Two electric circuits in my workshop fell out this summer. Rodents in the attic had nibbled on the wires, so I replaced most of them, but still no dice. When I flip the fuse lever on the circuit that feeds the lathe, the last digit on the rpm counter lights up, but as soon as I pull on the power knob, it begins to blink feebly and nothing happens. I have a separate fuse panel in my workshop, connected to the main panel in the garage. What course of action should I take?
You need to get an electrition out there pronto, and forget about the lathe. We're talking a very high likely hood of fire here, don't mess around! Call them Monday! Meanwhile, throw the main breaker off in there. You dont want to use it, get the attic smoldering, then leave. You could loose everything!
I did software engineering at home for years and once I heard a scratch-scratch-scratch in the ceiling over my computers. I banged on the ceiling and heard little feet running. I heard it a time or two again but was too lazy, er, busy with important stuff and didn't investigate until one day, scratch-scratch- --BANG-- the power went out.
I cut away the ceiling and found where a mouse had been enlarging a 1/2" through hole for a Romex cable until he chewed through the insulation, shorted the 110v, and exploded his brains all over the joists. This could easily have caused a fire.
In your case where you see a change when you apply a load could indicate a loose or partial connection (hanging by a thread or wires barely touching) which may have a high resistance which can let a very low current through at the full voltage. When the load is applied the current increases, the connection heats up due to the resistance, then the higher resistance causes the voltage to drop. Current through resistance: think light bulb filament. DO NOT USE THE CIRCUIT. The advice that it could be a fire about to happen is right.
I strongly suggest you immediately cut off the breaker to that circuit. If the entire shop is on a separate branch circuit or panel I suggest you kill the main power until the electrician can come. I personally would get up there and find the problem and fix it but if you are not highly experienced with wiring in structures it might be time to call in the electrician.
If you can easily locate the exact problem you might save money buy cutting away what is needed to give the electrician easy access. But be very careful. If a rodent damaged that one circuit it may have damaged another. Unless all the power is off, poking around could bump things, cause a direct short, and set fire to the building and/or electrocute you.
Oh, I thought of something else. There is also the chance that the wiring is ok and the VFD is flaky. Any way to plug it into a known good 220v outlet to test? Maybe remove the headstock and haul it somewhere, a buddy's shop?
A different load plugged into the suspected outlet could test it but if the wiring is in fact bad that test could cause the overheating problem.
The PM 3520 takes a 220 volt circuit, quite possibly when you ran new wires and hooked them back up you could have mistakenly wired the lathe to a 120 volt circuit. Also you said that you have a seperate fuse sub panel for the shop if so you're looking at 60+ year old technology, time for a qualified electrician. My day job is an Electrical Fire Underwriter Inspector.
Thanks guys for your input, which I took to heart. I ended up pulling all but one circuit out of the attic area of my woodshop so as to avoid more exposure to rodents. I will rewire everything "downstairs."
Here is my status: having ditched the nibbled wires, there is power from the sub panel to all circuits. BUT, as Robert suggested, the lathe circuit--from a 50 amp breaker--only puts out 110 volt (if my crappy volt meter is correct). What the hell is going on, to quote the trumpeteer.
And, PS, since I no longer have the original plug that came with the lathe, what kind should I get for that an the receptacle?)
Michael is right. Might be time for an electrician.
You can look up the plug and receptacle design by looking a NEMA chart. Looks Like a 6-50 to me, except that I can't imagine your lathe requires 50 Amps. Use a proper plug and receptacle to be sure you can't plug the wrong thing into this circuit.
A year or so ago I measured the current draw of my 3520B under no load, light load, and heavy load conditions, powered by a 220V (actually 240 V) circuit. This is what I found:
No load: 1.5 - 2 amps, at most
Light load: 2 - 3 amps, normal turning
Heavy load: up to about 5 amps.
By "heavy load" I mean the heaviest cut I could take on a 12" bowl blank, and really laying into it. I could only get it to 5 amps for brief intervals before I either dropped the cut or ran out of wood.
The smallest plug and receptacle for 220 V you will find at a big box store is likely to be rated at 10 amps or more. So, based on the above, there is no need to go with a really large setup.
Further, if you wish to add a switch to the input power cord, you can use a two-pole single throw switch that mounts behind an ordinary switch plate cover, like is used on an ordinary light switch. Again, there is no reason to go with a larger, more expensive unit.
Powermatic recommends a 220v, 20a circuit. The 3520B pulls 6.2a at full load. I have used the Leviton Pro Grade 20Amp outlet and plug with no problems for my 220v, 20a circuits. I am not an electrician so this is just my experience, no more.
Power input to the panel is by way of two "hot" wires and a neutral. (Unless the panel is only provided with one hot wire, which will give only 110V.)
If you measure the voltage between neutral and either one of the hot wires, you will get 110V (actually 120).
