motor 'downgrade'?

[Tom Donalek]

I've been looking to add a jointer to my 'shop' (somewhere, somehow?). The Grizzly G0586 looks like a great value for the kind of work I'd like to do. My problem is that in my 100 year old building, the 'biggest' circuit available is 20A/120v. (The whole service for the building is 70A, and the wiring is such that adding circuits is not a real option until we do a serious overall upgrade.)

From the specs on this unit, I see that it can be wired for 120v, but draws 24A at that voltage. Would it be crazy to swap out the motor for one that wouldn't blow the 20A fuse and put the 'proper' motor back in when we are finally able to upgrade the electrical service. Of course, my follow up question would be: what motor (specs) would be the best bet for this application?

Alternatively, is there a device out there that would 'throttle back' the current the device could draw to avoid blowing the fuse? (I'm obviously thinking of 'browning out' the device, rather than just killing it like a tripped breaker or blown fuse!) I've done some poking around on the web, but I guess that I don't know what I'm looking for or what this thing would be actually called. (I've found power or current limiting circuits or devices for audio equipment, but not for power tools!)

I understand that either 'solution' would limit how much 'work' the unit could do, but I'm not doing any real production work, and could live with making more, thinner cuts. In this thread:

http://sawmillcreek.org/showthread.php?t=28745

Dev speculates that 2HP is a reasonable low end for an 8" jointer, and I'm guessing that I would be talking about 1.5HP in order to meet the electrical requirements. Crazy idea, or should I just look at 6" jointers?

[Don Baer]

Current limiting the motor will probubly not be a viable option since it could burn out the motor. accept for starting the motor will draw whatever current is needed based on the mater being cut. I have been told that for every 4" of joiner you need 1 HP so the 2 HP is a reasonble number. In theory at 120 Volts a motor should draw ruffly 10 amps per horsepower but that number doesn't alwasy hold true since it depends on the design of the motor, some of the cheap motors are less effecient and will draw more current. I'd look at several manufacturers motors and get the highest effency that you can. Also by limiting the thickness and width of the material you can limit the anmount of current you draw.

Another thing to keep in mind is can you run a dedicated circuit using 12 gage wire you can then safely fuse it for 25 amps.

[Barry O'Mahony]

Another thing to keep in mind is can you run a dedicated circuit using 12 gage wire you can then safely fuse it for 25 amps.??????

NEC 240-3(d) states that the overcurrent protection for #12 copper branch conductors shall not exceed 20A.

[Walt Pater]

[QUOTE=Tom Donalek]
The whole service for the building is 70A, and the wiring is such that adding circuits is not a real option until we do a serious overall upgrade.)

Tom, in the grand scheme of things, that serious overall upgrade might do more for your woodworking than a jointer. Sorry to be the buzz-killer.

[scott spencer]

Up until quite recently, many 8" jointers sported a 1.5HP motor so I don't think it'd be all that unreasonable from a performance standpoint. The value of whole think might be another matter. While I respect most Grizzly machines, there are others that would fit your electrical requirements as a stock machine. I wonder if Griz has any more of their older 8" 1.5HP jointers in stock (G1018?).

The Bridgewood BW-8J seems to fit the bill. It has a 1/5HP Baldor motor that did quite well in a recent jointer test IIRC.

[Clint Malone]

I agree with Walt, do it right and fix the electrical problems.

[Charlie Plesums]

It has been what seems like 100 years since I took those motor engineering courses, but I suspect (can't prove, since I don't remember the details that far back) that the starting current will be roughly the same whether you have a 1 hp motor or 2 hp (or 3). It will be related to the inertia and the "friction and windage" of the motor, belts, cutters, etc. Likewise the running current will be based on the friction to keep it idling, plus the cutting load. A bigger motor may have slightly more inertia and friction, but I bet that will be a very small part of the equation.

Bottom line, if you downgraded the motor, I bet that you would find the current very close to the current required by the original motor. If you keep the original motor, and keep the workload on the machine light (as light as if you had the smaller motor), you probably won't pop the breaker.

[Tom Donalek]

Thanks for the replies! Regarding the service upgrade, it's on the priority list, but mine is only one vote among many, and no one else is having problems with the service limitations. :mad:

Regarding AC motors, I know very, very little, but I thought that normal AC motors draw a lot of current as they get up to speed. (I guess that you could also say that they are highly inefficient when they aren't running at their 'correct' speed) My TS, a DeWalt DW746, has a '1 3/4 HP' motor (MFR? Efficiency? Who knows?). It will blow a 15A fuse immediately as it tries to get up to speed. But on the 20A circuit, it's fine. I haven't really jammed it, but I've given it a fair amount of load at times, and it hasn't blown the 20A fuse. I'm guessing that a 2HP motor wouldn't draw more than 20A when idling or under a light load - but I do worry that it would blow a 20A fuse when getting up to speed! I wonder where they get the "24A" rating? Thanks again!

[Kent Fitzgerald]

There's another issue, which is that the G0586 comes with a 240V (only) magnetic starter. To run it at 120V, you'd need to replace the mag starter (another $50 or so), or "downgrade" to a manual switch. Considering this, I agree with the other replies that money would be better put toward upgrading the wiring.

[Dev Emch]

Given your particular situation, I think your on the right track. For the most part, 6 and 8 inch jointers are stick jointers. That is, they are used to establish accurate surfaces for gluing edges and some surface jointing (limited to 8 inches width).

Truth is, most folks dont monkey with the jointer setups. Once you get the right sweet spot cut (you know it when you hear it), you rarely change the setups (depth of cut). And this setup is usually about 1/16 inch or less. Sometimes it goes up to about 1/8 inch but that is an extreme. These are stick jointers and are not used the same way that aircraft carrier sized heavy iron is.

So as has been mentioned, it has been tradition that the motor on an 8 inch jointer was 1.5 hp. For years, everyone was happy happy. Pushing the power to 3 HP is more a marketing ploy to mimick heavy industrial iron. Its pretty hard to reaonsably push an 8 inch jointer to tax a 3 hp motor unless your taking a 1/2 inch thick single pass cut! Not Likely.

So to answer to your question. For the short term, you should be O.K. using a smaller motor of say 1.5 hp. But for the long term, I would seriously look into upgrading your wire job. Right now your power limited and this may hinder your future success. So go out and get a 1.5 hp motor compatible with your frame number and speed and repower your jointer. Keep the mondo motor that came with it. And eventually upgrade your power picture to allow you to use the larger motor and get larger toys as well.

Good luck in your quest for dust (shavings)...

[Curt Harms]

It will blow a 15A fuse immediately as it tries to get up to speed. But on the 20A circuit, it's fine. I haven't really jammed it, but I've given it a fair amount of load at times, and it hasn't blown the 20A fuse. I'm guessing that a 2HP motor wouldn't draw more than 20A when idling or under a light load - but I do worry that it would blow a 20A fuse when getting up to speed! I wonder where they get the "24A" rating? Thanks again!

I assume you're using screw-in fuses instead of circuit breakers. Can You find "slow blow" fuses? Any motor's starting amp draw will be several times its idling amps FOR A FRACTION OF A SECOND. If your 15 amp fuses are "fast blow", that may be part of the reason why the saw will blow the 15 amp fuse but not the 20 amp "slow blow" fuse.

If it were me, I might take a chance until I were able to swing an electrical upgrade. As someone else mentioned, you'd want to check into the switch situation. One other thought--do you have more than one 120 volt circuit in the structure? If so, is there any chance of converting 1 120 volt circuit to 240 volts? Where there's a new tool, there's a way:cool: Good luck.

Curt