Motor Circuit Breaker

[mull982]

Typically I've always understood that a specific motor circuit breaker was to be used in combination with a motor starter. When I say motor circuit breaker I am refering to an magnetic instantaneously only circuit breaker that is to only provide short circuit protection in combination with the motor overloads providing overload protection.

My question is weather or not a thermal-magnetic breaker can be used as the circuit breaker or means of short circuit protection in a motor starter. We want to get a motor back up and running and do not have an exact motor breaker as a replacement but do have a thermal-magnetic breaker avaliable. Can this type of breaker be used?

Also in looking through the Siemens catalog I notice there are tons of different Molded Case breaker types. Many of these breakers are labeled as General Purpose Breakers. What is it that distinguishes one of these type of breakers from another?

In other words what distinguishes a HED4 from a HFD6 from a HLD6 from a JDX6 ect....???

 

[Cold Fusion]

(cut)My question is weather or not a thermal-magnetic breaker can be used as the circuit breaker or means of short circuit protection in a motor starter. (to replace an instaneous in a listed combination starter) (cut)Blue is mine

Yes, a thermal-mag cb can be used as the cb or short circuit protection in a motor starter. Your issue is that an MCP is always part of a listed combination starter. Changing the CB to a different type is not part of the listing. It's a repair and may not fall under the NEC - but it certainly falls under OSHA.

Would I do it? Maybe, depends: Pick a thermal-mag with a rating per 430.52. Check the trip curve is inside of the one being replaced. Verify the interupt rating is equal to or greater than the original. Tag it so that everyone knows what you are doing and it doesn't look like you are trying to hide something that won't pass a sniff test. At least I know it is safe and I don't look like I'm trying to hide anything. Also order a new cb overnight freight.

Let the management know that if someone squawks and drops a dime to OSHA, they could be up for a violation.

If I could find another bucket with a thermal-mag, contactor, overloads, I'd change the bucket and would not have any heartburn over changing the cb to a different rating as long as the one I was putting in was within the bucket ratings.

(minor edit for clarity)

cf

 

[jim dungar]

Almost every combination starter that uses a magnetic-only breaker has an equivalent sibling that uses a thermal-mag breaker. Other than the trip setting of the breaker, the biggest difference is that most TM combination starters have lower short circuit ratings than their MCP counterparts.

 

[mull982]

Yes, a thermal-mag cb can be used as the cb or short circuit protection in a motor starter. Your issue is that an MCP is always part of a listed combination starter. Changing the CB to a different type is not part of the listing. It's a repair and may not fall under the NEC - but it certainly falls under OSHA.cf

So you are saying that an specified MCP is tested and listed for use in a combination starter? I'm assuming that this means that all specified type MCP's can be used in any combination starter.

It sounds like the issue with a thermal-mag cb is that it is not UL listed for use in a combination starter. So like you said it will probably work, but does not meet standards.

Would I do it? Maybe, depends: Pick a thermal-mag with a rating per 430.52. Check the trip curve is inside of the one being replaced. Verify the interupt rating is equal to or greater than the original.
cf

The interrupting rating is the same. Because this is a thermal-mag breaker does this fall under the I^2t column of 430.52? I know that with a MCP cb the current setting can be 800% of motor FLA, does this mean the thermal-mag breaker rating can only be 250%?

What part of the trip curve should I look at as you mentioned?

 

[Cold Fusion]

mull - all good questions. I'll rephrase my answers and hopefully do better. I used the term MCP and that is not correct. It should have been "Instantaneous CB". I'll use "ICB"

One thing making this discussion difficult is I don't know if the motor is a 5hp or a 200hp. See 430.52.C.3, ex2.

So you are saying that an specified MCP is tested and listed for use in a specified combination starter?

I added the blue.

I'm assuming that this means that all specified type MCP's can be used in any combination starter.

No. Combination starters are listed as a unit. The listing (mfg literature/catalog) will include which ICBs are okay to use.

