# Solid State Motor Starter Tripping



## paulgarett (May 8, 2012)

Two 10 HP 480 volt motor starters have tripped. These 10 HP motors are part of a group of 5 HP motors that dry cars at a car wash. 
All of the circuit conductors for the five 10 HP, 480 V motors (15 conductors plus ground) are bundled in the same raceway, 1 inch PVC. 
The start-up amps of one of these 10 HP, 480 V motors is between 75-90 Amps, then backs down to about 14 Amps. 
The five motors are on timers. The first one comes on right away, the next two motors come on 5 seconds later, enough time for the first motor start-up to back down. Then about 5 seconds later the last two motors start-up. 
These motors run all day intermittently and can be on continuously at times when the car wash is really busy. It has also been about 90 degrees during the day. 
My question are these: 

Can bundling all 15 of the motor conductors in the same conduit cause a motor starter to trip? 

The overload relay of a motor starter senses heat and trips the contractor.

Does bundling of the 15 conductors cause heat?


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## Big John (May 23, 2010)

paulgarett said:


> ...The overload relay of a motor starter senses heat and trips the contractor.
> 
> Does bundling of the 15 conductors cause heat?


 Bundling doesn't cause heat, but it prevents the heat that is normally created from being dissipated properly. Old bimetallic overloads actually did operate based on the heat of the element in the overload, and had to be adjusted for higher ambient temperatures to avoid false trips. But your bundles of conductors will not affect this, because that heat is happening remote from the overload.

Electronic overloads don't actually sense any heat. They are looking at a value of current flow through the conductor, and making an assumption about how that translates to stator heat in the motor. So neither the ambient temperature, nor the conductor temperature from bundling would ever come into play.

How old are the motors? What style of relay are these? How many trips has each one had?


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## paulgarett (May 8, 2012)

Thank you. The motor starters are Eaton Solid State. Brand new. The motors are also new. Don't have the nameplate info though. The MCC and motors are for a car wash. The starters did not start tripping until the last couple days when the weather has been in the 90s. The motors, however, are within the tunnel of the car wash. The MCC in the utility room. The motors are for the blowers that dry the car off after the wash period. They are on intermittently or continuously, depending on how busy the car wash is. The start up is 75-90 amps per motor (5 motors) then goes down to about 14 running amps. 
I am concerned the resistance due to bundled conductors may create voltage drop or some other problem that has to do with inductive loads and the magnetic effect of bundled conductors. I have not checked for voltage drop yet but will today. I am mainly concerned that 15 bundled conductors that serve five 480 volt inductive motor loads may cause problems with the motor starters, due to the effects of bundling or inductive reactance of the load. Let me know your thoughts on this. Thank you.


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## JRaef (Mar 23, 2009)

paulgarett said:


> Thank you. The motor starters are Eaton Solid State. Brand new. The motors are also new. Don't have the nameplate info though. The MCC and motors are for a car wash. The starters did not start tripping until the last couple days when the weather has been in the 90s. The motors, however, are within the tunnel of the car wash. The MCC in the utility room. The motors are for the blowers that dry the car off after the wash period. They are on intermittently or continuously, depending on how busy the car wash is. The start up is 75-90 amps per motor (5 motors) then goes down to about 14 running amps.
> I am concerned the resistance due to bundled conductors may create voltage drop or some other problem that has to do with inductive loads and the magnetic effect of bundled conductors. I have not checked for voltage drop yet but will today. I am mainly concerned that 15 bundled conductors that serve five 480 volt inductive motor loads may cause problems with the motor starters, due to the effects of bundling or inductive reactance of the load. Let me know your thoughts on this. Thank you.


Welcome to the harsh reality of people buying on price rather than capability.

Those Eaton SS motor starters are the cheapest junk on the planet. They were designed to be cheap and small, but sacrificed capability to function in the effort. 
Solid state starters use SCRs to control the voltage and thus the current. SCRs also create heat, so to avoid having them damage themselves in the process of starting a motor, you must either use a lot of heat sink material, or you must shut them down if they start to over heat. In that design, Eaton chose to use ZERO heat sink material, they just use the mounting plate of the starter as a heat sink, and it is totally inadequate. Instead, they do two other things: first they sense the heat in the SCR and as it rises, they just quietly close the bypass contactor that is built-in. The result is, the motor is NOT actually soft starting, although they flash the LED on the front tht says that it is. The motor is actually starting Across-The-Line. Your evidence to that fact is that your starting amps are upward of 600% FLC, which means it is seeing ATL current. Even if you set the Current Limit lower, it will still happen because it overrides the current limit and goes ATL to prevent damage to the SCRs. The secondary thing they do is that if you continue using it to the point where even a second or two of time on the SCRs is about to kill them, it just trips off. Again, that is what you are now seeing.

