i've spec'd out 250 mcm copper thhn for a machine we are installing. it has a rating of 245 amps at full load. it's a 3 wire 480v machine. acording to what i'm decifering in the code book, 250 mcm will give me 260 amp capacity. the mfg spec's say 2/0 copper. whose right? also, though i've never done this, i've heard u can parallel smaller size copper instead of the 250 mcm. what's the skinny on this.
size wire for 245 amp 480v machine
- Thread starter boday
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Re: size wire for 245 amp 480v machine
boday, you're not giving nearly enough information. Is this a factory built assembly? If so the manufacturer should spec the minimum/maxium service size. I worked for many years designing, building and installing custom built industrial machinery and systems and I always specified utility capacities and requirements to the buyer/user. If they won't or can't you need to get all of the motor specs and voltages and anything else that uses power on this machine and post it to this site.
Good luck
Hillbilly
P.S. Are you working in maintenence or otherwise involved in the actual install/start-up of this system?
boday, you're not giving nearly enough information. Is this a factory built assembly? If so the manufacturer should spec the minimum/maxium service size. I worked for many years designing, building and installing custom built industrial machinery and systems and I always specified utility capacities and requirements to the buyer/user. If they won't or can't you need to get all of the motor specs and voltages and anything else that uses power on this machine and post it to this site.
Good luck
Hillbilly
P.S. Are you working in maintenence or otherwise involved in the actual install/start-up of this system?
Re: size wire for 245 amp 480v machine
hillbilly: yes i'm in maintenance and involved with the machines install. the machine is a four head industrial sander. powered by 480v source. it has 2 40 hp polyphase motors, 2 25 hp polyphase motors and a 15 hp motor to drive the conveyor bed. the spec plate on the machine says total amp load is 245amps. i can supply additional info. it's a german machine so it may be telling me what i need to know except i can't read german. the factory men will be here to set it up. i need to have the electrical hook up done before they arrive. thanx for ur help- bj
hillbilly: yes i'm in maintenance and involved with the machines install. the machine is a four head industrial sander. powered by 480v source. it has 2 40 hp polyphase motors, 2 25 hp polyphase motors and a 15 hp motor to drive the conveyor bed. the spec plate on the machine says total amp load is 245amps. i can supply additional info. it's a german machine so it may be telling me what i need to know except i can't read german. the factory men will be here to set it up. i need to have the electrical hook up done before they arrive. thanx for ur help- bj
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: size wire for 245 amp 480v machine
Mfg may be correct, esp if all the motors can not operate at the same time or "Non-concurrent" operation. Typically conductor sizing for a factory machine is done per the mfg's nameplate, the answer to your question is Article 430 section 430.25.
And yes you can parallel conductors per Section 310.4, although you may not gain much under 250 KCML
Mfg may be correct, esp if all the motors can not operate at the same time or "Non-concurrent" operation. Typically conductor sizing for a factory machine is done per the mfg's nameplate, the answer to your question is Article 430 section 430.25.
And yes you can parallel conductors per Section 310.4, although you may not gain much under 250 KCML
Re: size wire for 245 amp 480v machine
Boday
You need to check your code book. 250kcm is not rated for 260 amps and if it were, it would not be the correct conductor size given the info from your post. As suggested above you need to check with the mfg and get the correct information.
Boday
You need to check your code book. 250kcm is not rated for 260 amps and if it were, it would not be the correct conductor size given the info from your post. As suggested above you need to check with the mfg and get the correct information.
- Location
- Massachusetts
Re: size wire for 245 amp 480v machine
I agree with Tom, the manufacturer will know the requirements of their product.
If I was selling equipment I would not tell customers to bring a feeder capable of running all the loads at the same time if I knew that the loads could not be run at the same time.
Also this is unit equipment/motor loads which are allowed to have larger breakers then the capacity of the conductors.
A 250 amp breaker with 2/0 could be entirely code compliant, and adequate.
No, it is rated for 255 amps, he was off by 5 amps or if he happens to have 90C terms it is rated 290 amps.
I agree with Tom, the manufacturer will know the requirements of their product.
If I was selling equipment I would not tell customers to bring a feeder capable of running all the loads at the same time if I knew that the loads could not be run at the same time.
Also this is unit equipment/motor loads which are allowed to have larger breakers then the capacity of the conductors.
A 250 amp breaker with 2/0 could be entirely code compliant, and adequate.
charlie tuna
Senior Member
- Location
- Florida
Re: size wire for 245 amp 480v machine
stay with the manufacturer's recommendations on wire size and overcurrent protection -- your butt will be covered. let me ask you a more important question "what size ground conductor are you going to install?"
stay with the manufacturer's recommendations on wire size and overcurrent protection -- your butt will be covered. let me ask you a more important question "what size ground conductor are you going to install?"
Re: size wire for 245 amp 480v machine
thanx u guys; i did make a mistake with the 250 mcm, and i agree with 2/0 seeing that the motors do not start all at once. it's a sequenced start. so u guys are great. ground, i was thinking no. 3. now, here's something to discuss. this is not the first machine of this type to be installed in the plant. the first 2 were before my time. they put 600 mcm on the machines which is way overkill. additional this type of sander, the conveyor bed is fixed and the whole machine moves up and down depending on the thickness of the wood doors it's sanding. their solution was to run 3' emt to the machine and use flex the last 3 ft. they're using thhn for the conductor. i'm not comfortable with this. i had considered using 2/0 welding cable but i don't think the insulation thicknes will be code. the ultimate solution is to hard pipe to a crouse-hinds non-fusible pin/sleeve disconnect , and make up a pin and sleeve pigtail using 2/0 sjo. however nobody makes a pin and sleeve over 200 amps, and i'm not sure i need that big of connector type system, seeing that the machine does not suck up 245 amps on start up. what do u think -bj
thanx u guys; i did make a mistake with the 250 mcm, and i agree with 2/0 seeing that the motors do not start all at once. it's a sequenced start. so u guys are great. ground, i was thinking no. 3. now, here's something to discuss. this is not the first machine of this type to be installed in the plant. the first 2 were before my time. they put 600 mcm on the machines which is way overkill. additional this type of sander, the conveyor bed is fixed and the whole machine moves up and down depending on the thickness of the wood doors it's sanding. their solution was to run 3' emt to the machine and use flex the last 3 ft. they're using thhn for the conductor. i'm not comfortable with this. i had considered using 2/0 welding cable but i don't think the insulation thicknes will be code. the ultimate solution is to hard pipe to a crouse-hinds non-fusible pin/sleeve disconnect , and make up a pin and sleeve pigtail using 2/0 sjo. however nobody makes a pin and sleeve over 200 amps, and i'm not sure i need that big of connector type system, seeing that the machine does not suck up 245 amps on start up. what do u think -bj
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