See 430.52.C.3 Instantaneous-only CBs (ICB) can only be used if part of a listed combination starter. You couldn't build up a starter using a separate ICB, contactor, overload. You could if you used separate TM, contactor, overload.

But you are not doing that. You are modifying a listed combination starter that has an ICB, by replacing the ICB with a TM. The listing gives the acceptable ICBs that can (could/should) be installed.

It sounds like the issue with a thermal-mag cb is that it is not UL listed for use in a combination starter. So like you said it will probably work, but does not meet standards.

As Jim said, you are likely okay because every listed combination starter with an ICB has a sister with a TM. Pick out the correct sister, use the TM that is used for that model.

Because this is a thermal-mag breaker does this fall under the I^2t column of 430.52?

yes

I know that with a MCP cb the current setting can be 800% of motor FLA, does this mean the thermal-mag breaker rating can only be 250%?

You can go a lot higher than 800% with an ICB and I tend to set ICB right up the the NEC max.

With a TM, yes, 250%, exception to 300% or 400%.

What part of the trip curve should I look at as you mentioned?

I didn't say that very well - actually really poorly.

The instaneous trip on a TM is always going to be outside of a properly set ICB.

As Jim said, the combination starter with a TM is probably a lower SCC rating that the ICB counterpart. I'm not sure why this would be but it is something I would check. So, If you are using the parts listed for the TM sister, and SCC the ratings meet your system needs, you are good to go.

If you picked an old, serviceable, Westinghouse out of the used parts bin to fit a Siemens starter and the bolt pattern is close enough then I would be closely checking the SCC. (No I am not even suggesting you would use junk - just would use what you had).

cf

 

[Cold Fusion]

(cut)In other words what distinguishes a HED4 from a HFD6 from a HLD6 from a JDX6 ect....???

Get out the mfg specifications. You are looking for differences in:
voltage (and maybe slash rating)
Interupt current rating
Current limiting
Trip unit options
Adjustable Instantaneous trip option
Available auxilary options

and a bunch of other stuff that I don't have a clue about.

cf

 

[kingpb]

Contact the manufacturer, they can tell you what the direct replacement is, that won't violate any listings.

It's a matter of them just looking it up in a catalog.

 

[mull982]

No. Combination starters are listed as a unit. The listing (mfg literature/catalog) will include which ICBs are okay to use.

See 430.52.C.3 Instantaneous-only CBs (ICB) can only be used if part of a listed combination starter. You couldn't build up a starter using a separate ICB, contactor, overload. You could if you used separate TM, contactor, overload.

But you are not doing that. You are modifying a listed combination starter that has an ICB, by replacing the ICB with a TM. The listing gives the acceptable ICBs that can (could/should) be installed.


As Jim said, you are likely okay because every listed combination starter with an ICB has a sister with a TM. Pick out the correct sister, use the TM that is used for that model.

cf

CF Thanks for the valuable post. Kingpb kind of answered my next question as well, but I wanted to find out some more information in regards to this issue with a listed combination starter.

When you say that combination starters are listed as a unit does this mean that they are listed (and therefore approved) with the breaker that they come with only? In other words can I replace a breaker in a starter with the exact same breaker and still be o.k. or is the starter only approved with the breaker that it is origonally manufacturerd/sold with?

I guess the part where I'm getting confused is weather or not a starter comes with a breaker and therefore is approved as a combination, or any particular ICB that has a approval listing can be replaced in a combination. In other words, If I want to replace an ICB breaker can I replace it with any approved breaker to be used in a starter combination?

Where can I find a list of what the approved breakers are to be used in a combination starter for a particular manufacturer, for both instantaneous and TM? I'm guessing that is should state this in the catalog like kingpb said. I'm dealing with Siemens starters and breakers in this case.

Based on whats been said, I'm assuming that it is a no-no then to use an Cutler Hammer breaker in a Siemens starter since it wont be approved.

I'm trying to understand this completely so that I can do the right thing. I appreciate the help.

 

[mull982]

I was looking throught the Siemens catalog and believe I have found out how to cross reference an ETI or ICB to its TM sister breaker. It appears that when cross referencing the TM breaker has the same frame size.