I'm not normally one to bash products, but I was associated with the soft starter industry for a long time and when this POS system came out from Eaton, it gave the entire industry a black eye because their field failure rate is incredibly high and a lot of people do not realize the extent of the design errors, so they think all soft starters are like this. Now unfortunately because of Eaton doing this, many other mfrs are starting to cut corners too in order to compete and the problems will continue to get worse.

If you do not have room inside of the MCC to fit a proper soft starter, and you probably don't, I would replace them with a feeder CB and put REAL soft starters on the wall, ones with heat sinks and proper ratings without shenanigans. 

Better yet, I have had a lot of success in using VFDs on car wash blowers. The reason is, during times of heavy use you can just reduced the speed in between cars instead of completely tuning them off right away. That way, the motors are not stressed as much from the on-off cycling. It doesn't really save energy so much as it saves wear and tear on the motors and the blowers themselves. Over zealous salesmen often convince people that using a soft starter will INCREASE the number of starts-per-hour that a motor is capable of, that is NOT true. It makes NO DIFFERENCE. A VFD however CAN do that, because the VFD can start the motor without exceeding FLC.


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## paulgarett (May 8, 2012)

thank you. the motor starters don't trip right away. Only two out the five motor starters have tripped. These two starters tripped after operating for about 3 hours and the ambient temperature become hot and the car wash became busy. 
the car wash will probably not want to pay to upgrade the MCC equipment after they just spend $$$$ on the whole car wash retrofit. I did not design the MCC. The car wash manufacturer designed the MCC. Eaton built it. 
I am hoping it is nothing that I did as the electrician and installer of the MCC unit, all the motors, and motor conductors. I am going to check the motor connections and do a load and voltage test on the motors today. I am also going to talk with the sales engineer at Eaton about this problem next business day. 
Is there anything I can do to solve this problem without upgrading the equipment? 
How can I communicate the problem cause to the customer?
Right now the two blower motor starters that tripped are turned off, so the car wash is operating with three blower motors, which is sufficient. So far no more motor starters have tripped. But if another motor starter does trip, then having only 2 blowers would be inadequate. Another option I thought about would be to install additional timers, so that each individual motor comes on sequentially, rather than in pairs.


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## micromind (Aug 11, 2007)

If the two motors that trip are started at the same time, it's possible that motor A has two wires from starter A and one wire from starter B. As the motors and fans age, the load will change as well, and it's possible that one of the starters is seeing an overload caused by operating 2/3 of one motor and 1/3 of another. 

As soon as one starter trips, the other motor will be single phased and it'll trip too. 

I agree though, the Eaton soft-starters were about as bad as you can get. 

Since the motors are being started across the lines anyway, one option would be to replace the soft-starters with basic full-voltage starters. 

If you do indeed replace with full-voltage starters, DO NOT use definite-purpose contactors with overloads. They cost less than any other type, but they will fail in a fairly short time. IEC starters won't last long here either, you need NEMA ones. I would also highly recommend using heater type overloads, not the electronic ones. 

With very few exceptions, you get what you pay for, even with NEMA starters. The cheap stuff won't hold up, the expensive stuff lasts a long time.


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## SteveBayshore (Apr 7, 2013)

Do you really have solid state motor starters or just IEC starters?
Are the conductors sized for the proper load and derating factors?
Small conductors = voltage drop = higher current.
What is the OL class?10-20-30?


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## Big John (May 23, 2010)

SteveBayshore said:


> Do you really have solid state motor starters or just IEC starters?


 I was wondering. Jraef's info makes a lot of sense if he does, but it almost doesn't sound like it.


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## xlink (Mar 12, 2012)

I had trouble with solid state overloads tripping on pump jacks. The loads averaged 70% - 90% of FLA. A co-worker tried over-sizing the overloads but they still tripped after a couple hours. The explanation what that the overloads couldn't compensate for the wild fluctuations in current as the jack shifted from lifting rods to weights. I wonder what is the fluctuation of the current in your application.

Of course, when all else fails, look at harmonics.


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## paulgarett (May 8, 2012)

The motor starters are not soft start. They are Eaton's top of the line motor contactor and overload relay combination. When a fan blows on the motor starters they do not trip. 
The door to the MCC needs to be open for the fan. The motor starters feel warm when in operation.


