Using harbor freight 20 amp DC with 13 amp saw on 20 amp circuit - Woodworking Talk - Woodworkers Forum
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post #1 of 13 Old 06-22-2019, 10:02 PM Thread Starter
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Using harbor freight 20 amp DC with 13 amp saw on 20 amp circuit

I have a 20 amp circuit to my garage.

Currently have a 9 amp rigid toolbox style vacuum, and a 13 amp table saw ( delta 36-725 ), they both work ok together, but the rigid dims when i start the saw, clearly pushing circuit limits already. It will also often have lights, computers, washing machine running, nothing is dedicated. Right now nothing is tripping the breaker.

I am looking at getting a harbor freight dust collector, either 1 hp or 2 hp, both of which have induction motors.

The 2 hp is rated at 20 amps, and concerned it might trip the fuse, though it seems a better deal. Redoing the wiring just isn’t an option, probably do that when i move.

The 1 hp is obviously less powerful, but it might be usable - thinking of using it with a thien directly hooked up to the saw, and that it can be made to work. Goal is for this to be all inside my table ( along with a router and down draft table ) via direct connects, not for a workshop sized system. I also roll the table out front, so fine dust is not the main concern.

But i would like a three way split, hooking up to attachment, to an under table hood, and to an over hanging arm, thinking the 2 hp would just work better, really comes down to if the fuse can handle it.

Anyone have the 2hp and a similar amp draw on their saw, is this pushing things too far? Or is the ratings just really high and they work ok together.
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post #2 of 13 Old 06-22-2019, 11:14 PM
where's my table saw?
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NOPE, you are overloaded!

The HF DC draws about 20 AMPs and that will trip the breaker. You need at least 2, maybe 3 more 20 AMP circuits. Have an electrician do the add ons and be safe, rather than sorry. Overloaded circuits will cause fires. I have wired 5 separate 100 AMP subs for my shops, garage and kitchen appliances, in addition to all whole house wiring, so I have some experience. I have 400 AMP service to the house at the meter, so there is plenty of power coming in. All my DIY wiring was approved by a licensed electrician before we hooked it up. Don't mess around, get it done right!

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 06-22-2019 at 11:17 PM.
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post #3 of 13 Old 06-22-2019, 11:14 PM
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My best guess is that even the 1 HP model will trip the breaker if you're running other gear at the same time. There's a high inrush of current in starting a DC that will certainly push the limits of your circuit.

We have the 2 HP on a 15 amp circuit in our garage and in testing I see it pulls about 12 amps, if I recall correctly. It's been a few years since I tested it, though. But when it starts it pulls a lot more than 12 amps for a second and then settles down. I think if I had something else running on that circuit and turned the DC on the breaker would trip.



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post #4 of 13 Old 06-23-2019, 07:29 AM
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There is something wrong with your understanding of what is on what circuit in your garage. If you had all that you list on one circuit and even a portion of it ran at one time it would blow the circuit. Also code in most places does not allow that collection to be on only one circuit.

I think that you have a need to hire an electrician to map your garage circuits and advise you.

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post #5 of 13 Old 06-23-2019, 09:35 AM
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Another thing to consider is when figuring a constant load on the draw of electricity it should be limited to 80% of what the breaker is rated at. When figuring a 20 amp circuit you need to think along the lines of 16 amps. Electricity generates heat just like the coils in a space heater. The breaker is just designed to blow at the very limits of the 12 gauge wire connected to that breaker before it starts glowing like the space heater. When the wire gets too hot the insulation starts breaking down and first thing you know the wires are touching each other which could lead to a house fire. If you are needing that much power more circuits are called for. Sometimes that means installing a sub-panel in the shop if there isn't enough spaces in the main box or the distance is too far.
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post #6 of 13 Old 07-06-2019, 03:45 PM
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You really need to consult a licensed electrician and find out what your options are, there is a limit as to how much you can run off one circuit safely.

Wise men speak because they have something to say; fools because they have to say something -Plato

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post #7 of 13 Old 07-06-2019, 05:29 PM
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Also beware of using a breaker as an amp meter, that seems to be what you are attempting to do and it is dangerous as hell

If you have all the things you stated running at the same time the breaker should have tripped already, I have seen 100 amp breakers trip at 10 amp draw, and I have seen 10 amp breakers not trip with a 100 amp draw

And if it is Federal Pacific, all bets are off, they were made in the late 70's to early 80's and they have burned down more buildings then arsonists
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post #8 of 13 Old 07-07-2019, 08:14 AM
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I think this topic is dead. The original poster has never been back.

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post #9 of 13 Old 07-12-2019, 04:28 PM Thread Starter
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The facebook login thingy was not working, so could not respond.

I think you basically answered my question, I am getting the 1 hp dust collector, which is at 7 amps. Again I specifically stated I am not redoing the electrical.

