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troubleshooting my new electric sub panel tripping breakers with TS

by jamsomito
posted 12-06-2018 05:25 PM


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100 replies

100 replies so far

View GrantA's profile

GrantA

1960 posts in 1946 days


#1 posted 12-06-2018 05:30 PM

You’re running on the ragged edge. That saw really needs it’s own 20a circuit. I’m surprised it has been satisfactory on a 15a but your chugalug comment is troubling. Is the heater still running too? What are specs on that? It’s probably 20+ too, then the shop vac can eat up 15, you’re over capacity

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jamsomito

434 posts in 964 days


#2 posted 12-06-2018 05:36 PM


You re running on the ragged edge. That saw really needs it s own 20a circuit. I m surprised it has been satisfactory on a 15a but your chugalug comment is troubling. Is the heater still running too? What are specs on that? It s probably 20+ too, then the shop vac can eat up 15, you re over capacity

- GrantA

To clarify, here’s a couple scenarios:
new 20A circuit #1: table saw
new 20A circuit #2: shop vac
old 15A circuit: IR heater
SAW TRIPS

old 15A circuit: table saw
Chugs to start, but runs fine.

No matter if I plug the TS into the new circuit #1 or #2 (both 20A), it trips the associated new 20A breaker. I understand if the 50A breaker for the panel trips, but I do’nt get why ONLY the table saw breaker trips. It’s 20A. It’s odd to me that that trips while the 15A garage circuit doesn’t – although maybe the wire is small enough to limit power draw enough that it can’t actually trip. It has been unsatisfactory for the last several years, but it only trips when under heavy load.

My heater was not going through the sub panel, but another 15A circuit on my main panel. It’s a 1000W electric radiant heater, so figure maybe 10A.

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GrantA

1960 posts in 1946 days


#3 posted 12-06-2018 05:40 PM

OK that clears it up a bit. It sounds like you might need to get the electrician back out.

View HokieKen's profile

HokieKen

11389 posts in 1677 days


#4 posted 12-06-2018 05:41 PM

Are the new breakers GFCI or AFCI? Maybe a wiring issue somewhere in your saw that wasn’t caught by a standard breaker but is caught now due to the nature of the fault.

I have the same saw and when I got it, it was wired for 115V. When I ran it on a 15 A circuit, I could trip the breaker depending on the load I was putting on it. I re-wired the motor for 230 and ran a new circuit and haven’t had any problem since. Something to consider. You should have the capacity for a 230V, 20A circuit on that panel.

-- Kenny, SW VA, Go Hokies!!!

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jamsomito

434 posts in 964 days


#5 posted 12-06-2018 05:46 PM



Are the new breakers GFCI or AFCI? Maybe a wiring issue somewhere in your saw that wasn t caught by a standard breaker but is caught now due to the nature of the fault.

I have the same saw and when I got it, it was wired for 115V. When I ran it on a 15 A circuit, I could trip the breaker depending on the load I was putting on it. I re-wired the motor for 230 and ran a new circuit and haven t had any problem since. Something to consider. You should have the capacity for a 230V, 20A circuit on that panel.

- HokieKen

Good questions, and I had exactly the same problems on my old 15A circuit. I have plans to try 220V, but I won’t have time for that until probably this next summer. In the meantime I figured a good clean 20A 120V circuit would be a big upgrade from what I had though.

The subpanel feeder is coming off a 50A GFCI breaker on my main panel. This way the whole subpanel is protected and it avoids needed every new circuit for the garage to have a new GFCI breaker – I can just use regular breakers there. It’s possible this is tripping the local regular breakers, but I just don’t know enough about it to say for sure. It seems to me if the GFCI protection was the problem that it would trip the 50A breaker in my main panel, not the 20A standard breaker in the subpanel.

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DBDesigns

232 posts in 536 days


#6 posted 12-06-2018 05:56 PM

Hokie has a point about rewiring the saw to 230v. It will use less power that way and your new sub-panel should handle a new 230 v circuit just fine.

