GE Breakers

[rcwilson]

Just curious - Do they check the instantaneous portion of the trip curve?

ice

When I did circuit breaker testing years ago, supposedly following NETA specs, the instantaneous function was tested first. The test set had a pulse feature that pushed current for a short pulse, about 5 cycles, to avoid heating the termal element. Current was raised after each pulse until the breaker tripped. The test set output current started at the peak of the voltage waveform to minimize the DC offset in the current. A peak hold meter read out the RMS trip current

Voltage drop at rated amps was measured to check for bad contacts and then a 300% load was appled for a thermal test. Three phase breakers were tested single phase to verify each pole operated correctly, unless an integral ground fault function had to be defeated. The allowable variation in trip time was quite large for a breaker to pass the test.

Most of these were in service breakers, or new construction undergoing acceptance tests sizes 30A - 4,000A. I recall less than 5% failures, not counting loose connections and miswired ground fault protection.

 

[mbrooke]

Just some personal design philosophy - certainly no minimalistic code:

Other than #14, #12 residential recetpacle circuits, OCPD does not protect the equipment, and does not always protect the conductors. Example motors: The motor is protected from overload by the design. The overloads are there to catch minor mechanical faults before the motor has a chance to burn up. One might say these are repairable. If the motor faults to where the CB trips, there is no motor to save - it's dead. The ocpd operates to put out the fire and hopefully trips inside of the conductor damage curve. Although, except for large feeders (say >1000A), the cable damage curve is rarely on the coordination curves. Still, one might say it could protect the couductors here.

Now, if the conductors develop a fault (forklift attack) again there are no conductors to save. The ocpd is there to put out the fire.

The ocpd is for protecting the structure.

JAO

ice

Not sure exactly what you mean. On a thermal curve the breaker even 1000 amp frames are supposed to trip before the insulation melts. Locally an arc will do considerable damage, and very high fault currents can cause conductors to lash about, but Im confused by what you exactly mean.

 

[kwired]

Now you're just being an ass.

I wasn't serious if that means anything, just having a little fun.

 

[kwired]

I don't expect to have to test new breakers to make sure they are good, but I don't usually buy GE unless there is an existing GE panel that I am running a new circuit to. I find it a little hard to believe their QC is that bad, but maybe it is. I do know the standards allow for a breaker to hold for time/amperage levels that some may think are kind of long/high, but remember these breakers are primarily protecting conductors, if you have certain equipment that you want more protection on then maybe some supplemental protection that meets the needs at that equipment is what is needed.

Going back to what I posted above, I don't expect to have to test new breakers, now maybe if you have $4.00 breakers not meeting the standards that may be a sign that you should be using something other than $4.00 breakers.

 

[don_resqcapt19]

I wasn't serious if that means anything, just having a little fun.

But it is a good point, what reason is there to expect that the quality control of the fuse manufacturer would be better than that of the breaker manufacturer? I guess there are more parts in a breaker giving more opportunity for manufacturing mistakes, but such mistakes are still possible with fuses.

 

[kwired]

But it is a good point, what reason is there to expect that the quality control of the fuse manufacturer would be better than that of the breaker manufacturer? I guess there are more parts in a breaker giving more opportunity for manufacturing mistakes, but such mistakes are still possible with fuses.

I don't know anything about fuse manufacturing but would guess they do some testing on a routine basis, like maybe at least every lot number, shift, or run of some kind gets some testing of what was made from that run as a QC measure, and circuit breakers are likely similar. Even certain individual components are likely run through some testing periodically instead of entire assemblies as a QC measure.

I have been around food processing more so than assembled items processes, and they take samples of everything, raw products, finished products or something in between if there is multiple steps and run them through routine testing in the lab to make sure it is safe for the final consumer, and to make sure whatever treatment has been done is what was desired to get the end product.

 

[mbrooke]

But it is a good point, what reason is there to expect that the quality control of the fuse manufacturer would be better than that of the breaker manufacturer? I guess there are more parts in a breaker giving more opportunity for manufacturing mistakes, but such mistakes are still possible with fuses.