I didn't have the dust collector, so I could not measure it, I was deciding which collector to buy which could work with my new 13 amp saw on a 20 amp circuit. Lot of this is getting off topic, and making assumptions - since there is ONE outlet in the garage, its definitely all on one fuse. Nothing I described really should exceed 20 amps in how its used, obviously not everything is being run at the exact same time, or actual amperage is lower than stated, and just assuming the fuse is bad sidetracks everything. I know how to measure amps, and will keep these issues on my radar.

Most homeowners, casual users, will hook up a vac of some sort to their saw, the new ones all have ports, they are not going to think about the electrical until their fuse starts popping. I assume this is why the low end delta is 13 amp (same as the lowest end ryobi tablesaw), partly why I got it over the higher end version was the slightly lower amperage, and probably why the low end 1 hp dust collector is 7 amps, they designed the saw to be sold to the homeowner with a single circuit in their garage. Just reading about the history of saws, a lot of the reasons why they are designed as they are, is what the average customers electrical is set up for, higher end saws in contrast need electricians to wire circuits for them, and often have special plugs. If i was doing that I would be getting a sawstop, not the lowest end delta.

As I get this working I will be measuring the actual amps, if its an issue then I will be adjusting the table to use less, not the electrical. When not in use, its not plugged in. Please focus on the point here, how do I design this "table" so it runs on one 20 amp circuit, ideally one where it can run a few other things which draw very little power, using ACTUAL amperage.

This is casual use, not continuous, machines which use a lot of amps are run at different times. The main issue is startup which spikes "higher" than stated amps, which should describe the running load. I am doing this with the assumption that I will be starting the saw only after the collector is at full speed. I also only need to do so many cuts to make frames, probably in comparison to others usage, mine will be lighter. I will likely use it for bigger projects intermittently, but this isn't for 3 hours at a time, hence the 80% does not apply. Most likely it will be on for a little bit, then off, and the whole thing will be unplugged after an hour or two. This basically means I can do it to 100%, not to just 80%, and be within code. Now there is nothing wrong with having a nice safe extra margin, its probably a good idea if you are setting up electrical for your shop, but its just not required here.

Even then a 2 hp dust collector really seems to require it's own circuit, even at 12 amps instead of is rated 20 amps, which is my original question, based on this so far, my conclusion that is just too much, and even my 9 hp shop vac is too much juice, so I went and got a 1 hp HF dust collector, with a induction motor, and will just deal with it being underpowered. Sounds like it works fine as far moving chips if hooked up to a single tool but is pushing things, and really not geared for fine dust collection.

Running the HF 1 hp full without any pipes or bags, then turning the saw on, both are able to run at full, the 9 amp rigid shop vac is audibly affected by the saw starting. Since the saw is 13 amps, and largely I won't be running other things beyond lights, should not be an issue even if its running at full stated amps, since it adds up to 20, and my fuse is 20.

Note I am not really using the saw at this point, I am just testing it to see if it can run, and will have actual measurements before I start using the saw under load. Dust collectors without ducts and bags and the like will run at far higher amperage than one which is doing the work of pulling dust from tools. Until I have it all set up and hooked up to ducts, it is premature to test the amperage being used.

Again, my parameters for this discussion are:
  • I am not planning on staying where I am long enough to warrant a electrician inspecting, or even coming out. If I had one come out and check things, I would either just set up dedicated lines for everything, including 220v, or set up the electrical myself and have someone I hire double check I ran everything right and perhaps do the final hookup to the main fuse box. But its not really an option.
  • My goal is making a single table which runs at 20 amps at most, ideally with enough extra so it does not preclude having lights on and a few other things on, which I can plug into an outlet via extension cord. I plan on moving this really heavy table to whereever my art studio is. If other things are an issue I won't run them at the same time, same as we can't run the toaster and the microwave at the same time without blowing a fuse.
  • I am specifically trying to be portable. My goal is to be able to move quickly, to have this setup in a way that fits onto a liftgate of a rented truck, and can be rolled into a new location and be ready to use once its plugged in. I am not building a workshop, its a table which lets me do wood working, so as long as I have a 20 amp circuit, I can use this.
  • Since the 1hp is rather underpowered, I am looking at the ducts being as efficient and short as possible. Really this is probably going to be trial and error mostly, but since I had to compromise on power, I have to really ensure this is optimized. The dust collection port on the saw is rather small, so might be revising that.
  • I also got a amperage LCD display which I can wire into the electrical directly, so I can keep track of it all the time. Planning on having one console where everything is controlled, with wiring set up so I can adjust it as needed, or have things turn on autmoatically. Using PVC to run lines to each device, which adds more safety. Also using GFCI outlets to detect shorts.
  • Part of this is curiosity, and I am a computer programmer, and have been making computer circuits for years, have done both computer repair and was a wire dog in the military, so wanting to look at things like pneumatic controls, small computers, automatically opening gates, and other automation. Some of the home brew CNC machines features are probably going to be added in eventually, though this is secondary, mostly right now the goal is to make the top and sides squared so I can add accurate rails at some point.