Also, don’t overlook the possibility that you may have bad breakers from the manufacturer. Everything is made overseas these days and their quality standards are not what we are used to. The fact that the saw works fine on the old circuit implies that it is fine, just too much draw.

I would call the electrician and ask some pointed questions before I had him come back.

-- I remember when Grateful wasn't Dead

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HokieKen

11389 posts in 1677 days


#7 posted 12-06-2018 05:59 PM

I agree. I don’t think it’s the GFCI. That breaker should be thrown if so.

What I would do briefly and just for a quick test is to swap the 15A breaker in the main panel and one of the 20A breakers in the subpanel. Then see if both still act the same way. Do not leave it this way because the wire in the 15A circuit is too small for a 20A load. But, if you do that and the 20A breaker acts like it should and doesn’t trip but the 15A does trip, it’ll tell you that there’s something in the wiring from the main to the subpanel. If that is the case, make the electrician fix it.

-- Kenny, SW VA, Go Hokies!!!

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GrantA

1960 posts in 1946 days


#8 posted 12-06-2018 06:03 PM

Kenny I remember from his other post that he had a QO panel put in the garage, most houses aren’t. My electrician looked at me like I was nuts when I specced all QO stuff (about 7yrs ago when we built). It’s just now the norm. Homeline, or some other brand are more popular. All that said meaning he may not be able to swap them. You plan to add more circuits anyway though so maybe just pickup a 20a breaker to try but I doubt you got 2 that are bad

Do you have a non-GFCI circuit near enough to try that? Is the old 15a circuit also GFCI? Strange things can happen on those

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HokieKen

11389 posts in 1677 days


#9 posted 12-06-2018 06:14 PM

AFAIK, QO works the same as any other panel/breaker, right? I don’t know much about it other than my son just had a QO subpanel installed in his garage.

I agree fully that GFCI can act funny. And, in fact, substantial current swings can cause it to trip even when the swings are normal operation. But, I don’t see how it would cause his subpanel breaker to throw but not throw the GFCI breaker the sub is ran off of.

Then again, I’ve always said electricity is black magic and only soulless demons can harness its power. So I’m far from an expert in the field ;-)

jamsomito – if Fridge doesn’t chime in on this thread, shoot him a PM. He’s one of those dark wizards and knows his stuff up one side and down the other. He’ll be able to tell ya which finger to lick and where to stick it ;-)

-- Kenny, SW VA, Go Hokies!!!

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GrantA

1960 posts in 1946 days


#10 posted 12-06-2018 06:18 PM

I just meant unless he has QO in the house he can’t try that breaker in the new QO panel ;-)
aha! Now I know how to tag someone, Kenny will it notify Fridge that you tagged him?

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HokieKen

11389 posts in 1677 days


#11 posted 12-06-2018 06:21 PM

Duh… Didn’t think about that. ;-)

-- Kenny, SW VA, Go Hokies!!!

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jamsomito

434 posts in 964 days


#12 posted 12-06-2018 06:22 PM

lol, ok thanks. Yes, it is a Square D QO panel. My main panel is a Cutler Hammer, so I was under the impression that the breakers are non-interchangeable. Those are all 20 years old though, so I didn’t foresee the need to swap any.

The 15A circuit in my garage is indeed GFCI, though that has a local GFCI outlet that all other garage outlets stem from (just a regular breaker). The garage door opener is on the same circuit, not GFCI protected.

I thought it could be a bad breaker on my new panel as well, but also agree it might be a stretch that both of mine are bad…

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HokieKen

11389 posts in 1677 days


#13 posted 12-06-2018 06:22 PM


Now I know how to tag someone, Kenny will it notify Fridge that you tagged him?

- GrantA

Nope. I didn’t really “tag” him. I just hyperlinked his home page. No tagging on LJs…

-- Kenny, SW VA, Go Hokies!!!

