I’m currently building my garage based shop and had a sub panel installed in the garage. The outlets are on separate breakers and I had a 220v line installed for my PM2000 3 hp table saw. The 220 line is connected to a double breaker of sufficient amps. When I start the saw, the breaker frequently trips. The problem has gotten worse when I installed the stacked dado blade. The breaker does not trip every time and seems to take 3-4 seconds to come up to full speed.
Also, I’m using a 10 ft 12/3 extension cord.
Any guidance would be deeply appreciated.
Rick Mantell
Edited 12/3/2008 8:18 am ET by rmantell
Replies
There is a separate line coming from the new main breaker panel. I "think" it's a 220 live running into the sub panel.
Thanks,
Rick
10/3 at a minimum.. I use 8 guage for extensions..
EDIT. With a twist lock plug and socket
Edited 12/3/2008 10:29 am by WillGeorge
The sub panel has a 220 outlet right below it on the plywood mounting board. The saw is 8 feet away. No doubt 10/3 would be better and our colleague uses 8/3...wow! Shouldn't the electrician have used a special breaker with a slight delay for the initial load?
Thanks for your input
What is the size of the breaker?
Is the breaker marked for HACR?
3-4 seconds to get up to speed is a long time.
Should be well under a second.
Most likely causes are that you have low voltage or a voltage drop under load, or a motor starting cap that is going bad.
William the Geezer, the sequel to Billy the Kid - Shoe
Bill:
Good info. I'll check out the breaker size. The scary part is that I hired a very expensive licensed electrical contractor to do the job.
Thanks
I'll check out the breaker size. The scary part is that I hired a very expensive licensed electrical contractor to do the job.
I would bet if you had a permit to do the job with that so called .. very expensive licensed electrical contractor to do the job. He/She will have to do it again,, The right way.... And then again you had the village or whatever electrical inspector to write off it was to standard!
Most circuit breakers installed in homes today are slow to pop. Similar to slow-blow fuses of old. Instant pop breakers are for special industrial applications.
3 or 4 seconds for the motor to start is way too long. A capacitor start motor should start almost instantly. Bad capacitors are one possibility for sure.
Breakers pop due to the heat generated by too much current for too long. Your extension cord is a bit too light of a gauge for my liking, but it's not the reason you're drawing too much current. As previously mentioned, a drop in voltage will cause an increase in current. I encountered a similar problem when there was a phase shift in the incoming power from the main line. The way to test for this is to use a voltage meter to test both incoming hot legs in relation to neutral. The best place to do this at the main panel. Be very careful not to electrocute yourself. Each leg should be 110V to 125V. They should be within a few volts of each other. Once that is verified, measure voltage between both hot legs. This should be almost exactly double (110 + 110 = 220). If you get something less than double, say 190V between hots, you have a phase shift. This is typically the power companies fault, and you need to call them.
If this checks out OK, make sure that you are actually getting 220V to the table saw. Do the same measurements as described above where the saw plugs into the extension cord. If you installed a double half-height breaker, commonly sold in home centers, it will not supply 220V. You must be connected to both hot legs in order to have 220V. The half-height breakers only contact one leg. They are for saving space and get you 2 110V circuits. The problem is that they are the same 110V leg. You need a big, old fashioned double-height breaker to get 220V. My guess is that this is your problem.
Running a 220V motor on 110V will start very slow and draw lots of current which will pop a breaker. It can also damage the motor.
Do some trouble shooting with a meter and post back if you need more help.
Actually the standard is 120/240 volts (for standard residential service). With an allowed tolerance 5%.But motors are speced at 115/230 (look on the label) so that they can work at minimal voltage levels..
William the Geezer, the sequel to Billy the Kid - Shoe
The exact voltage depends on where you are. If a motor is wired for 220/240, it cannot run properly on 110/120. If you try to, it will start slow, and draw twice the current on the 110/120 line, popping the breaker and possibly damaging the motor. I almost didn't post because of this type of reply.
"If a motor is wired for 220/240, it cannot run properly on 110/120."I never meant to imply that you could run 240 volt equipment on 120 lines. Sorry if I implied that.What I wanted to get across is that while people talk about 110 and 220 that those have not been the standard in US for decades. I have 2 old fractional HP motors. Not sure of the same but I know that both are pre 1950. One is a GE that looks like modern motors and it is labeled for 115 volts. The other is Kenmore that I suspect was from the 30's. It's nameplate is for 110 volts."If you get something less than double, say 190V between hots, you have a phase shift. This is typically the power companies fault, and you need to call them."190 is way to low for a motor that is rated for 230 volts. What you might be confused with is that the standard voltage on 3-phase WYE service is 120 hot to neutral and 208 leg to leg. It rare that residential service is 120/208. But in some place I have heard of it being used for LARGE single family homes and also in some apartments and condos.Now some motors dual rated for 230/200 for use on either 240 single phase or 2 legs of a 208 3 phase service. But they will also have two different current ratings. You will need to current ratings for use on 208. They will be higher..
