If I remember correctly the ones in my mill are 4 amps. If too much current passes through the heater it will open the contacts and stop the motor. They are essentially internal circuit breakers. You haven't mentioned what type of mill you have, but most commercial 3 phase models have overloads, sometimes referred to as "heaters" in each line. I could replace the 50 amp breaker with a 20 or 30 amp one, but that still wouldn't protect the machine. It doesn't need nearly that much power, just an outlet with that configuration to meet code. I have my Bridgeport running on a dedicated 50 amp circuit just because it was available in the load center. In that case I would 100% agree with your thinking - then 14 or 12 ga wire is the only option in that setting.Īs mentioned a circuit breaker upstream of the machine protects the infrastructure wiring, not the machine. That's why Federal is out of business (shame - I liked Stab-Loc until then) The other possible reason is that when you install breakers in an industrial panel, you usually choose the slower blowing breakers due to transients in factory settings. Thre are two possibilities as to why that didn't happen: Firstly is that if the breaker was a Federal Stab-Loc and manufactured in the right time period (30 years ago is about right) - they went through some serious quality control issues that burnt down a bunch of houses and a few factories (the breakers wouldn't trip). it should have tripped the breaker in under 100 milliseconds. breakers are there to prevent fires in case of a short. My welders all use 4 gauge 19 strand ultraflexible cables, because I hate cable failures, but I only need to make the lead in once for my has the right of it. All my machines except my welders use 12 ga 19 strand rubberized cable. Just use a 50A approved plug and reasonable lead in cable. I don't know how many table saws I've seen with burnt out motors that never tripped the breaker. Each circuit will deliver the exact same knockout punch to your motor. If you stall the motor - you will burn it out on a 20 am circuit just as badly as on a 50 amp circuit. If you overwork your motor, and it overheats, they you lose the motor. Remember: this does nothing to protect your equipment, and certainly not your motor. Even if you have a 12 ga lead to your machine and you somehow short it, it will still throw the breaker - if you use a 50 amp plug. but you aren't actually protecting anything. If you have extra breaker positions in your panel, by all means get a 20A breaker and make a new circuit. that's because it only has to trip a 15 amp breaker, which needs about 40-100 milliseconds to do. You cannot carry 15 amps for even 10 minutes on that cord, but until sewing machines became computerized there was NEVER a breaker or fuse in them. Step away from your current situation for a minute and consider your wife's 1/6 HP sewing machine with the 18 gauge line cord. I've been staying away from this one, but I just have to intervene. (I'm not sure the numbers in my example are exact because it was 35 years ago.) After a few seconds, before the breaker popped it was hot enough to bubble the outer jacket and so we went up to 14 Gauge. I disagreed but he didn't change his mind until I ran the cord on the concrete floor, shorted it at the end and turned on the breaker. Maybe put in a couple of other convenience outlets while you are at it.Ī very long time ago a former boss insisted that a ~40 Foot, ~18 Gauge SJT cord off of the output of an isolation transformer, protected by a 15A breaker was a good cost saving idea. It is not that difficult or costly to DIY. My advice is to do it right and put in a small, inexpensive sub panel with an appropriate breaker and appropriate wire gauge. So, the smaller wire is somewhat protected, to a point.Ī 15A protected short is less dramatic than a 50 Amp one. The cord usually has a large enough wire gauge and is short enough/low enough resistance to pop the 15A breaker quickly if shorted.
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