Help, please. My old jointer with a 3 hp single phase has a magnetic switch, with on and off, and a separate kill switch at knee height. Recently, when I push the on button, it starts, but then stops when I let up on the button instead of the motor staying on. I think I hear a click, which I am thinking is the release of the magnet. Any repair suggestions? A wiring diagram if I have to buy a new magnetic switch? (All of the wires inside the box are one color.) A good source for the switch if needed. I would like to retain the kill switch, unless the replacement comes with an easy off for safety.
Thanks to all of the pros out there for any suggestions.
Replies
s4s,
I'm not familiar with your machine, but the magnetic switch is probably similar to the Delta Unisaw's LVC (low voltage controller). I will describe how the LVC works, and maybe you can figure yours out. The description is aimed low, so forgive me if this is too basic.
The power to the motor is controlled by a double-pole relay. Think of the relay as just a pair of switches, one switch for each leg of the 220V supply. The relay's coil is energized by a 24V transformer controlled by the ON switch. The ON switch is a momentary-contact push-button. When you push the ON switch, the transformer supplies 24V to the relay coil, which pulls the relay contacts closed, turning on the motor. There is also a third set of contacts (normally open) which are connected in parallel with the ON switch. When the relay pulls in, this third set of contacts will keep the coil energized when you let go of the ON switch. The third set of contacts could be part of the relay, or it could be a micro switch that is mechanically linked to the relay. Either way, the function is the same.
The OFF switch is a normally-closed momentary contact push button that is in series with the third set of contacts. Anytime you hit the OFF switch, it kills power to the relay coil, turning off the motor.
Now, back to your jointer. Since the motor starts but does not stay on, there is most likely a problem in what I referred to as the "third set of contacts" for lack of a better name. There could be a bad connection or a dirty contact. If this third set of contacts is a separate micro switch, check the switch itself, the mechanical linkage to it from the relay and the connections to the switch.
The kill switch would be exactly like the OFF switch- momentary contact, normally-closed, wired in series with the OFF switch.
If yours is different from the above description, let me know and we'll figure it out; they're all electrically very simple.
Disclaimer and warning: I'm not an electrician (just an EE), always disconnect power, don't run with scissors.
Rick
Thanks for the information. How would I identify the third set of contacts? When I open the box, after unplugging the power cord, I see what looks sort of like circuit breakers. Where would I clean it? Seems to be a sort of sealed plastic box or two. I'll look closer when I get home. From the pix you probably guessed that the jointer, although dearly loved, is not part of my day job.
I'm wondering whether it wouldn't be easier to just replace the whole thing with a modern magnetic switch. Where would I go for one? Who supplies this sort of thing? Can I get it on the net? Are they expensive?
s4s,
Can you take photos of the guts and post them? It will look intimidating at first, but really simple when you get down to it. If you can take photos that show the wires and parts clearly it shouldn't be too hard to figure out. From your first post it looks like you have good photo capabilities. Awesome jointer- makes mine look like a toy, and some great lumber in the background too.
I don't know about replacement cost. Yours looks like an industrial machine, so I would guess that the magnetic switch is worth fixing.
Rick
I'll post a photo of the machine tomorrow if I can't fix it tonight. Thanks for the offer. The lumber is largely cherry. I found a flitch of 24-28" wide, 12' long 5/4, and bought to whole thing (from a 2d mortgage). It is going into a sideboard, but there will be much left. The sides are 18" single width, and the top will be 19-19 1/2" single plank. Enen that jointer will not handle that width. I will deal with it on the planer with a sled and wedges before hand planing and scrapoing to surface. I hate the look of sandpaper.
s4s,
CGREEN hit it on the head with the circuit diagram. It's the holding circuit that's suspect. The only difference from my description is how the control circuit is powered. In the low voltage system that I described, L1 and L2 in the diagram would be powered by a 24V transformer and the relay coil would be a 24V coil. This is done in some systems so that the ON and OFF switches can be located remotely from the control box, and you would have 24V instead of 240V in between. If your ON/OFF switches are mounted directly in the control box, you probably have the circuit that CGREEN has drawn. Notice that the main relay contacts are not drawn on the diagram.
Even if you end up hiring someone else to do the repair for you, at least you know enough not to get taken. I hate when a car mechanic tells me my muffler bearings are going bad. Good luck and be safe.