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## JRaef (Mar 23, 2009)

paulgarett said:


> The motor starters are not soft start.


Huh...


thread title said:


> Solid State Motor Starter Tripping


So, just for future reference, a "Solid State Motor Starter" is a soft starter, because the "starter" part of it is solid state. A motor starter with a contactor and a solid state overload relay is still an Across-The-Line electro-mechanical motor starter.



> They are Eaton's top of the line motor contactor and overload relay combination. When a fan blows on the motor starters they do not trip.
> The door to the MCC needs to be open for the fan. The motor starters feel warm when in operation.


It is dangerous and illegal to leave the doors open on an energized MCC.

Any motor starter with power going through it will "feel warm" unless maybe you are in Alaska in the winter with the doors open. Still dangerous though.

A solid state (if it is) overload relay should be insensitive to the starter ambient temperature, unless the temperature is exceeding the design temperature of the entire MCC. If that is the case, you have a much bigger problem and these failures are the tip of the iceberg. The upper operating range for the Eaton SSOL is 65C, which is nearly 150F. If they are falsely tripping because it is over 150F inside of the MCC, other things are going to start failing in short order.


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## paulgarett (May 8, 2012)

Thanks a lot. After I installed the MCC, the car wash in full operation, and the 5 blowers were on, the main breaker tripped. The manager of the car wash turned off two of the blowers and that temporarily solved the problem. The main breaker was getting really hot and at the tipping point of tripping, revealed through an amp test. I installed additional timers to sequentially start the blowers so start-up current would not be extremely high and stress the breaker. The full load amps of all the motors operated by the MCC is 178 amps. The MCC had a 125 amp main breaker. Called Eaton, they shipped out immediately a 250 amp main breaker. Installed that, which has been a problem because the door handle disconnect mechanism does not line up with the new 250 amp breaker. The main breaker does not trip now. I am worried the entire MCC is sized too small, since it was originally designed for 125 amps, but now with a 250 amp main breaker. The running amps of the MCC most of the time is 100 amps. When start-up occurs of the blowers, it may see up to 200 amps for a few seconds. Again, the timers help a lot with keeping the overall start-up current to a minimum. So the only problem I had to worry about was lining up the main breaker with the door handle (Eaton is helping me with this). But recently, after about 1 month of operation, two of the motor starters for the blower motors tripped. When they were turned back on, they tripped again, but not right away; it took a few hours. The manager of the car wash decided to place a fan in front of the MCC with the door open. With all of the blower motor starters turned on, they have not tripped for the past couple days. Now I am worried too much heat is being generated inside the MCC (mentioned in the previous post). Will call Eaton today about this.


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## xlink (Mar 12, 2012)

How did you size your wires that feed this mcc? If the main in the mcc was tripping, what about the over-current protection that you installed to feed the mcc?

It sounds like the designer of the system undersized the mcc. A thermal image of the running equipment might expose some interesting problems.


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## SteveBayshore (Apr 7, 2013)

I've worked on a few projects with Eaton's Advantage line, don't remember having and issues with them. If the problem is not overloading the MCC, make sure that the magnetic adjustment on the HMCPs is set properly for the motors. 
Now I'm confused again. Is it really an Eaton factory supplied Motor Control Center (MCC) with separate buckets and doors, or is it an OEM Motor Control Enclosure (MCE) with all equipment in one large enclosure. It's funny that Eaton would let you install a larger main breaker in a factory built MCC. I thought that they would have supplied a whole new bucket. Loads need to be recalculated ASAP. What size is the feeder to the MCC or MCE.

PICTURES


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## paulgarett (May 8, 2012)

The MCC is a custom built by Eaton, all in one. The enclosure is from a manufacturer that specializes in enclosures (not sure the name). All the equipment in the enclosure is Eaton. The main breaker in the MCC is fed with 3/0 conductor from a main breaker in the meter main. There are not adjustment dials on the overload relays; they are sized properly for the load. The main breaker to the MCC was not sized properly. This tells me the entire MCC is too small. Eaton engineer sent me out the new breaker which I installed. It does take a bit of skill to know how to install this breaker. I've done it before when I worked in the oil fields as an industrial electrician. I do not have a thermal imager (too expensive). A heat gauge (gun) is affordable. Need to get one though. I am afraid the overload relays trip because of the ambient temperature. 
If Eaton sends out a whole new MCC, then that would be big $$, that Eaton or the designer of the MCC unit will have to pay for. They are not interested in paying obviously and want the simplest cheapest solution.