I am looking at a three stated switch to turn the dust collector on, which is wired to both the 1 hp dust collector and the shop vac, this is important since both seem to do better at different things, and being on the same switch, ensures I am not running both at the same time. I want to run the shop vac when I am using handheld power tools like my sander, and the dust collector with the saw/router. But when I am just sanding, I might just use both together since its 7 amps and 9 amps ( per their rated amps ), well below the 20 amps, and be able to have a down draft table.

Thinking of adding an air tank and a .75 hp air compressor, this looks like 3-4 amps relatively quiet, and should not be running at the same time I am running the saw/dust collector. Rather the air tank will be full. I would like to look at using compressed air to open and close the gates, but this is mostly aimed at learning how pneumatically controls work, and a brad nailer. It might lose too much air velocity if I add in gates.

All of these will will be put into the heart of the table, soas to muffle and limit the noise with a very solid enclosure, and a baffle for the exhaust, since its an art studio noise is an issue. Obviously you can only do so much, but the goal is to minimize it as much as possible.

Right now I have a torsion box setup for the base, putting in locking casters ( rated at 500 lbs each ) and have some heavy duty rubber brackets which I have attached the dust collector to minimize noise. Dedicated 4" pvc "sewer" pipe is hooked up to the blower. The whole thing looks like something out of the steam punk scene, like a rocket on the back of a sled.

Last edited by Brian Meyer; 07-12-2019 at 04:32 PM.
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post #10 of 13 Old 07-12-2019, 05:28 PM
where's my table saw?
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Here's what actually matters .....

If you have a 20 AMP beaker and are running 12 GA wire to the only outlet, even two outlets with your machines running for the operation you need .... and it doesn't trip you'll be fine. GFI outlets are notorious for false trips so beware of that. As you know, starting AMPs are different than running AMPs so avoid starting more than one at a time. The 9 AMP shop vac seems a bit excessive, but a "Kill a Watt" meter will tell you what the draw is:

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #11 of 13 Old 07-12-2019, 07:57 PM
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Youre making a lot of very dangerous, very incorrect assumptions in that last response mate. First off, youre assuming that your 20 amp circuit breaker will always, and only, break at exactly 20 amps, and you can get the load up to 19.9 amps and never have any issues. It wont. Your breaker could blow at 18, or it could not blow until you hit 22 amps, and it probably wont be the same each and every time. To illustrate, your table saw ALREADY exceeds that rating on startup, induction motors draw massively more current then theyre rated for for a short time after turning them on.

Your second assumption is that your tools will always only draw the same amp load, and itll never exceed the nameplate. Thats just flat-out wrong. An electric motor, any electric motor, will draw more current in certain circumstances, that nameplate is just the max rated load. If you stall the motor on a table saw, even for a second, it could briefly draw 18 amps instead of the 14 its rated for. Even ignoring that possibility, every single motor will draw massively more current on startup, which will trip a breaker. A 1hp 10 amp motor might pull 2x that amperage on startup. If your line voltage varies from the 120v nominal, thatll effect the current draw of a motor. Say your house is on 110 service instead of 120 for whatever reason, thats an extra amp on a 10 amp load. Got an extension cable? Welcome to voltage drops, same if your outlet is too far from your breaker panel and the original electrician used the bare minimum gauge. Voltage drops to 100v because of that 15 foot 14 gauge cord youve got, congrats, youre drawing 2 extra amps over the rated at minimum, and thats assuming the motor actually starts and gets up to speed, instead of just constantly drawing inrush current trying to catch up.

Another mistake youre making is assuming that manufacturers know or even care what tools youre using with what tools. They dont, not even a little. The fact that your table saw is rated at 13 amps and a shop vac is rated at 7 amps is, to put it simply, dumb luck. That doesnt mean you can add the 2 together and end up with a 20 amp circuit, as already explained the math doesnt work like that. Go check the manual for your table saw, look at the section on power supply. Nearly every saw that you can find will recommend the same thing; a dedicated 20 amp circuit, no extension cords, nothing else running on the same line.

And for the record, i have that 2hp dust collector and that exact table saw. If i put both on the same 20 amp circuit, the circuit blows. Same thing with the smaller one. Youve had multiple people tell you this exact same information already, but it seems like youre just fishing for the answer you want to hear, so here it it: Yeah, sure, itll work, right up until it doesnt

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post #12 of 13 Old 07-13-2019, 12:23 PM
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Don't waste your time measuring amps, I can tell you the circuit is overloaded. I can't believe you haven't tripped the breaker yet.

The table saw and DC should be on their own circuits.

High amp draw are not good for motors and capacitors.

Be aware start up amps on an induction motor are much higher and are what cause the breaker trip.
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post #13 of 13 Old 09-07-2019, 12:51 AM
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Unless you have a very small shop the 1HP will not cut it. Also you need to add either a Thein Baffle or Cyclone to collect most of the dust before it gets to the impeller in the dust collector.

Can you add a breaker and outlet at the circuit breaker box and then use either an 8 0r 10 gauge extension cord which you can easily make.
Also look at and Bill has some EXCELLENT information about dust collection and Phil's site has a LOT of information about the Thien Baffle.
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