# 480V Motor Trips Breaker on 2nd ON Event



## Wirenuting (Sep 12, 2010)

What size heaters?
15hp is 24.15 heater, 21 amps running
20hp is 31.05 heater, 27 amps running 

Atleast gives you an idea to size what you have.

Without the code letter, you can’t determine what the inrush range is. 
5 seconds is awhile, but that could be the load, bearings, etc.


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## swimmer (Mar 19, 2011)

Wirenuting said:


> What size heaters?
> 15hp is 24.15 heater, 21 amps running
> 20hp is 31.05 heater, 27 amps running
> 
> ...


The MP is Eaton / Cutler-Hammer A308PN. The datasheet says 25HP at 460V. The word "heater" is in the datasheet but only that the MP has one. There is no data on the heater.


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## Wirenuting (Sep 12, 2010)

swimmer said:


> The MP is Eaton / Cutler-Hammer A308PN. The datasheet says 25HP at 460V. The word "heater" is in the datasheet but only that the MP has one. There is no data on the heater.


Here is the page with the data sheets on them. 

https://www.galco.com/buy/Cutler-Hammer-Div-of-Eaton-Corp/A308PN


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## gpop (May 14, 2018)

Large load being hauled up to speed would account for high starting amps. if the amps start dropping as soon as it starts that may be ok but 5 seconds sound a little to long.
As for tripping on restart that's not really strange as the overloads are already warm . 
I would change the overloads first then look at the way the vacuum is piped in to the system. The motor wiring may have been the problem or the result of a problem like a stuck dampner.

One concern i have is that you claim the motor in the beginning drew 130 amps for 1 minute before you fixed the wire. That shouldn't of happened as the overloads should have taken the motor out before that amount of time had passed.


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## John Valdes (May 17, 2007)

gpop said:


> Large load being hauled up to speed would account for high starting amps. if the amps start dropping as soon as it starts that may be ok but 5 seconds sound a little to long.
> As for tripping on restart that's not really strange as the overloads are already warm .
> I would change the overloads first then look at the way the vacuum is piped in to the system. The motor wiring may have been the problem or the result of a problem like a stuck dampner.
> 
> One concern i have is that you claim the motor in the beginning drew 130 amps for 1 minute before you fixed the wire.



130 sounds about right for starting current. 

The overload heaters are designed to allow this high inrush current to get the motor to base speed.


Burned connections to me are high resistance connections and are not high current connections.
Sometimes a high resistance connection will show open under load.


I would start at the breaker and follow/check and repair all the power connections until you reach the motor.
Seems you have a bad connection somewhere.
Could even be inside the breaker.

This motor does not start and stop much does it?


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## JRaef (Mar 23, 2009)

First, without knowing the motor nameplate FLA, you cannot properly protect that motor. 



The motor protector (MP) has adjustable thermal overload trips, not separate "heater elements". It's adjustable from 22-36Amps using a dial in the front. What does the dial say? It might be that because no motor info is available, someone has erred on the side of caution and set that too low, so it is tripping too soon and if it does, it will take longer to reset as well. You need to make more effort to get the actual motor nameplate data. Legally the nameplate had to be there, so if someone took it off, get a model number for the entire vacuum system and see what the manufacturer says they use. You can't keep driving blind here.


In addition, a vacuum (assuming you mean car vacuum) is powered by a blower, the vacuum is created by the inlet to the blower. These are usually centrifugal blowers, meaning the LOAD on the blower is a function of the air flow through it. So because load = flow, if you BLOCK the air flow, your motor has LESS load on it. Generally then, the vacuum system usually has a valve that is supposed to be CLOSED when you start it up, then open once the motor is at speed. What it sounds like is that this valve is open all the time and therefore the motor is loaded immediately, hence the long start-up time. The motor is not likely rated for this, hence the overload (MP) tripping. It happened for so long that it eventually burned up the wiring, meaning the burned wiring was the SYMPTOM, not the cause. Bottom line, someone needs to go through the entire machine and fix it.


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## 460 Delta (May 9, 2018)

What gauge is the wire and how long is the run? If it’s a relatively long run with maybe 10awg wire the voltage drop could be quite a bit making the startup time rather lengthy. I think you have more than one issue here and you’ll need to chip away at each one till you get them all resolved.