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## xlink (Mar 12, 2012)

Cooling fans and vents in the mcc would be better than leaving the door open. How do you feel about modifying the enclosure?


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## John Valdes (May 17, 2007)

IEC contactors and overloads are not your problem.


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## SteveBayshore (Apr 7, 2013)

xlink said:


> Cooling fans and vents in the mcc would be better than leaving the door open. How do you feel about modifying the enclosure?


If you have an electrical problem causing overheating, I would not recommend cooling fans as a permanent solution. Finding the cause and fixing the problem is the proper way to handle it. Post a picture of the enclosure with the door(s) open if you can. What amperage is the wiring and buss work on the load side of the new breaker rated for? 
What is connected to the new motor control enclosure? Is it just the (5) ten HP motors that you listed? The calculated load for (5) ten HP motors is only 73.5 amps at 480 volts. A 100 amp feeder would have been fine. 
What is the wire size on the load side of the starters? Code only allows (15) #10s in a 1"PVC, no room for an EGC. (15) current carrying conductors requires 50% derating. If you have a long run of conductors, you might have a voltage drop problem made worse by the number of conductors in one conduit.


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## paulgarett (May 8, 2012)

you caught me there. I did install (16) 10 AWG THHH, 15 conductors and 1 ground. 
10 AWG THHN is rated for 40 amps. Derated 50% per NEC, 20 amps.

The running current of the 10 HP 480 V motors is about 13 Amps. The start-up is about 75 amps. 

The voltage coming in from the meter main is about 490 volts. The voltage on the load side of the MCC main breaker is about 481 volts when the car wash in full operation and all motors are being used. 

There are about 15 motors on site, all in use intermittently. When the 10 HP 480 V blower motors come on, the voltage on the load side of the its contactor is 465 volts upon start-up of 75 Amps. The voltage then gradually increases to 480 volts in a few seconds, when the running current is about 13 amps. I assume 465 volts in sufficient for a motor, which lists on the nameplate 460 Volts. 

So my new question is: Is 465 volts sufficient for a 480 volt motor (nameplate 460 V) upon start-up?

You are right, fans are not the solution; they are temporary. The fans were kind of an experiment. When all 5 of the blower motors are on, and the fan is on the MCC unit, blowing directly on the motor starters, the motor starters do not trip. So I need to find out what the problem is. Is it the voltage? Is the MCC unit getting too hot? Are the 10 HP motor starters too close together, causing heat? Hopefully separating the motor starters by a few mm. may help heat dissipation. But... these motor starters are designed to be grouped, as described in the manufacturers web site.

Thanks a lot for you interest.


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## Jlarson (Jun 28, 2009)

Don't worry so much about the wire. 

What exactly did the clowns at Eaton send you? Without part numbers we don't have some critical pieces of information.

I have to agree with Jref's explanation as being the most likely right now. The little soft starts (DS7's if I remember right, Jref?) aren't all that top of the line, they peddle them that way but yeah...


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## SteveBayshore (Apr 7, 2013)

Are the starters the Advantage series or the Freedom series? If the line side is wired in and not bussed in, is it possible to space them apart like you thought? I had some problems with spacing of SquareD IEC components in the past.


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## Big John (May 23, 2010)

Enough words. We need pictures of the buckets.


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## paulgarett (May 8, 2012)

the motor starters are not soft start. There is one soft start motor starter in the MCC; it is for the top brush, you know the rotating brush that comes down and washes the front and top.


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## JRaef (Mar 23, 2009)

We may have a semantics issue going on here. 
To most of industry, a "Motor Control Center" is a specific form of enclosed modular power control system conforming to NEMA ICS-2 and UL845 standards. These standards include important safety considerations such as heat stacking, short circuit withstand testing and personnel safety. A "REAL" motor control center looks like this where each motor starter has its own "bucket", a separate enclosure that has stabs that connect to continuous bus bars:










Some people who build cheaper control panels that have "Grouped Motor Starters" in a SINGLE enclosure, mistakenly refer to them as "motor control centers", not knowing that there is an official accepted definition for that term. They often look like this:








Despite them calling is a "motor control center", it is not, it is a control panel. One major drawback to doing it this way is that they are often cobbled together by people who do not know about heat stacking effects of having multiple motor starters in a box and they fail to anticipate thermal build-up. However, there are no industry standards that they need to adhere to in building these things. That's why they are cheaper.

Which one does yours look like?


