Question for the machine electricians here.

I have a 20" KH (company now out of business, but Powermatic level construction) single phase surface planer. It was purchased new in 2009, ran well for 13 years, only changing one capacitor twice. Cutterhead motor is 7.5hp, feed motor is 1.5hp. Plates on the motors say the amperage draw is 44amps combined.

It was in storage for 2 years while we recently moved, and now my new shop is almost done getting set up. The electrician working on other parts of the house does not know an enormous amount about machine electric. He ran an 8awg wire and mistakenly put it on a 40 amp breaker. It popped the breaker and blew a capacitor. We swapped the 40 amp for a 50 amp breaker and replaced the capacitor. The electrician then put a meter on it at the breaker, turned the machine on and after a few seconds it popped the breaker again. The electrician said it had surged to 270 amps for a split second, then settled to 25amps before the breaker tripped. Those readings are confusing.

Contacted my former electrician (now retired) who did the wiring in our previous house, he said we should have run a 6awg wire, but is still stumped on why the surge to 270amps. Bad, or incorrect capacitor is one theory he came up with otherwise.

If there is anyone who has any advice, I would greatly appreciate it. Thanks.

44 amp draw needs to be 6 awg and a 50 amp breaker

Max breaker size for 8 awg is 40 amp

Yeah - I wondered about this too. I was thinking a 60A at least.

The machine ran for 13 years with a 50amp breaker and #6 wire. That is what is somewhat perplexing to all of this?

When my current electrician was doing the wiring for this machine, I was not present. I did remove and take the machine's wire when I moved and gave it to him to reuse, unfortunately he used it elsewhere without my knowledge and ran #8. This run of wire is 15' shorter than the previous, coming in at about 25'.

My previous electrician did recommend a 55amp, but I cannot find a Square D QO 55a. So would a change to 60a be wise? Or change the wire first and see what happens? Then try a 60 if still tripping?

Could there be a motor issue with it sitting for 2 years? (It was in a climate controlled machine/rigging company's warehouse.)

And thank you for your replies. The finer points of electric are not in my skill set.

1988PA-Aggie said:

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The machine ran for 13 years with a 50amp breaker and #6 wire. That is what is somewhat perplexing to all of this?

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Could be a lot of contributing factors. You were probably just on the edge of that breaker profile. If new breaker, slightly different curve. If same breaker, springs wear out over time, etc.

1988PA-Aggie said:

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My previous electrician did recommend a 55amp, but I cannot find a Square D QO 55a. So would a change to 60a be wise? Or change the wire first and see what happens? Then try a 60 if still tripping?

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The wire shouldn't affect the performance of the breaker in this case. You do want to change back to #6.

55A is a non-standard breaker rating, but guarantee they picked it because of the ampacity of #6 (55A). There's often misunderstanding when it comes to overcurrent protection, especially with motors, and a whole lot of "it depends". To keep it short, I'd personally use a 60A breaker. The code allows you to round up to the next standard rating (which in this case is 60A), if this is the only load on this circuit. NEC 240.4(B)(2). It's super easy and cheap to buy and swap the breaker in this case.

If this is the only load on this circuit (likely is), that's where you can get into higher circuit breaker ratings that Underoos described. If the planer is a cord-and-plug device, I personally wouldn't go above 60A without upsizing the cable bigger than #6. If the planer is hard-wired, I'd be OK with a bigger breaker. Just my opinion, but a lot of ways to go about it.

1988PA-Aggie said:

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Could there be a motor issue with it sitting for 2 years? (It was in a climate controlled machine/rigging company's warehouse.)

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Personally, I doubt it. But you never know.

See if you can get a high magnetic breaker. Essentially a "slow blow" breaker. ( Not sure you can get them that big though...)

BenTheGoodAg said:

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1988PA-Aggie said:

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The machine ran for 13 years with a 50amp breaker and #6 wire. That is what is somewhat perplexing to all of this?

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Could be a lot of contributing factors. You were probably just on the edge of that breaker profile. If new breaker, slightly different curve. If same breaker, springs wear out over time, etc.

1988PA-Aggie said:

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My previous electrician did recommend a 55amp, but I cannot find a Square D QO 55a. So would a change to 60a be wise? Or change the wire first and see what happens? Then try a 60 if still tripping?

