Electric question for dust collector

[Andrew Howe]

Hello all
I am getting ready to put in my delta 50-760 dust collector and run a dedicated circuit for it (20 ft wire away from my sub panel in basement and ran a circuit of 14/2 wire to it with a 15 amp fuse). The motor is 1.5hp 15 amp on sticker.
My question to you all is this OK? Per code I am OK but should I run 12/2 or just leave it?

[Thomas Hotchkin]

In my shop all large power tools are on there own circuit, wired with 12/2 with ground, or 10/2 with ground. This way you can up grade to a larger tool with out rewiring shop. 14 ga wire on 15 amp motor is right at the limit for that wire size. You should check with a electrician if you have not done this before. Tom

[Stephen Cherry]

Maybe check the manual. (12-2 dedicated circuit) A couple of bucks for the right wire and receptical isn't the place to cheap out.

[Norman Pyles]

I went with 12 on my Delta 50-760, but I had to run about 30 ft. It will still flicker the lights when I switch it on, and it's on it's own circuit.
Just to add; I am not an electrician, and I don't play one on TV. :)

[Andrew Howe]

I am inclined to chug it out to 20 amp circuit

[Jim Neeley]

Hello all
I am getting ready to put in my delta 50-760 dust collector and run a dedicated circuit for it (20 ft wire away from my sub panel in basement and ran a circuit of 14/2 wire to it with a 15 amp fuse). The motor is 1.5hp 15 amp on sticker.
My question to you all is this OK? Per code I am OK but should I run 12/2 or just leave it?

Greetings, Andrew..

Others here make good points about future upgradability but I'm going to address your question directly.

A good (conservative) rule of thumb is to limit your voltage drop to no more than 3%, although many use 5%. Assuming your #14 wire is 20 feet long (each way) and based upon 120V AC, you'll get a 1.5% voltage drop at 15A of current draw. You'll be fine.

That said, if you haven't run the wire yet and unless the couple of dollars is significant in your budget, I'd not install anything less that #12, especially with an induction motor. An induction motor, for a tiny fraction of a second at first startup, typically draws about 6x the nameplate current. In the real world no problem; just consider me wasteful with copper. :-D

You can easily run this calculation for any power requirement you may have by googling "voltage drop calculator" for any of many sites offering free calcs.

I'm created and uploaded a PDF of yours, for your perusal.

Jim

[Andrew Howe]

Jim
Thanks for your input and the calculation info. Since I am midway in setting this up I will run 12/2 with a 20 amp breaker.
Off to HD


Greetings, Andrew..

Others here make good points about future upgradability but I'm going to address your question directly.

A good (conservative) rule of thumb is to limit your voltage drop to no more than 3%, although many use 5%. Assuming your #14 wire is 20 feet long (each way) and based upon 120V AC, you'll get a 1.5% voltage drop at 15A of current draw. You'll be fine.

That said, if you haven't run the wire yet and unless the couple of dollars is significant in your budget, I'd not install anything less that #12, especially with an induction motor. An induction motor, for a tiny fraction of a second at first startup, typically draws about 6x the nameplate current. In the real world no problem; just consider me wasteful with copper. :-D

You can easily run this calculation for any power requirement you may have by googling "voltage drop calculator" for any of many sites offering free calcs.

I'm created and uploaded a PDF of yours, for your perusal.

Jim

[JohnT Fitzgerald]

Jim
Thanks for your input and the calculation info. Since I am midway in setting this up I will run 12/2 with a 20 amp breaker.
Off to HD

Andrew -I think that's the right call. I have that same DC, and I had read that some people were seeing occasional breaker pops @ startup on a 15A line. It could have been due to a long run, but you never know. On a new install, going with a 20A makes sense.

[Dan Hintz]

To add to Jim's points... a true 1.5HP at 120V is <10A actual draw (not counting startup pulls). At 20' you're perfectly fine, and if the line was alreayd in I would have no issues with leaving it as is. Since you're putting in a new circuit, I wouldn't think twice about making it a 20A with the expectation I'd put in something bigger down the road (or use another tool at that spot).

[glenn bradley]

That said, if you haven't run the wire yet and unless the couple of dollars is significant in your budget, I'd not install anything less that #12, especially with an induction motor.

+1 on what Jim said.


Jim
Thanks for your input and the calculation info. Since I am midway in setting this up I will run 12/2 with a 20 amp breaker.
Off to HD

Good call Andrew. You'll sleep better and possibly be glad later on.

[Myk Rian]

I believe a shop should be wired like a kitchen. 20 amp circuits everywhere.

[Tom Cornish]

To add to Jim's points... a true 1.5HP at 120V is <10A actual draw (not counting startup pulls).

There's not enough information to make this assumption. In another thread I did a brief survey of various motors in my shop and got numbers between 980 and 1150 watts per HP actual input current. Extrapolating, that's between 12 and 14.5 amps for 1.5HP at 120V..

The nameplate rating on the OP's machine is 15A, and dust collectors tend to draw maximum power all of the time (unless the intake is highly restricted), so I wouldn't use any number less than 15A.