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GrantA

1960 posts in 1946 days


#14 posted 12-06-2018 06:26 PM

that’s a shame, I thought I tagged him in another oak post haha

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DBDesigns

232 posts in 536 days


#15 posted 12-06-2018 06:28 PM

Y’all are underestimating the capacity of the Chinese to produce inferior products. Hell I wouldn’t be surprised if they shipped an entire container full of bad breakers!

-- I remember when Grateful wasn't Dead

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jamsomito

434 posts in 964 days


#16 posted 12-06-2018 06:30 PM

I’m going to try my 2HP HF DC on these circuits. Maybe that will give some clues. If I don’t reply in a half hour, call the fire department.

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HokieKen

11389 posts in 1677 days


#17 posted 12-06-2018 06:33 PM

One other thing I just thought of. On a subpanel, there is supposed to be a ground bus that is separate and isolated from the neutral bus. So, if your sub is run off of a GFCI breaker, that breaker is sensing the current that is returned via the neutral leg. But, if some of that current is bleeding off of the neutral leg and going to ground then the GFCI could sense a current drop that isn’t really there.

Now, that doesn’t really explain why the GFCI isn’t tripping instead of the subpanel breaker. But, just for poops and giggles, I’d connect the grounds to the neutral bus in the subpanel and see if the problem persists.

-- Kenny, SW VA, Go Hokies!!!

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HokieKen

11389 posts in 1677 days


#18 posted 12-06-2018 06:40 PM



Y all are underestimating the capacity of the Chinese to produce inferior products. Hell I wouldn t be surprised if they shipped an entire container full of bad breakers!

- DBDesigns

Oh yeah, I wouldn’t rule that out at all. And a 20A QO breaker is only $4 so it’s simple to investigate. I just tend to think that isn’t the situation since it’s only the tablesaw that’s popping them.

-- Kenny, SW VA, Go Hokies!!!

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jamsomito

434 posts in 964 days


#19 posted 12-06-2018 06:43 PM

Ok, 2HP HF DC check:

new 20A circuit 1: fine
new 20A circuit 2: fine
old 15A circuit: fine (little slower start)

checked the TS again, trips circuit 1 and 2. Runs fine on old 15A garage circuit.

I’ll open the panel and get a pic of inside.

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jamsomito

434 posts in 964 days


#20 posted 12-06-2018 06:57 PM

Checked the panel, clean as a whistle. Ground bar is isolated from neutral.

Checked the 50A GFCI breaker at the main panel. The test button worked fine, tripped like it should.

One other thing to point out is this is a repurposed a 6ga wire that used to run out back of my house to a hot tub. We cut the wire inside the house, put in a junction box in my basement, and ran new wire out to the garage from there. The idea was we could always switch back to that wire if needed to run a hot tub (which I’ll likely never put in), or power to a shed or something out back. However, in the junction box, each wire is just connected via wire nuts. I was a little surprised they didn’t used Polaris connectors or something similar, but apparently this is to code and I’m not running anything extremely power hungry for extended durations in my little wood shop. I don’t suspect this is the issue since the local breakers are tripping, but maybe?

Lastly, I’m starting to think this has something to do with my table saw. Let’s assume for a moment my TS wiring is the culprit. What do I look for? What would even cause this that doesn’t trip the 15A garage breaker? It seems like startup is just so intense that it trips the breaker. Now that it has a big enough pipe, it is capable of pulling more than 20A at startup? That would lead me to believe it’s the breakers again. But if it’s the saw, it could only possibly be the switch or the motor wiring, which hasn’t been touched in 20 years.

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GrantA

1960 posts in 1946 days


#21 posted 12-06-2018 07:05 PM

Umm, why’s the green insulation still on the ground wire? Unscrew that and strip it bare, retighten and try again.

