Breaker has started to trip on my cyclone

[John Spitters]

I have a Grizzly 3hp cyclone and the motor is rated at 22 amps. I have it wired on it's own 30 amp breaker with 10g wire in the walls, the run is relatively short at apx. 30 ft from the panel. Lately the breaker has started to trip on startup but this only happens after several successful starts on the cyclone. The brand of breaker is Siemens, I'm thinking that at startup the cyclone motor must be drawing well in excess of the 22 amp rating on the motor and the breaker does not have a long enough delay for the high amp draw on startup. Is there a breaker that I could install that would account for this heavy startup draw.


John

[Dan Case LR]

How long has it been installed? Was the breaker new when you installed it, or previously used? How long does the cyclone run each time before the breaker starts to pop? Is the breaker warm to the touch?

Most breakers in residential and commercial installations use thermal elements to detect overloads. If your motor is working hard and warming that thermal element enough, it could cause exactly the behavior you've described. It would be interesting to put a clamp-on ammeter on the motor circuit and see what it's really drawing--if the motor is heavily loaded, the current may be higher than you think. A typical residential/light commercial breaker is designed to continuously carry 80% of it's rating without problems--in your case, 24 Amps. You're right at that limit. Running a breaker that close to its practical limit will cause it to fail sooner, so if I were doing that installation I'd probably upsize to #8 wire and a 40A breaker.

Most motors do have substantial start-up current spikes. There are breakers available with trip curves designed to accommodate that, but they may not be available to fit your breaker panel (they're usually only available for heavy industrial applications). I work with broadcast transmitters that have the same problems with startup surge (Big motors AND big power supplies), and we often use fused disconnects with time-delay fuses to feed those rigs.

D.

[John Spitters]

Dan
This was all a new installation, shop was built apx. 2 yrs ago and all worked fine with the cyclone till maybe six months back when it would occasionally trip at startup.
The breaker has never been even warm to the touch, and sometimes the trip will happen when I first turn on the cyclone that day.
But as I said this only happens after several successful starts with out the breaker tripping.
All wiring is in the wall and I really would not want to redo the existing wiring as at this point it would need to be surface mounted if I did.
I should add that I am able to run the cyclone for hours at a time and never at any point does the breaker ever heat up or become warm to the touch, so the issue is definitely with the startup draw.

John

[Jim Neeley]

John,

Although generally a pretty reliable device, if it were me I'd replace the breaker with another 30a just to see if the problem goes away. Most breakers are not designed to trip often and can "weaken" with trips. I see this typically on very large breakers but it'd be an inexpensive way to ensure it's not that and may fix the problem relatively painlessly (no wire changes, etc.)

Jim

[Dan Case LR]

Since it ran without problems for 18 months, something must have changed--either the breaker has become more sensitive (it happens), or the motor for some reason is drawing more. If you have a spare, try changing the breaker.

D.

[Perry Holbrook]

Start up current on a cyclone motor is higher if you have a blast gate open, the larger the gate the higher the current draw. Some mfg of cyclones recommend starting with all gates closed because of possible breaker trips.

Don't know if this helps, but just wanted to add a little bit to the puzz;e.

Perry

[Rod Sheridan]

Since the motor will have a non polarised electrolytic start capacitor, I would check that first. This a text book example of the symptoms of a reduced capacitance capacitor.

The breaker may simply be doing what it's supposed to do................Regards, Rod.

[Matt Meiser]

Mine did this the first several starts when new but I haven't had a problem since.

Don't discount the possibility of a bad breaker either. I tripped the main on my shop this summer. The first time I thought it was a power outage until an hour later when I found the power on in the house. The next time I went right in and the breaker was very hot. It didn't happen again after the breaker was replaced.

[Joe Angrisani]

I don't know if this applies to you, John, but when I was doing my shop about a year ago, there was a pretty good sized recall of Siemens breakers. Check their website then look at the manufacturing date code on your breaker.

[John Spitters]

I guess at this point in time I'll just replace the breaker if the proplem persists though maybe I'll need to look at upgrading the wires and install a heavier breaker. This could still be done by running the wires through the loft space above, then I would only need to open the wall at the panel.