If you measure the voltage between the two hot wires, you will get 220V (actually 240).
A breaker for a 110 V circuit only makes contact with one of the hot wires. A breaker for a 220 V circuit has two output terminals, one of which connects to one hot wire, and the other to the other hot wire.
If you measure the voltage between the two output terminals of the 220V breaker, you should get 220V. (That is, black lead to one terminal; red lead to the other.)
If you measure from neutral or ground to either terminal of the 220V breaker, you will get only 110V. (Black lead to neutral; red lead to either terminal.)
Hope this makes sense. It's really quite simple after you've been working with it for about 50 years!
Aage, since the circuit apparently puzzles you, do you possibly know someone nearby with a good meter and some experience who can look at it? A second pair of eyes might quickly see the problem.
As others said, 50 amps is excessive for the lathe. Does that circuit feed the lathe only or other things as well? And more important, what gauge wire is used and how long is the run?
I use some 50 amp breakers in my shop, for example to feed my little welding room. All my welders and plasma cutter came with the huge plugs needed for 50 amp and the wire I ran is huge too and and quite difficult to work with. No way could I connect the big copper in that wire to the 20 amp 220v receptacle the Jim pictured!
If the wire connected to a 50 amp breaker is too small for 50 amps, you have a serious potential hazard. A direct short could overheat the wire and start a fire before the breaker can cut off the power.
A story: I did electrical work in a children's camp in central Mexico for a missionary friend. In their main building someone had installed a water heater 100 ft from the breaker box. Two very bad things: they used a 50 amp breaker and 100 ft of 14 ga wire strung across the attic, WAY to small for 50 amps! The 14 ga Romex cable was quite warm to the touch. A dead short on the far end would have likely burned the building down. The closest electrical supplies were a 10 hr drive. It was two years before I could get back and bring new wire and breakers. Yikes.
I recommend you get experience to look at your wiring. It might be something very simple or something horribly dangerous. If you don't know someone who can, I still recommend calling the electrician. Depending on the situation, a fix could be easy. As the honorable Doc Green pointed out, all this becomes extremely obvious with a bunch of experience!!
I'm in no way qualified to give advice on electrical stuff, but I think there's an answer. Is the 50 amp breaker a 2 pole breaker? The electrical panel has a supply that's split into 2 "legs" Each leg carries 110 volts. Breakers for 110 volt circuits can be inserted into a leg but to get 220 volts the breaker needs 2 contacts (or poles) to pick up 110 volts from each leg to give you 220 volts.
I grew up with 220 coming out of every socket (Norway) so I never had to think about these things. Dick Hines called me last night and explained what Doc lays out and when I rechecked the feed wire to the lathe (which is thick enough that I imagine it can handle 50 amps), two of the wires lit up both 110 and 220 volts, while the other combination of two wires showed 110.)
A friend of mine wired in the subpanel and he was the one who put in a 50 amp breaker combo. Since it only feeds the lathe, should I replace it with a 20 amp?
The breaker should not be rated for a higher amperage than the smallest wire downstream of it. If both are rated for 50 amps, and the lathe is the only draw on the breaker, . . .
>>> rechecked the feed wire to the lathe (which is thick enough that I imagine it can handle 50 amps)
The cable should have some numbers running down the length. These numbers will tell the gauge of the wire. If the wire gauge is too small for the amperage (and the length), the breaker absolutely needs to be replaced. If the gauge is large enough for 50 amps, as I wrote before the wire might be physically too big to use with a 20 amp receptacle. Without knowing the gauge, it is only possible to guess.
If you a clear about how to measure the voltage across the breaker AND between each leg of the breaker and the common, then you can trace from the breaker to the outlet. The problem could be as simple as a connection that is not tight. If you are not clear on this, you can learn how or get some help. If you don't have a good meter, any auto parts store, Walmart, or RadioShack will have one - it's worth having.
I HAVE seen breakers that were bad. It should be obvious if the voltage across the two screws is not correct. But be very careful measuring voltages inside the breaker box, wear good shoes, gloves and safety glasses. One slip can vaporize the meter probes and blow sparks and fire in your eyes. I do NOT recommend working in the breaker box unless you understand exactly everything inside. Even paying someone to help would be cheaper than a funeral!
Note that according to code the breaker is sized to protect the wires in the circuit, not the device powered from the circuit. The electrical code doesn't care about the device plugged in. You can easily run a very small motor on a 50 amp circuit. A motor problem might burn up the motor but it won't hurt the wiring.
However, again, a thick copper cable is difficult to work with and probably impossible to connect properly to a 20 amp receptacle and I believe it would be against code. If I had a thick #8 or #6 awg cable already run in the wall from the 50 amp breaker to the place where I wanted to use a 20 amp outlet, I would either run a new cable or put a small breaker box at the end and put some appropriate breakers in that box with a new piece of cable to receptacle for the lathe.
