Table saw motor capacitor fried

[Dean Karavite]

Hi Everyone,

Preparing for a nice 10 day vacation with most of the time in the shop, but today my Delta contractor saw motor starting smoking and stinking up the place (good news is I finished cutting my tenons). One of the capacitors is a mass of goo. I read a bit online and it seems I can get a replacement at Graingers (there is one near enough to my house).

I am not an expert on motors. Is this the smart path to take? Seems worth a shot. Also, I have not been over burdening the saw - I was cutting poplar and plywood today with sharp blades - what might cause this to happen?

I hate to even bring this up, but when I bought the saw, used, I replaced the power cords and switch. I was beyond anal in making sure everything was wired correctly, used 14 gauge wire, use a 20 amp 110 outlet with nothing else on the circuit and have run the saw over two months since. Again, I am dead certain I didn't, but if I by chance mixed live and neutral, would this cause a capacitor to burn out?

P.S. Any advice on the best thing to use to clean up the burned out capacitor oil?

[scott spencer]

It's not unusual the caps to just go sometimes....doesn't have to be something you did.

Grainger is one possibility, but any motor shop, or even an electrical surplus house might have something suitable. Be sure the new cap will physically fit inside the enclosure, be sure the electrical rating is at least as high, and get the capacitance value close...doesn't have to be exact. Should be < $10.

[Dean Karavite]

Thanks Scott. I am seeing that a new motor will be $200 easy, so I might as well try it out.

[Mike Henderson]

There's essentially nothing you could do to the motor which would cause a capacitor failure. I could imagine the motor getting really hot and affecting the cap, but it would have to get *really* hot. The average load on a table saw is very low in most situations (idling most of the time, with short peaks of load).

As Scott said, caps just fail sometime. Go buy a new one and hopefully that will correct the problem.

Regarding switching hot and neutral, that will not affect the motor. Your supply is alternating current so it's just two wires carrying the power. In the United States, neutral is connected to ground but it should not be used as a safety ground - you should have a separate green wire for that.

In most situations in the United States, black is hot and white is neutral.

Mike

[Dave Beauchesne]

It's not unusual the caps to just go sometimes....doesn't have to be something you did.

Grainger is one possibility, but any motor shop, or even an electrical surplus house might have something suitable. Be sure the new cap will physically fit inside the enclosure, be sure the electrical rating is at least as high, and get the capacitance value close...doesn't have to be exact. Should be < $10.

Dean:

I agree with Scott, however, it is important that the ' start capacitors ' in this case ( black plastic case ) be replaced with a mfd rating equal to and up to 20% higher than the original, and the voltage rating must be equal to or greater than the original. You should replace them both as the one that is not fried will have been stressed as well.

The motor likely has a centrifugal switch to ' cut out ' the capacitors when the motor gets up to speed - if you are slowing it down ( bogging ) considerably and the centrifugal switch is cutting the caps in and out, it will be hard on them. As for the 14 gauge cord on a 20 amp circuit - 12 gauge would be the better choice.

Good luck -

Dave Beauchesne

[Mike Henderson]

You'd have to really slow the motor down to get the centrifugal switch to cut back in (to put the starting capacitor back into the circuit). A regular capacitor start induction motor has a characteristic torque curve with a peak at maybe 3/4 of the maximum RPM. That peak is called the "pull out torque". If your load exceeds that torque, the motor will rapidly slow down - it logically slides down the back side of the torque curve - and stalls (stops and hums) until you remove the load.

If you're regularly stalling the motor, you need to get a thin kerf blade, put a larger motor in your existing saw, or buy a saw with a larger motor (more HP).

Mike

[Dean Karavite]

Hey thanks Scott, Mike and Dave for all the information. Also, I have to correct myself - I did use 12 gauge wire. I'll replace both caps and hopefully this will take care of things. Like I said, start next Thursday I am off for 10 days and am planning to have a lot of fun in the shop - lots of projects.

You guys seem to know all about this stuff, but I did find a pretty comprehensive page on motors: http://liutaiomottola.com/Tools/Motor.htm

[John Downey]

HVAC suppliers are another source for motor caps if Grainger washes out. MSC is another if you can wait for the mail - they also tend to be cheaper than Grainger, though I find their website search to be not as good as Graingers.

Cap failure is one of the most common motor faults, nothing you did would have caused it.

[Jim O'Dell]

Ditto on replacing the caps. Grainger is where I bought mine for a sprinkler system motor. They should have them in stock.
Might not hurt to take a few minutes and take the cover off and clean the centrifugal clutch to make sure it is disengaging when the motor gets up to speed. If not, that might cause a start cap to go. At least so I've heard. I'm not an electrical motor guru. ;) Good luck with the repair! I'm sure you'll have it up and running before your vacation starts! Jim.

[Chip Lindley]

Capacitor failure on a motor is akin to the water pump going out on your car's engine. It just Happens! No need for a brand new engine, just replace the water pump! Start caps are much easier to replace than today's water pumps tho! Yer Lucky!

