Whoops, Brock you were posting as I was writing!
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| Question about Electrical Service http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10102&t=13940 |
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| Author: | Brock Poling [ Mon Oct 08, 2007 8:03 am ] |
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I have a question about electrical service (I admit I really don't know a lot about this stuff). In my panel I have a dedicated circuit for my bandsaw. It has 2 20A breakers ganged together and wired to a single 220 outlet. Is this a 20A circuit or a 40A circuit? I am trying to figure out if I can plug my 28A table saw into this outlet. |
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| Author: | David Collins [ Mon Oct 08, 2007 8:15 am ] |
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20A. Twice the wattage of a 20A 110V circuit by means of doubling the Voltage, but the amperage rating stays the same. What on earth motor do have that's rated at 28A? That would be enough amperage to power a 7 or 8 hp motor at 240v. Are you sure the 28A rating is for 220, or is that the 110 rating (which would put the 220 at 14A)? |
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| Author: | Brock Poling [ Mon Oct 08, 2007 8:57 am ] |
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It is a Grizzly 1023ZX 5HP 220V 10" Cabinet saw. The manual says it needs to draw 28A. |
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| Author: | davidmor [ Mon Oct 08, 2007 8:58 am ] |
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Actually according to the NEC, the full load current of a 230V 5hp 1ph motor is 28A. Of course, you need to look at the nameplate to get the actual rating, but the NEC is usually pretty darned close to nameplate. Double check the nameplate and make sure you aren't reading the wrong amperage rating if you have a smaller motor. Many motors are dual voltage and have ratings that look something like this Voltage 115/230 Amperage 16/8.8 . The first voltage goes with the first amperage, the second goes with the second. If it really is 28 amps nameplate, code requires the circuit be 125% of the nameplate which would be 35 amps. That is #8 copper on a 40 amp breaker (40 amp double pole both breakers rated at 40 amps.) You could go with a 35 amp breaker, but good luck finding one! |
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| Author: | davidmor [ Mon Oct 08, 2007 8:59 am ] |
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Whoops, Brock you were posting as I was writing!
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| Author: | Bruce Dickey [ Mon Oct 08, 2007 9:10 am ] |
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Check the Motor for a plate similar to this one. It gives two voltages, then two amperages, normally. Evidently this motor will run on 208, so it has a third voltage and amperage. This motor will run on the following: 115 Volts at 17.4 Amps, or 208 Volts at 8.9 Amps, or lastly at 230 Volts at 8.7 Amps. Your choice of breakers is 30 amp single pole 115 Volts, or double pole 20 amps 23 Volts. The reason you need a 30 instead of a 20 on the 115 Volt circuit is the 80 percent rule of use on a breaker. A 20 amp will only net you output of 16 amps, so you have to go 30 amps which nets you 24 amps, if you run a 115 V. Circuit. This is the math, not for your motor, which we are unsure of, but the label above for a motor on Ebay. Ebay is a great place to get electric motors for a fraction of it's value. Good luck, get it right. Know the definition of Ampacity. |
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| Author: | A Peebels [ Mon Oct 08, 2007 11:33 am ] |
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Looks like we have a good supply of very competent electricians. All correct info. Al |
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| Author: | James W B [ Mon Oct 08, 2007 12:36 pm ] |
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Plug it in and see if it throws the breaker.If not, your in there. James |
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| Author: | David Collins [ Mon Oct 08, 2007 1:18 pm ] |
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And just to make sure you know, you certainly should never just replace a breaker with a larger one. If it has a 20 amp breaker right now, that probably means it has 12 gauge wire running to the outlet. If you were going to up the breaker to 40 amps there are a few other things to consider. Of course the overall rating and load of the box as a whole, and you would need 8 awg wire past the breaker to meet standard electrical codes. Even that can depend on the length of the run, and things like a 90 degree turn may equal 10 or 20 feet, and it may even differ depending on whether you are running in conduit, rafters, or in a wall. Check with your local codes (or better yet, a local electrician) to make sure. But don't just change to a larger breaker because it's popping. |
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| Author: | David Collins [ Mon Oct 08, 2007 1:32 pm ] |
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I should say that I bring this up because my brother just had a house fire start inside a wall a few weeks ago due to a stupid mistake someone made 20-some years ago, before he bought the house. The fire department was there in about 10 minutes, and all that was damaged was one interior wall, the electrical, and smoke damage to a few rooms. It could have been much worse. Wiring is certainly not something suitable for jury-rigging. Make it right. After all, it is National Fire Prevention Week, ya know. 
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| Author: | Bruce Dickey [ Mon Oct 08, 2007 10:36 pm ] |
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Something tells me Brock is going to be running new service from the panel. But oh what a joy running a great cabinet saw can be.... oh yeah! |
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| Author: | donh [ Tue Oct 09, 2007 12:45 am ] |
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The manual downloaded from the Grizzly site says "The motor supplied with the Model ZX is a 5HP 220V single-phase motor. Under normal use, the motor draws approximately 25 amps. Use a 30-amp circuit breaker or 30amp slow blow fuse for 220V operation." Then they describe the NEMA L6-30 plug and socket they recommend for wall termination, and recommend a dedicated circuit. If they have upped this recommendation since this manual was created, then you should go for the 40amp circuit and an upgraded plug/socket. |
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| Author: | Brock Poling [ Tue Oct 09, 2007 1:16 am ] |
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[QUOTE=Bruce Dickey] Something tells me Brock is going to be running new service from the panel. But oh what a joy running a great cabinet saw can be.... oh yeah![/QUOTE] Yes, this will be a new circuit. I actually had an electrician come out and install a new sub panel for me (I think it is a 100A service -- it's half as big as the main panel) It only has 2 circuits in it now, the one for the bandsaw, and another for a 20A receptical. I feel comfortable wiring recepticals etc (provided I know what the right ratings are on parts etc.) but I don't feel comfortable doing panel work. Afterall... this is in my house where my kids sleep. 
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| Author: | Bill Greene [ Tue Oct 09, 2007 1:22 am ] |
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I had the pleasure of meeting, and hanging out with, Al Peebels for a few hours on Saturday. Among other things, Al works tests and rebuilds large electric switch controllers for nuclear power plants. He was testing circuits on some of their "smaller" machinery with 6000+ amps - on a machine that runs to 100,000 amps. Scary, scary stuff. Bill, who can't rewire a light switch |
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