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## Introyble (Jul 10, 2010)

JRaef said:


> Welcome to the harsh reality of people buying on price rather than capability.
> 
> Those Eaton SS motor starters are the cheapest junk on the planet. They were designed to be cheap and small, but sacrificed capability to function in the effort.
> Solid state starters use SCRs to control the voltage and thus the current. SCRs also create heat, so to avoid having them damage themselves in the process of starting a motor, you must either use a lot of heat sink material, or you must shut them down if they start to over heat. In that design, Eaton chose to use ZERO heat sink material, they just use the mounting plate of the starter as a heat sink, and it is totally inadequate. Instead, they do two other things: first they sense the heat in the SCR and as it rises, they just quietly close the bypass contactor that is built-in. The result is, the motor is NOT actually soft starting, although they flash the LED on the front tht says that it is. The motor is actually starting Across-The-Line. Your evidence to that fact is that your starting amps are upward of 600% FLC, which means it is seeing ATL current. Even if you set the Current Limit lower, it will still happen because it overrides the current limit and goes ATL to prevent damage to the SCRs. The secondary thing they do is that if you continue using it to the point where even a second or two of time on the SCRs is about to kill them, it just trips off. Again, that is what you are now seeing.
> ...


 
I once had to work with Omron. Had 5 brand new in the box just delivered then handed to me 7.5HP starters. 3 of them had open coils:blink: True story, swear to you.


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## paulgarett (May 8, 2012)

Thanks for the pictures. I will have to upload pictures from my camera to the computer.
The second picture describes the "mcc", so it is a control panel, not a mcc. The starters are grouped. The five starters that control the blowers are grouped next to each other. 3 of the starters are fed with 10 AWG. The other two with 12 AWG. The running current is 13 Amps. 13 x 3 = 39 amps, the absolute max of 10 AWG. 13 x 2 = 26 amps, the absolute max for 12 AWG. The voltage upon start-up current (75 amps) is 465 volts, then goes up to 480 volts at running current (13 amps). Is 465 volts for a few seconds ok? Do the feeders that send power to the starters, the 10 AWG and 12 AWG, need to be upgraded to bigger wire? One of the starters that trips belongs to the first group of 3 fed with 10 AWG. The other starter that trips belongs to the other group of 2 fed with 12 AWG. 
I took temperature readings. The 10 HP, 480 V, blower motor starters are reading about 100 degrees F. All of the other motor starters including, 15 HP, 480 V, starters are reading about 85 degrees F. When I place my finger on the blower motor starters they feel very warm. If I keep my finger there for a period of time, it becomes uncomfortably hot.


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## SteveBayshore (Apr 7, 2013)

JRaef said:


> We may have a semantics issue going on here.
> Which one does yours look like?


I asked the same question in post #14. Never got a reply. Our common terminology is:
MCC = motor control center
MCE = motor control enclusure


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## SteveBayshore (Apr 7, 2013)

Never undersize conductors. It causes heat and voltage drop problems. Replace the small feeder conductors to the groups of starters first. Might cut down on some heat. Are the 15 motor conductors entering the MCE much warmer than other conductors that are in the enclosure (that aren't undersized)? 
On the production plants that we wire, our motor cables are always at least one size up from what the NEC requires. On large fan and crusher motors with high inertia loads, 50 to 500 hp, our cables are sometimes 75% above what is required by NEC calculations, and no motor conductors are grouped.


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## varmit (Apr 19, 2009)

I have worked on some of these "car wash kits" before. They are usually designed and built in the cheapest possible way. The problem that you are having is common with the car wash dryer blowers. The usual problem is the starting of these motors too many times per hour. As a general "rule of thumb" divide the HP of a motor into 60. This will give you the approximate permissible starts per hour. Often the "kit" program will start-stop the dryer blower(s) for every car. This overheats the motors, starters, wire, fuse and breakers. I have seen starters explode and melt or get so hot that they would blacken the paint on the wall from this scenario.

A possible fix, if this "kit" has a PLC, would be to modify the program so that when a motor starts, it will run for a specific time duration- say 15 minutes and if another car enters the wash in these 15 minutes, the 15 minute timer restarts- essentially the fan stays running as long as cars are being washed. If there is no PLC, you can add timers to serve the same purpose. It may not sound energy efficient, but it can save on utility billing charges by lessening the peak demand of so many high inrush starts.

If you have a panel with a bunch of 10 to 15 HP IEC starters jammed together without any air circulation- you will have over heating problems.

I would not want to run that many motor leads in one conduit.


