Gloatworthy Unisaw Purchase?

[Chuck Lenz]

Tim, I'm just telling you what the manual says. Price out a new motor for that saw and I'll bet you'll change your mind about that 30 amp breaker you got in there.

[Tim Lynch]

Chuck,

Sorry, I'm not trying to be argumentative... I was responding to a question that was there a minute ago, but I don't see now. It said something to the effect of "what does the manual say?"

[Jim O'Dell]

If I could be so lucky when the time comes to get a cabinet saw!! CONGRATS!! Jim.

[Mark Rios]

I believe the breaker is sized to protect the outlet, not the wire. Code requires the breaker not to exceed the rated capacity of the outlet.

Enjoy your Unisaw, great saw at a fantastic price. I've got the 3 HP model. I found the HTC to be a good mobile base, but think about one sized for the an extension table should you want one in the future.

Actually Fred, this information has been discussed at length numerous times here in the Creek and in other forums. Here are a couple of references,

http://www.sawmillcreek.org/showthread.php?t=17552 Post number 10, 4th sentence.

http://www.sawmillcreek.org/showthread.php?t=3677 Post number 10, 3rd sentence.

http://www.inspect1.com/articles/arndhse3.html Point number 12.

There have been a number of electrical folks here that have told us this info many times. I also just called an an electrical engineere that I know to confirm.

However, as you mention, one MUST use the proper electrical receptacle for the circuit size. But one must match the receptacle to the size of the circuit (not the circuit to the receptacle), and the circuit must meet the needs of the load. The receptacle is merely a junction between the tool/machine/load and the curcuit that carries the load.

While I work in the building trades for my day job, reomdeling and so forth, I'm merely parroting what other, more knowledgeable folks have been kind enough to impart to us here and in other forums.

[Andrew Williams]

Nice gloat Tim!


Send me a PM and maybe I can drop over with my TS-aligner Jr...


Andrew

[Rod Peterson]

The Delta 36-L51 Unisaw manual says : For five horsepower single phase ( 230 V ) units the circuit should not be less than #10 wire and should be protected with a 40 Amp time lag fuse.

Just to illustrate that a manufacturer's documentation isn't always dependable, it would be a code violation to follow the minimum instructions (#10 wire and a 40 A fuse). #10 wire is a 30 A circuit and you can't use a larger protective device than the ampacity of the wire.

Moreover, where, in this day and age, do we have fuse boxes? Yeah, I know, old work, etc. Still, the standard protective device in the home for the best part of the last half century is a circuit breaker. The manual should, at the very least, note that a circuit breaker will perform the exact function of a Slo-Blo fuse, namely not nuisance trip with starting currents.

I suggest you read the manual before you ruin your saw, and maybe even call a electrician if you have any doubts.

I doubt very much one is going to ruin a motor by running it on a marginal circuit (which 30A really isn't for a 5 HP motor). Maybe, if it was running all day hogging hard maple every working minute, which, in any event, would trip the thermal device on the motor, but otherwise, I don't see the risk in a hobbyist environment.

[Grant Vanbokklen]

I bought the saw on eBay. I had been a regular watcher for Unisaws and Powermatics.

Great deal! How long a time have you been searching actually?

Now this has me more hopeful that I should hold off and keep searching eBay more often. I've kind of stuck local and watched Craigslist and only wondered over to eBay here and there because my gut tends to want to avoid shipping. I wonder how often deals like this happen.

But Sawmill is a great source for deals, and I'm sure with help from everyone here or luck on eBay and the like I'll get a saw that I'll be happy with.

[Tim Lynch]

Thanks for the comments Rod; I agree.

I wouldn't consider a #8 circuit marginal, since it has plenty of ampere capacity, and moreover, the #8 wire will have no appreciable voltage drop over the short distance from the panel at 220V. Not much risk there of harming the motor.

As far as breaker size, I was only expressing my surprise that a 20A breaker would start a 5HP motor. I expected it to trip on startup current and/or possibly when the saw was loaded. As long as it doesn't trip and inconvenience me, it poses no risk to the motor. It can't restrict current; it can only shut it off.

Other info: My twist-lock outlet and plug is rated 250V, 30A and the Unisaw came wired with #12 wire plug cord. So the outlet is the limiting element in the circuit, but one could certainly argue that to protect the 20A plug cord, one should use a 20A breaker.

With regard to the manual, I'll just say I'm big on manuals. I read it twice online before I got the saw, followed it during assembly, and then once more for good measure.

I appreciate that folks are looking out for me and I don't want this response to come across the wrong way. The Creek is a great place.