Rick
So, the problem continues, due to my lack of electrial skill. Attached are photos of the switches, with covers removed. I went to Graybar, and they recommended a magnetic starter, model No. 8536scg1v02 from Square D at $230. Yikes. So, I ordered a 3 hp magnetic switch from Woodworkers Supply for $59. If it works at all, I will try to wire in the separate kill switch. How wrong am I so far?
s4s,
Your magnetic switch is not a low voltage type, so the circuit would be as CGREEN has drawn. That makes it even simpler. From the picture, I can't see how it could work... there must be other connections that can't be seen in the photo. You said this used to work? The part that says Sylvania is the relay, or contactor. I need to be able to see the connections to the relay- need a photo from above and below the relay to figure out the connections for the holding circuit. Your ON/OFF and kill switch should be fine, so you could put those back together.
One thing you could try: remove the plate that says Sylvania and you should be able to access the contacts for cleaning. Please make sure you have the machine unplugged- I like to have the plug right in front of me to make sure.
Yup, industrial magnetic starters are not cheap. I don't know about the $59 one. I would fix the one you have.
Rick
Does that say press press to reset on the top right hand corner? Have you tried that?
I don't know if this will help but have a look anyway. The circuit shown will not allow the machine to start after a power failure or after pushing the emergency stop switch.
The circuit work like this. Power enters through L1 (the Hot lead) to the emergency stop switch. Under normal operation the switch is closed which means the power travels through it to the stop button which is also closed. Power is also sent down to the motor control auxiliary contact. This contact is closed only when the motor is running. When you push the start button the power passes through the start button to the motor control relay. The power energizes the magnetic coil and closes the motor control relay auxiliary contact and seals in the motor control relay. When you release the start button the power then, instead of going through the start button goes through the auxiliary contact to keep the motor control relay energized. Electricians call this a sealing circuit or a holding circuit. Without power going to the motor control relay the motor will not run. By pushing the stop button you momentarily deenergize the power from the the control relay and the motor shuts off. If your machine is wired in this way pushing the emergency stop button will break the path that the power to flows and nothing will work. My guess is after all the rambling I'm doing is the motor control auxiliary contact is not closing. I say this because you said the motor will run as long as you hold the start button. Depending on the type and size of the magnetic starter on the machine the contact could be a separate relay or it could be attached to the side of the motor control relay.
I hope this helps good luck.
Don't you have a motor repair shop in your area? Have you contacted the switch manufacturer to see if parts are still available? They have technical support typically. It might be cheaper to put a new switch on if it's an old one. The new switch supplier can also give technical support on how to wire it. Again your local motor shop can help. Only take electrical advice from a known professional or hire an electrician. Not worth the risk of getting hurt or damaging your motor. I repair the equipment in our shop and this is the procedure I typically follow. Not an electricain but I pretend to be one at work.
Rick
Edited 8/7/2002 8:12:24 AM ET by rsl
Before you go throwing money at your problem, take your air hose and completely BLAST all the sawdust out of the controler box and switch box(es) if they are not in the same box. Many times the only problem is that enough dust and dirt settle onto the contacts and stops the power from flowing. Also, take a screwdriver and make sure ALL screws with wires under them are snug. If the unit is plugged in, check all the screws at the plug and the socket AND the breaker box. I had this trouble several times and found that one of the three wires at the breaker had loosened up. Voltages at the controller box were 110, 110, 82 !!
SawdustSteve
Thanks. I tried to do this last night, but found that my compressor took one too many trips to a job site, and has a leak. Could only get about 30 lbs out of it, which did no good. Now, two tools to fix. Why isn't life easier? I suppose there are worse problems.
check for an overload reset on the relay, had this happen on a sliding table saw. Two electricians messed around all morning because of this.
Overloads would not cause the problem. There are 2 types of overloads that are commonly used with motors. The first employs a heat sensitive switch the is mounted inside or on the motor (red reset button). When the temperature of the motor gets too high the switch opens and the motor power is shut off. The second is normally mounted in the circuit after the motor control relay (otherwise called the starter). This type of overload also opens the feed to the motor. It does this with a device called a heater. These heaters are like the element in a toaster except they don't toast your toast, they heat a bi-metalic spring that is mechanically connected to a contact that is in series with the coil in starter. When a heavy current draw occurs the heaters heat up and in turn heat up the bi-metalic spring causing it to bend which in turn causes the overload contact to open which shuts down the motor. This type of overload is far better than the motor mounted type switch because it senses the current going to the motor. In other words it will only allow a certain amount of current to go to the motor. These overloads are selected so that the overload contact opens if the current draw is more than what the motor manufacturer specifies as full load amps (amps current are the same thing). The motor in this case never gets hot enough to cause motor damage. The motor mounted type overload senses the temperature of the motor itself and only opens after the motor heats up. If the motor is repeatedly heated in this manner the insulation will eventually break down and short out.
So if the motor will start and run as long as the start button is held in, the overload contact must be closed.