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## tates1882 (Sep 3, 2010)

paulgarett said:


> Thanks for the pictures. I will have to upload pictures from my camera to the computer.
> The second picture describes the "mcc", so it is a control panel, not a mcc. The starters are grouped. The five starters that control the blowers are grouped next to each other. 3 of the starters are fed with 10 AWG. The other two with 12 AWG. The running current is 13 Amps. 13 x 3 = 39 amps, the absolute max of 10 AWG. 13 x 2 = 26 amps, the absolute max for 12 AWG. The voltage upon start-up current (75 amps) is 465 volts, then goes up to 480 volts at running current (13 amps). Is 465 volts for a few seconds ok? Do the feeders that send power to the starters, the 10 AWG and 12 AWG, need to be upgraded to bigger wire? One of the starters that trips belongs to the first group of 3 fed with 10 AWG. The other starter that trips belongs to the other group of 2 fed with 12 AWG.
> I took temperature readings. The 10 HP, 480 V, blower motor starters are reading about 100 degrees F. All of the other motor starters including, 15 HP, 480 V, starters are reading about 85 degrees F. When I place my finger on the blower motor starters they feel very warm. If I keep my finger there for a period of time, it becomes uncomfortably hot.


I don't think temp is your problem, the motors can handle way more heat then your hand. Also 460v is sufficient for start up. I think with soft starts the starts per hours will exceed anything anything you find. What size starter? And what's tripped the ol's or ocpd? Who is the motor manufacturer? What's the over load set at?


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## paulgarett (May 8, 2012)

Manager said two of the five motor starters (the same two as before) tripped again. He did not have a fan on. The MCE door was closed.
They tripped after about 3 hours of operation. When manager felt the starters with his finger, they felt hot, too hot to keep his finger on.
He turned off those two starters and will leave them off. He turned the fan on with the door to the MCE open 
for the rest of the day. 

can't photos, won't let me for some reason.
see:
http://www.eaton.com/Eaton/Products...arters/ManualMotorProtection/index.htm#tabs-1

These are my observations: 
Start-up current: 75 amps 
Running current: 13 amps
Start-up voltage: 465 volts
Run voltage: 480 volts
Motor Conductors (from starter to motor): 10 AWG
All 15 motor conductors (5 motors x 3 conductors) are grouped in the same raceway to a j-box about 70 feet away.
From the j-box, flex is run to each individual motor.
With the fan on all day, the motor starters did not trip (on the day I observed). 
Eaton brand. 
The overload relay is set for about 15 amps.
The disconnect to the motor starter is tripping, not the overload relay. 



See attached photos. The five motor starters at lower left of MCE are for the blower motors.
See the photo of the nameplate of a blower motor. 
The first three in a row are fed with 10 AWG from the load side terminal block of the main breaker. 
The remaining two are fed with 12 AWG.

What are probable causes for the motor starters to become so hot?
Why are only two motor starters (the same two) tripping after a few hours of use? 
Is it possible that connections at the motor are bad?
Are the motor starters undersized?
Are the motor starters defective? 
Is it the start-up current, or the running current causing the heat? 
Are the motor starters designed to be stopped and started frequently (every 10 minutes) ? 
Is grouping the 15 motor conductors in the raceway for 70 feet causing a problem (all the conductors are grouped in the MCE behind the "wire managers")?

What are possible solutions? 
PLC, timers, bigger starter, upgrading the wire, separate MCE for the blower starters, built-in fan 

Thank you.
Paul Wilson


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## tates1882 (Sep 3, 2010)

Step the starters up to the next size.


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## SteveBayshore (Apr 7, 2013)

paulgarett said:


> Manager said two of the five motor starters (the same two as before) tripped again.
> 
> The disconnect to the motor starter is tripping, not the overload relay.
> 
> ...


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## JRaef (Mar 23, 2009)

If they are using those manual Motor starters shown in that link, then the "disconnect" is actually the disconnect, SCPD and OL devices all in one. There is unfortunately no way of knowing whether it tripped on Thermal OL or Short Circuit, but I would expect it is Thermal OL, because SC is instantaneous. I'm not surprised though, given the numbers you put up. 13A running current is likely very close to FLC on a 10HP 460V motor. 

I'm smelling a poor control panel design. In typical fashion, people tend to cram too many of these little starters into a box "because they fit", but without regard to the thermal consequences of doing so. If you never run a motor beyond 75% of rated current, they likely never see a problem. But when you run 5x 10HP starters at nearly full rated current all jammed next to each other, the heat gets trapped around them and they adversely affect the trip time of the Thermal OL sensing elements. That would explain why they don't trip when the door is left open.