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CaptainKlutz

1948 posts in 2033 days


#22 posted 12-06-2018 07:06 PM

+1 Call the electrician and ask him to investigate.
Don’t want to disappoint, but IMHO you paid $1500 for 2 circuit sub panel install that has <$250 in parts including wire, SO he was very well paid – even considering cost of permits. Around here I could have had a 4-6 circuits installed with up sized 150ft feeder line for same money. He should be happy to return once to help you make sure his panel is working.

Electrician with voltmeter and amp meter can figure out issue in less than 10 minutes.

+1 My 1st thought is breakers are bad.

But FWIW –
Had a similar issue once on 1.75HP metal lathe with a new panel years ago: the problem ended up being the switch on machine was arcing inside and failing. Replaced the switch and breaker stopped tripping.
What was happening; the old 20A house circuit had long wire and enough extra resistance to slow down the inrush current, and breaker never tripped. But shorten the wires to lathe, and the inrush current was 4x higher, and the breaker only 30ft away with less resistance was tipping.

In a table saw there are 2 switches in motor circuit; the power button (or magnetic starter), and centrifugal switch on back of motor. Either one of those could be having issues and causes a breaker trip. Power switch failure would likely be making breaker trip almost instantly, the motor switch would trip after blade starts moving and it coming up to speed. OH yea, and a failing- yet still working motor capacitor can trip breaker as well.

Need meter to makes some measurements to figure this one out.

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

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HokieKen

11389 posts in 1677 days


#23 posted 12-06-2018 07:06 PM

I’d pull the ground wires from the ground bus first and connect them to the neutral bus. See if the problem continues. If it doesn’t, then it’s the GFCI and there’s possibly something in the saws wiring causing a short to ground.

Quick things to do on the table saw. Bypass your switch. Wire the plug directly to the motor leads so when you plug it in, it turns on. This will tell you if the issue is in the switch. If that doesn’t help, check all your leads in the motor and switch for any nicked insulation or bare wires or bad connections. Make sure the motor is properly grounded as well. blow any and all sawdust out of the motor.

After that if there’s no resolution, I’d grab 2 more 20A breakers from a different store and swap them out and see what happens.

-- Kenny, SW VA, Go Hokies!!!

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jamsomito

434 posts in 964 days


#24 posted 12-06-2018 07:08 PM



Umm, why s the green insulation still on the ground wire? Unscrew that and strip it bare, retighten and try again.

- GrantA

They just pulled the insulation back a quarter inch or so. It has a good connection to the ground bar.

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HokieKen

11389 posts in 1677 days


#25 posted 12-06-2018 07:12 PM



Umm, why s the green insulation still on the ground wire? Unscrew that and strip it bare, retighten and try again.

- GrantA

+1. And it would appear that only one circuit is grounded. It may be that the 2 circuits share a ground somewhere downstream? Not sure that’s “legal” though and not sure why it would be done like that unless both circuits enter the same box somewhere.

-- Kenny, SW VA, Go Hokies!!!

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GrantA

1960 posts in 1946 days


#26 posted 12-06-2018 07:16 PM

Do you have a non GFI circuit you can try the saw on? I’d do that, if it works then somethings up with the saw. To hell with redoing something you paid a pile of money for

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jamsomito

434 posts in 964 days


#27 posted 12-06-2018 07:20 PM


Umm, why s the green insulation still on the ground wire? Unscrew that and strip it bare, retighten and try again.

- GrantA

+1. And it would appear that only one circuit is grounded. It may be that the 2 circuits share a ground somewhere downstream? Not sure that s “legal” though and not sure why it would be done like that unless both circuits enter the same box somewhere.

- HokieKen

They go to the same 4-receptacle box.


Do you have a non GFI circuit you can try the saw on? I d do that, if it works then somethings up with the saw. To hell with redoing something you paid a pile of money for

- GrantA

Not within reach. I’d have to string an extension cord to my kitchen, probably 30+ feet. It would take 2 of my extension cords. Not sure I want to do that.

