electrical problem

[ahoiberg]

i FINALLY finished assembling my new table saw this weekend. it's a delta 36-979 and took it for a test drive during which it performed flawlessly. i then cut a small piece of plywood and stopped using it for a while. i came back about an hour later and it tripped the breaker on the motor, i reset that, and then it continually tripped the breaker on my panel in the basement. it's a 20 amp breaker, which i thought would handle the load OK (the motor only says 15 amps) and it seemed to during the first few runs of the saw.

so, i thought maybe i needed to put a 20 amp receptacle in. tried that, still trips the breaker each time it tries to start. i even tried unplugging everything in the garage, turning off the lights so all the juice could go to the saw, no avail. it will start spinning, so I think the motor is fine, but just trips after maybe 3-5 seconds. i know the best way to fix this is to convert it to 220 and have a separate line run to the garage, but I'd rather not spend the money on that.

is it possible that the breaker is bad? i've heard of these high magnetic load breakers, might one of those help? might it be the motor (god, i hope not)? any ideas? i can't stand that i spent a week putting it together and now i can't even use it!

thanks in advance for your help.

 

[Marc Phillips]

I think I would try spinning up the motor without a belt on it just to see if the motor is able to spin up freely... then also check to see if the blade/arbor spins freely without a belt on it.

Breakers do go bad after being tripped a few times... but I would be more interested in finding out why it tripped in the first place....

 

[Russianwolf]

In the 3-5 seonds that it sp\ins, does it seem slower than it should be?

Could be the breaker went bad, which is a cheap easy fix.

Or it could be the windings on the motor went bad, happened on my brand new Grizzly when I bought it. Used it fine for 30 minutes. went back an hour later and she wouldn't spin past 800 rpm and would pop the breaker even after resetting the speed. Griz sent a new headstock and no problems since.

 

[ahoiberg]

thanks for the replies so far. mike, it does seem a little slower than it should be, but it almost seems like it's just digging in for amps, but those symptoms you describe sound similar to what's happening to me. i'm going to give Delta a call tomorrow and see if they've got any suggestions.

 

[pssherman]

Could be the start capacitor on the motor. If this went bad it would cause the motor to start very slow, or not at all, and draw a lot more current, which could trip the breaker.

 

[RonSchmitt]

How old is the breaker panel, and what brand is it?
Breakers DO get weak over time, and if it is an older style panel you may have trouble finding a replacement. If you run into that problem LMK, I can help with that.

 

[ahoiberg]

is there any way i can test the motor to see if that's the problem? or can an electrician test it for me? ron, the breaker box is most likely the original and that would put it's age around 18 years, so it's got the "modern" style snap-in breakers. i don't know if this is any indication or not, but the breaker feels really weak when i go to reset it after tripping. you know how most feel a pretty hefty 'click' when you reset them, this one feels flimsy... also, the breaker makes some sort of 'hum' (my wife noticed it when we had a few heaters on last week while working in there), so i guess that might be a sign it's bad also. there's another few 20 amp circuits around the house, i haven't located exactly where they lead to yet, but i hope one is for outdoor types of things and i can try to run the saw on one of those to see what happens (if it's near the garage).

 

[btboone]

I assume that you are not using an extension cord of any kind. That will eat a lot of power right there.

 

[ahoiberg]

bruce, the odd part is that i did use an extension cord for the time when it worked. once it wouldn't start fully, i disconnected the extension cord and did all my tests, etc. and it still wouldn't fire.

 

[btboone]

I agree to try a no load test without the belt to see if it's the friction of the system or the motor or some other factor. If it runs fine, you have your answer, if not, it could be the motor, wiring, breaker, a starting capacitor, or something else.

 

[ahoiberg]

mark/bruce, thanks for the tip. i just tried it w/o the belt and it fired right up. does this point to misaligned pulleys or something? the blade/arbor spun just fine without the belt also.

 

[btboone]

You'll have to just look for friction where you can find it. If the blade spins freely, this suggests improper belt tension or misalignment or something like that. Is there any chance that the belt is rubbing a cabinet or the blade twisted and rubbing on the cabinet when the belt is tight?

 

[pssherman]

OK, another test. With the power off spin the motor in the reverse direction (with the belt off) and then turn the motor on. If the motor continues to run in this direction then the capacitor is definitely bad. Replace it or take to electric motor shop to have them do it.

Another test (only if you are comfortable in doing this one) is to grab the pulley and see if you can prevent it from turning as you turn on the power. Be prepared for a jerk as the power is turned on. If the capacitor is bad, you should be able keep the motor from turning. Be sure there are no burrs or edges that can catch your skin if the motor should turn.

As for the possibility of misaligned pulleys, this won't stop the motor unless they are way off and very tight. If they were off this much the misalignment would be extremely obvious.

