Quick electric ?

[Fred Voorhees]

Well, I thought that this weekend was going to be a washout since I've been sick all week and it looked like more for the weekend. Some prescription meds found me waking up Sat. morn feeling kinda ok and got some stuff done in the shop. Managed to run romex for a dedicated circuit for my tablesaw (simple Delta contractors unit) that will now have a receptacle right underneath the outfeed table instead of being fed from a nearby wall and having the cord lay across the floor. Just curious, am I right in thinking that a simple 15 amp breaker will suffice for this? :confused: I'm pretty sure that it is, just wanted to check before going to pick it up. The breaker will only be serving the saw.

[Joe Breid]

If it is running on 120 volts I would recomend a 20 amp breaker for the table saw. That is what I have on mine and every now and then it will still trip when the saw is first turned on. I have a 1.5 HP motor, 120 volt on my saw.

Joe

[Fred Voorhees]

Thanks Joe - that is exactly why I came on and asked. I would have assumed that because a single machine was going to be on it, that 15 amps would be fine. I will go with the 20 amp. It'll be nice to not have that cord laying across the floor. Ran this circuit because I now have a hole in the floor right below the outfeed table for the installation of the five inch ductwork that will be installed shortly for the dust collection system. While the hole is there, why not take the opportunity to run the circuit, and while I'm at it, as recommended to me by another "Creeker", upgrade the wiring so that when I upgrade to a bigger tablesaw, the same 12 guage wiring could be used.

[Robert Ducharme]

Careful now.

To decide if you need to have 20 Amps or 15 Amps for your saw, you need to answer what is the peak horsepower (generally on startup or loading) and running horsepower.

Assume a motor with a peak load of 2 hp, that would mean you can draw 1500 watts (approximately). At 120 volts (or are you running 110 volts), this is 12.5 amps. If 110 volts, this is 13.64 Amps. Borderline for a 15 amp circuit - especially on those binding situations. Of course, if you have only 1.5 hp peak, that is okay.

Next, you have already run the romex. What size wire did you use? If you used 12 guage, 20 Amps is acceptable. If you used 14 guage, you should set your breaker to a maximum of 15 Amps. This will avoid system meltdown - wires overheating, etc. If this is the case, set a slow-trip 15 A breaker to handle those momentary overloads.

[Jim Martin]

If you are running a dedicated circuit anyway, why not wire it with 10 guage wire in case sometime in the future you get the itch for a cabinet saw? It is good for 30 amps and you still can use your 20 amp breaker on it for now until you upgrade. Running the wire is usually the toughest part of a job like this and the price difference between 12 and 10 is not that great.

[Fred Voorhees]

According to the label on the motor, the HP is 1 1/2 - 2 - now does that mean it's a 1 1/2 hp with a peak of 2 at start up or because its a dual voltage motor 120/240 motor, its 1 1/2HP at 120 and 2 HP at 240? Sorry about the questions, I'm sort of "electrically challenged". Just don't want to trip a breaker often and also don't want to fry the shop.

As far as the difference in 10 and 12 guage wiring, I was under the assumption that that is why I ran 12 guage wiring, because when I decided to upgrade to a cabinet saw, the 12 guage would handle it and I would merely have to swap out the breaker and the receptacle.

[Jim Becker]

Fred the 12 guage wire and 20 amp breaker and receptical is great for your present saw and the wire will be re-usable for a 20a 240v circuit when you upgrade your saw. (And hire a crane to get it up there... :D )

[Julie Wright]

while we are on the subject of electricity - Currently I have a 13" ridgid planer, Jet 1236 lathe, 12" CMS, router, 14" Grizzly band saw and a table top table saw. Would like to run a window a/c unit this summer without burning out any motors...

Someday, but not in the near future I am planning on upgrading to a contractors saw, larger bandsaw and BIGGER LATHE. :D :D

YES, the entire garage (err shop) is wired on ONE circut. and so is part of the house... Can't believe it passed inspection when it was sold..

So, I was planning on adding 3 new circiuts for the shop...
20amp breakers with 12g romex.. How does that sound ???

Thanks
Julie

[Robert Ducharme]

The 1.5 - 2 probably means 1.5 hp with peak of 2. The HP would not change in changing the voltage. Only if changing the phase. I agree with Jim that if you want to run 240 V in the future, you should use 10 guage. However there is yet more to the story. Hopefully the following quick reference will help. The particular situation you are in may cause values to vary. The information is also based on "short" runs of wire. This is generally less than 100'. Anything longer I would drop a guage to avoid voltage drop.

All values are based on using Copper wire ONLY!!!! Do not use Aluminum.


120 V systems - use 2 wires with a ground (generally black/white and green (ground)).

240 V systems - use 3 wires with a ground (black/red/white(neutral) and green (ground)). Note that in many cases the neutral is sometimes not attached - read your instruction manuals and ask specific questions if this situation arises.

15 Amp: 14 guage
20 Amp: 12 guage
30 Amp: 10 guage
40 Amp: 8 guage

Remember, 1 HP ~= 745.6999 Watts (I would use 750 for ease of computation). 1 Watt = 1 amp * 1 Volt
Therefore, 1 Amp at 120 V = 120 Watts or .16 Hp

Now for another gotcha. The class of insulation used on the wire can also change the legal level of amps you can use the wire for. Also, if you place this in conduit, that will also affect the number of wires that can be in the tube. For the most part, the type of wire obtained from Home Despot can be used for the amps above. You can (and probably should) contact your local state electrical board for detailed questions related to meeting code. You should also have this inspected to avoid any problems with insurances if a fire occurs.