———————-

I called my electrician. He is coming out this afternoon to look at it. He thinks the Square D QO breakers are just higher quality and sensing the spike and tripping whereas my older breakers allow a bit more time delay on amperage spikes before tripping. I could see this feasibly being the case, and also why both breakers are exhibiting the same problem.

We’ll see what his proposed solution is, but he knows the intent of this install was to run my shop, which it’s currently not doing.

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jamsomito

434 posts in 964 days


#28 posted 12-06-2018 07:25 PM

Also, just looked at the nameplate – the saw is only 1-1/2 HP, not 1-3/4. It says 18A on it, so other than startup it should be well within spec on a 20A breaker. Can’t believe it’s worked as well as it did on 15A.

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HokieKen

11389 posts in 1677 days


#29 posted 12-06-2018 07:29 PM

Yes, no reason it shouldn’t run on a 20A circuit. Definitely update us after the electrician fixes ya!

-- Kenny, SW VA, Go Hokies!!!

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Pixxture

27 posts in 610 days


#30 posted 12-06-2018 07:48 PM

Didnt find a 63 on the powermatic site but found a 64b, same rating you gave, 1-3/4 hp.
This is their statement
“..It is recommended that the table saw, when operated on 115 volt power, be connected to a dedicated 30 amp circuit with a 30 amp circuit breaker or time-delay fuse marked “D”….”
You may want to re-check your 63 manual. Your new 20A circuit could be short of the power you need.

BTW This is the same recommendation Laguna gives for their 1-3/4 hp saws.

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jamsomito

434 posts in 964 days


#31 posted 12-06-2018 07:55 PM



Didnt find a 63 on the powermatic site but found a 64b, same rating you gave, 1-3/4 hp.
This is their statement
“..It is recommended that the table saw, when operated on 115 volt power, be connected to a dedicated 30 amp circuit with a 30 amp circuit breaker or time-delay fuse marked “D”….”
You may want to re-check your 63 manual. Your new 20A circuit could be short of the power you need.

BTW This is the same recommendation Laguna gives for their 1-3/4 hp saws.

- Pixxture

Hmm, interesting, thanks. Mine is only rated at 1-1/2 HP though, I remembered wrong. Nameplate doesn’t lie though. What sucks is it runs fine on an old 15A circuit but trips a new 20A circuit.

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HokieKen

11389 posts in 1677 days


#32 posted 12-06-2018 08:04 PM

IIRC, the 64 had the bigger motor, solid wings, was left tilt and had a different fence.

-- Kenny, SW VA, Go Hokies!!!

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GrantA

1960 posts in 1946 days


#33 posted 12-06-2018 08:08 PM

Wait so you only got a single 4” box with 2 receptacles, this subpanel with 2 breakers and some #6 wire feeding from a junction box, not even from the main panel – for $1500? Did he buy you a drink first? Sorry man

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jamsomito

434 posts in 964 days


#34 posted 12-06-2018 08:08 PM


IIRC, the 64 had the bigger motor, solid wings, was left tilt and had a different fence.

- HokieKen

Correct. It is a better saw.

I just looked through the original manual here. The pages feel like what I imagine the original declaration of independence feels like nowadays. There is no mention of circuit amperage. It has a chapter on grounding and stresses a 115-203V extension cord needs to be used, but nothing about amperage. It specs the motor as 1.5HP, 115-203V, 1 phase. Nothing else.

I think my options are:
1. time-delay breaker. Not sure availability or cost, but apparently they exist
2. upsize circuit. would require fishing new wire through conduit, new breaker.
3. add 230V circuit. Would require additional breaker, likely additional conduit and receptacles. Also needs rewire of saw, maybe new switch.

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000

2859 posts in 1437 days


#35 posted 12-06-2018 08:15 PM

I would just put a 30 amp breaker in there and call it a day.
If the saw still trips you have other problems.

