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What size electrical wire?

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Forum topic by Oldschoolguy posted 10-05-2019 08:37 PM 657 views 0 times favorited 11 replies Add to Favorites Watch
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Oldschoolguy

108 posts in 691 days


10-05-2019 08:37 PM

Hey guys, Finally had it with contractor saws. So I returned the Dewalt table saw to H-D and purchased a hybrid table saw from Grizzly. Anyways, to be on the safe side I would like your opinions and comments or thoughts. The saw is 2 hp. and prewired to run on 120 volts 20 amp. circuit. I have to run an extension cord about 50 ft. So what size wire would be appropriate? Thanks y’all.


11 replies so far

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CaptainKlutz

3609 posts in 2349 days


#1 posted 10-05-2019 09:15 PM

Hmm, Have you read the manual for new saw regarding power requirements?
You may have fallen into a common trap for first time 2HP motor users:

Most true 2HP 120v motors recommend a 30A breaker in panel, as 2HP 120v motor has a 24A FLA (full load current).
So to answer your question: With a 30A capable circuit for a 2HP motor, normal wiring would be 10AWG wire. Hence, for 50ft 30A 120V extension cord, would also need to use 10/3 cord.

While TS motor only draws more than 50-70% of FLA current at start up; it might work like normal, or it might trip a 20A breaker on start up. It’s a gamble based on motor load, voltage and wire resistance.
Breakers are meant to be safety devices, not switches. If you repeatedly trip a breaker (50+ times), it becomes more sensitive, tripping at even lower current levels. Eventually, it will not work anymore, or trip every time you start the saw. :-(

Since switching a breaker from 20A to 30A requires new 10AWG wiring to replace the old 12AWG wire, and same amount of work as installing a new circuit; suggest you might want to install 240v circuit, and run the saw on higher voltage?
YMMV

Be safe, not sorry.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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CaptainKlutz

3609 posts in 2349 days


#2 posted 10-05-2019 09:55 PM

Just looked at a couple of Grizzly 2HP rated saws (g0771z & g0833p).
Interesting marketing specifications!

While the motors are marketed as 2HP, the actual current/voltage ratings are same as ~1.5HP motor. They also recommend a 20A outlet. Be really curious to see the motor name plate rating on the motors used, that allows this marketing misinformation?

This means:
if using one of these 15-16A rated ‘2HP’ TS motors from Grizzly, you can use 12/3 cord for extension cord, along with a normal 20A breaker and 12 AWG wiring circuit.

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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Oldschoolguy

108 posts in 691 days


#3 posted 10-05-2019 11:01 PM

Ok guys, this is the GO771Z model. I looked at the spec sheet and this is some of what I found for power requirements: 120v or 240v single phase 60hz. Full-load current rating: 15 Amps at 120v 7.5 amps at 240v. Minimum circuit size 20 amps at 120v, 15 amps at 240v. I don’t even know what this all means. Anyways, I should have looked at the spec sheet before hand, but they call for 14 AWG gauge wire within 6 foot of receptacle.

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ArtMann

1480 posts in 1671 days


#4 posted 10-05-2019 11:05 PM

I have a Grizzly G0715 2 horsepower saw that has been running quite satisfactorily on a 120V, 20A circuit for a couple of years. It came configured for 240V but the previous owner converted it over. I am quite certain the motor is more powerful than 1.5 horsepower because that is the size of motor I had on my Ridgid table saw before I acquired this one. The Grizzly is decidedly more powerful. The saw is running on a 6 foot 12 gauge extension cord but I would think twice before using 50 feet of extension cord that small.

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squazo

185 posts in 2500 days


#5 posted 10-06-2019 12:08 AM

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squazo

185 posts in 2500 days


#6 posted 10-06-2019 12:09 AM

id say double it to feel comfy

View Rayne's profile

Rayne

1315 posts in 2394 days


#7 posted 10-06-2019 12:29 AM

The manual specifically calls out 12 AWG up to 50ft on a temporary basis as they don’t recommend an extension cord. I think most table saws says the same thing though and most of us still use them. I’d be weary going 10awg as you still want to trip the breaker if something’s wrong.

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ArtMann

1480 posts in 1671 days


#8 posted 10-06-2019 03:23 AM

Are you saying that 10 AWG wire will somehow keep a breaker from tripping? I would like to hear the logic behind that assessment!


The manual specifically calls out 12 AWG up to 50ft on a temporary basis as they don t recommend an extension cord. I think most table saws says the same thing though and most of us still use them. I d be weary going 10awg as you still want to trip the breaker if something s wrong.

- Rayne


View ibewjon's profile

ibewjon

1974 posts in 3648 days


#9 posted 10-06-2019 01:05 PM

Definitely use a 10awg cord. Larger wire will have less voltage drop. Lower voltage increases current draw and power loss. So if you are right on the edge of tripping, it could possibly prevent tripping, but I would only use 10awg cord. (Sears always rated their tools in funny ways, such as “developed horsepower” , whatever that is, and I believe many modern motors are rated in a similar way. I took it to mean running with no load, but who runs a tool and doesn’t use it to do anything?) Voltage drop for 50’ of 12, over 3 volts and 55 Watts of power. With 10, it is less than 2 volts drop, and about 30 Watts lost. I run my tools on 240v AND 10awg wire. Voltage drop is less than 1 volt at 50’, but most of my cord are about 10’.

View splintergroup's profile

splintergroup

4007 posts in 2077 days


#10 posted 10-06-2019 02:46 PM

You are on the edge for 120V/20Am but the Captain’s advice is good. Dedicated 120/20A circuit (no other outlets or lights on the circuit) would be prudent and a 12/3 extension cord as short as practical. You want the proper receptacle (5-20R).

Ideally a 220V circuit would be the cats meow

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Rayne

1315 posts in 2394 days


#11 posted 10-06-2019 03:41 PM



Are you saying that 10 AWG wire will somehow keep a breaker from tripping? I would like to hear the logic behind that assessment!

The manual specifically calls out 12 AWG up to 50ft on a temporary basis as they don t recommend an extension cord. I think most table saws says the same thing though and most of us still use them. I d be weary going 10awg as you still want to trip the breaker if something s wrong.

- Rayne

- ArtMann


Yep, you’re right; no logic in that. Not sure what I was typing last night. Probably too tired to pay attention exactly what I was saying. I think at the time, I was thinking if the tool short circuited generating a ton of heat, the #10 wire is more than capable of handling the heat instead of somehow tripping the breaker (yeah, not making sense). The breaker needs to be the proper size, not oversizing of the wiring. Can’t edit my reply, so it’ll be a reminder to be focused when replying on things of this nature.

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