the breaker terminals. Seems like a tough challenge with a thermo magnetic breaker. :)

Besides, would you want to feel a breaker that ran that much hotter then loaded 75 C breakers? :smile:
 
Status
Not open for further replies.
Top