John

[John Spitters]

Thanks for the info on the breakers, mine were installed prior to this date but it does raise a red flag as I know that the breakers that are in my panel were made in Mexico. Tomorrow I will check them out and compare the code numbers on the breakers.

John

[Alan Schaffter]

Another possible cause is a bad centrifugal switch in the motor. Does the breaker trip immediately or after a second or two during which the motor just hums? The times the breaker pops, has the motor ever spooled up to full RPM?

The centrifugal switch connects the start capacitor to the start winding when the motor is off and disconnects it when the motor gets up to RPM. My old 3 hp Grizz reacted exactly like you describe while wired to a 30A breaker w/15' of 10 ga. wire. The centrifugal switch contacts were pitted badly, but sometimes they made good enough contact so the DC started fine, other times they didn't make good contact and the breaker would pop after a second or two as the motor struggled to start and was drawing excess current.

[John Spitters]

Hmmmm The breaker pops immediately on start up, within the first 1/2 second.

John

[Rod Sheridan]

I guess at this point in time I'll just replace the breaker if the proplem persists though maybe I'll need to look at upgrading the wires and install a heavier breaker. This could still be done by running the wires through the loft space above, then I would only need to open the wall at the panel.

John

John, it is more likely that you have a starting problem with the motor due to a bad starting capacitor or centrifugal switch.

I would inspect the starting capacitor first.

Regards, Rod.

[John Spitters]

Another possible cause is a bad centrifugal switch in the motor. Does the breaker trip immediately or after a second or two during which the motor just hums? The times the breaker pops, has the motor ever spooled up to full RPM?

The centrifugal switch connects the start capacitor to the start winding when the motor is off and disconnects it when the motor gets up to RPM. My old 3 hp Grizz reacted exactly like you describe while wired to a 30A breaker w/15' of 10 ga. wire. The centrifugal switch contacts were pitted badly, but sometimes they made good enough contact so the DC started fine, other times they didn't make good contact and the breaker would pop after a second or two as the motor struggled to start and was drawing excess current.


John, it is more likely that you have a starting problem with the motor due to a bad starting capacitor or centrifugal switch.

I would inspect the starting capacitor first.

Regards, Rod.

So if this is really the issue how do I go about finding the problem, what exactly should I do as I really know nothing about motors, what should I take apart and look for? If you could give me the "blind mans tour" of just what to do maybe I can solve this problem. And if it's an issue with the motor itself maybe I could still get it replaced through Grizzly's warrantee.

John

[Rod Sheridan]

Hi John, the starting capacitor is often located in a metal "can" on the outside of the motor.

Disconnect the power and open the can to visually inspect the capacitor. Leaking, swollen, burned are bad.

The capacitor will have 2 specifications, the capacitance in micro-farads, and the voltage rating.

If it looks OK, take it to a local motor shop and ask them to test it for you as some failures can't be seen.

The centrifugal switch is tougher, it's inside the motor and makes a click when the motor slows down. That's the mechanism that moves the switch contacts inside the motor to disconnect the starting winding once the motor is up to about 75% of rated speed.

I'm still betting on the capacitor at this point.............Rod.

[Ken Fitzgerald]

I agree with Rod's diagnosis and explanation.

The capacitor is the most likely culprit.

[John Spitters]

Thanks Rod and Ken

I'll have a look at the Capacitor over the next few days when I have the time.

John

[Alan Schaffter]

Definitely check the capacitor first.

But if it looks ok, then you need to check the centrifugal switch. This is not quite like trying to describe heart surgery but it would be best if you did a little research on the INTERNET so you have a picture of what you are looking for. Most centrifugal switches are inside the back of the motor case (though I have seen at least one Shop Fox motor where it was at the shaft end). Each motor is a little different, but for a TFEC (totally enclosed fan cooled) motor you need to remove the fan cover at the back (sheet metal with louvers) which is usually held on with just 3 or 4 screws, slip off the fan, then remove the back of the motor. Inside the back you should see the centrifugal switch - a mechanism made from a plate of non-conductive material, usually phenolic, bushings and other metal parts, a couple of springs, counter weights, and wires connected to a set of contacts. Check the mating surfaces of the contacts- if the contacts are totally shot you will need a new centrifugal switch. If they just have some pitting, you can clean them with an emory board and polish them. Use your fingers to actuate the switch to see that it opens and closes properly. Also check the wiring and connections here and in the junction box in/on the motor. Make sure all binding screws and wire nuts are tight.