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## joebanana (Dec 21, 2010)

What's the input voltage at the disco? Do you have a "low-ohms" meter, or megger?
The yellow phase seems to have issues, could be a winding short in the motor, or high impedance connection between incoming to the brkr., and motor, causing an imbalance.


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## varmit (Apr 19, 2009)

JRaefs's post provides some very good info. 

Typically, the motors at a car wash start and stop (way too) often. If the wire and contactors are not over sized there will be problems. 

If the FLA of the motor really is 25 amps, I would use at least a 60 amp contactor and #8 wire for this application. 130 amps is not a bad inrush for a 25 amp FLA.

You may have a broken motor winding that only opens under load/heat.

On the breaker powering this, check the connections to the panel buss bars. Then check every termination from the panel to the motor.


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## swimmer (Mar 19, 2011)

varmit said:


> JRaefs's post provides some very good info.
> 
> 
> You may have a broken motor winding that only opens under load/heat.



Would this show up as excessively high or low current on one of the phases?


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## Cow (Jan 16, 2008)

At some point, when this thing burns up, someone will replace it with a new motor that has a nameplate. Then you will know the amp rating.

Just trying to see the silver lining here....

Otherwise, I'm with Jraef. You need to track down the nameplate amps doing whatever it takes, calling the manufacturer, putting it on the customer to do, or both. It's the customers equipment, they should have some vested interest in seeing it get repaired and functioning properly. Most customers don't have a problem helping out with clear direction. This is their equipment, it is as much their responsibility to find the vacuum motor amp rating as it is yours. If you can't make that clear to them or can't find the info you need, you can let them know you will turn the dial up a little more on the MP, but it may self destruct the motor.


Your MP may be getting weak too, but it's all a guessing game without nameplate amps.


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## paulengr (Oct 8, 2017)

5 second starting is long but anything under 6-10 seconds at full load is normal (NEMA MG-1). Check voltage at the motor peckerhead. If it's low and by this 2-3% on one leg will cause major issues as 1% voltage imbalance is a 6-8% current imbalance and 10-15% current imbalance is the limit. This will trip the overload but yours didn't after basically in rush for 1 minute. Overloads should trip in 10 minutes at 200% of FLA and in either 10, 20 or 30 seconds at 600% of FLA but yours didn't. The 600% point is set by the overload class. 20 is standard under NEMA. This corresponds closely to the IEC class 10 curve.

Stall on a motor is a consequence of the motor stator impedance. It is generally about 600% of FLA but smaller motors go up to about 1000% for fractional sizes. There is also inrush that lasts about 1 cycle that should not exceed 17 times FLA per NEC but some rerated IEC motors (Toshiba and Siemens are notorious for this) can be over 20x FLA.

Some overloads do wear out. The eutectics lose solder over time so they trip early. Bimetallic ones like yours drift in either direction. Microprocessor trips are close to the cost of a new relay or less and don't drift. Installs heaters have a second major problem. They heat and cool at the same rate. A motor that is not turning cools much slower than a running one. So repeatedly starting a motor with numerous heaters will burn it up. This won't happen with eutectics or microprocessor overload relays.

You can get more with smaller motors but starting a motor heats it at a rate of about 25-40 times it's normal running condition. Motor heating is proportional to the square of the current. On motors the size you have usually it will start about 3 times an hour before it trips on overload. 10 minutes of running (cooling) isn't enough. It sounds like it's slightly overloaded or at least under a lot of load on starting so you might not get a full 3 starts. If you need more starts per hour a small soft start can be set to limit starting current. It will extend start times but cuts inrush/stall current so you get more starts per hour. On a compressor generally you can limit starting current to around 350% of FLA with pretty much a normal start and plenty of high end torque in current limiting mode.

Agreed with the post about compressor not starting unloaded.

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## gpop (May 14, 2018)

just out of interest. In the picture it looks like a silver plate just in front of the eye bolt and 2 labels tied to the eye bolt. Is there anything written on them or is this a generic picture of a motor that looks the same.


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## Dennis Alwon (May 9, 2009)

What size breaker is it? My guess is you can have a 60 amp breaker and still be compliant


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## varmit (Apr 19, 2009)

swimmer said:


> Would this show up as excessively high or low current on one of the phases?


Yes it would - if the break was open at the time that you checked the current. 

IEC style electronic overloads and MP units are VERY prone to failure.


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## paulengr (Oct 8, 2017)

swimmer said:


> Would this show up as excessively high or low current on one of the phases?