What would happen if you used a larger frame size for a TM than an approved ICB?

Does the NEC say what the maximum frame size of a breaker can be, or only its trip rating?

For a motor ICB does the 800% refer to the amp rating listed on the breaker, or the adjustable settings for the range of that breaker?

 

[weressl]

mull - all good questions. I'll rephrase my answers and hopefully do better. I used the term MCP and that is not correct. It should have been "Instantaneous CB". I'll use "ICB"

One thing making this discussion difficult is I don't know if the motor is a 5hp or a 200hp. See 430.52.C.3, ex2.

I added the blue.

No. Combination starters are listed as a unit. The listing (mfg literature/catalog) will include which ICBs are okay to use.

See 430.52.C.3 Instantaneous-only CBs (ICB) can only be used if part of a listed combination starter. You couldn't build up a starter using a separate ICB, contactor, overload. You could if you used separate TM, contactor, overload.

But you are not doing that. You are modifying a listed combination starter that has an ICB, by replacing the ICB with a TM. The listing gives the acceptable ICBs that can (could/should) be installed.


As Jim said, you are likely okay because every listed combination starter with an ICB has a sister with a TM. Pick out the correct sister, use the TM that is used for that model.


yes


You can go a lot higher than 800% with an ICB and I tend to set ICB right up the the NEC max.

With a TM, yes, 250%, exception to 300% or 400%.

I didn't say that very well - actually really poorly.

The instaneous trip on a TM is always going to be outside of a properly set ICB.

As Jim said, the combination starter with a TM is probably a lower SCC rating that the ICB counterpart. I'm not sure why this would be but it is something I would check. So, If you are using the parts listed for the TM sister, and SCC the ratings meet your system needs, you are good to go.

If you picked an old, serviceable, Westinghouse out of the used parts bin to fit a Siemens starter and the bolt pattern is close enough then I would be closely checking the SCC. (No I am not even suggesting you would use junk - just would use what you had).

cf

MCP stands for Motor Circuit Protector, it should not be used as a standalone OCPD for anything else but as a component of a listed Combination Motor Starter.

The MCP's trace their origin to generic MCB's or Molded Case Circuit Breakers whose thermal, long time protective element was removed. MCB's employed two elements, magnetic for the 'lower' and thermal for the 'upper' portion of a fuse curve. Since combination motor starters require an overload element that is essentially a duplication of the thermal element that resided in the MCB so it can be removed. There are circuit breakers availabel in the EU(CE) market that have an adjustable thermal element built in the circuit breaker sized for motor protection. That is the otehr way to skin a cat....

 

[Cold Fusion]

mull -
If you have not done so, read: 430.52(C)(3) on special conditions to use an ICB. That is the key.

(cut)When you say that combination starters are listed as a unit does this mean that they are listed (and therefore approved) with the breaker that they come with only? (cut)

AFAIK (minor disclaimer - I'm not an expert on exactly how listings read) The listing for a particular model of ICB combination starter has a list of part numbers for the ICB, contactor, and overload unit. As kpb said, the primary reference would be the MFG parts list. And the mfg may well change the parts list over time - obsolete stuff out - newer stuff in. If the mfg told me I would have to use an xyz overload to repair a 20 year old starter because they no longer made the abc version, I'd believe them. A replacement ICB for a listed combination starter might even be a different model number for an old starter.

(cut)can I replace a breaker in a starter with the exact same breaker and still be o.k. (cut)

Absolutely

(cut)I guess the part where I'm getting confused is weather or not a starter comes with a breaker and therefore is approved as a combination, or any particular ICB that has a approval listing can be replaced in a combination. In other words, If I want to replace an ICB breaker can I replace it with any approved breaker to be used in a starter combination?(cut)

The way you phrased this (or the way I'm reading it) makes it hard to answer. I'll rephrase and see if it helps:

First, you will not find a UL label (read "UL" as a generic listing sticker) on an ICB. ICBs can not be listed by themselves. A combination starter will have the listing sticker on the box and it applies to all (ICB, contactor, and overload) of the stuff in the box (cubicle). The sticker will have a number on it, and that number will refer to the parts that the starter was tested with.