[Tim Lynch]

Hi Grant,

I've been an eBayer for years, so it's hard to say how long I've been looking. Months at least, but usually half-heartedly. Something possessed me to bid this time around. The shipping estimate didn't seem too bad, and I already had a fence, so this one fit the bill pretty well. I was quite surprised that I won it.

[Rod Peterson]

Thanks for the comments Rod; I agree.

I wouldn't consider a #8 circuit marginal...

I was saying marginal tongue in cheek, that's why it was in italics. And actually, I was referring to a 30A circuit as marginal (italics again--same reason) for a 5 HP motor, which it probably isn't anyway.

...the Unisaw came wired with #12 wire plug cord.

If it's like the 3HP Uni, it has a 15A plug on it, too (both blades horizontal). Much like 120V circuits, there's an exception in the NEC (don't ask me to quote chapter and verse) which permits 15A receptacles (15A pin configuration, not 15A capacity) on 20A circuits.

So the outlet is the limiting element in the circuit, but one could certainly argue that to protect the 20A plug cord, one should use a 20A breaker.

Actually, no. I'm now stepping slightly beyond my knowledge base here and certainly beyond my supporting documentation base, but it's my understanding that the protection of the circuit by the breaker stops at the receptacle. That's one reason why you can plug lamps corded with 18 ga wire into receptacles supplied by 15 or even 20 A circuits.

A common misunderstanding about electrical wiring is that a circuit forces current into a device. In truth, a device only draws current that it needs (if there's a short, it needs a lot!). Even though the circuit may be a 20A circuit, it doesn't supply any more current than the device demands. That's why we don't have little 500mA fuses on our clock radios plugged into a 15A circuit.

With regard to the manual, I'll just say I'm big on manuals.

Well, you have to be. That's really the only fall back position you have when it comes to warranty (should they decide to press an issue). I was only making the point that sometimes they can have information that isn't as correct as they intended or is ambiguous enough to be open to alternate interpretations. In those cases, I would think a conversation with someone in the technical department would be in order. Follow it up in writing if you're nervous about it.

I remember a discussion a year or so ago where someone was reluctant to heed the advice of several informed responders to put in a 30A circuit for his new blurfl. He said the manual called for a 20A circuit and he didn't want to wreck the motor or void the warranty. There are whole universes of lack of understanding that were in that statement that had me screaming at the monitor as I read it.

I didn't mention nice score before, so I'll conclude by saying, you suck!

[Frederick Rowe]

Mark - I see your point. I read the threads you listed and in hindsight my comment was somewhat oversimplified. It would probably be better to simply state that the breaker protects everything downstream (wiring, plug/receptacle, motor) by preventing excessive amperage; provided that all downstream components are properly sized. Properly sized being defined as the capacity to operate within it's design limits; both minimum and maximum amperage.

I think many of us tend to view 220v electrical runs like 110v circuits. In one of the referenced threads, there was discussion about splitting, or adding a second 220v receptacle to an existing one. If each tool was 20 Amps, one might reasonable conclude that the breaker should be 40 Amp. However, unless both tools are always running at the same time, as would a combination DC and secondary power tool, you would create a potential problem if only one was running as it would effectively be a 20 Amp tool running on a 40 Amp breaker. The breaker would only trip it 40 Amp was exceeded, far in excess of the tools rated amperage. As you rightly stated, this applies for the wiring as well as any electrical device drawing the power.

Best practice to evaluate the entire circuit, wiring and all.

[Rod Peterson]

...It would probably be better to simply state that the breaker protects everything downstream (wiring, plug/receptacle, motor)...

wiring Yes
plug/ No
receptacle Yes
motor No

The circuitry protected by the breaker ends at the receptacle. The best way to think about this is to go into your bedroom and look at your clock radio. The circuit it's plugged into is probably wired with 14 ga wire and is protected by a 15A breaker. The cord to the radio is almost certainly no larger than 16 ga and may even be 18 ga. From the plug to the clock radio no part of that is protected by the breaker. Moreover, there are no 1A protective devices anywhere along the way (except possibly internal to the clock radio) to protect the plug or wire.

To reiterate, the breaker's purpose is to protect the wiring in the wall.

And by the way, "rated capacity of the outlet," a phrase you used in an earlier post, does not refer to the ampacity of the receptacle in a 15A or 20A circuit (both 120V and 240V circuits)--it refers to the NEMA pin arrangement. 15A receptacles (and plugs) are fully capable of handling 20 amps, and they're permitted by the NEC, as well.