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Norm, Master Electrician
Category: Electrical
Satisfied Customers: 67
Experience:  Registered professional electrical engineer and licensed master electrician.
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I have an industrial (mid-size) combination shredder/baler

Customer Question

I have an industrial (mid-size) combination shredder/baler donated to us. It runs on 480 and requires 36 running amps, with a surge of 42. The power in our warehouse is 208 @ 200 amps. I have space in my primary panel for connection but will néed to "step up" the voltage from 208/220 to 480. I am not sure how to size the transformer and what I need to look for. I can follow wiring diagrams and wired our warehouse (it was approved by the electrical inspector) and have required motors for higher and lowers voltages over the years. I know how to use a volt meter and don't take shortcuts when it comes to safety. Can anyone out there tell me/explain to me what size transformer I need.
Submitted: 4 years ago.
Category: Electrical
Expert:  Norm replied 4 years ago.
Hi, I'm Norm and I'd like to help. First, I think you need to look at your total available power in the warehouse. 36 Amps at 480 Volts 3-phase is almost 30 kVA, and will require almost 100 Amps at 208 Volts. That's half your total capacity. Can you supply that much beyond what you are already using? And that's not all. Starting the shredder will take 5 to 6 times that much, which may well trip your main breaker, depending on what it is. A transformer would have to be rated more than 30 kVA to be able to start something that size and maintain adequate voltage. Just how much bigger is a question to be addressed to the manufacturer of the machine. If you think you can spare that much power, I can dig a little deeper if you supply the information from the shredder nameplate, and we can see what size transformer they would recommend. I looked at a few transformers and it looks like a new one in the 45 kVA range might run $2-3000. Please let me know if you want me to get more info.

Customer: replied 4 years ago.
Sorry I didn't get your message until now. I left the office about 8:10.

I will have to get the additonal info from the plates tomorrow. They were painted over and I will "gently" use some paint remover gel I bought on the way home. I'll send you pictures afterwards so you have the complete info.

My ratings were based upon technical support from the manufacture for the machine's serial #. Admittedly, not the most exact way of getting the numbers. But your cost for a transformer might preclude us from using it in the short term unless we can buy a used one on Craig's List, get a used one donated or horse trade with a local contractor. Before I started down this path I wanted an independent electrician (you) to review the possibilities so I could be an "educated consumer."

I will also send you a list our current electrical loads. How should I send you the pictures. Is this possible?

Also, we provide employment and training for adults with developmental disabilities. So I don't take any shortcuts when it comes to safety. Thanks. For your questions. I'll get back to you tomorrow. Jack

Expert:  Norm replied 4 years ago.
You can send pictures through the paper clip icon on the JustAnswer screen. If you would rather, you could just list the other loads on the 208 Volt panel and I might be able to see where you stand from that.

Expert:  Norm replied 4 years ago.
The more I think of your situation, the more I think the shredder is just too big for your service. Table 430.52 of The National Electrical Code permits an instantaneous trip breaker as much as 8 times the motor running current and the MAIN breaker on your service panel is only twice the shredder running current. If that breaker were an inverse time delay type (doubtful), it could be as low as 2.5 times running current. I think it likely that a shredder will be a hard-starting load and would trip the main breaker on your panel when it tries to start. If you can get me the nameplate and manufacturer information, I can dig deeper and maybe I'm just being pessimistic, but we should have more information about this machine before you commit to buying a transformer for it.

Customer: replied 4 years ago.



Sorry for the poor form in getting back to you. Life, family and work got in the way. I believe that you are right. While we are only using about 40% of capacity currently, we will need to begin using ac units to keep the sheltered workshops cool during the summer. The 4 units will take us over 50% of available power.

I looked into adding extra power and it's way out of our budget. So I think we are going to sell the unit and try and get another paper cutter hooked up instead.


Thanks for your help and giving me the information I needed to make a decision. Let me know what I need to do so that you can get paid.





Expert:  Norm replied 4 years ago.
Hi Jack,

All you have to do is click "accept" on your screen. Thanks for your response and good luck with your project.


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