Breakers
- Thread starter pridelion
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charlie
Senior Member
- Location
- Indianapolis
Re: Breakers
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- <font size="2" face="Verdana, Helvetica, sans-serif">Running hot with less than 80% load (could be a bad connection at the circuit breaker also.)</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Not holding in for no reason.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Tripping for no reason.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Making lots of noise for no reason.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Burnt where it contacts the bus.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Apparent damage.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">It has been under water or has been in the presence of some other corrosive agent.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Anything else that seems unusual.</font>
charlie tuna
Senior Member
- Location
- Florida
Re: Breakers
high internal temperature with no reason, like "b" phase internal contact 20 degrees hoter than the other two phases and the load is equal on all phases. and this heat can cause premature tripping of the breaker. this would be seen in an infrared scan!
high internal temperature with no reason, like "b" phase internal contact 20 degrees hoter than the other two phases and the load is equal on all phases. and this heat can cause premature tripping of the breaker. this would be seen in an infrared scan!
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: Breakers
I would add vibration as a symptom, and a pool table in River City as a primary cause.
I would add vibration as a symptom, and a pool table in River City as a primary cause.
tx2step
Senior Member
- Location
- North Texas, DFW area
Re: Breakers
Newt -
Are you saying to measure the voltage across the circuit breaker (i.e. from the supply buss of phase A to the load lug, phase A, of the circuit breaker; repeat for other phases) to look for a voltage differential through the breaker?
I haven't tried that, but I would think that if you had burned contacts or other internal resistance causing breaker heating, then you would read some voltage differential across the breaker.
How much voltage differential across the breaker have you found to indicate a bad breaker?
Newt -
Are you saying to measure the voltage across the circuit breaker (i.e. from the supply buss of phase A to the load lug, phase A, of the circuit breaker; repeat for other phases) to look for a voltage differential through the breaker?
I haven't tried that, but I would think that if you had burned contacts or other internal resistance causing breaker heating, then you would read some voltage differential across the breaker.
How much voltage differential across the breaker have you found to indicate a bad breaker?
brian john
Senior Member
- Location
- Leesburg, VA
Re: Breakers
The Fall Of Potential (FOP) method of isolating thermal problems is completed at stated measure across the distribution equipment with the problem, if this is a 2 pole of 3-pole device with balanced loads the isolation of the problems is simplified. You can identify a problem in a safety switch by measuring across different portions of the switch. There must be a load and your multimeter must measure in millivolt range.
There is no published data on acceptable millivolt drop, but something in the 20 MV to 100MV seems typically depending on load and once again the type of equipment.
The Fall Of Potential (FOP) method of isolating thermal problems is completed at stated measure across the distribution equipment with the problem, if this is a 2 pole of 3-pole device with balanced loads the isolation of the problems is simplified. You can identify a problem in a safety switch by measuring across different portions of the switch. There must be a load and your multimeter must measure in millivolt range.
There is no published data on acceptable millivolt drop, but something in the 20 MV to 100MV seems typically depending on load and once again the type of equipment.
tx2step
Senior Member
- Location
- North Texas, DFW area
Re: Breakers
Brian,
We do new work, not maintenance/testing, so some of this info is new to me (I probably should know it already, but... what can I say? ). But we do have to occasionally trouble-shoot problems with new equipment or on warranty calls, so I need to understand this maintenance/testing aspect as well.
If I understand what you are saying, if (at full load) I measure the voltage across one phase of a circuit breaker (from the line (bus) connection to the load lug) and I measure over 20 millivolts, then there is enough internal resistance to indicate bad contacts or other problems within the breaker and it should be replaced. Is that correct?
This same procedure could be used for a disconnect switch (measure from the line-in lug to the load lug, or even just across the knife switch contacts). Again, any voltage over 20MV would be bad, indicating that there is a problem?
This same procedure could be used for checking busbar connections or other mechanical connections. Over 20MV would indicate that the connection needed fixing?
Of course, all measurements must be made under full load conditions, and you would have to check each pole of a circuit breaker, switch or other multiphase device.
Am I understanding you correctly?
What conditions raise this measurement to 100 Millivolts before a problem is indicated?
[ April 07, 2005, 07:08 PM: Message edited by: tx2step ]
Brian,
We do new work, not maintenance/testing, so some of this info is new to me (I probably should know it already, but... what can I say?
). But we do have to occasionally trouble-shoot problems with new equipment or on warranty calls, so I need to understand this maintenance/testing aspect as well.If I understand what you are saying, if (at full load) I measure the voltage across one phase of a circuit breaker (from the line (bus) connection to the load lug) and I measure over 20 millivolts, then there is enough internal resistance to indicate bad contacts or other problems within the breaker and it should be replaced. Is that correct?