And, as Jim mentioned, make sure the centrifugal switch is sliding freely in your motor. These spring-loaded plastic sleeves slide up/down the end of the stator shaft. Sawdust can enter an open drip-proof motor. If it's TEFC, chances are less but check none-the-less.

[Dave Cav]

Another source of start and run caps is McMaster-Carr. They have a big selection and pretty fast shipping.

[Dean Karavite]

Sorry, I think I got it, but want to be sure. The remaining capacitor is labeled:

300uf.
125 VAC
50/60HZ
It is 3 1/2" long and 1 7/16" diameter.

Dave suggested I get a capacitor +20%, so I should be looking for a cap at around 360 MFD, correct?

McMaster-Carr has a motor starting capacitor with these specs:

AC Motor-Start Capacitor
110-125VAC
340-408 Rating (no lower range available in this size)
3 3/8" long, 1-7/16" Case Diameter
110-125 VAC

One last dumb question. There are two terminals and two wires and no labeling on either. Does it matter which is connected to which?

[Ken Fitzgerald]

If the original was 300uf....then he's means 300-360uf.....what ever the working voltage is....the replacement must have an equal or greater working voltage rating.
Dean:

I agree with Scott, however, it is important that the ' start capacitors ' in this case ( black plastic case ) be replaced with a mfd rating equal to and up to 20% higher than the original, and the voltage rating must be equal to or greater than the original. You should replace them both as the one that is not fried will have been stressed as well.

The motor likely has a centrifugal switch to ' cut out ' the capacitors when the motor gets up to speed - if you are slowing it down ( bogging ) considerably and the centrifugal switch is cutting the caps in and out, it will be hard on them. As for the 14 gauge cord on a 20 amp circuit - 12 gauge would be the better choice.

Good luck -

Dave Beauchesne

[Dennis Ford]

It does not matter on the two wires (plug & play)

[Dave Beauchesne]

Sorry, I think I got it, but want to be sure. The remaining capacitor is labeled:

300uf.
125 VAC
50/60HZ
It is 3 1/2" long and 1 7/16" diameter.

Dave suggested I get a capacitor +20%, so I should be looking for a cap at around 360 MFD, correct?

McMaster-Carr has a motor starting capacitor with these specs:

AC Motor-Start Capacitor
110-125VAC
340-408 Rating (no lower range available in this size)
3 3/8" long, 1-7/16" Case Diameter
110-125 VAC

One last dumb question. There are two terminals and two wires and no labeling on either. Does it matter which is connected to which?

Dean:

Assuming the original capacitors were both the same microfarad ( mfd ) rating, you will be fine with what you have - no numbers available off the one that failed ? Only a single mfd value on the original(s)?

The response as to the two 1/4 '' male tabs being non-essential as to the ' polarity ' is correct.

I am a HVAC guy in the trade for 30 years - deal with single phase motors on a regular basis. Good idea about the centrifugal switch - they do get plugged up sometimes, but if it is TEFC ( totally enclosed fan cooled ) it is sealed.

Good luck;

Dave Beauchesne

[Dean Karavite]

Hi David, the one that failed was a cooked mass and unreadable. It was in one of the two compartments/humps on the outside of the motor. The other has no MFD range listed and the only information on it is:

300uf, 125VAC, -40 to + 60 C and 50/60 Hz

It's a JKD, Jiekeda, CD60A.

[Dave Beauchesne]

Dean:

I would say install two new capacitors and go for it.

Do you know anyone with an ammeter that you could test the motor while sawing a respectible piece of wood?

The amperage should not exceed the FLA ( full load amperage ) of the motor under load. That's what I would do, but then again, I am in the business, so to speak.

Dave Beauchesne

[Dean Karavite]

Hey Dave, now I am showing my newbie-ness. There is a capacitor in the range of 270-324 or 324-389, but they are smaller in size - 2 3/4 long vs 3 1/2. So, the age old question here, does size matter?

[Myk Rian]

270-324uf

Get that one.

[Bruce Wrenn]

Your motor has two capacitors, one is the start (usually the larger value) and the run. The run is always in the circuit, and the start is added when starting. List the model # of you actual motor, and some one here can pull theirs to get you a value for your fried cap. Just went to the shop and checked my Delta 1.5 / 2.0 HP motor by Marithon. The start cap is about 300 uf, and the run is 50 mdf @ 240 volts. Be sure and get a run capacitor.

[Dean Karavite]

Wow Bruce, you just saved me some grief for sure. Thanks! The thing was so fried and melted and I assumed both caps were the same.

My motor says Delta part number 902905. It is 1.5 HP, 3450 RPM, 60 Hz, 115 or 230 Volts, 15/7.5 amps. I have searched on the web and nothing on that part number, even on Delta's part site. I will try calling them tomorrow as well.

[Dean Karavite]

Man, this is the only place I can get help. I called, but Delta does not have information on the run capacitor, nothing. I even spoke to their senior tech. They don't even know who made the motor.

Even though the label on the motor says Part # 902905, the actual part number of the motor is a 644244 and it is used on many Delta contractor saws - 36-349, 36-650, 36-675, 36-678, 36-679, 36-680, 36-680X, 36-680XL, 36-681, 36-681 XL, 36-682, 36-682XL.

