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Specs for wiring a 3HP Delta Unisaw

Nathan Barnard's picture

Just wondering if anyone has the specs on the amperage rating of Delta’s 3HP unisaw motors (36-830a). I just ordered one on Amazon and need to run a new line a circuit from the panel to power it. Was thinking that 20 amps should be lots so I’d use 12 gauge wire (it’s only a 30’ run). Is there any chance of blowing a 20a fuse @ 240v, and therefore should use 10/2 and 30amp fuses?


 


Cheers,


Nathan

JohnWW's picture

(post #100303, reply #1 of 39)

For the little bit of extra money run the 10 gauge.  That way you will be able to run a second machine at the same time, or a larger machine that you might buy in the future, without having to upgrade the wiring.  You should also consider running a third neutral wire, the saw won't need it but again it might prove useful in the future.


John W.


Edited 1/19/2007 9:54 am ET by JohnWW

John White Shop Manager for FWW Magazine, 1998 to 2007

Stuart's picture

(post #100303, reply #2 of 39)

The first thing to do is look at the owner's manual for the saw - it should tell you what size circuit Delta recommends.  If you want to do the work before the saw arrives, the manual should be available from the Delta website, or maybe even from the Amazon website.


It can be difficult to size the circuit based on the hp rating from the manufacturer...I don't know if Delta is as bad as some other companies, but it's not uncommon for some of them to exaggerate in their advertising.  You need to know the full load amp rating of the motor, rather than its horsepower, to properly size the circuit.

bones's picture

(post #100303, reply #3 of 39)

Look at your manual for the requirements. The general rule is stay at 80% of capacity. So if you have the stuff and it will meet your requirements do it. Just remember if its 12 wire the breaker cant be more than 20, and the plug has to be a minimum of 20. I would agree that 10 wire is reccomended if you ever are going to put another piece of equipment in that would require 30a, you would not have to upgrade the wiring. (10gauge with 30a breakers), just the breaker.  If you are not sure, have an electrician do it for you.  Good luck. 

Government's view of the economy could be summed up in a few short phrases:
If it moves, tax it. If it keeps moving, regulate it.
And if it stops moving, subsidize it.

...For that old machine lovers:  http://vintagemachinery.org/home.aspx

Nathan Barnard's picture

(post #100303, reply #4 of 39)

The manual states 12 gauge minimum with 20a breaker. I was wondering what the typical amps is with the 3HP motor. If it is rated for 12amps then 20a should be lots.


Does anyone know what the amp ratings are for these 3HP unisaw motors?


Also, 10/2 is over double the cost of 12/2. I realize that you could run more things simultaneously on a 30a circuit, but question sizing a circuit for this reason alone. Also, I am leery of using 20a receptacles on 30a breakers. By that logic I could use 30a 120v circuits for appliances in the kitchen. While the 30a fuse would protect the wire, it wouldn’t protect the motors/appliances and could be potentially quite dangerous and ruin the motor before blowing a fuse.


Maybe I’ve got this all wrong in that induction motors are protected thermally and therefore don’t need breakers. Anyhow, anyone who wishes to explain would be appreciated. I do have a separate 15a 120v circuit for my DC, potentially it could be rewired for 240v and share the circuit with the TS, freeing up a slot on the panel. This is one of my concerns, as it is getting full.


Nathan


 

Daryl's picture

(post #100303, reply #5 of 39)

When I had the 3 HP Unisaw, it ran for a decade on a 20A, 220 line with no problems. It came with a plug already installed, a 12 ga. line.

Rich14's picture

(post #100303, reply #6 of 39)

Nathan,


You should use 10 ga wire. Although it will carry more current, you cannot run multiple devices off this circuit. It must serve only one device plugged in. The 10 ga wire will give you a margin of safety. Notice, your manual said 12 ga minimum.


Use a 20 amp breaker. That will suffice for the continuous load current and the brief (higher) start-up current. If necessary, the breaker will trip long becore the 10 ga circuit can heat up under an overload or short.