Increasing the size of the starter may not help. I would look into venting that box with fans, and also spreading the motor starters apart as much as possible to allow air to flow around them. But if it is in the common air space with the car wash, that may be problematic too because you don't want to suck in moisture. That then means adding an Enclosure Air Conditioner. So much for making the "Motor Control Center" cheaper than a _REAL _MCC.


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## tates1882 (Sep 3, 2010)

You could try the Siemens Sirius starter line, I have used them before on a car wash application. The rep claims they have used them in marine applications up and down the west coast with good results. There may be an indicator that shows a ol trip on your combo starter some have a small square window that has a orange flag when ol trip happens.


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## Introyble (Jul 10, 2010)

Just a stupid side note. I once nearly got my azz kicked by a simple radial fitted fan cooled motor. Kept tripping the overloads and I was logging high RLA to support the OL. So, I pulled the cooling fan motor and sent it off for testing since I could not prove a fault.

Motor came back tested well within tolerance and I was completely lost for explanation. Turned out, part of the rear housing for the impeller had been removed by who knows who and why. This housing acted as an air damper and due to the fact it was removed, the impeller was drawing an excessive amount of free air and thus excerbating the FLA of the cooling motor.

Had I not been careful in my observations I may have never found the problem since just by accident I stumbled upon the rear guard and placed it back onto the assembly. I noticed a significant drop in RLA and just laughed and realized what an idiot I was.

Never in my career had I encountered a motor that would OL due to the fact of a missing "guard" and my logic toward nuisance trips never would have steered me in that direction. I mention due to the fact you suggested fan motors and since we can't observe the environment, we can't really rule this possibility out.


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## paulgarett (May 8, 2012)

Thanks for your all your help. I agree; the motor starters are probably undersized. Motor starter ratings actually have to be de-rated when motors are started numerous times continuously. There are different motor starter ratings for non-jogging and jogging. Starters are sized up if jogging (motor starting numerous times) occurs. I also agree that the starters are all crammed into an enclosure that is too small. The space for the conductors was at its limit.  The wire bending space for the feeders was also at its limit. The enclosure should have been bigger. I will try to upload a picture later. 

I have a question about conductor sizing for motors:
Motor conductors are sized based on Tables 430.247 through 248, then increased by 125%. This conductor sizing does not take into account the inrush current. 

Can inrush current damage the conductors (especially if the inrush current occurs many times per day) if the conductors are sized for the running current? 

Are there any NEC articles that relate to this question?

Again, the inrush current is about 75 amps. The running current is about 13 amps. 
The conductor size installed was 10 AWG, derated 50% for 15 current carrying conductors in same conduit. The inrush lasts for about 3-4 seconds. The running current may last from 2 minutes up to 10 minutes, depending on how busy the car wash is. 

Thank you.


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## SteveBayshore (Apr 7, 2013)

FLAs and conductor sizes from the NEC and motor starters already take inrush current into account. One of the times you would need to increase conductor sizes drastically for inrush would be for high inertia loads (huge fans, rock crushers) that have an extended inrush time to get the load up to speed. We have worked on controls for old crushers that take the overload out of the control circuit until the motor is up to speed.


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## denny3992 (Jul 12, 2010)

Might try this



http://www.newmantools.com/vortec/cabcoolerindex.htm


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## JRaef (Mar 23, 2009)

paulgarett said:


> ... Motor starter ratings actually have to be de-rated when motors are started numerous times continuously. ...


Just to be clear, that is the case for IEC motor starters, but NEMA motor starters ALREADY are sized for inching and plugging duty, up to and including the starts-per-hour limits of the motor they are used on. So if you were using NEMA rated contactors, if the motor is rated for the number of starts-per-hour you need, then you do NOT need to de-rate the starter. If you over size the motor in order to get a higher number of starts-per-hour, then sizing the NEMA starter to match the new motor rating still follows. That's the big trade off that people make when they say 'IEC starters are just the same". They are not.


SteveBayshore already adequately answered the conductor sizing question. If you read something that said that you DO need to de-rate conductors, it was likely something that was associated with those IEC starters, intended for IEC customers. There is no mention of it in the NEC because we have different conductor sizing rules to begin with which, as he said, already take it into account.