If it helps breakers entirely rely on mechanical action of several moving parts to clear a fault. Any one of which can fail, rust and of course during manufacturing must be precise. Any slight defect or any slight altercation in the order/way the parts are assembled can lead to failure. More is involved in actually opening the contacts in the breaker than the mechanism that unlatches the breaker to trip it (bi metal). This hold true for all resi breakers and most large amp frame breakers. If a breaker fails to unlatch, there is no weak link. The mechanical parts and conductive braid(s) just act like wire, the will make lots of heat and by the time they start to fuse open the wire is in the same stage if not already there.


Most fuses on the other hand have no moving parts. Some MV fuses have a small amount of propellent and a pin that will help in dropping the fuse down after it melts yes, but nearly all fuses simply rely on a weak link. That weak link is far more likely to be free of manufacturing defect or error since much less is involved in its manufacture. Further a fuses age, the weak link does not seize up like mechanical breakers. Dirt, contamination, moisture, has less if no impact. Finally, if a weak link (fuse element) is defective in the sense its oversize, misshaped or the thickness is in excess from manufacturing specs due to defect, all that will change would be the amperage, but if a hard bolted fault took place that fuse would clear that. A fuse failing in the on position is exceptionally rare when the right rating is used, but a breaker failing I regret to say happens to be a norm. I have seen that more than once in regards to breakers.

Plus, a breaker that has repeatedly tripped on a fault can explode when closed back into one since hard faults pit the contacts and glaze up the insides. A molded case breaker for resi per UL is only guaranteed to clear 2 or 3 (brain fart moment) bolted faults without issue. The rest is a bargain.

 

[iceworm]

... OCPD does not protect the equipment, and does not always protect the conductors.

Not sure exactly what you mean. On a thermal curve the breaker even 1000 amp frames are supposed to trip before the insulation melts. Locally an arc will do considerable damage, and very high fault currents can cause conductors to lash about, but Im confused by what you exactly mean.

Conductors/cables have defined time-current thermal damage curves. Unless the curve is laid out on the coordination, how do you know if the conductor is protected.

Generally speaking, the "normal" thermal-magnetic CB with a "normal" trip curve is inside of the thermal damage curve of the conductors allowed by art. 240.

However, there certainly are exceptions. I will say, the exceptions are outside of the GEthqb/SQDQOapplications.

ice

 

[iceworm]

... When I did circuit breaker testing years ago

... following NETA specs, the instantaneous function was tested first.

...Most of these were in service breakers, or new construction undergoing acceptance tests sizes 30A - 4,000A. I recall less than 5% failures, ....

rc -
Were these the GEthqb/SQDqo type? Non-adjustable molded case (such as SQD F frame)? Insulated case? Metal clad?

If these were molded case (little or big), The 5% failure rate seems really high. I had no idea the out-of-the-box failure rates are that high.

If the tests (years ago) were mechanical trip elements on adjustable trip units, then I would not be a bit surprised that 5% were out of spec.

I am a bit surprised that testing molded case in the instantaneous range was/is common - didn't know that.

ice

ice

 

[don_resqcapt19]

If it helps breakers entirely rely on mechanical action of several moving parts to clear a fault. Any one of which can fail, rust and of course during manufacturing must be precise. Any slight defect or any slight altercation in the order/way the parts are assembled can lead to failure. More is involved in actually opening the contacts in the breaker than the mechanism that unlatches the breaker to trip it (bi metal). This hold true for all resi breakers and most large amp frame breakers. If a breaker fails to unlatch, there is no weak link. The mechanical parts and conductive braid(s) just act like wire, the will make lots of heat and by the time they start to fuse open the wire is in the same stage if not already there.


Most fuses on the other hand have no moving parts. Some MV fuses have a small amount of propellent and a pin that will help in dropping the fuse down after it melts yes, but nearly all fuses simply rely on a weak link. That weak link is far more likely to be free of manufacturing defect or error since much less is involved in its manufacture. Further a fuses age, the weak link does not seize up like mechanical breakers. Dirt, contamination, moisture, has less if no impact. Finally, if a weak link (fuse element) is defective in the sense its oversize, misshaped or the thickness is in excess from manufacturing specs due to defect, all that will change would be the amperage, but if a hard bolted fault took place that fuse would clear that. A fuse failing in the on position is exceptionally rare when the right rating is used, but a breaker failing I regret to say happens to be a norm. I have seen that more than once in regards to breakers.