Yes. A three phase motor can put out up to about 2-3 times rated torque. This works mechanically and electrically. If it loses a phase in a three phase motor for instance the remaining two phases almost double the current. Obviously this is not true with single phase motors.


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## swimmer (Mar 19, 2011)

gpop said:


> just out of interest. In the picture it looks like a silver plate just in front of the eye bolt and 2 labels tied to the eye bolt. Is there anything written on them or is this a generic picture of a motor that looks the same.


I affixed the shiny tag at left. It tells me that this is Motor 6 and is controlled by MP-6 and contactor M-6 in the control panel.

I'm sure I've tried reading the 2 trashy tags but now that you've mentioned it, I'll take another look.


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## swimmer (Mar 19, 2011)

Dennis Alwon said:


> What size breaker is it? My guess is you can have a 60 amp breaker and still be compliant



The data sheet for Eaton / Cutler-Hammer A308 says 50A


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## Bird dog (Oct 27, 2015)

You really need the nameplate to fix this. IIRC codewise that motor may require a "Motor Protector" because it is a high efficiency motor with an extremely high startup current, type or class E?.


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## John Valdes (May 17, 2007)

Burned connections are the only thing to keep in mind. Burned connections in many instances have zero to do with the motor.
In fact my money says its not the motor. My guy says the breaker is bad and the only way to know is to replace it.
A bad contact in a breaker or starter is not always easy to locate. In most every instance this shows up as zero amps under load.


Have you inspected the contactor. Taken it apart and looked at the contacts?
Have you gone through the circuit and double checked every motor feeder connection?
Everything you have said tells me it is not the motor. 

BTW. Here on page 20 is frame size dimensions.
http://www.goevans.com/filesSite/EHB_pgs0803.pdf



You know the voltage, you can find your frame with the link. If you can check RPM of the motor, you can narrow it down. Since you know the voltage, you can estimate fairly accurately the HP and the current rating.
Page 14 has HP and current rating.
I'm certain you can find just about everything you need to know about this motor. 

Do you have a set of calipers to measure some of the important frame dimensions?


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## JRaef (Mar 23, 2009)

swimmer said:


> I affixed the shiny tag at left. It tells me that this is Motor 6 and is controlled by MP-6 and contactor M-6 in the control panel.
> 
> I'm sure I've tried reading the 2 trashy tags but now that you've mentioned it, I'll take another look.


I'm with gpop, that tag affixed with rivets that is just to the right of the eye bolt looks like the motor data plate. It might be worn down a lot, but sometimes the data is stamped in and if it is, but it's too hard to read, you can do a rubbing over it with a sideways pencil and a clean white piece of paper to reveal some info. Also if you can't get your head in there, get your phone up close to it, touch the image to focus it and snap a picture. Then if it's still hard to read, a trick I've found is to use a photo editing program and "reverse" the image to look like a negative, it will make very subtle or faded lettering appear more clearly.


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## micromind (Aug 11, 2007)

WEG tags are always very hard to read even when new. 

Sometimes shining a light at an angle helps but the printing is still bad.


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## paulengr (Oct 8, 2017)

Bird dog said:


> You really need the nameplate to fix this. IIRC codewise that motor may require a "Motor Protector" because it is a high efficiency motor with an extremely high startup current, type or class E?.



Yes. WEG motors almost always are. Energy is not cheap in Brazil. I haven’t seen a non-E WEG motor in 20 years. Doesn’t mean they’re not out there but got to be getting rare.

Motor protectors are usually the way to go. Inrush blew by 6-10x FLA (a standard breaker setting) years ago and are bumping up against the current NEC limit if 17xFLA but the big issue is stall current of 6xFLA for 2-6 seconds trips the inverse time protection. MCPs just don’t have inverse time since the overload relay takes care of that, or they make a combined IEC manual motor starter which is a combination of disconnect, MCP, and overload in one unit. Technically acceptable but when they trip you can’t tell if it’s an overload or an electrical fault.


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## swimmer (Mar 19, 2011)

JRaef said:


> Generally then, the vacuum system usually has a valve that is supposed to be CLOSED when you start it up, then open once the motor is at speed. What it sounds like is that this valve is open all the time and therefore the motor is loaded immediately, hence the long start-up time. [/QUOTEJ]
> 
> JRaef, Do you know where that valve is located on the blower in this picture?
> Is it removed from the exhaust port?


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