At 20' you're perfectly fine, and if the line was alreayd in I would have no issues with leaving it as is. Since you're putting in a new circuit, I wouldn't think twice about making it a 20A with the expectation I'd put in something bigger down the road (or use another tool at that spot).

One additional factor is that most breakers are rated for only 80% continuous capacity. Long-term draw at or near the breaker rating will likely eventually trip, due to manufacturing tolerances and accumulated heat. I would put in 12ga with a 20A breaker without question for this machine.

[Chip Lindley]

...and ran a circuit of 14/2 wire to it with a 15 amp fuse...

Fuse? Or Breaker? If, indeed, you have a fused panel instead of breakers, you do not want nusiance trips! Fuses are a PITA! Good call on the #12 wiring / 20A fuse?/breaker. #14 wiring on a 15A circuit is the absolute minimum meant to save contractors money.

[Tom Cornish]

Andrew -I think that's the right call. I have that same DC, and I had read that some people were seeing occasional breaker pops @ startup on a 15A line. It could have been due to a long run, but you never know. On a new install, going with a 20A makes sense.
A long run of wire actually reduces the current drawn - it does not increase the likelihood of a tripped breaker.

Let's say the resistive equivalent of our tool is 10 ohms (around 1.3 HP or so). If we plug this tool into a power source that has an infinite current supplying ability without any voltage drop, we can calculate that this load will dissipate 1440 watts (P = V^2/R). The current flowing through the tool is 12A (I = V/R).

Let's say we now take this same tool and plug it into 100' of orange BORG 16ga extension cord. The resistance per foot of 16ga wire is .00473 ohms/ft (which may be optimistic considering how many splice points there are if you use 4 25' cords instead of 1 100' cord for example). Multiplying this by 200' (need to count the round trip distance of the wire) gives us a total resistance of .946 ohms.

This gets added to our tool load, so now our effective resistance of the tool plus wiring is 10.946 ohms. Using Ohm's law again, we find that our current has actually dropped from 12A without counting the wiring losses to 10.9A. Obviously a 10.9A load is less likely to trip a breaker than a 12A load.

The reason for using large wire and short runs is so that we aren't wasting power in the wiring and starving our loads. Again taking the 100' extension cord example, we can find that our tool which really wants 120V of input power for maximum performance will only be operating on 109V, consuming 1188 watts, due to the losses of the small wiring. We've lost 250 watts of potential work output due to the higher load impedance of the circuit and the resistive losses of the wiring.

[Tom Cornish]

I went with 12 on my Delta 50-760, but I had to run about 30 ft. It will still flicker the lights when I switch it on, and it's on it's own circuit.
Just to add; I am not an electrician, and I don't play one on TV. :)
These momentary brownouts are a fact of life and do not necessarily indicate an undersized branch circuit (though that would certainly make it worse).

My house has a 200A service but I'm 300' from the utility pole. When I kick on either my 5HP dust collector or 5HP table saw (worse with the dust collector because it's trying to pull full power longer to get the impeller up to speed where as my table saw is only briefly loaded to get the blade spinning) I get a pretty good dip momentarily.

All of my wiring exceeds the supply requirements of my tools, but the sum total of the branch circuit wiring, my long feeder length to the utility pole, and the particulars of my neighborhood distribution situation all contribute. There isn't much I can do about it, but it doesn't really hurt anything either.

[Rod Sheridan]

A long run of wire actually reduces the current drawn - it does not increase the likelihood of a tripped breaker.

Let's say the resistive equivalent of our tool is 10 ohms (around 1.3 HP or so). If we plug this tool into a power source that has an infinite current supplying ability without any voltage drop, we can calculate that this load will dissipate 1440 watts (P = V^2/R). The current flowing through the tool is 12A (I = V/R).

Let's say we now take this same tool and plug it into 100' of orange BORG 16ga extension cord. The resistance per foot of 16ga wire is .00473 ohms/ft (which may be optimistic considering how many splice points there are if you use 4 25' cords instead of 1 100' cord for example). Multiplying this by 200' (need to count the round trip distance of the wire) gives us a total resistance of .946 ohms.

This gets added to our tool load, so now our effective resistance of the tool plus wiring is 10.946 ohms. Using Ohm's law again, we find that our current has actually dropped from 12A without counting the wiring losses to 10.9A. Obviously a 10.9A load is less likely to trip a breaker than a 12A load.

The reason for using large wire and short runs is so that we aren't wasting power in the wiring and starving our loads. Again taking the 100' extension cord example, we can find that our tool which really wants 120V of input power for maximum performance will only be operating on 109V, consuming 1188 watts, due to the losses of the small wiring. We've lost 250 watts of potential work output due to the higher load impedance of the circuit and the resistive losses of the wiring.

Tom, reducing the voltage to an induction motor causes an increase in motor current during normal operation, with a corresponding increase in motor heating.

Reducing the input voltage during start up can reduce the inrush current, however it will prolong the duration of inrush current.