Intrestingly a TM CB can have a UL label on it and generally does.

So when you say, "can I replace it with any approved breaker to be used in a starter combination?", I'm not sure what you mean by "approved". If you mean a CB with a part number that is on the mfg parts list for the specific model starter you are working on - then sure.

(cut) I'm assuming that it is a no-no then to use an Cutler Hammer breaker in a Siemens starter since it wont be approved.(cut).

You are right, it would not.

I'm trying to understand this completely so that I can do the right thing. I appreciate the help.

I'm getting a little confused:
When this started, I was under the impression you needed to get going right away and would make a perminent fix later. Now I'm getting the feeling you are looking to make a perminent change. Two different things. If you are looking to scrape off the ICB combination listing sticker, and make the change to a TM cb, I really don't have any help. You could call Siemens - But I suspect they may tell you to bya new bucket.

Again I missing some context here - 2hp or 200hp?

cf

 

[Cold Fusion]

(cut)What would happen if you used a larger frame size for a TM than an approved ICB? (cut)

The screw holes won't fit:smile: But you probably already knew that. Seriously, I don't know, it depends on your concern:
Listing fracture - you already did that changing from an ICB to a TM.
Osha violation - frame size won't change that.
Increase risk of fireball - You broke the listing, you're now the engineer of record. You get to decide this.

(cut) Does the NEC say what the maximum frame size of a breaker can be, or only its trip rating? (cut)

Just the trip rating.

(cut) For a motor ICB does the 800% refer to the amp rating listed on the breaker, or the adjustable settings for the range of that breaker?

The adjustable setting. The amp rating on the CB handle is susposed to be a continuous current rating - but I seriously doubt that it is. 100A F frame ICBs can have amp numbers anywhere from 3A to maybe 100A and I highly suspect the contacts in all are the same. The adjustable trip range is all that matters.

The key is 430.52. Concentrate on (C)(1), (C)(3), T430.52, all the notes, all the exceptions.

cf

 

[Jraef]

I work for Siemens, this is my specific field. Maybe a little history can clear some of this up for you.

It used to be that TM MCCBs (Molded Case Circuit Breakers) had fixed magnetic trips as well as fixed thermal trips. Most of them had the mag trips set at 400% of the breaker rating. So if you wanted to build a motor starter with one, the fact that the mag trip settings were not adjustable meant that in order to get a mag trip setting high enough to avoid nuisance tripping on inrush, you usually ended up exceeding the NEC rules for sizing based on the thermal trip rating. So to solve that problem, manufacturers came out with magnetic only breakers with adjustable magnetic trips which allowed settings as high as 10X the breaker rating. Of course because they had no thermal long time trip elements, they could ONLY be used in motor starters where an overload was available to protect the conductors.

But times have changed. Almost all newer TM MCCB designs now come with adjustable magnetic trips. In fact if you look, you will see that the adjustment ranges are exactly the same. So in effect, there now is no difference in the breakers, except the cost. If you are the manufacturer, it is less expensive to use a mag-only breaker in your motor starters. But there is no reason why you, as an end user, cannot swap the TM breaker for a defective mag-only.

As to the combination starter issue, no you cannot substitute one brand for another at will, technically. The only valid use of mag-only breakers is as part of a LISTED combination starter. Mag-only breakers are not UL "Listed", they are UL "Recognized", which means they can only be used as part of a factory assembled system. They can never be used in the field other than for direct replacement. So then if Siemens is making a combination starter, I can assure you we are not going to pay to have our starter listed with a Square-D breaker and the reverse is true as well. In the case of someone such as Allen Bradley who does not make circuit breakers, they have to choose. Years ago you could actually buy an A-B combo starter with either a Siemens or a Westinghouse breaker in it, but the cost of UL listing and maintaining that listing makes that prohibitive and A-B now only uses the Eaton (ex- Westinghouse) breakers.

