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unisaw wiring? 20 or 30 amp circuit?
im wiring my shop and have 2 pieces of equipment i am not sure of. a
true 3 hp compressor and a 3 hp unisaw. is a 20 amp circuit enough for each or these or do i need to go to 25 or 30 amp? the compressor says it needs 15.4 amps and the tablesaw says 15.5 amps. thanks all ... skeez |
#2
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unisaw wiring? 20 or 30 amp circuit?
In article ,
skeezics wrote: im wiring my shop and have 2 pieces of equipment i am not sure of. a true 3 hp compressor and a 3 hp unisaw. is a 20 amp circuit enough for each or these or do i need to go to 25 or 30 amp? the compressor says it needs 15.4 amps and the tablesaw says 15.5 amps. thanks all ... NEC limit for permanently attached devices is 80% of breaker rating. Which is 16A for a 20A breaker. So, you're OK on _that_ basis. Then, there is the issue of 'start up' load, vs 'running' load. Virtually any motor draws more power spinning up, than it does running 'at speed'. However, with the table-saw, the start-up current draw is _probably_ not going to approach the draw of a maximum-load cut. The compressor probably has 'smarts' so that the motor starts up 'unloaded', and then picks up the load. Me, I'd 'over-engineer' the solution, and see what happens. After all, wire is _cheap_. Pull 10 ga. wire, and use a 20A breaker, initially. Preferably a 'motor rated' (or slo-blow) one, if I can lay hands on it. In the context of _that_ wiring approach, If the 20A breaker trips too frequently, it _is_ safe to replace the 20A breaker with a 25A or 30A one. |
#3
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unisaw wiring? 20 or 30 amp circuit?
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#4
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unisaw wiring? 20 or 30 amp circuit?
Easy answer---call the permit guy. They are paid to give you free
advice on such matters. Then go one size over on whatever they tell you---ie if they say 12ga wire, use 10, if they say 25 amp use 30. You could look it up in the code yourself if you want, but I would rather go to the dentist. permited and inspected also. im thinking 30 amp is the best way to go |
#5
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unisaw wiring? 20 or 30 amp circuit?
"skeezics" wrote in message ... i didnt think about the startup draw. thanks. this is going to be permited and inspected also. im thinking 30 amp is the best way to go but i am not sure if i can use a three wire plug or if i have to use a 4 wire plug and change all my equipment over to 4 wire. i know i need 4 wire for such things as dryers and stoves but that seems to be overkill for ww equipment. any ideas? skeez I wouldn't assume that 30A is the best way to go. Your startup current is unlikely to be so great that you need to go that high. 20A should be fine. What are you using now? Are you tripping breakers? What does the equipment manufacturer recommend? One idiosyncrasy about posting questions like yours here is that you can get a lot of not-so-informed opinions from a lot of very well meaning people. Often, they tend to the recommendation that more is better, and that is simply not always true. There are places to go and get the factual information you need and you would be better served seeking those out. Have you asked an electrician? There are some who post here - it would be worth your while to wait on their input if you don't do any other research. -- -Mike- |
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unisaw wiring? 20 or 30 amp circuit?
If you are running 10ga why would you ever use less than a 30a breaker on a
motor load? BTW If this was a test question the correct answer would be min14 ga wire and a max40a breaker. (long story but it is on the inspector's test) hint: you can use 310-16 at the full rating on a motor not 240.4(D), O/C device can be 250% of FLA and round up to next breaker size. I guess the real answer is "what do the instructions from the manufacturer say?" |
#7
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unisaw wiring? 20 or 30 amp circuit?
If there is no neutral load (all 240v) you don't need 4 prong plug.
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#9
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unisaw wiring? 20 or 30 amp circuit?
skeezics wrote in
: On Wed, 28 Jul 2004 15:29:29 +0000, (Robert Bonomi) wrote: In article , skeezics wrote: im wiring my shop and have 2 pieces of equipment i am not sure of. a true 3 hp compressor and a 3 hp unisaw. is a 20 amp circuit enough for each or these or do i need to go to 25 or 30 amp? the compressor says it needs 15.4 amps and the tablesaw says 15.5 amps. thanks all ... NEC limit for permanently attached devices is 80% of breaker rating. Which is 16A for a 20A breaker. So, you're OK on _that_ basis. Then, there is the issue of 'start up' load, vs 'running' load. Virtually any motor draws more power spinning up, than it does running 'at speed'. However, with the table-saw, the start-up current draw is _probably_ not going to approach the draw of a maximum-load cut. The compressor probably has 'smarts' so that the motor starts up 'unloaded', and then picks up the load. Me, I'd 'over-engineer' the solution, and see what happens. After all, wire is _cheap_. Pull 10 ga. wire, and use a 20A breaker, initially. Preferably a 'motor rated' (or slo-blow) one, if I can lay hands on it. In the context of _that_ wiring approach, If the 20A breaker trips too frequently, it _is_ safe to replace the 20A breaker with a 25A or 30A one. i didnt think about the startup draw. thanks. this is going to be permited and inspected also. im thinking 30 amp is the best way to go but i am not sure if i can use a three wire plug or if i have to use a 4 wire plug and change all my equipment over to 4 wire. i know i need 4 wire for such things as dryers and stoves but that seems to be overkill for ww equipment. any ideas? skeez I asked my electrician, who is also a woodworker. We put in a 30 amp circuit for my new Unisaw a couple of years ago. With a twist lock receptacle. We also put in a master cutoff switch, with a place for a padlock, to lock out everything on the new subpanel. The lights are on the old subpanel, as are the plugs for the freezer, and non-shop tools. I don't want unsupervised use of the shop by my grown sons, until I'm certain they have a little more experience and safety training. They didn't take shop in school... A master electrician did it right, and I don't worry about it. I have enough to be concerned about. Patriarch |
#10
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unisaw wiring? 20 or 30 amp circuit?