Rich

Nathan Barnard's picture

(post #100303, reply #7 of 39)

Ok, I think I get it...the manual is saying minimum 12 gauge wire, due to line loss on long runs, but breaker should be 20a, regardless of the wire size (12 or 10 gauge). Point taken on having a dedicated circuit for the TS though, thanks Rich.


Considering that it is a small basement shop, will be a dedicated line, and is only a short distance from the panel, I think 12/2 wire makes sense.


I think you have to look at total line resistance, having a short, small diameter wire technically should be the same as a long, large diameter wire. That’s why a 1500watt electric kettle or skillet can use a short 16 gauge wire, but still pull about 13 amps.


Thanks to all for the suggestions.


Nathan

Rich14's picture

(post #100303, reply #8 of 39)

Well,


Since it's a short run, how much is the incremental cost of the larger wire? A few bucks? Why not wire with 10 ga and give yourself the margin of safety?

Nathan Barnard's picture

(post #100303, reply #9 of 39)

Oops, I was thinking it would cost $140 for 10 gauge wire, but forgot that they gave me pricing by METER, not by foot. A 35’ run would be $50 for 10/2, or $23 for 12/2, Canadian. Still, ever worked with 10 gauge, it’s THICK! Guess the price difference isn’t that much, though.


 


Nathan

Rich14's picture

(post #100303, reply #10 of 39)

Nathan


"The manual states 12 gauge minimum with 20a breaker."


Good luck then. 12 gauge will certainly run the saw. $29 extra for 10/2. Not much, in the scheme of things. If it's too THICK! to handle, don't.


Your manual states the minimum. I get uncomfortable limiting my safety measures to "minimum."


Rich


Edited 1/19/2007 4:02 pm ET by Rich14

bones's picture

(post #100303, reply #11 of 39)

If your manual says you can use it, do it.  I have a 3hp saw with 20a breaker and 12a wire.  been running fine. Trust your documentation from the manufacturer. You will not be wrong if you use a bigger awg wire i.e. 10, but you don't have to.  The drawback is if  upgrade to say a 5hp saw that would have a 30Amp requirement, you would have to change plug, wire, and breaker. Then the cost would be greater.  In my view, I had the wire already, so it did not make sense to put in the bigger stuff. I upgrade latter, ok I replace it, and I was wrong, but odds are it ain't going to happen.  Take care. 


P.S. If it really took a bigger wire for safety and the manufacturer reccomened a lower rated wire and it caused a problem, they would be sued to oblivian.  The question you need to ask is will I need 30 amps in the future.  Match the wire to the breaker to the plug and don't share circuits where both devices would be on at the same time.


Government's view of the economy could be summed up in a few short phrases:
If it moves, tax it. If it keeps moving, regulate it.
And if it stops moving, subsidize it.


Edited 1/19/2007 4:21 pm by bones

...For that old machine lovers:  http://vintagemachinery.org/home.aspx

JohnWW's picture

(post #100303, reply #12 of 39)

I suspect that the wiring recommendation in the Delta manual is for a cord to hook up the machine, not for the wiring in the wall.


Unless the wire is very easy to replace later, I would definitely use 10 ga. wiring, I could make a living just on the number of shop wiring upgrades I have done in the last ten years.


John White, Shop Manager, Fine Woodworking Magazine

John White Shop Manager for FWW Magazine, 1998 to 2007

Nathan Barnard's picture

(post #100303, reply #16 of 39)

John, thanks for the suggestion. If I had a larger shop with the possibility of purchasing a machine requiring 30a then I would definitely agree with you and put in 10 gauge wire. This, however, is not the case.

Also, I DID read the manual and it is indeed referring to circuit wire size. There is another section (table) which refers to extension cords sizing.

http://www.dewaltservicenet.com/Documents/English/Instruction%20Manual/Delta/En%20422-04-651-0064.pdf

HowardAcheson's picture

(post #100303, reply #21 of 39)

>> Also, I DID read the manual and it is indeed referring to circuit wire size. There is another section (table) which refers to extension cords sizing.

Then, I guess I wonder why you made the original posting?