Starting an induction on a circuiut with too much voltage drop can cause the breaker to trip, or fuse to melt because the inverse time curve of the protective device has been exceeded.

Regards, Rod.

[John Coloccia]

Personally, if I were going to rerun anything, I would run 10/3. If you ever want to upgrade to a larger collector later, you'll be good for 240V/30A and you'll have the neutral for running your relay. I'm not recommending you rerun anything but if I were going to take the time to do it, I would do it once and never revisit it again.

[Andrew Howe]

I appreciate everyones input and calculations. I ended up salvaging the 14/2 wire run for my overhead filtration unit and ran the 12/2 with a 20 amp breaker.

[Dave MacArthur]

I have a Delta 50-760, and I ran a 12ga for it.
(DOH! I see that while I typed all this, you made the right call and posted! Well, it took me too long to write, I'm not deleting it, and I can kinda tell you are an astute reader of the more discerning shop wiring threads anyways! Read on!)

This question comes up all the time, so I took the time to write a thread detailing how the NEC treats putting a motor, especially a DC motor, on a circuit, and stepping you through all the calculations for what would actually get permitted, not just the "that should work!" WAG.
You may find it useful to read for this and future wiring projects:

Sizing Wires and circuit breakers for 3HP and 5HP shop motor circuits (http://www.sawmillcreek.org/showthread.php?t=153271)

If you spec'd it all out, here's what I get:
1.5HP motor must be use NEC table 430-148 , Full Load Current for single phase AC motors. This says the number you MUST use for that motor is 20A. For continuous duty, which you must use for any motor if it's POSSIBLE to run it continuous (which it clearly is for a DC), you must use 125% of FLC for your minimum wire ampacity. That means 25 Amps. This is primarily for heat dissipation, not expected current flows.

You must size the wire for termination criteria as well as ampacity. Using 14-2 or 12-2 NM cable, you must use the 60C table for termination criteria, from table 310-16. The table shows that 25A at 60C can NOT be run on 14ga wire, but only on 12 ga and above. Therefore, you must use at least 12 ga wire, due to termination criteria of the wire hooking up to the circuit breaker itself. Why? Because the NEC knows that a it will take a 12 ga wire heated by possibly a 20A FLC, running continuously, to keep the wire heat low enough to not damage the CB it's screwed onto.

THEN you look at ampacity ability, and derate the wire for both temperature and bundling of wires (conduit etc.). NM cable has THHN inside it, so you could use the 90C table for ampacity. You can see that in fact, 14ga wire will run 25A current and stay below the 90C insulation damage point for THHN wire. However, if you had 4 or more wires through a conduit of > 2ft, you'd have to derate that by 80% multiplier, and if your wire ran through any ambient temp > 86F, you'd have to derate it further. So you likely have > 86F in the summer, which would derate the wire by .96 multiplier... which would drop 14ga below it's required 25A the NEC requires it to carry for FLC*125% of a 1.5HP motor. And the NEC doesn't care what the "real" or faceplate amps are, if it says 1.5 on that thing (it does, I have one), then you must use it's numbers. So, short answer is that in all liklihood if your shop gets > 86F, you have to use 12ga anyways for ampacity of the wire. Both required wire checks say you need 12 ga, so 12 ga it is.

If it was a dedicated circuit just for that DC, then you could protect the circuit by a 25A CB, all the way on up to 250% of the 25A FLC from table, 62.5A, and then bump it up to next normal CB of 70. This is because that DC motor is thermally protected for overload, so CB is not required to protect for that. HOWEVER!!!! This is not likely the case, or required for your setup--it is ONLY a special case for dedicated motor circuits properly calculated and attached.
If you are running that circuit as a general circuit that is not absolutely dedicated to the DC (which 99% you are, since it's just a plug in for a normal 20A circuit...) then you will be limited to 20A CB on that 12 ga wire due to the 240-3d "small conductors" requirement that 12ga must be protected by 20A CB (unless excepted as in the example above). Since the 20ACB is expected to protect the wire from the actual load you expect to run, (here you can use the nameplate one), 15A, you're good.

Whew!

OK..... Allll that being said, here's the REAL answer: that machine can be re-wired to 230V with two screw changes, and the directions for how to do so are on the inside of the elec box. DO IT! Now your amperage is just 7.5, and you actually COULD run it on 14ga if desired (bad plan for circuits), but you can certainly run it on a 12ga circuit with no concerns and plenty of circuit power left over to plug your jointer in there too! ;) I changed mine over to 230V, took 2 min.

Good luck, happy NEC reading!

[Bud Millis]

For the little extra cost - go big! 10/2 wiring thur the shop. That will meet the needs for pretty much anything in the future. 20 amp circuits, also dedicated circuits for things are always a plus.

If your going to do it, do it right the first time.

[Derek Stockley]

My local electrical inspector told me I should be running my delta 50-760 on a 20 amp dedicated circuit with a t-slot receptacle because the natural intention of a machine like this is to run it for a considerable length of time and while other machines are running.