 

[ahoiberg]

an odd twist. i just went out to do paul's second test. i turned it in reverse, fired it up, it spun back the right way. then i put the belt back on to see if i could see where it was dragging, nothing. i tried turning it on, same thing, slow start and tripped breaker. so, i took the belt off again and when i tried the motor by itself again, it wouldn't fire all the way up, as if the belt was still on and the breaker tripped... argh!

this belt is gravity tensioned, the motor just hangs off the back of the saw, so the tension isn't adjustable and everything is pretty well lined up, so i doubt if it's anything related to that... i don't know...

 

[pssherman]

Ok, it sounds like you don't have a bad "start" capacitor, but since the motor lacks power it could be a bad "run" capacitor. Does the motor have 1 or 2 bulged covers attachted to the case? If there are 2 then you have separate start and run capacitors. I there is only 1 then open the bulged cover and see if there are 2 or 3 terminals on the capacitor. If there are 3 then both start and run capacitors are a single unit. If there are only 2 then it is a run capcitor and you have a self-starting motor (does not neet a start capacitor). The most common configuration is the 3 terminal start/run capacitor.

Is this motor under warranty? If it is, contact the manufacturer and see if they will replace it. If not, take a picture of the label on the capacitor(s) and post it. I have some capacitors left over from a 3 phase converter project which may work. Do not disconnect any of the wires from the capacitor(s) until you are ready to replace it.

Of course you could take the motor to a motor shop and they would probably test the capacitor(s) for you and also sell/install any replacements that are needed.

 

[ahoiberg]

paul, it's got 2 bulged covers. i believe the motor is under warranty, i'm going to call delta tomorrow to see if they have any advice and if not, hopefully they will replace whatever is needed. is there a way to tell if the capacitor is bad or does that need testing?

 

[ahoiberg]

if it helps at all, it's a 1.5 HP, 115V/230V, 60Hz, induction motor.

 

[pssherman]

Usually the only way to determine if a capacitor is bad is with testing. They rarely have visible signs of failure. Some do have a pressure release vent that may show signs of failure. First call Delta and if they can help. If they can't, or won't (not likely though), the capacitors can be tested at a motor shop. Let us know if you need any additional help and we will see what we can do. I'm sure there are others who have as much as or even more knowledge of motors than I do.

 

[btboone]

Mouser Electronics is a place online that has all kinds of capacitors and stuff.

 

[ahoiberg]

had an electrician out to the house today. he thought it was definitely a circuit related electrical problem. i also talked with delta; they thought it was a motor problem... i hope to get the electrical guy from my work out to my place this weekend to help me run a new 20A dedicated circuit for now and maybe a subpanel later. i'd like to see if it's the electrical system before i get a new motor. thanks for everyone's help, i'll let you know how it turns out.

 

[Randy_]

Why not have the guy run a 30 amp circuit? The cost difference should be minimal and it will give you some flexibility if you want to purchase a big tool at some later date.

 

[ahoiberg]

Randy, good thinking. but would this require a 30A receptacle as well? all the ones i was looking at looked like they wouldn't accept the traditional 3 prong plug.

 

[pssherman]

Originally posted by ahoiberg

Randy, good thinking. but would this require a 30A receptacle as well? all the ones i was looking at looked like they wouldn't accept the traditional 3 prong plug.

No, you just need 2 or more receptacles that add up to at least 30 amps. I suggest using several 20A receptacles since some machines may need more than 15 and you never know where you will want to plug it in.

 

[Gadget]

One other thing to check for would be the length of the wire run from the box to the outlet. The longer the wire the more resistance you get. Thats why extension cords should not be used unless they are a heavy guage. If you have a long run a 30 amp circuit would help, Bigger wire = less resistance. I cooked a saw motor like this with a long run and 50 ft extension cord the motor burst into flames. I wonder if damage has already been done with the use of the extension?
Just my 2 cents.

 

[Randy_]

Originally posted by ahoiberg

Randy, good thinking. but would this require a 30A receptacle as well? all the ones i was looking at looked like they wouldn't accept the traditional 3 prong plug.

Andrew: The 30 amp plug and receptacle are different than the 20 amp units we are all used to looking at.....the three prong guys(2 flat,one round). If you look carefully at the 30 amp "pattern", you will see that the 30 amp receptacle will accept either a 20 amp or a 30 amp plug. OTOH, the 30 amp plug is designed to fit only in the 30 amp receptacle and will not fit the standard 20 amp receptacle.

 

[Randy_]

Originally posted by pssherman

Originally posted by ahoiberg

Randy, good thinking. but would this require a 30A receptacle as well? all the ones i was looking at looked like they wouldn't accept the traditional 3 prong plug.

No, you just need 2 or more receptacles that add up to at least 30 amps. I suggest using several 20A receptacles since some machines may need more than 15 and you never know where you will want to plug it in.

Paul: I don't quite understand your comment? Electrical codes will certainly require that 30 amp receptacles be installed on a 30 amp circuit.

