Motor Circuit Breakers

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mbrooke

mbrooke

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Question. Why don't they make circuit breakers specifically designed for motors? For example a breaker with a +20x magnetic trip and a thermal time current curve which mimicks overload heaters? Maybe an adjustment dial to take LRA differences into account?

Also why are modern circuit breakers listed "HACR type"? What does this mean?
 
HACR Rated Circuit Breaker
HACR stands for Heating, Air-Conditioning, and Refrigeration breaker. HACR rated breakers open within a specified time curve, similar to a fuse, to protect group motor equipment (fans for combustion air, exhaust control, heated air handling, AC compressors, etc). Years ago, breaker manufacturers were not consistent on this tripping time, hence HVAC equipment was typically certified by UL using fuses. This eventually led to the HACR breaker which has the same time/trip curve regardless of who makes it. For an acceptable installation, the end-use equipment must be marked to indicate that “HACR Type” circuit breakers may be used for branch circuit overcurrent protection. The 2005 NEC permits the use of any inverse-time type circuit breaker in heating, air-conditioning and refrigeration equipment comprising group motor installations. Back in the mid 80's UL changed their testing procedure with the end result that today all "new" multi-pole breakers are automatically HACR rated. This makes life easy, you can pick up a standard two-pole breaker for $8-9 bucks and have what you need to protect your HVAC equipment.
 
mbrooke said:
Wait. Doesn't multi motor equipment have its own overloads built in? Why would the breaker matter?
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Type TP motors do but that’s not necessarily the norm. Or if you mean don’t HVAC control panels have built in overloads, yes they do but the discussion is at the component level.
 
mbrooke said:
Question. Why don't they make circuit breakers specifically designed for motors? For example a breaker with a +20x magnetic trip and a thermal time current curve which mimicks overload heaters? Maybe an adjustment dial to take LRA differences into account?

Also why are modern circuit breakers listed "HACR type"? What does this mean?
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As to first question yes but terminology gets in the way.

A circuit breaker has at a minimum an inverse time trip function or it is just a switch when controlled by an external protection relay. There can be other trip functions but that is the minimum,

A Motor Circuit Protector only has an instantaneous (magnetic) trip function. It is technically not a circuit breaker because it does not have an inverse time function. It is classified as supplemental protection. They are part of a Listed assembly (MCC) so they can’t be used independent of some kind of assembly.

A Manual Motor Starter is a self contained assembly that is a complete starter assembly. So it includes disconnecting, short circuit (instantaneous tripping) protection, and overload protection. The overload is usually a dial that you set in FLA. The only thing the MMS does not include is remote control so if it is not used manually (think on/off switch), you have to add a contactor and usually an aux contact to shut down the control circuit if the MMS trips. Only real trouble with the MMS is that on some you can’t tell if the trip is overload or short circuit. This is an issue because OSHA treats overloads and electrical faults differently. Also they are limited to smaller sizes. And I haven’t seen one yet with adjustable short circuit tripping.

So yes what you are asking for already exists.
 
mbrooke said:
Question. Why don't they make circuit breakers specifically designed for motors? For example a breaker with a +20x magnetic trip and a thermal time current curve which mimicks overload heaters? Maybe an adjustment dial to take LRA differences into account?

Also why are modern circuit breakers listed "HACR type"? What does this mean?
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They do make those. They are called "Motor Protection Circuit Breakers" (MPCB). Not all of the mfrs have them, but most do. UL only recently started allowing them to be called "Circuit Breakers" however, because the UL standard for "circuit breakers", UL489, did not allow for adjustable thermal elements. So up until then they had to be called "Manual Motor Starters" and were listed under UL508 as a motor circuit component, meaning technically, you STILL had to have a CB or fuses ahead of them. Once UL caved and allowed this "new" category of MPCBs, it allows you to have it all in one device. The concept has not yet caught on in a big way though, people don't like change...