Bruce, I have searched a number of sites for a run capacitor of 50 mdf @ 240 volts, but all seem to start at 370 VAC or higher. I can't find a 240 VAC run cap anywhere. Am I missing something? If anyone can help me find this run capacitor, I would really appreciate it.

EDIT. Never mind, the knowledgeable guy at Graingers said I could use a 370 VAC 50 MFD cap - he says you can always go higher on the voltage.

[John Denture]

I'm trying to find a start capacitor for a Dayton Electric 1/3HP motor. It had an old Sprague capacitor rated at 101-194MFD, 110-400V. The motor is a 115V motor, but since new capacitors aren't rated the same way as this old one (they all seem to be rated at a single voltage with a narrow capacitance range), I'm wondering what to get...

[Myk Rian]

Get one about 150uf and 200+ volts.

[Bruce Wrenn]

I'm trying to find a start capacitor for a Dayton Electric 1/3HP motor. It had an old Sprague capacitor rated at 101-194MFD, 110-400V. The motor is a 115V motor, but since new capacitors aren't rated the same way as this old one (they all seem to be rated at a single voltage with a narrow capacitance range), I'm wondering what to get...John, don't sweat small things. Any capacitor in the range between 101MFD, and 194MFD will work. Newer capacitors are made to closer tolerances. The larger the value, the more starting torque.

[Bruce Wrenn]

Man, this is the only place I can get help. I called, but Delta does not have information on the run capacitor, nothing. I even spoke to their senior tech. They don't even know who made the motor.

Even though the label on the motor says Part # 902905, the actual part number of the motor is a 644244 and it is used on many Delta contractor saws - 36-349, 36-650, 36-675, 36-678, 36-679, 36-680, 36-680X, 36-680XL, 36-681, 36-681 XL, 36-682, 36-682XL.

Bruce, I have searched a number of sites for a run capacitor of 50 mdf @ 240 volts, but all seem to start at 370 VAC or higher. I can't find a 240 VAC run cap anywhere. Am I missing something? If anyone can help me find this run capacitor, I would really appreciate it.

EDIT. Never mind, the knowledgeable guy at Graingers said I could use a 370 VAC 50 MFD cap - he says you can always go higher on the voltage.I assume your saw is a newer left tilt, most likely made in China. Mine is American made, with Marathon motor, which draws 14.2 / 7.1 amps. Go over to woodnet, and search for "MsNomer. I think her saw has the same motor as yours. She is a sweet gal, and probably would take time to break down motor, and get exact value for you. My run capacitor has a metal case, FYI

[Dave Beauchesne]

Your motor has two capacitors, one is the start (usually the larger value) and the run. The run is always in the circuit, and the start is added when starting. List the model # of you actual motor, and some one here can pull theirs to get you a value for your fried cap. Just went to the shop and checked my Delta 1.5 / 2.0 HP motor by Marithon. The start cap is about 300 uf, and the run is 50 mdf @ 240 volts. Be sure and get a run capacitor.

Dean:

Bruce makes a great point - my saw has two start capacitors, but indeed, it could be a run cap - usually ( but not always ) the run cap has a metal case - you better make sure - get the fan motor off and with an accurate part number, get what is applicable.

With two start caps, it would be a CSIR ( Capacitor start, induction run ),
a run and start cap would be a CSR ( Capacitor start, capacitor run ), or the all too common KSHIR ( Kick start, hope it runs ) Just kidding on the last one - the first two are correct terminology.

Dave Beauchesne

[Dean Karavite]

Thanks Dave. On closer inspection, it looks as though the run capacitor, the one that spontaneously combusted, was replaced at some time (bought the saw used - I feel like I'm a character on CSI some times with this thing). Meanwhile I can't get an answer from Delta on who made this motor or any specs on what cap it needs. I decided to punt and ordered a new Leeson motor. It will be here Tuesday. I try not to give up and work through these kinds of things, but this one just seemed easier than making more fruitless phone calls and/or plugging in caps that may or may not be the right part.

I bought this saw used pretty cheap. With a new motor it will continue to be a very good saw. The table is large, I have made lots of upgrades (pulleys, belt, PALS, dust collection...) and it is really dialed in.

[Dave Beauchesne]

Thanks Dave. On closer inspection, it looks as though the run capacitor, the one that spontaneously combusted, was replaced at some time (bought the saw used - I feel like I'm a character on CSI some times with this thing). Meanwhile I can't get an answer from Delta on who made this motor or any specs on what cap it needs. I decided to punt and ordered a new Leeson motor. It will be here Tuesday. I try not to give up and work through these kinds of things, but this one just seemed easier than making more fruitless phone calls and/or plugging in caps that may or may not be the right part.

I bought this saw used pretty cheap. With a new motor it will continue to be a very good saw. The table is large, I have made lots of upgrades (pulleys, belt, PALS, dust collection...) and it is really dialed in.

Dean:

Probably a good idea - IMO, what you likely had was 2 start capacitors wired in parallel - however, it could have been a CSR as well. Without ' knowing ' for sure, you risk damaging the windings and / or the centrifugal switch.

Good luck -

Dave Beauchesne