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The wire shouldn't affect the performance of the breaker in this case. You do want to change back to #6.

55A is a non-standard breaker rating, but guarantee they picked it because of the ampacity of #6 (55A). There's often misunderstanding when it comes to overcurrent protection, especially with motors, and a whole lot of "it depends". To keep it short, I'd personally use a 60A breaker. The code allows you to round up to the next standard rating (which in this case is 60A), if this is the only load on this circuit. NEC 240.4(B)(2). It's super easy and cheap to buy and swap the breaker in this case.

If this is the only load on this circuit (likely is), that's where you can get into higher circuit breaker ratings that Underoos described. If the planer is a cord-and-plug device, I personally wouldn't go above 60A without upsizing the cable bigger than #6. If the planer is hard-wired, I'd be OK with a bigger breaker. Just my opinion, but a lot of ways to go about it.

1988PA-Aggie said:

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Could there be a motor issue with it sitting for 2 years? (It was in a climate controlled machine/rigging company's warehouse.)

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Personally, I doubt it. But you never know.

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Update: we put a 60amp breaker on. Same result.

The machine has two push-button switches, one to start the cutterhead, the next to start the feed rollers. We started the cutterhead first, it seemed to never come up to speed, maybe a few hundred RPM's, the meter went to 270amps again, ran for about 4 seconds, then it tripped. Didn't hit the feed roller switch. We tried several times with the same result.

We have not changed the 8g wire to 6g wire yet. But do you think that will make a difference? It seems like only running a few seconds would not allow the wire to heat up enough to trip the breaker (temp in the shop is about 45 degrees currently).

I have been struggling to find a manual or spec sheet on this machine. The company is no longer in business and it seems like this machine (made in 2007) never existed as far as the internet goes.

Darn. Starting to seem like it could be the motor. Starting capacitor is a good idea - they can still age when not in use, so it at least tracks. I'm sure you've checked to make sure it's not obstructed and spins freely (thinking bearings). Does it seem like it's starting sluggishly compared to what it used to?

The 8 AWG to 6 AWG wire won't affect the performance of the breaker in this case. Truthfully, if I was in your shoes, I'd probably be trying to nail down the issue just like you are before swapping it. You can get away with it for a time. As you mentioned, not getting hot enough for this limited use, but not what you want for permanent install.

It'd still be super easy to try the 80A breaker, but the fact you haven't even hit the feed rollers says a lot to me. The 80A breaker is only providing short circuit protection and the overloads on the planer are protecting everything from overload current (which is why the physical wiring is so important).

The only other thing that comes to mind is if your old setup was 240V and now you're on a 208V system? Very often, equipment is dual rated, but it does bump up the starting current. Even then, this 10% bump in current seems unlikely to be enough.

Thank you for the response.

I imagine the RPM's of the cutter head (20" helical) is probably in the 8000 RPM range? When it was running well, two years ago, it would take 3-4 seconds to come up to speed. The helical head helps reduce noise quite a bit over straight knives. It would start with a low hum but as the RPM's rise, the pitch gets higher.

Now tying to start it, it has a lower pitch hum, but the pitch doesn't change as the speed never ramps up beyond a few hundred RPM's. The head definitely spins and it doesn't sound like anything is grinding or scraping.

Ben, how would I know if I am on a 208v system? In the previous home where my shop was located, we had a single 200a panel. While renovating, we added another 200a as a second panel, not replace with a 400amp. We did the same thing in this current home, a second 200amp. Does this have anything to do with 240v vs. 208v and/or the utility company's service? I have a 5hp jointer (same KH brand) and a 5hp table saw (3 phase with a phase converter) currently that both run perfectly.

There are two capacitors within the machine. A few weeks ago I popped one capacitor. Replaced it with the same exact brand and model. This capacitor is holding steady. But can a capacitor only work...partially? Or a chance somewhere along the way, years ago, when I blew a capacitor that I mistakenly put an incorrect capacitor on and have replaced them recently with another, but still incorrect capacitor? I never got a manual on these machines unfortunately when I purchased them, and can't find any specs on the internet.