But (there are always a lot of "buts" in this industry), now that most TM breakers have the same adjustability and ranges of MCPs, you can actually replace almost ANY MCP with ANY TM breaker in a combination starter. That's because, being UL LISTED devices, they are suitable for field installation. All you need to do is make sure the ratings are correct. You may find, however, that making the handle accessories fit will be problematic when switching brands.

 

[mull982]

But (there are always a lot of "buts" in this industry), now that most TM breakers have the same adjustability and ranges of MCPs, you can actually replace almost ANY MCP with ANY TM breaker in a combination starter. That's because, being UL LISTED devices, they are suitable for field installation. All you need to do is make sure the ratings are correct. You may find, however, that making the handle accessories fit will be problematic when switching brands.

Jaref thaks for the history, it helps understand alot. In your last paragraph you say that since TM MCCB's are UL listed they are o.k. to use them in a combination starter.

When using a TM breaker table 430.52 says the the max rating can only be 250%. Is this rating the actual trip plug rating of the breaker, or the adjustable magnetic portion of the breaker? Or since the magnetic element is adjustable do you follow the 800% and treat this adjustable range per the instantaneous rating?

Since ICB's have adjustable ratings, does a frame size really come into play. In other words a Siemens 400A ICB I'm assuming has a 400A fram size but is adjustable up to 4000A which is well over its frame size? Therefore when replacing it with a TM breaker should the TM breaker have this maximum 400A frame size?

I'm getting a little confused:
When this started, I was under the impression you needed to get going right away and would make a perminent fix later. Now I'm getting the feeling you are looking to make a perminent change. Two different things. If you are looking to scrape off the ICB combination listing sticker, and make the change to a TM cb, I really don't have any help. You could call Siemens - But I suspect they may tell you to bya new bucket.

Again I missing some context here - 2hp or 200hp?

cf

CF you are correct I did need to get going and was looking for a quick replacement which I found. I am ordering the correct ICB replacement as a permenant fix as to make sure I do things correctly.

The one positive that comes out of these types of problems is that it gives me a learning opportunity to learn more about the details surrounding the problem that occured. A lot of my follow up questions are for me to understand better the priciples of the different breaker types so that I will understand them when future problems occur or if I am ever involved with a design role.

The motor is a 200hp.

 

[mull982]

One other thing that popped into my head.

If using a TM breaker in a starter is it possible that the overload curve of the breaker falls to the left of that of the overloads and thus the breaker trips first on motor overloads rather than the overloads themselves?

 

[coulter]

...now that most TM breakers have the same adjustability and ranges of MCPs, you can actually replace almost ANY MCP with ANY TM breaker in a combination starter. That's because, being UL LISTED devices, they are suitable for field installation. All you need to do is make sure the ratings are correct. ...

(emphasis is mine)

Jraef -
With all due respect, I have never seen any Listing agency documentation, vendor documentation, nor any intrepretations from AHJs that would support this thinking.

My understanding of what you are saying is: Supose I send Siemens an email telling them I have a size 5, listed combination starter with a 400A frame mag only CB feeding a 200hp motor, 240A FLA, and I am going to change out the CB for a UL listed, 600A TM (which is likely a a frame size change). Could I really expect Siemens to send me a letter/email back saying: "Sure thing. It won't change the listing at all. UL, AHJ, Osha will be just fine with this." ?

Really? Siemens would do that?

carl

 

[Jraef]

(emphasis is mine)

Jraef -
With all due respect, I have never seen any Listing agency documentation, vendor documentation, nor any intrepretations from AHJs that would support this thinking.

My understanding of what you are saying is: Supose I send Siemens an email telling them I have a size 5, listed combination starter with a 400A frame mag only CB feeding a 200hp motor, 240A FLA, and I am going to change out the CB for a UL listed, 600A TM (which is likely a a frame size change). Could I really expect Siemens to send me a letter/email back saying: "Sure thing. It won't change the listing at all. UL, AHJ, Osha will be just fine with this." ?