Plus, a breaker that has repeatedly tripped on a fault can explode when closed back into one since hard faults pit the contacts and glaze up the insides. A molded case breaker for resi per UL is only guaranteed to clear 2 or 3 (brain fart moment) bolted faults without issue. The rest is a bargain.

So in other words breakers should not be used

 

[kwired]

So in other words breakers should not be used

I think in some cases that is what it sort of comes down to, especially with high available fault current levels, if the breaker is available for the application the fuse may still be the more economic route to go anyway.

 

[don_resqcapt19]

I think in some cases that is what it sort of comes down to, especially with high available fault current levels, if the breaker is available for the application the fuse may still be the more economic route to go anyway.

But the engineer has to do his homework for both, fuses have a current, just like breakers, where if you are under it, you are not in the current limiting range, and just like breakers they take longer, at the lower current lever, to open the circuit and the incident energy goes up. The fuse people have a lot of misinformation that strongly implies that this is not the case for fuses.

 

[GoldDigger]

So in other words breakers should not be used

No, they should always be new.
Otherwise you have no idea where they have been. :angel:

Tapatalk!

 

[rcwilson]

rc -
Were these the GEthqb/SQDqo type? Non-adjustable molded case (such as SQD F frame)? Insulated case? Metal clad?

If these were molded case (little or big), The 5% failure rate seems really high. I had no idea the out-of-the-box failure rates are that high.

If the tests (years ago) were mechanical trip elements on adjustable trip units, then I would not be a bit surprised that 5% were out of spec.

I am a bit surprised that testing molded case in the instantaneous range was/is common - didn't know that.


ice

I was doing that work 25-30 years ago on a combination of existing and new equipment. My 5% figure was a guess. Most failures I recall were high millivolt drop on molded case breakers and tripping or latching issues on older air frame breakers. Only one client (a Bell telephone company) required maintenance testing molded case breakers at less than 100A. That practice stopped also for financial reasons.

On an annual maintenance contract, the third or fouth time we came through the facility, most of the issues we found were problems we created from the previous tests such as damaging the lugs attaching our test leads.

IMHO, it is better to spend testing money on infared surveys and operate the breakers manually at least once a year to free up the contacts and exercise the mechanism. You could also use Zog's "Technician in a Can" to lubricate the air frame breaker mechanism so it works freely. It will then be able to trip, but only for a few hours after you leave before it siezes up again.

 

[iceworm]

... On an annual maintenance contract, the third or fouth time we came through the facility, most of the issues we found were problems we created from the previous tests such as damaging the lugs attaching our test leads. ...

PM unto death. Yep - been there done that :weeping: Often hard to explain to management why sometimes run-to-failure is an excellent option.

... IMHO, it is better to spend testing money on infared surveys and operate the breakers manually at least once a year to free up the contacts and exercise the mechanism. ...

Yes

... . You could also use Zog's "Technician in a Can" to lubricate the air frame breaker mechanism ...

I missed that when it came up. What is it? WD-40?

ice

 

[mbrooke]

So in other words breakers should not be used

Weigh you options. Application will determine it all. If high fault interruption, reliability with minimal maintenance is the name of the game go with fuses. If coordination, and reliability is less of a concern but ease of reseting is your like go with breakers. One area breakers win hands down over fuses is 3 phase tripping and the ability to add shunt trip, ground fault protection ect. Fuses have the disadvantage of clearing only the faulted phase leaving the others energized in a possibly dangerous condition. But a fuse is nearly fail safe, and there is no such thing as one seizing up mechanically.

I think in some cases that is what it sort of comes down to, especially with high available fault current levels, if the breaker is available for the application the fuse may still be the more economic route to go anyway.

True, but its all based on what your trying to accomplish.

No, they should always be new.
Otherwise you have no idea where they have been. :angel:

Tapatalk!

Breakers, and I REPEAT with EMPHASIS, should always be new, whether it be a 15 amp QO or a 6000amp switch gear draw out unit. You dont know the history or if its been improperly maintained.