Or you could just take the motor to a motor shop where they have the right equipment to check the capacitor and switch.

There are a lot of sources with explanations and diagrams, but few with photos. There is a side view of one type of centrifugal switch on page 9 of the document at this link (http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=18&ved=0CKIBEBYwBzgK&url=http%3A%2F%2Fschool-up.com%2FAAA_CHEESE_INDUSTRY%2FM2%2FAA__CLASSES%2F AAA__MOTORS%2FZZZZ__EXTRA_MOTOR_STUFF%2FSingle_Pha se_Motors.pdf&ei=-prfTo3wGeunsQK46s2gBw&usg=AFQjCNEvBeGJWLlkOZRyifT3eNwu_eYKOA&sig2=oGPULaRTifayZ3oSiotk-g). There is another one here (http://www.tpub.com/ceb/107.htm). Here are pics of six. (http://www.aliexpress.com/product-fm/331251392-centrifugal-switch-wholesalers.html).

D' Oh! I just realized you can Google "Induction Motor Centrifugal Switch" and select "Images" at the top to see tons of them like these!!!

http://i00.i.aliimg.com/img/pb/516/406/381/381406516_099.jpg

http://i01.i.aliimg.com/img/pb/158/955/387/387955158_204.jpg

[John Spitters]

Definitely check the capacitor first.

But if it looks ok, then you need to check the centrifugal switch. This is not quite like trying to describe heart surgery but it would be best if you did a little research on the INTERNET so you have a picture of what you are looking for. Most centrifugal switches are inside the back of the motor case (though I have seen at least one Shop Fox motor where it was at the shaft end). Each motor is a little different, but for a TFEC (totally enclosed fan cooled) motor you need to remove the fan cover at the back (sheet metal with louvers) which is usually held on with just 3 or 4 screws, slip off the fan, then remove the back of the motor. Inside the back you should see the centrifugal switch - a mechanism made from a plate of non-conductive material, usually phenolic, bushings and other metal parts, a couple of springs, counter weights, and wires connected to a set of contacts. Check the mating surfaces of the contacts- if the contacts are totally shot you will need a new centrifugal switch. If they just have some pitting, you can clean them with an emory board and polish them. Use your fingers to actuate the switch to see that it opens and closes properly. Also check the wiring and connections here and in the junction box in/on the motor. Make sure all binding screws and wire nuts are tight.

Or you could just take the motor to a motor shop where they have the right equipment to check the capacitor and switch.

There are a lot of sources with explanations and diagrams, but few with photos. There is a side view of one type of centrifugal switch on page 9 of the document at this link (http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=18&ved=0CKIBEBYwBzgK&url=http%3A%2F%2Fschool-up.com%2FAAA_CHEESE_INDUSTRY%2FM2%2FAA__CLASSES%2F AAA__MOTORS%2FZZZZ__EXTRA_MOTOR_STUFF%2FSingle_Pha se_Motors.pdf&ei=-prfTo3wGeunsQK46s2gBw&usg=AFQjCNEvBeGJWLlkOZRyifT3eNwu_eYKOA&sig2=oGPULaRTifayZ3oSiotk-g). There is another one here (http://www.tpub.com/ceb/107.htm). Here are pics of six. (http://www.aliexpress.com/product-fm/331251392-centrifugal-switch-wholesalers.html).

D' Oh! I just realized you can Google "Induction Motor Centrifugal Switch" and select "Images" at the top to see tons of them like these!!!

http://i00.i.aliimg.com/img/pb/516/406/381/381406516_099.jpg

http://i01.i.aliimg.com/img/pb/158/955/387/387955158_204.jpg

WOW !
Thanks so much Alan,
This is the type of info that I need.

John