 

[Gadget]

A 30 amp circuit requires the correct wire and outlet. I believe 10 ga wire and a 30 amp outlet. Change the plug on the saw to a locking plug that is much stronger and secure any how. I like the twist lock plugs as they dont fall out. make sure to change the cord to the saw to a 10 ga flexable cord as well. I may not be 100% right here but I use this method in my cabinet shop and have no problems.

 

[Randy_]

Originally posted by Gadget

.....make sure to change the cord to the saw to a 10 ga flexable cord as well......

I agree with everything you say except the above. Your saw will come with a cord that is properly sizes or it will not be approved for the UL seal and will not be legal for sale. You will not need to change either the plug or the cord on a 15 amp tool to plug it into a 30 amp circuit and a tool that requires a 30 amp circuit will come already wired with the correct plug and cord.

 

[pssherman]

Originally posted by Randy_

Originally posted by pssherman

Originally posted by ahoiberg

Randy, good thinking. but would this require a 30A receptacle as well? all the ones i was looking at looked like they wouldn't accept the traditional 3 prong plug.

No, you just need 2 or more receptacles that add up to at least 30 amps. I suggest using several 20A receptacles since some machines may need more than 15 and you never know where you will want to plug it in.

Paul: I don't quite understand your comment? Electrical codes will certainly require that 30 amp receptacles be installed on a 30 amp circuit.

Randy,
I don't think that a 30 amp circuit requires a 30 amp receptacle, but it might. It will certainly require sufficient receptacles to meet or exceed the circuit capacity. For example, 2 15 amp receptacles could carry a total of 30 amps. IIRC the receptacle rating is not based on the circuit that it is connected to, but the current that can be deliverd to the plug. The current that travels along the circuit does not go through the receptacle, only the current being deliverd to the plug goes through the receptacle. You would not want to plug a 30 amp device into a 20 amp receptacle, but since the 30 amp plug will not fit into a 20 amp receptacle this is not a problem. If you anticipate possibly getting a 30 amp device, then put in a 30 amp receptacle. Although this could be done at a later date should the need arise.

It would be helpful to know what the National Electric Code says on this subject. Does anyone have a definitive answer?

 

[Randy_]

OK, Paul, I get it now.

After thinking some more about this situation, I decided to do a little more research. The NEC is very complicated and can be quite intimidating to amateur electricians and the situation is always complicated by the fact that local electrical codes can and do vary from the NEC on occasion. Nonetheless, it looks like Paul and I were both right. If Andrew wanted to install a 30 amp circuit, it seems it would be permissible to use multiple 15 amp(NEMA 5-15R) or 20 amp(NEMA 5-20R) receptacles. If he chose to do that, however, it would most likely be necessary for the circuit to be GFCI protected since it would feed the garage. OTOH, if it were wired as a single outlet dedicated circuit, it would most probably require a 30 amp receptacle(NEMA 5-30R); but, would not need a GFCI. Checking with a licensed electrician who is familiar with local code is certainly the prudent course of action.

Now to clear up an earlier mistake I made that might confuse some folks. A receptacle for a bladed 30 amp 120v plug will "NOT" accept the standard three-prong plug (NEMA 5-15P) that is found on many household appliances and tools which is a 15 amp plug. The 15 amp plug will, however, fit in a 20 amp(NEMA 5-20R) receptacle.

This link will show those who are unfamiliar with them, the blade and pin patterns for the plugs and receptacles not generally found in the home environment. Sorry for the earlier confusion.

 

[ahoiberg]

thanks again guys, i've had a few electricians come out to check the situation and have gotten quotes from them. bottom line is i need to have a dedicated circuit for the saw and would like to have all the power i need out there (60A subpanel). i still can't test if the motor has anything wrong with it until i get sufficient power out there. so, hopefully (with a little tax return love) i can get this taken care of and be able to use the saw again.

by the way, i don't think it meets code (here at least) to run anything besides a 30A plug/receptacle off a 30A breaker. however, i could feed the subpanel with 2 30A breakers and run subsequent 15A or 20A lines off of it in the garage.

 

[ahoiberg]

just an update...

i was able to have the electrician from work come help me install two new 20A lines out to the garage... we put in a twin 20A breaker in the one free spot in the panel and so now I've got 3 20A circuits for the garage, which should be more than enough for a good while.

secondly, the motor still wasn't working properly, so i took it down to the 'big city' to the delta/dewalt/porter cable store since the national delta people told me the motor/saw was on backorder until late June... turns out all the service stores around the country are on the same backorder... so, hopefully i'll be able to use the darn thing by July... they never told me what was wrong with it, they just said, you're right, it doesn't work properly and it's easiest to just replace it.

thanks again for everyone's help.

 

[ahoiberg]

the motor showed up way ahead of schedule... got it all installed and plugged into one of my new receptacles and she's humming. the only problem was the lack of packaging, part of the bottom plate was a little bent up in the corners... i wasn't about to go through the return process again, so i just eased the plate flat again and it went on without any problems.

thanks again for everyone's help!