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HokieKen

11389 posts in 1677 days


#36 posted 12-06-2018 08:20 PM

No new switch needed to wire the saw for 230. No new nothing needed for the saw itself besides a new plug. But yes, also new breaker, and another outlet. I don’t buy it though that it won’t run off a 20A circuit. Could still just be a matter of cleaning up the wiring as-is. Corrosion and dirty terminals/contacts can definitely increase current draw due to increased resistance. I’d also still give bypassing the switch a shot to see if it makes a difference. Could be the switch itself is causing the increased current pull.

-- Kenny, SW VA, Go Hokies!!!

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HokieKen

11389 posts in 1677 days


#37 posted 12-06-2018 08:22 PM


Correct. It is a better saw.
...

- jamsomito

Debatable. I think the Vega fence is superior. Superior enough to outweigh the rest arguably.

-- Kenny, SW VA, Go Hokies!!!

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bmerrill

64 posts in 612 days


#38 posted 12-06-2018 08:39 PM

Question the qualifications of the electrician.

GFIC breaker used as the disconnect to the subpanel, though not to bad of an idea. Prefer to have this type breaker in the subpanel so if it trips only one circuit is effected. #6 wire is rated for 60amps, could have used a 60 amp main breaker.
No main disconnect in the subpanel.
Ground wire for the right breaker looks to still have insulation on it.
Looks like the feed to the left breaker doesn’t have a ground wire.

-- "Do. Or do not. There is no try". Yoda

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jamsomito

434 posts in 964 days


#39 posted 12-06-2018 09:10 PM


Question the qualifications of the electrician.

GFIC breaker used as the disconnect to the subpanel, though not to bad of an idea. Prefer to have this type breaker in the subpanel so if it trips only one circuit is effected. #6 wire is rated for 60amps, could have used a 60 amp main breaker.
No main disconnect in the subpanel.
Ground wire for the right breaker looks to still have insulation on it.
Looks like the feed to the left breaker doesn t have a ground wire.

- bmerrill

What? I should question my electricians qualifications because of your preferences? He gave me the choice, explained the pros and cons of each, and I chose to keep the GFCI on the feeder breaker in the main panel. It will save cost and complexity of installing my own additional circuits later. My preference.

#6 wire is rated for only 55 Amps, and they don’t make 55A breakers. Lots of people get away with 60A, and I was again given the choice on that, but I already had a 50A GFCI to reuse, so I kept the 50, not to mention it’s safer (albeit slightly).

It is against code to have a breaker on both the sub panel and the main panel. I chose to keep it at the main.

Ground wire for the branch circuit is making good contact, the insulation pulled back enough for the connection. If it bothers everyone so much, I’ll go pull it off. It doesn’t bother me.

The two circuits serve the same receptacle box and share a ground.

Look, guys, I know this electrician. He is qualified and knows more about local codes than I do. I did my own research and almost pulled the trigger to do it myself, but for the sake of time and CYA on insurance and permits I decided to hire someone to do it quickly so I don’t have to work in a 15 degree shop and trip my house breaker every other cut on the table saw. I understand you can do it yourself cheaper. I could have done it myself cheaper. But I know the costs and how much I’m paying him. It was on the upper end of what I was expecting, but frankly the guy is respectable, they did a bang-up job on the install, got it done ASAP, and I enjoy working with him. Also, I have not gotten a bill yet – that was the estimate going in. It will probably come in less due to how it went while they were installing. Please stop throwing crap at them and the local codes. So – can we please focus on the issues at hand?

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jamsomito

434 posts in 964 days


#40 posted 12-06-2018 09:17 PM

Ok, electrician came by and got some very interesting info. In the end, he was comfortable putting in a 30A breaker just so I could use my machines. He is looking into options and is going to get back to me. I’ll definitely keep you updated.

What he found was the TS pulled about 14A once it was up to speed and not cutting anything. It spiked to about 48 amps on startup. Seems simple enough.

