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Forum topic by Chris posted 10-22-2016 03:52 PM 702 views 0 times favorited 13 replies Add to Favorites Watch
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Chris

17 posts in 2402 days


10-22-2016 03:52 PM

Hello everyone,

Since I’ve moved into a new house, I’ve been troubleshooting my Powermatic 66-TA Saw 220V 3HP (single-phase) table saw not turning on. It has the magnetic type switch. Taking the switch cover off and forcing the magnetic coil closed (brown button) starts the motor, but it turns off as soon as I release it. I’ve read numerous posts that either the coil or holding circuit might be bad, but then I came across this thread on Google Groups which led me to check the phases of the leads coming into my house for 180 out of phase:

https://groups.google.com/forum/#%21topic/rec.woodworking/bxp2Ct0raw0

For background info, I’m a renter and move frequently so I’ve always ran an extension cord from the dryer outlet. It’s always worked. Both legs test ok at 122V, but when testing across them it reads 0L intead of 220V. Testing the service wires coming into my breaker panel yields the same result; each tests 122V independently, but 0L when read across them. Is this incorrect? Do 220V motors require the 120V legs be 180 degrees out of phase? I’m thinking I might need to call the electric company, but I’m just checking if this is correct or not because I have other 220V appliances in the house (dryer, furnace and stove) but they’re all heating appliances so I don’t think the phase requirement is the same.

The fact that the motor turns on when forcing the coil shut leads me to believe the 120V poles being in the same phase does not make a difference to the motor, and that the coil might be burned out, or the latching circuit is not working properly.

For the hell of it, I attached a picture of the table saw switch I’ve been troubleshooting in case it ends up being the problem after all. I’ve already blown out all the dust from it, which there wasn’t much – it was sealed quite well.

Thank you all for your help!

Chris




13 replies so far

View 01ntrain's profile

01ntrain

210 posts in 908 days


#1 posted 10-22-2016 06:11 PM

So, your saw worked OK at the previous house?

I’m suspecting that your breaker is connected improperly. A rental house could have just about anything. OY Vey!

There was another thead about this awhile back and the person found that his breaker was off a space in his panel. 120v each line to ground, but not line to line would explain Ov.

It’s a possibility that your hookup and subsequent first-fireup could have damaged the coil, as well.

Definitely take off your panel cover and inspect it….make sure the breaker is picking up both L1 and L2.

After reading your explanation a little closer….you have 0V L1 to L2 at the top of your breaker panel? I would def be calling the utility company, they can at least check at the meter to see if it’s on their end.

View Aj2's profile

Aj2

1177 posts in 1636 days


#2 posted 10-22-2016 07:59 PM

I have no idea what might be your problem.
But I can help you with this.
Each side of your electrical panel is feed with about 120 v.So if you install a 240 breaker it will grab 120 from each hot leg.120+120=240v it’s really that simple.
So make sure your really plugged into 240.With a little goggling you should be able to figure out the breaker size and wire size.I leave that fun part to you.

Aj

-- Aj

View WhyMe's profile

WhyMe

910 posts in 1399 days


#3 posted 10-22-2016 08:36 PM

If you have 120V on each leg but have 0 across the two legs the DP breaker is installed so that it’s picking up the same leg of the panel. Move the breaker to a space where it connects to stabs on both legs. As said getting 0 across the two legs of the service is not right. Is this a sub-panel you are testing? It may only be a 120V panel.

View MrUnix's profile

MrUnix

6006 posts in 2037 days


#4 posted 10-22-2016 08:41 PM

Testing the service wires coming into my breaker panel yields the same result; each tests 122V independently, but 0L when read across them. Is this incorrect?

Yes. If you don’t get 240v across the two incoming service wires at the breaker box, something isn’t right and would explain why your dryer outlet acts the same way.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View Chris's profile

Chris

17 posts in 2402 days


#5 posted 10-22-2016 08:45 PM

Yes, each pole of the double pole breaker is picking up the same leg (reads 0L across both legs), however, I measured across the services lines coming into the panel and THAT reads 0L as well. The breaker is installed in the correct slot such that it picks up from each leg, but the service lines themselves are what seems to be the problem. Reading across the legs should read 240V, not 0, correct? Am I missing something? I’m assuming the electric company has something messed up on their end (since they should be 180 degree out of phase with each other), I’m just hoping they won’t charge to fix it.