Flexible wire (multiple strands) can actually handle more current than solid core wire but use the amp ratings shown above (to be conservative).

In addition, use the appropriate receptacle type for the Amp ratings. You will see in HD the difference between the recepticals (2 vertical prongs, vertical/side prongs, ...)

Good luck

[Mike Cutler]

Fred. The 15amp breaker will work with a contractor saw with a motor up to 1 1/2 hp. A 20 amp breaker would be better in that application. The 12awg will be more than adequate for either a 120 or 240 application. I posted this "Rule of Thumb" a few weeks ago, I hope it helps you out.
"Rule Of Thumb For Small Motors" ( And we all know what happens to thumbs that stick out there!)
1HP=746 watts.
HP=IxVxPFxEFF/746,where PF( Power Factor)=.86 and EFF ( Motor Efficiency)=.81. Using this formula current can be calculated as follows for a 1HP single phase motor.
I=HPx746/(VxPFxEFF) or,
I=1X746/ (120 x.86x.81) or,
I=8.9 amps.
Current for the same Motor connected to 240 would be.
I=1x746/ (240x.86x.81) or,
I=4.46 Amps.
Julie. Is it possible to run a sub panel for your "Shop/ Garage" needs. Having a single branch circuit must be stretching it at times for you.If you could sub off of your main panel it would allow you to install dedicated lighting circuits and have 240 branch circuits for larger machines and the A/C unit.I know what you mean about the single branch service in the garage. Before I rewired my garage/shop I had 2 light bulbs off of a single circuit that could be turned on from 5 locations in the garage, never made sense to me. Addy protocol in effect here. I am not a liscensed electrician, but I do have a very strong electric/electronic background and I work for your electric company.

[Tyler Howell]

Julie and All,
Yes Romex is legal (meets code) and yes they sell it to you. :mad: But....... It isn't always the best solution. I am a strong proponent, advocate, user, and installer of EMT, Greenfield, and armored cable. Especially in the shop where you are swinging large boards, moving heavy equipment, and driving nails and screws into the walls you just wired.
I cringe at some of the shop tours I've seen with the latest of tools and safety equipment, and a Rube Goldberg, kluged together wiring job.
Metal conduit, and boxes are resistant to direct attack from a 2x4 and dissipate a lot of heat. A wire captive in conduit requires much more force to dislodge than these new plastic utility boxes with the plastic hooks. A circuit breaker is only guaranteed for one short circuit. (That's 1 over current condition.)Conduit is very flexible. You can increase, replace or upgrade the wire contents.
I can't tell you the number of fires I've been to where the home handyman wired up his, house, shop, and or garage.
A proper wiring job can determin if insurance will pay off in a catastrophe even it it wasn't wiring related.:eek:

I’m not trying to protect any union brother’s job. :rolleyes:
I kinda like you folks. :cool: You have given me good direction and I want to share my personal experiences with you.
I am the biggest advocate of do-it-yourself. Behind every tedious electrical code is a fire, disaster, law suite or death.

Play safe;)

[Mike Cutler]

Tyler. I was remiss in my previous post to add, That if in the SLIGHTEST DOUBT about any wiring modificatoin or installation, consult with a LOCAL Liscensed Electrician. He/She will be cognizant of all national,state and local codes that prevail in your area. When I was in tech school a zillion years ago they taught that all those pesky codes were " To maintain and protect the integrity of the conductor". I think the first device I saw that was specifically for humans in the code was a GFCI receptacle. By the way, it was 40deg. here today and I was able to wash the cars finally, have you chipped yours out of the ice yet? Take care and stay warm.

[Robert Ducharme]

Strongly agree with you Tyler. :cool:

I only use EMT and metal boxes in my shop. It is a little more expensive but lets you change wiring as required. Also if you do enough wiring, it actually becomes cheaper than romex. It is definitely safer than romex. Especially if you are running equipment in the center of a room.

Also, romex is generally solid core not flexible core wire (remember what I said about ability to carry current). Solid core is harder to bend/work especially when you get up to 10 guage. :)

[Jim Becker]

240 V systems - use 3 wires with a ground (black/red/white(neutral) and green (ground)). Note that in many cases the neutral is sometimes not attached - read your instruction manuals and ask specific questions if this situation arises.

240v circuits for machinery that do not require 120v do not need the fourth wire and are typically installed with 12/2 or 10/2 cable. Only ovens, ranges and some electric dryer circuits, etc., are installed as dual voltage with xx/3 cable...at least around here. Some local codes may require the extra wire, however, even if it goes unused.

[Jim Becker]

Would like to run a window a/c unit this summer without burning out any motors...

Julie, you'll really need to get additional circuits to your shop before you deal with the A/C. Even most small units require a dedicated circuit. I agree with the other post that suggested a subpanel for the shop...it makes for easy installation of the additional circuits you need and makes for flexibility as time goes on.

[Tyler Howell]

Mike,
About 35 here today too with a little rain. Sat. was perfect. Believe it or not, I did some outdoor wiring after my siding job.
2 new GFICs in liquid tight flexible conduit.
Hey we are up and running around here and getting ready for our next two seasons. Poor skiing, and road construction.