Here’s where it gets interesting. I fired up my 2HP HF DC, and he got a peak startup amperage of 62A. Much more than the TS, and the DC was running just fine, no issues. It also took longer to start up than the table saw. Both of these are confusing.

I’m starting to think it’s an issue with my TS. How frequently do old motors need servicing? I’m wondering if it has something to do with the capacitor. Would that somehow affect power factor, which in turn affects the load the breaker sees? It is about 30 years old I think. It sat covered for about 20 of those years. Other than clearing out dust and rust I haven’t done much with it. It does make a clatter when it’s running, but I always figured it was just the nature of a contractor saw. The belt cover is a tad loose and makes a lot of noise in particular.

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HokieKen

11389 posts in 1677 days


#41 posted 12-06-2018 09:41 PM

Hmm that’s strange that the TS draws less inrush current but trips the breaker. I assume the in-rush is just sustained for a longer period. Even so though, that should mean it’s throwing the 30A breaker too. I’m inclined to agree with you that there’s something in the TS.

I’d bypass the switch and see what happens.

My PM63 motor starts as soon as I throw the switch and comes up to speed almost immediately. In addition to bypassing the switch, you could try taking the belt off and starting the motor unloaded. Maybe some bad bearings in the arbor are overloading it at startup?

-- Kenny, SW VA, Go Hokies!!!

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CaptainKlutz

1948 posts in 2033 days


#42 posted 12-06-2018 10:00 PM

I m starting to think it s an issue with my TS. How frequently do old motors need servicing? I m wondering if it has something to do with the capacitor. Would that somehow affect power factor, which in turn affects the load the breaker sees? It is about 30 years old I think. It sat covered for about 20 of those years. Other than clearing out dust and rust I haven t done much with it. It does make a clatter when it s running, but I always figured it was just the nature of a contractor saw. The belt cover is a tad loose and makes a lot of noise in particular.

- jamsomito

Yes, power factor changes level and duration of inrush current.

Yes, Capacitor or centrifugal switch on motor can trip breakers as they are beginning to fail, but still appear to be working.

Motor servicing is art form, not a hard science; as no two motors see same usage conditions. Mfg data sheet lifetime on motor start capacitor is ~25 years with proper design.
IMHO a 30+ year old table saw motor, deserves to get new start capacitor and bearings if you want it to last another 20 years.

Suggest three things:
1) bypass the saw start switch. test it. Replace switch if breaker does not trip.
2) open up the back end of motor housing and blow dust out of centrifugal switch. Test it.
3) Remove the belts from motor and test current draw. This will reduce the load and likely reduce the duration of the inrush current.
If the breaker does not trip, I would consider replacing $10 start capacitor to as a possible fix.
If breaker trips, tear down the motor, replace bearings, clean/adjust/replace centrifugal switch and capacitor to remove the most likely sources of problem. Can also take motor to repair shop for testing, and rebuild if you don’t want to mess with motor rebuild.

looks like Kenny and I were typing same time,
+1 HokieKen. :)

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

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Sparks500

255 posts in 869 days


#43 posted 12-07-2018 01:51 AM

Square D makes a 25A breaker. Probably have to order it.
I’d check the CH breaker in the main panel. CH uses aluminum bus and they can get corrosion where the contact the breaker. Is it a new breaker?

-- A good day is any day that you're alive....

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jamsomito

434 posts in 964 days


#44 posted 12-07-2018 02:16 AM

Looks like I’ve got some reading up to do on induction motors. I’m a little gray on the centrifugal switch…?

What would the cost of a rebuild be as opposed to a new motor? Seems I could get a brand new 1.5HP motor for $250 (ish)? I’m assuming a rebuild would not involve re-winding.

I can try bypassing the physical switch and running unloaded, will let you know. Might be tomorrow.

The 50A GFCI breaker on the CH panel is probably 10 years old. Good point about the aluminum oxidizing. I doubt it’s that because I haven’t had any other issues in the panel, but I can check it.