This same procedure could be used for a disconnect switch (measure from the line-in lug to the load lug, or even just across the knife switch contacts). Again, any voltage over 20MV would be bad, indicating that there is a problem?
This same procedure could be used for checking busbar connections or other mechanical connections. Over 20MV would indicate that the connection needed fixing?
Of course, all measurements must be made under full load conditions, and you would have to check each pole of a circuit breaker, switch or other multiphase device.
Am I understanding you correctly?
What conditions raise this measurement to 100 Millivolts before a problem is indicated?
[ April 07, 2005, 07:08 PM: Message edited by: tx2step ]
brian john
Senior Member
- Location
- Leesburg, VA
Re: Breakers
It does not have to be full load , but more load is better, on 2 pole and 3 pole equipment with balanced load it is easier to locate problems. Like on a 3 pole fused safety switch with 2-poles at 38 MV, while the 3-phase is 99 mv.
The range (20-100mv) is an average range based on experience, different equipment will have different ranges, but above 100 MV and the CB is nusiance tripping I would say it is a good candidate for replacement.
But two 20 amp CBs one with 5 amps and one with 16 amps will have a higher FOP, but if the 5 amp CB has a higher MV drop, than once again this warrants investigation.
Experience helps, and many electricians do not know about this, for a variety of reasons. I say never be afraid to admit you do not know something or to ask questions, that is the only way to learn. I use to tell my students the only dumb question is the one that goes unasked.
Much of what we know is what we have been lucky enough to be exposed to. Where I live there is very little manufacturing, when I go to manufacturing facilities I am amazed at what I see.
I tell factory electricians I am from Washington DC the only thing we manufacture is paper work and BS.
[ April 09, 2005, 12:40 PM: Message edited by: brian john ]
It does not have to be full load , but more load is better, on 2 pole and 3 pole equipment with balanced load it is easier to locate problems. Like on a 3 pole fused safety switch with 2-poles at 38 MV, while the 3-phase is 99 mv.
The range (20-100mv) is an average range based on experience, different equipment will have different ranges, but above 100 MV and the CB is nusiance tripping I would say it is a good candidate for replacement.
But two 20 amp CBs one with 5 amps and one with 16 amps will have a higher FOP, but if the 5 amp CB has a higher MV drop, than once again this warrants investigation.
Experience helps, and many electricians do not know about this, for a variety of reasons. I say never be afraid to admit you do not know something or to ask questions, that is the only way to learn. I use to tell my students the only dumb question is the one that goes unasked.
Much of what we know is what we have been lucky enough to be exposed to. Where I live there is very little manufacturing, when I go to manufacturing facilities I am amazed at what I see.
I tell factory electricians I am from Washington DC the only thing we manufacture is paper work and BS.
[ April 09, 2005, 12:40 PM: Message edited by: brian john ]
tx2step
Senior Member
- Location
- North Texas, DFW area
Re: Breakers
Brian,
Thanks! All of that makes sense!
What type of meter do you use for these measurements? I know you use a multimeter, but any particular brand, model or type that you have had good results with?
[ April 09, 2005, 04:57 PM: Message edited by: tx2step ]
Brian,
Thanks! All of that makes sense!
What type of meter do you use for these measurements? I know you use a multimeter, but any particular brand, model or type that you have had good results with?
[ April 09, 2005, 04:57 PM: Message edited by: tx2step ]
brian john
Senior Member
- Location
- Leesburg, VA
Re: Breakers
Fluke 88III or 83III think. and some older flukes
Fluke 88III or 83III think. and some older flukes
Brightlight
New member
Re: Breakers
What kind of loads are on these circuits. Is there alot of lighting or is there any power correction caps on system?
What kind of loads are on these circuits. Is there alot of lighting or is there any power correction caps on system?
brian john
Senior Member
- Location
- Leesburg, VA
Re: Breakers
Bright:
In regards to what issue.
Bright:
In regards to what issue.
Re: Breakers
Here is an interesting publication covering SqD molded case CB maintenance. Look at pages 11-13. They allow a lot more Vd than I would have expected. For example, an FA 100A frame, 20A rating, loaded to 16A, allows 5W, which translates to .020 Ohms, which would be .320V at 16A.
However, these aren't QO breakers.
SqD molded case CB maintenance
carl
Here is an interesting publication covering SqD molded case CB maintenance. Look at pages 11-13. They allow a lot more Vd than I would have expected. For example, an FA 100A frame, 20A rating, loaded to 16A, allows 5W, which translates to .020 Ohms, which would be .320V at 16A.
However, these aren't QO breakers.