Howie.........
Howie.........
Nathan Barnard's picture

(post #100303, reply #22 of 39)

Howie,

The manual states MINIMUM 12 gauge wire. I needed to know the amperage rating of the motor to help me decide if it was worth using 10 gauge. I don't want to be tripping breakers any time in the future. If the motor was rated at 18amps @ 240v then I would consider 10 gauge with the potential for upgrading it to 30a in the future, if the motor was 12-14amp then I would never worry about throwing a 20a breaker, and therefore use 12 gauge wire. I wanted to make an informed decision.

Rick C confirmed that the max load would be about 15 amps. I am comfortable with that margin, and therefore will stick to 12 gauge wire.

My question has been answered. Thanks to all who contributed.

Nathan

tinkerer2's picture

(post #100303, reply #24 of 39)

"if the motor was 12-14 amp, then I would never worry about throwing a 20 amp breaker" 

There is an old saying, "never say never."  In my humble observance, I've seen a breaker get "tired" and not carry its rated amperage.  Trip at far less then than its rated amperage.  I've also experienced a 20 amp breaker not tripping during a dead short and instead tripping the 100 amp main breaker.  This is the dangerous one.  What I am saying is that if the 20 amp breaker does trip, don't sit back in disbelief.  Find the problem.  It could be as simple as changing the breaker.

DJK's picture

(post #100303, reply #25 of 39)

I just love the electrical threads, better than the festoool vs "whatever rail".

DJK

woodenfish3's picture

(post #100303, reply #26 of 39)

I am inclined to think that 12 AWG is plenty for any 230V 3hp motor, even those with FLA of 17 or 18 Amps.


Why? I think the NEC says so.


I am not very certain but I think I am right about the current carrying capacity of wires and cables. 


For vitually all applications we need, there are only two current carrying wires in the cable. If I understand the NEC correctly (for discussion but assertion), when there are only two current carrying wires in the cable, 14 AWG can safely carry 17 or 18 Amps, not 15 as commonly known. For 12 AWG more than 20 amps, likely 22 or more amps.


The induction motor has high current surge when started, but I think using 12 AWG instead of 14 AWG has already taken this factor into consideration. The circuit breakers  are designed to take brief surges into consideration.  A 14 AWG is not going to heat up excessively if it carried 20 amps for a second or two.


The advantage of using 230V is that one can use a smaller wire to obtain the same power because the amp would be halved that of 115 v. The IR loss in the wire, which also generates heat,  would be halved. In wanting to use 10 AWG, I think many people are mentally affected by the biggness of the power of a motor.

try50772's picture

(post #100303, reply #28 of 39)

I was thinking the same thing. What scares me is that many of the posters do electrical wiring in their own homes and shops and most likely never get permits or inspections.

I wonder what would happen with a thread:

I need to wire my shop for my new Saw Stop Table Saw, but I want to also run my Festool Vac on the same circuit???


Edited 1/26/2007 7:39 am ET by try50772

Dave45's picture

(post #100303, reply #32 of 39)

What are the scoring catagories for this pizzing match?


Aim?


Form?


Style?


Distance?

PADDYDAHAT's picture

(post #100303, reply #27 of 39)

Tinker, they (our wood butcher friends) obviously don't know about having a Federal Pacific service panel in their house. In a commercial setting we would just open the door of the electric closet(a little room with several service panels for a floor of 30,00 sq.ft.) and listen to the snap, crackle and pop-just like rice crispies.(that stuff was junk, cheap, favored by builders and blessed by the NEC) In a residential setting a friend had an electrician upgrade the builders 100 amp. to a 200 amp. panel and the first thing he said was "wow it hasen't burned yet?"


All jokes aside I would NEVER run a 20 amp. circuit in my home less than 12ga. or a 220 line less than 10 ga. I even use 10 ga. xj cord for all of my extension cords with commercial level ends . No home dopy or loweses junk, go to an electrical supply house. A few bucks more -YES- but I sleep real good. The NEC-National Electrical Code- is a minimum safe solution that you could never be blamed for if you follow it, but do you really want to walk on the MINIMUM edge with your home or your expensive power tools , forget about performance. Paddy

HowardAcheson's picture

(post #100303, reply #13 of 39)

You still haven't gotten the answer to your question. You should contact Delta and ask them what the amperate draw is on the motor supplied with that saw. Delta has a couple of 3hp motors and I do not know what the amperage is for the one you will be supplied.