Thanks for all the help everyone.

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jamsomito

434 posts in 964 days


#45 posted 12-07-2018 02:26 AM

Ah, well this is mighty helpful: https://www.youtube.com/watch?v=M-j6PhthXJY

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MrUnix

7502 posts in 2737 days


#46 posted 12-07-2018 02:27 AM

What would the cost of a rebuild be as opposed to a new motor?
[...]
- jamsomito

A “rebuild” basically consists of cleaning things out and putting in new bearings. For single phase motors, perhaps cleaning of the centrifugal switch contacts and testing/replacement of the start capacitor (and run capacitor if present). You can replace the bearings yourself for under $20 and cleaning switch contacts is free :)

Cheers,
Brad

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

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TheFridge

10859 posts in 2024 days


#47 posted 12-07-2018 02:59 AM

Sq D makes good stuff

All signs point to the saw. 14A at no load is way too much. Grainger usually carries caps. Good bearings aren’t more than 20$. Ntn skf nsk etc etc. don’t go cheap. We’re talking 3$ vs 8$ Apiece for 2 bearings.

Gfci breaker or gfcis technically required in shop/garage. I don’t use them in the shop. They don’t last long under motor loads. If it bots tripping then it doesn’t sound like it’s broken so don’t fix it.

Dust collector sounds like it’s not drawing as much under normal load would be my guess.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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jamsomito

434 posts in 964 days


#48 posted 12-07-2018 05:06 PM

So the plot thickens. I pulled the cap and got it tested at a local motor shop. It’s 500mf, measured 520, looked pristine, so good to go there.

(I laughed at the red paint under the cap… cap. Baldor motor?)

The motor shop guys were a little stumped too. Next step for them is a $20 diagnostic- I bring it in to their shop and they hook it up to their electrical and see what happens. Would need to leave it with them as they have a backlog. They thought running it on the 15A circuit maybe caused some damage to the starter coil, but didn’t really know.

I’ll pop the end cap and fan off and have a look at the centrifugal switch later today. I’d consider doing the bearings but I don’t have a puller and I’d rather not spend a day fiddling with it.

Also, it looks like Square D makes a QO 20A High Magnetic (QO120HM) breaker designed for high inrush loads. It’s between $30-60 depending. After reading up on it, Square D breakers trip sooner than others. Maybe this is all it needs. Linky: https://www.schneider-electric.us/en/faqs/FA96714/

edit: nevermind, HD has it for a couple bucks more than the standard QO120CP

Anyone else have a 1.5HP saw running on a 20A circuit on a Square D QO panel? Is it just me, or would this configuration simply make the problem?

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GrantA

1960 posts in 1946 days


#49 posted 12-07-2018 05:56 PM

Anyone else have a 1.5HP saw running on a 20A circuit on a Square D QO panel? Is it just me, or would this configuration simply make the problem?

- jamsomito


I do, run it often and have never tripped a breaker.

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HokieKen

11389 posts in 1677 days


#50 posted 12-07-2018 06:22 PM

Spin the motor by hand with no load on it. If it doesn’t spin freely and/or you can hear or feel grinding, you need to do the bearings. If it spins freely without complaint, it can wait. I would suggest getting to them before they go bad though. The motor could likely live as long as you or I with a single bearing change in the next couple years.

I have that exact motor but I run it off 230V now. However, prior to running a 230 circuit for it, I ran it off of a 15A circuit for a while. I did trip the breaker several times. But, never unloaded as you are seeing. It would trip if I were loading it heavily cutting really thick or really hard woods. The 15A could handle the inrush and the motor running under moderate load though. But, I was definitely riding the hairy edge in that situation.

I would definitely try the HM breaker. Like Fridge said though, 14A is an awful lot of current draw for the saw to be running under no load. I still lean to there being something going on at the saw that’s at least contributing to your condition.

-- Kenny, SW VA, Go Hokies!!!

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