By the way, they don't make them that have 20x adjustments to the mag trips though, because the breakers themselves have a 10x limit to what they can handle from a mechanical forces standpoint. Even if you buy a "Molded Case Switch", which is a circuit breaker without "any" trip elements, it technically still has one, factory set for 10x the rating and not adjustable, because that's the mechanical limit of the breaker mechanism itself.
 
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I like mpcb, aka type e and f starters. We use a bunch of them. Relatively cost and space efficient. Many of the smaller ab drives can use them as ocpd. They are especially useful if you have a bunch of small motors. Can run a single set of conductors to the bus bar accessory as a feeder.
 
Jraef said:
By the way, they don't make them that have 20x adjustments to the mag trips though, because the breakers themselves have a 10x limit to what they can handle from a mechanical forces standpoint. Even if you buy a "Molded Case Switch", which is a circuit breaker without "any" trip elements, it technically still has one, factory set for 10x the rating and not adjustable, because that's the mechanical limit of the breaker mechanism itself.
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Wait, I'm confused. Older breakers had trip over 10x, some didn't have it at all yet equipment was rated 22, 65kaic ect.
 
Jraef said:
They do make those. They are called "Motor Protection Circuit Breakers" (MPCB). Not all of the mfrs have them, but most do. UL only recently started allowing them to be called "Circuit Breakers" however, because the UL standard for "circuit breakers", UL489, did not allow for adjustable thermal elements. So up until then they had to be called "Manual Motor Starters" and were listed under UL508 as a motor circuit component, meaning technically, you STILL had to have a CB or fuses ahead of them. Once UL caved and allowed this "new" category of MPCBs, it allows you to have it all in one device. The concept has not yet caught on in a big way though, people don't like change...

By the way, they don't make them that have 20x adjustments to the mag trips though, because the breakers themselves have a 10x limit to what they can handle from a mechanical forces standpoint. Even if you buy a "Molded Case Switch", which is a circuit breaker without "any" trip elements, it technically still has one, factory set for 10x the rating and not adjustable, because that's the mechanical limit of the breaker mechanism itself.
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I'm also confused by how a 225 amp frame breaker designed to trip at 100 amps has a lower withstand than a 225 amp trip breaker assuming the 100 amp breaker trips at 1000 amps and 2,250 amps respectively. What stops a 100 amp breaker from tripping at 2,250 amps or even a 60 amp breaker at 2,250 amps?
 
mbrooke said:
I'm also confused by how a 225 amp frame breaker designed to trip at 100 amps has a lower withstand than a 225 amp trip breaker assuming the 100 amp breaker trips at 1000 amps and 2,250 amps respectively. What stops a 100 amp breaker from tripping at 2,250 amps or even a 60 amp breaker at 2,250 amps?
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For that matter you can start with say a 225 A breaker and put a 100 A trip unit in it. In insulated case breakers they have rating plugs to do this.
 
paulengr said:
For that matter you can start with say a 225 A breaker and put a 100 A trip unit in it. In insulated case breakers they have rating plugs to do this.
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Right, but why doesn't the rating plug give you a 15x mag trip? It seems they always stop at 10x. Being honest I feel like everything is unnecessarily complicated in the LV electrical industry.
 
mbrooke said:
Right, but why doesn't the rating plug give you a 15x mag trip? It seems they always stop at 10x. Being honest I feel like everything is unnecessarily complicated in the LV electrical industry.
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This appears to be something to do with for instance UL.

Look at this:


Read the chart at the bottom of page 10.

No disagreement. Everything is highly over-engineered. Some things in a good way, others not such a good idea.
 
paulengr said:
This appears to be something to do with for instance UL.

Look at this:


Read the chart at the bottom of page 10.

No disagreement. Everything is highly over-engineered. Some things in a good way, others not such a good idea.
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Can you tell me what page 10 hints at?