SqD molded case CB maintenance
carl
wirenut1980
Senior Member
- Location
- Plainfield, IN
Re: Breakers
Mr. Brian John,
Mr. Brian John,
I don't like speaking for others, but I think brightlight was thinking of harmonics resonating with capacitor banks causing extra heating on the breaker?
brian john
Senior Member
- Location
- Leesburg, VA
Re: Breakers
Ahh..in regards to types of loads, if the circuit breaker is tripping on thermal you can locate this with a IR cam, handheld thermometer or the old reliable hand touch.
I think the Square D data may be out of line. But I will do some testing to verify and report back.
We have been around the block with manufactures over the years regarding failing their equipment during field testing. Most say the test is WRONG INACCURATE UNRELIABLE.
Ahh..in regards to types of loads, if the circuit breaker is tripping on thermal you can locate this with a IR cam, handheld thermometer or the old reliable hand touch.
I think the Square D data may be out of line. But I will do some testing to verify and report back.
We have been around the block with manufactures over the years regarding failing their equipment during field testing. Most say the test is WRONG INACCURATE UNRELIABLE.
Re: Breakers
Some problems that I have had ( not mentioned above or not quite in detail ):
1. A 50 amp 2-pole Pushmatic circuit breaker tripping withnonly 25 amps of load. Cleaning the wire strands and busbar connections and treating with Ilsco Deox? fixed the problem.
2. Buildup if silver sulfide over time will cause the contacts to become insulated ( open circuit ). Opening and closing the circuit breaker with the load connected will generate enough arcing to convert the silver sulfide into silver oxide, which is an electrical conductor.
3. Exercising a Federal Pacific circuit breaker such as when changing a broken receptacle will restore ability to sense and trip out on overloads. The customer then discovers that they have 30 or 40 amps of load on a 20 amp circuit.
Also, some loads such a arc welders, motors that are deliberately overloade on a cyclic basis, and similar loads can spot weld contacts and turn a circuit breaker of motor controller into something that isn't.
Some problems that I have had ( not mentioned above or not quite in detail ):
1. A 50 amp 2-pole Pushmatic circuit breaker tripping withnonly 25 amps of load. Cleaning the wire strands and busbar connections and treating with Ilsco Deox? fixed the problem.
2. Buildup if silver sulfide over time will cause the contacts to become insulated ( open circuit ). Opening and closing the circuit breaker with the load connected will generate enough arcing to convert the silver sulfide into silver oxide, which is an electrical conductor.
3. Exercising a Federal Pacific circuit breaker such as when changing a broken receptacle will restore ability to sense and trip out on overloads. The customer then discovers that they have 30 or 40 amps of load on a 20 amp circuit.
Also, some loads such a arc welders, motors that are deliberately overloade on a cyclic basis, and similar loads can spot weld contacts and turn a circuit breaker of motor controller into something that isn't.
brian john
Senior Member
- Location
- Leesburg, VA
Re: Breakers
1. Then the circuit breaker was not tripping for the load but a combination of load and bad connection, this is a thermal magnetic device and any thermal condition or combination of the load, high resistance connection or high ambient can cause a trip of this device. This is often referred to as nusiance tripping , I feel this is a device telling you hey I need repair/service not a nusiance but doing what it was designed to do.
2. All devices can and will oxide or experience some detriation of the contact service area over time (depending on the environment), larger devices require regular service measuring the contact resistance and cleaning PROPERLY. NOT SAND PAPER as many electricians utilize. We have found through testing that opening andd closing circuit breakers can lower the contact resistance, though I have never followed up on this field fix to see if it addresses the problem in the long term.
3. Circuit breakers in general should be exercised, older circuit breakers utilized petroleum based lubricates, this will solidify and affect the tripping ability. Dirt dust moisture, operating at maximum load will affect all distribution equipment and should be addressed in an approved manner to minimize these deterating elements and the problem that can arise from them over time.
1. Then the circuit breaker was not tripping for the load but a combination of load and bad connection, this is a thermal magnetic device and any thermal condition or combination of the load, high resistance connection or high ambient can cause a trip of this device. This is often referred to as nusiance tripping , I feel this is a device telling you hey I need repair/service not a nusiance but doing what it was designed to do.
2. All devices can and will oxide or experience some detriation of the contact service area over time (depending on the environment), larger devices require regular service measuring the contact resistance and cleaning PROPERLY. NOT SAND PAPER as many electricians utilize. We have found through testing that opening andd closing circuit breakers can lower the contact resistance, though I have never followed up on this field fix to see if it addresses the problem in the long term.
3. Circuit breakers in general should be exercised, older circuit breakers utilized petroleum based lubricates, this will solidify and affect the tripping ability. Dirt dust moisture, operating at maximum load will affect all distribution equipment and should be addressed in an approved manner to minimize these deterating elements and the problem that can arise from them over time.
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