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The Water Cooler
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220 electrical question
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<blockquote data-quote="Ahall" data-source="post: 4352894" data-attributes="member: 49426"><p>overcurrent protection</p><p>This is how I think about it.</p><p>The breaker in the wall panel is sized to prevent overheating of the wires at the maximum amperage they are rated for. You can pull up to that many amps through the wires without issue.</p><p></p><p>When you plug in a device rated for lower amperage, you need to provide overcurrent protection at that device - a fuse, a breaker, heaters in a motor starter, etc.</p><p></p><p>Table saws are easy enough to bind on heavy rip cuts and the locked rotor current of a single-phase capacitor start motor can quickly fry the capacitors and windings. The concern about protecting the saw from electrical damage is valid, and I write with the wisdom that only comes with experience. If you ever pay someone to rewind a motor with a goofy frame, you will appreciate the value of good overcurrent protection.</p><p></p><p>Having rebuild, rewired and repaired many wood working machines, something jumped out at me. The first post indicated 17 amps at 220 V, that's roughly 5 hp, which is typical of a cabinet saw, like the Powermatic 66 or Delta Unisaw. Classic light professional class saws.</p><p></p><p>All bets are off on a used saw that bubba messed with, but from the factory most equipment in the 5hp range had a motor starting system that was more sophisticated than your average light switch.</p><p>There is a very good chance the saw has some kind of overcurrent device already engineered into the motor starting device on the saw. Use the breaker to protect the wires to the plug. Incorporate a second device at the machine to protect the machine. This has been the normal approach in light professional woodworking machines for well over 50 years.</p><p></p><p>Before spending money on additional overcurrent protection post some photos of the electrical gear on the saw. You may already have the overcurrent device your worried about needing.</p><p></p><p>Also, if you decided to change the saw from 110 to 220V, by swapping some wires at the motor, good chance there are other things in the motor starter that need to be addressed as well.</p></blockquote><p></p>
[QUOTE="Ahall, post: 4352894, member: 49426"] overcurrent protection This is how I think about it. The breaker in the wall panel is sized to prevent overheating of the wires at the maximum amperage they are rated for. You can pull up to that many amps through the wires without issue. When you plug in a device rated for lower amperage, you need to provide overcurrent protection at that device - a fuse, a breaker, heaters in a motor starter, etc. Table saws are easy enough to bind on heavy rip cuts and the locked rotor current of a single-phase capacitor start motor can quickly fry the capacitors and windings. The concern about protecting the saw from electrical damage is valid, and I write with the wisdom that only comes with experience. If you ever pay someone to rewind a motor with a goofy frame, you will appreciate the value of good overcurrent protection. Having rebuild, rewired and repaired many wood working machines, something jumped out at me. The first post indicated 17 amps at 220 V, that's roughly 5 hp, which is typical of a cabinet saw, like the Powermatic 66 or Delta Unisaw. Classic light professional class saws. All bets are off on a used saw that bubba messed with, but from the factory most equipment in the 5hp range had a motor starting system that was more sophisticated than your average light switch. There is a very good chance the saw has some kind of overcurrent device already engineered into the motor starting device on the saw. Use the breaker to protect the wires to the plug. Incorporate a second device at the machine to protect the machine. This has been the normal approach in light professional woodworking machines for well over 50 years. Before spending money on additional overcurrent protection post some photos of the electrical gear on the saw. You may already have the overcurrent device your worried about needing. Also, if you decided to change the saw from 110 to 220V, by swapping some wires at the motor, good chance there are other things in the motor starter that need to be addressed as well. [/QUOTE]
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