Conductors/cables have defined time-current thermal damage curves. Unless the curve is laid out on the coordination, how do you know if the conductor is protected.

Generally speaking, the "normal" thermal-magnetic CB with a "normal" trip curve is inside of the thermal damage curve of the conductors allowed by art. 240.

However, there certainly are exceptions. I will say, the exceptions are outside of the GEthqb/SQDQOapplications.

ice

But doesnt the NEC and UL to some degree dictate the breaker must trip on a time current curve based on a thermal damage curve?

I know the conductors to motors may be under sized with breakers only be for instantaneous magnetic trip protection, and networks often rely on cables to burn a fault clear, but cant think of other times when conductors are heated beyond the damage curve.

 

[iceworm]

Breakers, and I REPEAT with EMPHASIS, should always be new, whether it be a 15 amp QO or a 6000amp switch gear draw out unit. You dont know the history or if its been improperly maintained. ...

Can't say I agree. I deal with plenty of stuff that is sufficiently old that I have to deal with a rebuilder. I do all I can to pick good ones. No generally not with 15A qob.

... If coordination, and reliability is less of a concern but ease of reseting is your like go with breakers. .

Don't agree. If coordination is an issue - CBs, electronic trips are likely mandatory. Mains, feeders, ansi damage points (xfm), cable damage curves, overload curves, motor starting curves. Get them pounded on to one T-C coordination curve and sometimes the contortions to get coordination is severely interesting. I recall one noted authority saying, "You can coordinate anything - It's just a matter of money."

.... One area breakers win hands down over fuses is 3 phase tripping and the ability to add shunt trip, ground fault protection ect. Fuses have the disadvantage of clearing only the faulted phase leaving the others energized in a possibly dangerous condition. But a fuse is nearly fail safe, and there is no such thing as one seizing up mechanically. ....

Yes,
Yes,
and Yes

...But doesnt the NEC and UL to some degree dictate the breaker must trip on a time current curve based on a thermal damage curve? .

Yes, as long as one sticks to standard stuff, GEthqb, SQDqo, molded case

...I know the conductors to motors may be under sized with breakers only be for instantaneous magnetic trip protection, and networks often rely on cables to burn a fault clear, but cant think of other times when conductors are heated beyond the damage curve.

Some curves are really strange:
Inverse (normal)
very inverse
extremely inverse (might be wrong on this one)
i^2t
i^4t
LSI
LS (no I)
LSIG

And sometimes these are what it takes to get bent around so one can get coordination.

However, my point was about things like unlimited outside taps. The OCPD at the end of the tap should protect against overload - all the electrons going in from the xfm end have to come out the ocpd end. Invariabily some one will ask so what happens if the xfm secondary overload in the middle and it doesn't show up at the ocpd. That is a backhoe attack. The protection against that is concrete and steel - not an ocpd.

Motor feeders, overload is set to 140%. CB is a T-M set to 250% fla. Cable protection looks pretty marginal. If this was any size, I'd be lookin for the cable damage curve.

The rest is design philosophy. I consider the motors and conductors are protected from overload by design. One protects the cables with concrete and steel. The CB is to put out the fire and save the structure - and generally can also protect a cable

Just some thoughts - I'm not stuck

ice

 

[kwired]

No, they should always be new.
Otherwise you have no idea where they have been. :angel:

Tapatalk!

But apparently new ones still need to be full functionality tested before you use them:blink:

 

[jim dungar]

But a fuse is nearly fail safe, and there is no such thing as one seizing up mechanically.

The fuse may clear, without maintenance, but that is only half the battle. Without proper PM, about every 5 years, there is something like <50% chance that a 'bolted pressure' style fusible switch (>800A) will physically open. If the switch hangs up mechanically, how is it much different than a breaker?

 

[kwired]

The fuse may clear, without maintenance, but that is only half the battle. Without proper PM, about every 5 years, there is something like <50% chance that a 'bolted pressure' style fusible switch (>800A) will physically open. If the switch hangs up mechanically, how is it much different than a breaker?

It still has overcurrent protection, but becomes a not so good disconnecting means, however following good safety procedures should have you checking for voltage first thing after opening a disconnect.