Motor Starter Wiring

makes perfect sense. I will look into that, I do have a small transformer I can mount on there. Maybe I will just get 120v coils then.
 
Just one other small note here: Current code will not allow remote push button voltages greater than 120v. The only time full voltage push buttons is allowed today is when the buttons are integrated into the starter enclosure by the manufacturer.
 
Just one other small note here: Current code will not allow remote push button voltages greater than 120v. The only time full voltage push buttons is allowed today is when the buttons are integrated into the starter enclosure by the manufacturer.
Interesting. I've been out of the industrial side for awhile now. What code is this? I'm assuming the IEC?
 
Interesting. I've been out of the industrial side for awhile now. What code is this? I'm assuming the IEC?

I'd assume it's from NFPA 79 Electrical Standard for Industrial Machinery. In Chapter 9.1.1.1 they state "Where control circuits are supplied from an ac source, control transformers shall be used for supplying the control circuits . Control circuits shall not be derived from autotransformers. Control circuits supplied from windings of multiwinding power transformers shall be permitted if the output voltage of the winding supplying the control circuit does not exceed 120 volts ac and the available short-circuit does not exceed 1000 amperes rms." When they specify "shall" it is required & not optional. Reading NFPA 79 can be a 'carreer' pita but if you are designing or producing machinery for others it's recommended to comply. For personal use equipment nitpicking might be over looked. My only concern would be if one were to sell a machine that "violated" these rules they might be liable legally for any injury. The above quotes are from NFPA 79 2012 Edition.
 
I thought of that code just after I posted. I don't have a copy available. It reads like a separate control circuit would be OK if not supplied from a transformer.
 
I thought of that code just after I posted. I don't have a copy available. It reads like a separate control circuit would be OK if not supplied from a transformer.

A separate circuit is OK, also a circuit supplied by a control transformer is OK, but an autotransformer is not allowed.
 
That's exactly how I read it jimdawson

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A separate circuit is OK, also a circuit supplied by a control transformer is OK, but an autotransformer is not allowed.

I don't think so. Regarding a separate circuit, they simply state that 120 vac control power SHALL be supplied with a control transformer. My take on that is that control power is insulated from higher supply voltages and is also current limited. The 480 vac situation previously discussed would subject operators to potential arc flash since much higher currents can be available. This will preclude using 120 vac from a supply panel if that is what you meant by a separate circuit. Also, as you probably know, NFPA is the agency that writes the NEC.
 
A project such as this is usually way over the head of someone who does not do this work daily. Hence the reason I suggested earlier to hire a pro. They have to eat too you know! The real problem here is safety. Not only yours but others. I lived with the NEC and inspectors for over forty years. I also had a UL508 certification for building industrial control equipment.

Please, if you won't believe me, believe uncle harry, when the code says you shall, it means you "WILL". No arguments, no exceptions, no nothing.

Also if you have not checked into it yet, depending on what starter you are dealing with, the parts can be hard to find and damned expensive when you do. Translation, you can probably buy a used starter for way less then two replacement coils. Go on fleabay and look up reversing starters. I have found units there so cheap compared to new it is crazy. I have purchased units good for 5hp for as little as $40.00. Only thing left then is to find the correct heaters for the overload block. All manufacturers have changed to electronic adjustable overloads making finding separate eutectic heaters a harder and more expensive venture. Keep this in mind when choosing a starter. Also, believe it or not, electrical components wear out. Just like most other things so maybe a newer starter even has more merit.

Even after all these years I still do not feel relaxed around 480v equipment like I do at the lower voltages. Just be safe, 480v will kill you in less than a heartbeat.
 
A project such as this is usually way over the head of someone who does not do this work daily. Hence the reason I suggested earlier to hire a pro. They have to eat too you know! The real problem here is safety. Not only yours but others. I lived with the NEC and inspectors for over forty years. I also had a UL508 certification for building industrial control equipment.

My thoughts exactly. There very basic nature of the original question suggests that this should be done by a professional.


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