If the motor amperage is 16 amps or less, then 12 gauge wire in the wall and a 20 amp breaker will be fine.

The info on wire size in the Delta manual is for wiring from the wall to the tool which, not to get technical, can be of a lesser size. Wire in the wall is required to be larger to ensure it does not get hot.

Howie.........
Howie.........
RickChristopherson's picture

(post #100303, reply #14 of 39)

Of all the people that have told you emphatically to use #10 wire, ask how many of them have actually utilized the 30-amp capacity of the circuit unless it was pre-disposed for another purpose. I suspect you will hear some crickets chirping. Either that, or some tall tales.

It’s one thing to plan ahead and plan for the future, but it is quite another to just blindly overkill without forethought. Going with a 20-amp circuit is already planning ahead because this will suffice for any 4 horsepower motor, let alone the typical 3-hp found on most woodworking machines. The minimum circuit size to run a 3-hp Delta Unisaw is 15-amps, and if someone doubts this, look at the end of the plug before you respond and tell me I am wrong. (Don’t worry, I do know NEC quite well.)

It bothers me that you asked a straightforward question and no one gave you the proper answer.

Although I would not recommend it, technically your cord-and-plug connected Unisaw will operate fine on a 15-amp, 240-volt, 14-ga circuit, and be perfectly compliant with the National Electric Code. I would recommend using a 20-amp circuit with 12-ga wire for both a margin, and for future use. The 20-amp circuit would also be compliant if you hardwired the saw without a cord-and-plug receptacle, because this is when you need to derate the circuit.

Because you have a cord-and-plug connection, you do not need to derate the circuit. Personally, I wouldn't derate the circuit for a 3-hp wardwired motor, but I can't advise you to do that, even though it is logical.

I believe you also asked what the maximum current draw would be for your saw. A 3-hp motor will draw 15 amps when it is under its maximum rated capacity, but under most conditions, the motor will only be drawing 7 amps at idle, and 10 amps under moderate cutting.

Rich14's picture

(post #100303, reply #15 of 39)

Rick,

In your typical overbearing, derrogatory and scolding manner, you have criticised anyone with whom you have a disagreement. It's beyond you to simply say that you have a different opinion. Rick is the only one who knows what's best.

But, as usual, you have also misstated the advice that others have given, in your blind anger about their daring to have a point of view different from yours.

No one advised Nathan to use 10 guage wire in order to use the 30 amp capacity of the circuit.

Forgive us, "Mr. Expert-in-Everything," to have advised a course of action that is "just blind(ly) overkill without forethought. Horrors. We advised a course of action that might cost $29 more than another in the interest of safety and future expansion.

Y'know Rick, you are right. Those of us who advised 10 gauge wiring should be taken out and shot!

Nathan Barnard's picture

(post #100303, reply #18 of 39)

Rich14,
I don't think your last post helped anyone. If someone bothers you that much then use Options --> Ignore this Author.

RickChristopherson's picture

(post #100303, reply #19 of 39)

Rich14 Said:Nathan,
You should use 10 ga wire. Although it will carry more current, you cannot run multiple devices off this circuit. It must serve only one device plugged in. The 10 ga wire will give you a margin of safety. Notice, your manual said 12 ga minimum.

Use a 20 amp breaker. That will suffice for the continuous load current and the brief (higher) start-up current. If necessary, the breaker will trip long becore the 10 ga circuit can heat up under an overload or short.So where in your posting did you answer this person’s question? Like others, you stated that he needed to use 10 gauge wire regardless whether he would ever have a use for it or not. People state this as though it is such a common occurrence that other people read it as a requirement, and then they repeat the same thing themselves.