The whole mag trip thing is rather elusive, a confusing world all on its own.
 
mbrooke said:
Can you tell me what page 10 hints at?

The whole mag trip thing is rather elusive, a confusing world all on its own.
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Bottom of page 10 shows UL types C, E, and F starters. Type C shows I think a thermal magnetic breaker rated at 250% times 10 so trips at 25x. Using the same idea a type 2 fused starter would be 12.5x and a type 1 fused starter would be 17.5x. Type E is not clear but I think it’s a MPCB and type F is definitely MMS. Both are shown as trips at 10x. Until it was mentioned here I have not heard of starter “types”. UL often uses terms not used by anyone else (so does IEC) and this is one of them.

Magnetic only breakers (MCPs) have been around since at least the 1980s or earlier. Nothing new at all. Not confusing at all.

What is missing here is that all of these are designed specifically for motors. Or at least all but the general purpose thermal magnetic breaker. So they will avoid inrush by design so unless you are calculating arc flash or adjusting the instantaneous trip for inrush we don’t care if it trips at anything over 10x because there is enough delay it gets past inrush anyway. Only electronic thermal magnetic breakers tend to be an issue.
 
paulengr said:
Bottom of page 10 shows UL types C, E, and F starters. Type C shows I think a thermal magnetic breaker rated at 250% times 10 so trips at 25x. Using the same idea a type 2 fused starter would be 12.5x and a type 1 fused starter would be 17.5x. Type E is not clear but I think it’s a MPCB and type F is definitely MMS. Both are shown as trips at 10x. Until it was mentioned here I have not heard of starter “types”. UL often uses terms not used by anyone else (so does IEC) and this is one of them.

Magnetic only breakers (MCPs) have been around since at least the 1980s or earlier. Nothing new at all. Not confusing at all.

What is missing here is that all of these are designed specifically for motors. Or at least all but the general purpose thermal magnetic breaker. So they will avoid inrush by design so unless you are calculating arc flash or adjusting the instantaneous trip for inrush we don’t care if it trips at anything over 10x because there is enough delay it gets past inrush anyway. Only electronic thermal magnetic breakers tend to be an issue.
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I don't get why they can't make general purpose breakers with different magnetic pickups like the IEC does in order to address motors and lights. UL has no common sense, that much I know.
 
mbrooke said:
I don't get why they can't make general purpose breakers with different magnetic pickups like the IEC does in order to address motors and lights. UL has no common sense, that much I know.
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Adjustable magnetic trips are totally legal and available. It’s only the long term trip curve that is locked down. But adjustable magnetic trips are expensive extras. These days starting at around 250 A. The microprocessor based ones are cheaper than the old mechanical ones.
 
paulengr said:
Adjustable magnetic trips are totally legal and available. It’s only the long term trip curve that is locked down. But adjustable magnetic trips are expensive extras. These days starting at around 250 A. The microprocessor based ones are cheaper than the old mechanical ones.
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Not for smaller sizes, and there is no reason for the added cost either.
 
mbrooke said:
Not for smaller sizes, and there is no reason for the added cost either.
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Yes. One of the most popular for years was the GE Spectra RMS. Great breaker. So GE discontinued and replaced with the Wavepro’s which are junk. So cheap the contact tips fall off. ABB also has a decent one but availability is rotten. Fortunately AB private brands and stocks them at reasonable prices. I’d expect this to replace the GE MCCBs too now that ABB owns GE. Also the LSIS Sisu is a decent adjustable one. Conspicuously absent is Eaton. Square D has the Masterpact which is fully electronic. Even available in ILine form.
 
mbrooke said:
Do you have a list of all thermal mag breakers? Being honest I like to avoid electronics altogether.
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No but even the GE that appears “thermal mag” is electronic (microprocessor). In breakers the least reliable are analog electronics like the old SqD SE’s. Next most reliable are thermal mags. Most reliable are microprocessor trip units.
 
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