skeezics wrote in message . ..
im wiring my shop and have 2 pieces of equipment i am not sure of. a true 3 hp compressor and a 3 hp unisaw. is a 20 amp circuit enough for each or these or do i need to go to 25 or 30 amp? the compressor says it needs 15.4 amps and the tablesaw says 15.5 amps. thanks all ... skeez I have had no problem running my Unisaw on 240/20. |
#11
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unisaw wiring? 20 or 30 amp circuit?
I had the same in my shop. Both are wired to 20amp circuits and work
fine. I did the work myself but had it inspected and approved by a licensed electrician who said the 20A was correct. skeezics wrote in message . .. im wiring my shop and have 2 pieces of equipment i am not sure of. a true 3 hp compressor and a 3 hp unisaw. is a 20 amp circuit enough for each or these or do i need to go to 25 or 30 amp? the compressor says it needs 15.4 amps and the tablesaw says 15.5 amps. thanks all ... skeez |
#12
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unisaw wiring? 20 or 30 amp circuit?
On Wed, 28 Jul 2004 14:44:09 GMT, skeezics
wrote: thank you all for the advice. an electrician told me 20 amp was minimum code and should be fine but not to add any 110 outlets off that. if i were to do that he said go to 25 or 30 amp. both the compressor and the saw have newish motors so i guess 12 wire and 20 amp will be ok. if it proves to be a problem i can change it after the inspection. the shop is unfinnished so changing stuff is no big deal. skeez |
#13
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unisaw wiring? 20 or 30 amp circuit?
"skeezics" wrote in message im wiring my shop and have 2 pieces of equipment i am not sure of. a true 3 hp compressor and a 3 hp unisaw. is a 20 amp circuit enough for each or these or do i need to go to 25 or 30 amp? the compressor says it needs 15.4 amps and the tablesaw says 15.5 amps. thanks all ... Whatever you decide on ampacity, run 10 ga wire, then use the c'brkr size of your best informed choice. The Unisaw will run fine on a 20 amp breaker (mine does), and if for some reason you feel that you need 30 amps later on that circuit, the 10 ga wire will allow the increase without further ado ... you'll be glad you did. -- www.e-woodshop.net Last update: 7/10/04 |
#14
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unisaw wiring? 20 or 30 amp circuit?
"skeezics" wrote in message ... im wiring my shop and have 2 pieces of equipment i am not sure of. a true 3 hp compressor and a 3 hp unisaw. is a 20 amp circuit enough for each or these or do i need to go to 25 or 30 amp? the compressor says it needs 15.4 amps and the tablesaw says 15.5 amps. thanks all ... I have my unisaw on a 30 amp fwiw SH |
#15
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unisaw wiring? 20 or 30 amp circuit?
In article ,
Greg wrote: If you are running 10ga why would you ever use less than a 30a breaker on a motor load? Me? Like I said, I'll 'over-engineer' the physical -- the cost difference is minimal, and it provides additional flexibility for 'later'. At the same time -- and particularly for 'dedicated' applications -- I tend to match the breaker 'as closely as possible' to the _actual_ load. So that it trips 'as soon as possible' in case of device excursion into "abnormal" territory. Call it 'defense in depth', against Mr. Murphy. grin |
#16
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unisaw wiring? 20 or 30 amp circuit?
"Robert Bonomi" Me? Like I said, I'll 'over-engineer' the physical -- You're throw'n a dart with the lights out, dude. Holy cow - what a thread!! RTFM!! http://media.ptg-online.com/media/dm...9-09-19-03.pdf Top of page 5. If this isn't your manual, click around and find the right one. Good thing it doesn't matter much (!!) because either you're throwing breakers, or relying on your motor's thermal protection - Nate |
#17
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unisaw wiring? 20 or 30 amp circuit?
In article , Nate B wrote:
"Robert Bonomi" Me? Like I said, I'll 'over-engineer' the physical -- You're throw'n a dart with the lights out, dude. And you, Bubba, are a 10 watt bulb in a 100 watt fixture. Holy cow - what a thread!! RTFM!! http://media.ptg-online.com/media/dm...9-09-19-03.pdf Top of page 5. If this isn't your manual, click around and find the right one. It isn't mine. _I_ don't have a unisaw. What the manual for a UniSaw says is also *irrelevant* to the last question asked -- which was why would I use something smaller than a 30A breaker on 10 ga. wire. Note that that is a _generic_ question, and was answered as such. Good thing it doesn't matter much (!!) because either you're throwing breakers, or relying on your motor's thermal protection *ASSUMING* the motor _has_ thermal protection, that is. While on a UniSaw it likely does, it is -not- guaranteed on all other devices. Heck, some devices don't even _have_ motors. Or internal overload protections. It is an indisputable fact that if a device --_any_ device -- will operate satisfactorily -- under all rated conditions -- on a circuit with a 20A breaker and 12 ga. wiring, it will also operate _exactly_ as well on a circuit with a 20A breaker and 10 ga. wiring. |
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