You fall into this same category. You are not speaking from knowledge or experience; you are just repeating what you have heard someone else say. As a result, the information is no longer in the original context where it was applicable when it was stated. It is just blindly repeated without fully understanding why it was stated originally.

The person didn’t ask what you wanted him to install, he asked what was required. You told him he should use 10 ga wire as though it was required. This is the same thing you did back with the Neutral wire discussion. You are content spewing your misinformation as long as someone doesn’t correct you on it, but heaven forbid if someone does correct you.

So the question still stands: How many tools in the average hobbyist’s woodshop require 30-amp circuits? How many woodworkers will upgrade to a 3-hp Unisaw, but then later decide that they want a 5-hp saw instead?

There is nothing wrong with installing a larger circuit, as long as it is clear that this isn’t a requirement, nor is it even likely to pay off for the average woodshop. People blindly repeat this advise without ever stopping to question it.

P.S. I also just noticed that you were stating (or at least implying) that a 240 volt circuit cannot (your emphasis) feed more than one device (or outlet). Since you are so knowledgeable in Code, would you mind stating what section of the NEC specifies this requirement? Am I being condescending right now; you bet your adz I am!

So before you get steamed that I am correcting you, why don’t you defend your information in the first place. If you can defend your statements with factual information, then I will publicly issue a heartfelt apology to you and to the others in this thread that posted similar information.

woodenfish3's picture

(post #100303, reply #23 of 39)

My 1997 Unisaw has a 3hp motor that is rated at 12.6 amps. The manual says 14 AWG min.


I'm using 12 AWG only because I already have then pulled. I have also been deliberately using a 15 Amp circuit breaker on 12 AWG to protect my motor, which does not explicitly say thermally protected. So far it hasn't tripped yet. If it trips just once, I'll go back to 20 Amp Circuit breaker.


I think 10 AWG for a 3hp 230 v motor is quite a bit overkill; 12 AWG is quite good IMO.


For those do not have 230 v (why?) and have a 2hp motor that draws 20 amps, 12 AWG would be better or required.


 

t_mauery's picture

(post #100303, reply #29 of 39)

Rick,


You wrote:

P.S. I also just noticed that you were stating (or at least implying) that a 240 volt circuit cannot (your emphasis) feed more than one device (or outlet). Since you are so knowledgeable in Code, would you mind stating what section of the NEC specifies this requirement?


What does the NEC say about more than one outlet on a 240V circuit?  I've acquired some new 240V tools, and I'd prefer not to put in more circuits than I have to.


Common sense would indicate that it's reasonable to have more than one device on a 240V circuit; most of Europe is on 240V, and I doubt every outlet is on a dedicated breaker.


 

RickChristopherson's picture

(post #100303, reply #30 of 39)

The NEC does not make any distinction between 120 volt and 240 volt circuits. There is nothing wrong with sharing circuits between outlets, so all you need to do is plan ahead as to what tools may be running simultaneously to ensure that you don't overload the circuit. For example, even though your tablesaw and jointer may be running at the same time, it is unlikely that they will both be operating at their maximum rated power at the same time. On the other hand, compressors and dust collectors operate near their rated power all the time. An idling motor draws about 50% of its full rated power.

ibew481's picture

(post #100303, reply #31 of 39)

2005 NEC 430.22 Single Motor


(A) General.  Conductors that supply a single motor used in a continuous duty application shall have an ampacity of not less than 125 percent of the motor's full load current rating as determined by 430.6(A)(1)


(E) Other than continuous duty.  Conductors used for a motor used in a short-time, intermittent, periodic, or varying duty applications shall have an ampacity of not less than the percentage of the motor nameplate rating shown in 430.22(E)


Based on the nameplate Current Rating Percentage you may use conductors of lower ampacity.


 


2005 NEC Table 430.248   Full Load Currents in Amperes, Single phase a/c


Horsepower=3


FLA=17 @ 230V


 


Calculate Ampacity of conductor if considered continuous duty


17A X 125% =  21.25A  


CU AWG # 12 rated for 25 A @ 60*C


 


2005 NEC Article 110(3)(B)


Installation and use.  Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.


Follow manufacturers directions.