Yes, the saw worked at the old house perfectly fine. I initially thought it might have been the wiring inside the switch or dust because loading and unloading the saw subjected it to a good bit of vibration from the ridges on Uhaul’s loading ramps.

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Chris

17 posts in 2402 days


#6 posted 10-22-2016 08:46 PM

To make it more confusing, every other 220V appliance in my house works fine. But they’re not 220V motors, they’re heating elements.

View Chris's profile

Chris

17 posts in 2402 days


#7 posted 10-22-2016 10:09 PM

Ok well it turns out I’ve been using my multimeter on the wrong voltage setting. Voltage is OK to the saw switch. I took apart the switch to separate the coil and the overload relay, and tested the coil and latching circuit by itself. The saw worked and stayed on just fine. So something is wrong with the overload relay. I have it set to how it’s shown in the manual with the amperage dial set to 18 and the other selector set to “test,” though I’m not sure what either of these means. I was hoping there was some kind of reset function but I couldn’t find one. I’ll probably just try to buy a replacement for that since I know that’s what the problem is with now.

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MrUnix

6006 posts in 2037 days


#8 posted 10-22-2016 10:26 PM

The “18” is the current limit for your motor for overload protection. Check your motors data plate and see what it’s rated at – should be 18A or thereabouts if the switch is set properly. The other switch has “test” and “auto”... manual doesn’t really explain what the ‘test’ setting does, but logically it would seem that it should be switched to the ‘auto’ position for normal operation.

If it still acts like you say, I’d check the wiring and voltage of the control coil… if it is bad, then the switch will not latch in the on position, but would work when manually pushed to close the contacts.

Cheers,
Brad

PS: I was pondering your “OL” reading, which indicates an overload condition. Normally in voltage mode, you will read “0” (zero) volts on a dead circuit, not overload. But not all meters are the same.

-- Brad in FL - In Dog I trust... everything else is questionable

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Chris

17 posts in 2402 days


#9 posted 10-22-2016 10:37 PM

Ok well I took apart the series overload relay casing because I heard a rattle. There was a little tiny magnet that was used to hold the switch in the normally closed position so it was out of place. I manually flipped the toggle to where it was supposed to be, and put everything back together and the saw works normallly. But of course, I now have no confidence that the overload function will work as intended, so I’ll be ordering a replacement soon ($30 for that part online vs. $75 for a whole new switch). Thanks for all your responses.

Chris

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Aj2

1177 posts in 1636 days


#10 posted 10-22-2016 10:42 PM

Good for you I’m glad it’s working.
Sorry if my first post came across as if I were talking down to you.I didn’t mean it that way.
Okay dokay.:)

Aj

-- Aj

View klassenl's profile

klassenl

183 posts in 2497 days


#11 posted 10-23-2016 12:28 AM

That’s a good bit of troubleshooting.

-- When questioned about using glue on a garbage bin I responded, "Wood working is about good technique and lots of glue........I have the glue part down."

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splintergroup

1702 posts in 1060 days


#12 posted 10-23-2016 02:48 PM

One thing to note is that most digital MMs, especially those that “auto range” will always show some voltage (several millivolts) on high voltage circuits. They tend to pick up the noise. When I see a “0.000” I know something is probably not correct.

Now a good Fluke on the other hand…

View Chris's profile

Chris

17 posts in 2402 days


#13 posted 10-23-2016 04:56 PM


Good for you I m glad it s working.
Sorry if my first post came across as if I were talking down to you.I didn t mean it that way.
Okay dokay.:)

Aj

- Aj2

No not at all! It helped to confirm what I already thought since I’m not an electrician.


That s a good bit of troubleshooting.

- klassenl

It was. It helped to isolate the problem by separating the relay coil from the overload relay to see which component was the problem.


One thing to note is that most digital MMs, especially those that “auto range” will always show some voltage (several millivolts) on high voltage circuits. They tend to pick up the noise. When I see a “0.000” I know something is probably not correct.

Now a good Fluke on the other hand…

- splintergroup

That’s exactly what I was thinking! I was dreading spending $75 on a new switch so I got the cheapest meter I could since it didn’t need to be terribly accurate. A Fluke is certainly on my list now.

Thanks everyone for your responses!

Chris

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