Really? Siemens would do that?

carl

UL would not say so because technically ANY change to a listed product violates the UL listing, but then again UL is not concerned with a system already installed. In a retrofit application, if it was going to be inspected, you would have to take it up with the AHJ. But being that the TM breaker is UL LISTED, not just recognized, it is appropriate for field installation and you have a good argument, especially if the settings are identical to what was taken out. Remember that in a motor starter, it is the OVERLOAD relay that is protecting the wires from long-time over currents, the breaker is only there for short circuit protection. SO if the short cuircuit protection is the same on both breakers, what's the problem? Realistically though, a 400AF to 600AF change would entail a lot of other issues that might prove problematic. I was referring to a size-for-size replacement.

I can't speak for other manufacturers but in the specific case with Siemens, all of our starters are listed with TM breakers as well as ETI (Mag only) versions, so yes, I would write that letter to an AHJ for you, in fact I have done so. I have seen however that when old equipment is upgraded, AHJs have accepted new breakers of a different brand as long as they are LISTED (TM) breakers. In fact it's fairly common because a lot of companies have gone by the wayside or been absorbed by competitors, so exact replacements of old breakers are no longer available. Westinghouse is a good example. You cannot get an original old-style Westinghouse MCP any more. Eaton will sell you a C-Line replacement, but if it is being inspected, technically that C-Line HMCP is not able to be used in a starter listed with the old version. If you used a TM breaker with adjustable mag trips however, it would be a suitable, and legal, replacement.

 

[coulter]

... AHJs have accepted new breakers of a different brand as long as they are LISTED (TM) breakers. In fact it's fairly common because a lot of companies have gone by the wayside or been absorbed by competitors, so exact replacements of old breakers are no longer available. Westinghouse is a good example. You cannot get an original old-style Westinghouse MCP any more. Eaton will sell you a C-Line replacement, but if it is being inspected, technically that C-Line HMCP is not able to be used in a starter listed with the old version. If you used a TM breaker with adjustable mag trips however, it would be a suitable, and legal, replacement.

This whole idea of a "legal replacement" leaves me baffled. The only thing that makes a substitution "legal" is the AHJ's acceptance - that's generally called a waiver and that's on a case by case basis. There is nothing inherent in using a TM with mag-only tips that makes it legal to replace an ICB in a listed combination starter - unless it comes with a letter from the AHJ saying it's okay

carl

 

[coulter]

One other thing that popped into my head.

If using a TM breaker in a starter is it possible that the overload curve of the breaker falls to the left of that of the overloads and thus the breaker trips first on motor overloads rather than the overloads themselves?

If you sized the CB and the overload correctly this won't be a problem. But that is what a coordination study is for. You won't need etap. Get a copies of the CB trip curve and the overload trip curve - generally available on the mfg website. Print them out and lay them one over the other. About the only time the two curves get close is if you have a slow starting high inertia load and a high inrush motor. Then you change to a class 30 ovld.

carl

 

[Jraef]

This whole idea of a "legal replacement" leaves me baffled. The only thing that makes a substitution "legal" is the AHJ's acceptance - that's generally called a waiver and that's on a case by case basis. There is nothing inherent in using a TM with mag-only tips that makes it legal to replace an ICB in a listed combination starter - unless it comes with a letter from the AHJ saying it's okay

carl

No argument from me on that.

I only used the term "legal" in a relative sense. My point was, you can make a pretty good argument to an AHJ for replacing a mag-only breaker with a similar TM breaker that has adjustable mag trips and the AHJ will not have a valid engineering reason to reject it. He still can because he always can, but it will not be based on anything electro-technical in nature. I have never had an AHJ reject a TM replacement for an MCP, but I have seen fixed trip breakers be unable to hold in on inrush without oversizing, and THEN I have seen AHJs reject the over sized breaker. The point I was trying (and will quit trying) to make was only that because of changes in the breaker marketplace, the difference between TM breakers and mag-only breakers is not as clear cut as it used to be. Retrofit is possible.