William the Geezer, the sequel to Billy the Kid - Shoe
Thanks for posting back. I'm not at all referencing 3 phase. I have had 2 separate occasions in two different commercial buildings having a phase shift between the 2 hot legs of a 2 phase service. The 2 120V legs are supposed to be 180 degrees out of phase with each other. One is positive 120V while the other is -120V. This is how you get 240V. If one or both of the legs is not 180 degrees out of phase with the other, you will get some "other" voltage reading between the hots while they will still measure 120V each. I arbitrarily chose 190V as an example. My situation was more like 175V. I never said that 190V was adequate. I said it was a problem. This probably isn't the poster's problem, but it could be. I was trying to offer a couple of troubleshooting methods to help this person out, not give a class in electrical theory. I suspect that they do have 120V at the saw and not 240V.
Wow... that was an awesome teachable moment provided by your post. Great analysis of the problem and I deeply appreciate everyone's thoughtful assessment. I'm very upset because the saw is brand new, the electrical work is new and was completed by licensed electricians for top dollar. I spent the bucks to have it safe and "perfect". When the electrical guy shows up on Friday, I'm giving him a copy of your post, as well as the others of our dear woodworking community.
Thanks so much
Rick
Rick, you are wise in having the electrical guy return on Friday to check things out. I expect he will quickly locate the problem. You did the right thing in bringing in the pro. These electrical threads get so "hot" at times that it is almost comical -- most of us just stay out of them to avoid the flare ups. Bill Hartman is an expert in this stuff, as someone pointed out, and likely others are too. But, as you can see, there are several variables that come into play, and well as several interpretations of what one person means when he makes a comment. Feel good about yourself that you made the right choice bringing in the pro -- you won't regret it.Woody
Did the electrician find the problem?
The electrician stated that each hot lead coming into the panel was 123v and 247 in combo. We measure voltage coming into the panel, the receptacle and at the end of the 10' extension cord. The no load amperage on the motor was 6.5 Amps with the start up load jumping to 106 Amps. We replaced the 20 amp breaker with a new one(20A). Of course I couldn't get the breaker to trip while the guy was there. Called Powermatic and the tech said they recommend a 30 amp breaker for the 3 hp motor.
I'm thinking I want a 30 amp HACR breaker replacement with the possibility of checking the motor cap if the problem persists.
Thanks a ton for your kind assistance and interest.
Rick
Did you check all the connections in the magnetic switch to make sure they were all tight?
Also, there are some defective motors on these saws. Follow the link below for some information about this.
http://sawmillcreek.org/showthread.php?t=85938&highlight=2000+motor&page=2
Life is what happens to you when you're making other plans .
"Life is not a success only journey." Dr. Phil
Edited 12/7/2008 11:28 am ET by JerryPacMan
You're welcome. I know it has to be frustrating to buy the best table saw on the market and have the problems you are having.Definitely no phase shift then. It is sounding like the cap. I don't think a different circuit breaker will make a difference, but you can try. No circuit breaker provides magic electricity. Powermatic probably won't want to take things to the next step until you do what they recommend. One last thing to check, if you haven't already, is the connections to the motor itself. If that isn't right, it would obviously cause problems. If it runs with full power after it's running, then this is unlikely.It's normal for the current to spike when you first turn on a motor. It should only be for a fraction of a second if the start cap is doing its job. If it runs with full power after it is running, the start cap is bad.
Has anyone asked you what amperage your breaker is? Moreover, your use of 12 gauge wire is too small -- might not even be to code.
Normally, 12 gauge is for 120-volt, 20 amp max fixtures. Look at your motor; what is the amperage? If it's even 15, let's say, you're probably going to pop a 20-amp breaker. Use a minimum 10-gauge wire.
Additionally, the fact that it takes a while for the breaker to pop makes me think you don't have a double-pole circuit breaker.
Mo
Edited 12/3/2008 7:43 pm ET by zehutiman
I didn't see the point in nit picking about 110/115/120V. Voltages delivered vary around the country but do stay pretty close to 120. So what. The reason why manufacturers rate motors at 115/230 is to avoid this very argument. I knew someone was going to post what Bill did. I would have bet a million dollars on it.
The point is to troubleshoot the problem. Bill said you can run a motor on 120 or 240 which is only true if you wire it properly. The original poster said he is configured for 220V, so that is what I refereed to. It doesn't matter if it is 110 or 120. It is within tolerance. Most motors on table saws can be configured for 120 or 240 (I'm very sorry, 115 or 230), but they must be configured for what you're going to run. You cannot configure it to run on 240 and simply plug it into 120 and think it will run properly.
Forgive me for trying to relay my 20 plus years of troubleshooting electrical problems in commercial and industrial applications.
Maybe Bill is a nice guy, but it didn't come across that way.
"12 gauge wire is for any voltage, usually up to 600V.
20A normal after derating.
To say that it is normally used for 120V is misleading and not helpful in finding the problem in this situation."
You're obviously not paying attention.
There's a good chance he's not providing 240v to his tablesaw. Therefore, at 120v and the resultant amperage draw, he's in danger of overheating his 12-gauge wire.
So, you see, your reference to 600v is not very helpful in finding the problem in this situation, but you probably already knew that, and posted anyway.
Mo
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