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## paulgarett (May 8, 2012)

Are some motor starters both IEC rated and NEMA rated? 
I saw a table reprinted from NEMA (want to try to find this table on their website)
that has one column for non-jogging and another column for jogging. So I am confused now. If NEMA has a table that lists both jogging and non-jogging rated contractors/starters, then it seems that you have to take jogging or non-jogging into consideration. Will have to find that table and paste the address on another post. 
thanks.


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## LATTC (Feb 12, 2012)

Me think, there is a ambient temperature difference between the motor and controller causing the trip.


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## paulgarett (May 8, 2012)

That is an interesting comment. 
What would cause an ambient temperature difference between the motor and controller?
How does an ambient temperature difference between the motor and controller cause the controller to trip? 
What happens to motor circuits if all the circuit conductors are bundled without de-rating? Does it effect voltage (voltage drop) due to increased resistance. Will it cause motor starters to overheat?
If the motor circuit conductors are all bundled and sized properly for derating, would bundling still cause the starters to overheat?


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## LATTC (Feb 12, 2012)

http://www.ab.com/en/epub/catalogs/12768/229240/229248/10521726/10551021/10551660/


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## paulgarett (May 8, 2012)

Thank you. Great info. 
The starters are Eaton IEC type. 
Noticed the web page you provided are for Allan-Brandley.
It would be great if Eaton had a similar guide. Maybe someone knows
of a guide considering Eaton starters.


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## JRaef (Mar 23, 2009)

paulgarett said:


> Thank you. Great info.
> The starters are Eaton IEC type.
> Noticed the web page you provided are for Allan-Brandley.
> It would be great if Eaton had a similar guide. Maybe someone knows
> of a guide considering Eaton starters.


They are not the same. The AB reference page is because the OL relays discussed on that page are eutectic melting alloy (solder pot) OLs, which cannot be ambient compensated other than by selecting a different heater element. IEC style bimetal OLs and Solid State OLs are all ambient insensitive or compensated, so unless the temperature difference is really extreme, as in the motor being inside of an oven or venting hot gasses, you do NOT consider the differences. Eaton does not sell eutectic melting alloy OL relays, therefore they don't need a page discussing it.

The IEC bimetal OL relay design has a 4th bimetal strip fixed inside that is calibrated for a 20C (68F) ambient, the temperature the OL trip curve is designed for. If the temperature inside the box holding the OL relay increases above 20C, that compensating element shifts the trip point over to adjust it to delay the tripping a bit. There is no way to accomplish anything like that for a eutectic melting alloy, you cannot delay the melting of the solder.

Older NEMA type bimetal OL relays needed ambient compensation as well, but most mfrs of that type have switched to using their IEC designs for bimetal applications. For example if you had the old Citation Series Cutler Hammer starters with bimetal OLs, you had to do ambient compensation the same as discussed in the AB paper, but Eaton quit making those a long time ago.

Solid state OLs are looking directly at current going to the motor, not heat created by the current in the starter, so ambient temperature of the OL relay is irrelevant. 

Your problem has nothing to do with a temperature difference, I still think the issue is too much stuff in that box with no ventilation.


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## JRaef (Mar 23, 2009)

paulgarett said:


> Are some motor starters both IEC rated and NEMA rated?
> I saw a table reprinted from NEMA (want to try to find this table on their website)
> that has one column for non-jogging and another column for jogging. So I am confused now. If NEMA has a table that lists both jogging and non-jogging rated contractors/starters, then it seems that you have to take jogging or non-jogging into consideration. Will have to find that table and paste the address on another post.
> thanks.


The NEMA design specs call for a certain amount of inching (jogging) and plugging (reversing to stop a motor) capability without de-rating. But what happens is, some IEC mfrs who have no true NEMA*design* starters, use simplistic NEMA sizing rules to CLAIM that certain sizes of their IEC contactors are "NEMA rated". But in order to keep from showing how drastically different they really are, they leave out the inching and plugging duty requirement, since hardy anyone does that, and give you another chart to add it back in if you do. It's kind of a cheat, but NEMA is not a testing or regulating authority so everyone "self regulates" their claims and they get away with it.


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## LATTC (Feb 12, 2012)

JRaef said:


> Your problem has nothing to do with a temperature difference, I still think the issue is too much stuff in that box with no ventilation.


If it's bimetal, it should have a adjustment knob.
Since it was working before, I would double check all wiring and termination and let the powers that be decide.


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## paulgarett (May 8, 2012)

Thanks for that great info and stating the difference between eutectic and bi-metal.
The info about the 4th bi-metal strip is interesting as it relates to the trip curve. 
Good stuff.


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