Would it matter that that the electrician wired it with a twist lock plug? Planer was hard-wired previously. He did the same with the jointer which works fine.

Just throwing anything out there that may be suspect. Thanks again.

1988PA-Aggie said:

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Thank you for the response.

I imagine the RPM's of the cutter head (20" helical) is probably in the 8000 RPM range? When it was running well, two years ago, it would take 3-4 seconds to come up to speed. The helical head helps reduce noise quite a bit over straight knives. It would start with a low hum but as the RPM's rise, the pitch gets higher.

Now tying to start it, it has a lower pitch hum, but the pitch doesn't change as the speed never ramps up beyond a few hundred RPM's. The head definitely spins and it doesn't sound like anything is grinding or scraping.

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Anecdotal opinion, but doesn't sound like a clean startup. Just curious (and likely not an issue), is there a gearbox between the motor and the cutter head? Does it need new lubrication?

1988PA-Aggie said:

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Ben, how would I know if I am on a 208v system? In the previous home where my shop was located, we had a single 200a panel. While renovating, we added another 200a as a second panel, not replace with a 400amp. We did the same thing in this current home, a second 200amp. Does this have anything to do with 240v vs. 208v and/or the utility company's service? I have a 5hp jointer (same KH brand) and a 5hp table saw (3 phase with a phase converter) currently that both run perfectly.

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Based on the description, it's unlikely you have a 208V system. 208V is typically found in commercial and industrial settings. It's a true three-phase system and you can supply 3 phase or 1 phase loads, and often 208V single phase loads are interchangeable with 240V machines. 240V is a typical residential system, and often called a "two-phase" system, though this is technically incorrect as it still uses a single transformer winding to generate this voltage. If you had a 208V 3 phase, you wouldn't need a phase converter. You can measure voltage between the two hots with a volt-meter to be sure, but I'd put money on 240V.

1988PA-Aggie said:

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There are two capacitors within the machine. A few weeks ago I popped one capacitor. Replaced it with the same exact brand and model. This capacitor is holding steady. But can a capacitor only work...partially? Or a chance somewhere along the way, years ago, when I blew a capacitor that I mistakenly put an incorrect capacitor on and have replaced them recently with another, but still incorrect capacitor? I never got a manual on these machines unfortunately when I purchased them, and can't find any specs on the internet.

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Because manufacturers do similar things, I thumbed through a few random 7.5HP JET and Grizzly planer manuals and am guessing that they're using two start capacitors as opposed to a start/run capacitor. I would almost always replace both start capacitors at the same time. If one has popped, there's a good chance the other is damaged. Really, I think if you've got a 250VAC capacitor with 200-400MFD capacitance, you're probably OK. If one of them is a run capacitor, it's much lower capacitance and higher voltage.

1988PA-Aggie said:

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Would it matter that that the electrician wired it with a twist lock plug? Planer was hard-wired previously. He did the same with the jointer which works fine.

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No - this wouldn't affect it.

1988PA-Aggie said:

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Just throwing anything out there that may be suspect. Thanks again.

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If you have a nameplate for the cutter head motor, feel free to share a pic.

I'm assuming the feeder motor starts and runs with no issue?

1988PA-Aggie said:

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When it was running well, two years ago, it would take 3-4 seconds to come up to speed. The helical head helps reduce noise quite a bit over straight knives. It would start with a low hum but as the RPM's rise, the pitch gets higher.

Now tying to start it, it has a lower pitch hum, but the pitch doesn't change as the speed never ramps up beyond a few hundred RPM's. The head definitely spins and it doesn't sound like anything is grinding or scraping.

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If your electrician told you to try a 55A breaker, of which they ain't none, I'm gonna toss the benefit of the doubt on common sense out the window. Is this a 240V machine he wired at 120V accidentally or dumbassedly? Stick a vacuum cleaner on a long ass extension cord and you can hear the difference in the motor. It'll be a low hum. Low humming and low speed on motors often screams under voltage. Might could also be how you blew a cap. Might also explain why your inrush is so high. I would check the voltage at the motor and at the twist lock. You accidentally swap a hot and a ground in the plug or receptacle and you'll get 120V hot to ground instead of 240V hot to hot.