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Forum topic by yinjuehua posted 12-21-2011 09:52 PM 1135 views 0 times favorited 6 replies Add to Favorites Watch
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yinjuehua

11 posts in 1394 days


12-21-2011 09:52 PM

My shop is a small stand-alone shed. It has a 20 amp fuse in it, and I also have circuit breakers in my house. The 20 amp fuse burns every time I cut something like 2.5 inches maple on my table saw with my vac running. (I’m using a thin kerf blade already..)

My table saw is DEWALT DW745 with a 15 Amp motor, and my vac is 6 HP RIDGID WD1450.
I did some research and find out:

amps (A)= 15 and volts (V)=120 then
A X V =1800 watts (W)
1800 watts X .00134 =2.412horsepower
So, my 6HP vac is two times powerful than my 15 Amp table saw? Harborfreight Industrial Dust Collector has a 2 HP motor, so it actually use less electric intensity to run?

Grizzly G0715P table saw is a 2 HP machine:

2 HP / .00134 = 1490 watts

1490 watts / 120 V = 12mps

Why does a big hybrid table saw use less electricity than a small contractor saw? If I brought a Grizzly saw, a Harborfreight dust collector, and used a 25 amp fuse, will I have any electrical or safety issues´╝čThanks.


6 replies so far

View Lifesaver2000's profile

Lifesaver2000

524 posts in 1835 days


#1 posted 12-21-2011 10:03 PM

First of all, you should not replace the existing 20 amp fuse with a larger fuse without confirming (preferably with a qualified electrician) that the wire that fuse is protecting is large enough to safely carry 25 amps.

Secondly, the horsepower ratings on just about everything is pretty much nonsense, especially if you are trying to compare one type of item (like a saw) to another (like a vac).

As far as the saw to saw comparison, it might be that the Dewalt has what is called a Universal motor, compared to the induction motor on the on the Grizzly. The induction is probably more efficient, therefore creating more power at a lower amperage.

There are lots of people that know a lot more about this type of stuff here, and these types of threads usually attract lots of attention, so you will probably be getting a lot more information.

View brtech's profile

brtech

698 posts in 1645 days


#2 posted 12-21-2011 10:03 PM

The HP ratings of motors are always a bit suspect. A spec sheet says the Rigid requires 10A, which means it’s less powerful than your 15A saw.

Your problem is very simple: your Rigid pulls 10 A, your saw pulls 15 A, so your demand is 25 A but you have a 20 A fuse. Now, probably the vac doesn’t need 10 A while running, but still, your problem is 25A need fused at 20.

What is the size of the wire and what is the rating on the circuit breaker? Just changing the fuse to 25A may not work.

View Ocelot's profile

Ocelot

664 posts in 1361 days


#3 posted 12-21-2011 10:03 PM

Hello and welcome!

I would be very surprised if your shopvac motor really is 6HP, no matter what it says on it. A 6hp electric motor is quite large and heavy (at least 50lb). Also, to get 6HP from 110v, the motor would have to draw something like 40A (actually more, since the motor will not be 100% efficient) – which is beyond the rating of any normal 110v circuit.

But still, you are blowing the fuze or tripping the breaker – and that’s a real pain. Have you considered just running an extension cord out from the house? You might be able to supplement the meager power in your shed by running a 12-AWG or (if you can find one) 10-AWG extention cord out there. Plug the vac into one circuit and the saw into the other.

-Ocelot

View Sawkerf's profile

Sawkerf

1730 posts in 1791 days


#4 posted 12-21-2011 10:50 PM

Forget all the calculations – your shop is grossly underpowered if it only has a 20 amp fuse. Since it’s a fuse, there’s a good chance that the wiring is ancient too. Is the fuse box fed from your house? If so, how far is it from the house? Depending on the wire gauge between the house and your shop, you may be seeing substantial line loss just getting to your fuse.

You really need to get an electrician to check everything from the house to your shop and upgrade your service to something that will let you run a few tools at the same time.

-- Adversity doesn't build character...................it reveals it.

View thebigvise's profile

thebigvise

190 posts in 1623 days


#5 posted 12-21-2011 11:06 PM

I wholeheartedly agree with Sawkerf! Yea, it’ll run you a few bucks, but you’ll be happy when adequate power is in the shop.

-- Paul, Clinton, NC

View Ocelot's profile

Ocelot

664 posts in 1361 days


#6 posted 12-22-2011 12:11 AM

The guys are right. Upgrade the electricals would be the right solution. My shop has 100A of 240v. I hoipe it’s enough. My planer will draw 25A of that. But… if you are on a tight budget, and don’t work in the shop every day, the extension cord from the house might get you by for now.

-Paul

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