"Overload" was the wrong wording. But the relay in question had a reset device on the side the same color as the relay and was close to invisible!
Which side? I'll look for it. The digital camera has better eyes than do I. On this relay, the largish aluminum plate portion on the front (the Sylvania name) goes in and out; it is part of the magnet portion of the relay it seems. Moves about 1.2". If I can't find a reset button, can I unscrew the front portion to clean? Will it all fall apart, springs a-flying?
Look at the plate with sylvania written on it follow right till you see the small nut and just above there is the writing. and above there is what looks like a reset lever. (small ridges from side to side). Push it and hopefully thats it.
I'll try this, and let you know. Thx.
Late at the office, but always a few minutes to look over a beloved but winged tool. There is no reset on the relay. The metal squarish buttons are buttons, which release a plastic piece on the top, I assume for adding parts to adjust utility, different voltage, etc. On the left side, there are two connections there, in use; on the right, just plugs.
I decided I couldn't hurt anything, so took off the cover of the magnetic device. Found three pairs of contacts. One never in use, it seems, and two with light burning. Blew it out (not much came out), put it back together, and no change in operation. Should I try to file off the burn marks? Can't hurt, I guess.
Further to come, and I thank you, and all others, for the time to try and help.
Edited 8/9/2002 7:15:27 AM ET by s4s
I think the contact you should be looking at are on the very left side of the starter with the red wires on the top and bottom screws. If I am right this is the auxiliary contact that I was talking about in my previous post. When the motor is not running these contact should be open. When the motor is running the contact should close. You should get 120 volts both top and bottom when the jointer is running and 120 volts on the top or the bottom with the jointer off. I don't know if you have a test light or meter. I must warn you that the voltage in all the boxes is 120 volts, so be very careful not to touch any connection with the power on or you could be electrocuted. If you are not comfortable with fooling around with deadly voltage you should call a electrician. Any electrician should be able to find and repair the problem as it is a very basic circuit that is taught in electricians school. Again I warn you BE CAREFUL you life is not worth loosing for a jointer that won't stay running.
I appreciate the cautions, and am being quite careful. Another I think gave the same advice, and I will be trying it. I cleaned the contacts, without effect.
Much thanks to all, and esp. Rick (Trees2dust). He solved the problem, and without a single new part. He was kind enought to give me a phone number, and we talked extensively. He looked at the photos I had posted, and another one or two I sent along. Here is his solution, verbatim.
--------------------------------------
"I looked at the photos that you sent and it's all clear to me now. I
initially had mixed up the motor and line cables. Now I realize that the
left cable is the power plug, and the right goes to the motor. Whith that
cleared up, please disregard the modification that I mentioned earlier.
Also, cleaning the contacts will do no good. The pictures also confirmed
that the relay is in fact 110V, and the ground wire is used to get 110V to
the relay coil.
The auxilliary contacts come out at the terminals marked 2 and 3 at the top
LHS. There are two red wires at #3 and one red wire at #2. The problem, as
we guessed in the forum, is most likely in the holding circuit. That points
to 2 things: 1) the aux contacts, 2) the relay coil ground as we discussed.
Check the ground connection first. The fault could be anywhere from the
breaker panel, extension cord or anywhere in between.
If the aux contacts are bad, you can get around it by using the unused L1
contacts, by doing the following:
- remove the red wire from terminal 2 and move it to terminal L1
(top)
- remove the 2 red wires from terminal 3 and move them both to the
corresponding bottom L1 terminal
It should work if the aux contacts and the ground are sound.
As I mentioned, the ground wire is not supposed to carry current unless
there is a short to ground. So even though it works, I believe there needs
to be a fourth wire, neutral, which would replace the green ground wire
going to the relay bottom RHS terminal. This is getting into the
electrician's realm of electrical codes that I'm not familiar with though,
so don't take my word for it. Let me know how it turns out."
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I rewired the switch to take advantage of the empty circuit, and it works fine. Cleaning the contacts was not helpful.
The point of all of this is a confirmation of my long-held belief that almost all serious woodworkers (and those that want to be) are truly community spirited, non-competitive individuals who derive satisfaction from not only solving thier own problems, but those of others.
Again, a warm thank you to all, and esp. Rick.
Amazing how everyone hung in there to help with the problem.. Good deal. As noted above, nice community..
If your motor is 240v, and the coil is 120v. you said the coil gets the 120v from the ground and 1 side of the power then this means your grounding is now a current caring conductor. If you have a break in your grounding this jointer is the other half of the circuit. very dangerous! You need to add an additional wire to your power supply....a neutral( a 4 wire cord) 2 hot wires a neutral and a ground
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