Nuisance tripping of 80 amp CB?
- Thread starter Mustangx3
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wirenut1980
Senior Member
- Location
- Plainfield, IN
Re: Nuisance tripping of 80 amp CB?
Will the circuit be protected by the 100 Amp circuit breaker? If yes, then why not give it a shot? I do think there needs to be some investigation into the other "happenings" going on with your building power.
Re: Nuisance tripping of 80 amp CB?
Not sure if just putting a 100 amp CB on 6 AWG wire is the smart thing to do. (sort of if the fuse blows put in a bigger fuse). Oh, anyone know how to find out what the actual "over amp" time is for a Siemens ED63B080 breaker is? One engineer is REALLY interested in this info. a.k.a. "how long does the over amp condition need to last before the breaker trips". We haven't been able to find this info on Siemens cut-sheet for the CB.
Not sure if just putting a 100 amp CB on 6 AWG wire is the smart thing to do. (sort of if the fuse blows put in a bigger fuse). Oh, anyone know how to find out what the actual "over amp" time is for a Siemens ED63B080 breaker is? One engineer is REALLY interested in this info. a.k.a. "how long does the over amp condition need to last before the breaker trips". We haven't been able to find this info on Siemens cut-sheet for the CB.
tony_psuee
Senior Member
- Location
- PA/MD
Re: Nuisance tripping of 80 amp CB?
Mustang,
The trip time is dependent upon the over current event. Could be milliseconds to hours. There should be a trip curve that will give you an idea of the time based on the current.
Tony
Mustang,
The trip time is dependent upon the over current event. Could be milliseconds to hours. There should be a trip curve that will give you an idea of the time based on the current.
Tony
- Location
- Massachusetts
Re: Nuisance tripping of 80 amp CB?
Mustang am I correct that you have a 3 phase 40 HP motor running 460 volts?
Table 430.150 shows that size motor as a 52 amp load.
The 80 amp breaker may be (probably is) too small for this motor.
430.52 allows a breaker 250% of the load current and you can move up to the next standard size.
52 x 2.5 = 130 amps.
The next standard size is a 150 amp.
You could safely, code compliantly move up to a 125 amp or a 150 amp breaker leaving the 6 AWG in place and still not worry about 'smoke'.
The feeder breaker has nothing to do with overload protection of the conductors.
By the way, the 8 AWGs you said where originally installed where not code compliant for a 52 amp motor.
[ June 15, 2005, 04:12 PM: Message edited by: iwire ]
Mustang am I correct that you have a 3 phase 40 HP motor running 460 volts?
Table 430.150 shows that size motor as a 52 amp load.
The 80 amp breaker may be (probably is) too small for this motor.
430.52 allows a breaker 250% of the load current and you can move up to the next standard size.
52 x 2.5 = 130 amps.
The next standard size is a 150 amp.
You could safely, code compliantly move up to a 125 amp or a 150 amp breaker leaving the 6 AWG in place and still not worry about 'smoke'.
The feeder breaker has nothing to do with overload protection of the conductors.
By the way, the 8 AWGs you said where originally installed where not code compliant for a 52 amp motor.
[ June 15, 2005, 04:12 PM: Message edited by: iwire ]
Re: Nuisance tripping of 80 amp CB?
Hey, thanks for the info. We can always reference the tables to help with any concerns. We never did get a trip curve chart with the CB so we're still in the dark on that one. Always good to know we won't let the smoke out, it's always too hard to push it back into the wires!
Hey, thanks for the info. We can always reference the tables to help with any concerns. We never did get a trip curve chart with the CB so we're still in the dark on that one. Always good to know we won't let the smoke out, it's always too hard to push it back into the wires!
Re: Nuisance tripping of 80 amp CB?
I'll let all you guys know when the engineers decide to really do (100, 125 or 150 amp) and IF the CB trips again. Hope it's been entertaining so far.
Don't forget now... this has been running fine for 12 years (with the old CB's, 8 AWG wire, etc.) till they did all the electrical work in the building back in Feb. However, the voltage sags (to 330 or so) still are not going to be addressed. We'll see if larger breakers will "hold".
I'll let all you guys know when the engineers decide to really do (100, 125 or 150 amp) and IF the CB trips again. Hope it's been entertaining so far.
Don't forget now... this has been running fine for 12 years (with the old CB's, 8 AWG wire, etc.) till they did all the electrical work in the building back in Feb. However, the voltage sags (to 330 or so) still are not going to be addressed. We'll see if larger breakers will "hold".
- Location
- Massachusetts
Re: Nuisance tripping of 80 amp CB?
[ June 17, 2005, 02:58 PM: Message edited by: iwire ]
I did not forget and it is a curiosity why it started acting up now after all this time.
[ June 17, 2005, 02:58 PM: Message edited by: iwire ]
Re: Nuisance tripping of 80 amp CB?
Oh, the breakers have been changed out with new ones (80 amp direct replacements) already. The contactors have also been upgraded as has the wire itself (8awg to 6awg). And the motor was changed too. About the only thing we haven't changed is the hydraulic oil! That may be next
Oh, the breakers have been changed out with new ones (80 amp direct replacements) already. The contactors have also been upgraded as has the wire itself (8awg to 6awg). And the motor was changed too. About the only thing we haven't changed is the hydraulic oil! That may be next
Re: Nuisance tripping of 80 amp CB?
We got smoke! OK, today the cooling tower condensor thing-a-ma-bob up on the roof (which comes off the same panel as our elevator) went up in smoke from a short "somewhere" in the system. While this is being repaired the engineers have decided that the "problem" is now the timing between start/run contactors (again, they have been set at 1.4 seconds for 12 years and worked fine till Feb.). They figure that the new value should be 1.8 seconds between wye/delta transition (this is unfortunantly an open transition type but has worked for 12 years).
We got smoke! OK, today the cooling tower condensor thing-a-ma-bob up on the roof (which comes off the same panel as our elevator) went up in smoke from a short "somewhere" in the system. While this is being repaired the engineers have decided that the "problem" is now the timing between start/run contactors (again, they have been set at 1.4 seconds for 12 years and worked fine till Feb.). They figure that the new value should be 1.8 seconds between wye/delta transition (this is unfortunantly an open transition type but has worked for 12 years).
Re: Nuisance tripping of 80 amp CB?
Keep those can's of smoke handy Mustang. Looks like a lot of your equipment is about to get "tired" of the voltage sag problem. Sometimes it takes about 4 different things to go bad before the infamous "THEM" realize there is a common problem.
Keep those can's of smoke handy Mustang. Looks like a lot of your equipment is about to get "tired" of the voltage sag problem. Sometimes it takes about 4 different things to go bad before the infamous "THEM" realize there is a common problem.
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
Re: Nuisance tripping of 80 amp CB?
keep the info coming mustang!
Thanks.
keep the info coming mustang!
Thanks.
Re: Nuisance tripping of 80 amp CB?
Engineers have decided that maybe going from 80 amp CB's to 90's or 100's might be too small so they're opting for the 125 amp CB's... at least for today. The 125's should be installed next week. Oh, while the tower was down for repairs, the elevator magically worked flawlessly. Once they put the towers back online the elevator tripped the 80 amp CB on it's very first try to move. What's with that?
Engineers have decided that maybe going from 80 amp CB's to 90's or 100's might be too small so they're opting for the 125 amp CB's... at least for today. The 125's should be installed next week. Oh, while the tower was down for repairs, the elevator magically worked flawlessly. Once they put the towers back online the elevator tripped the 80 amp CB on it's very first try to move. What's with that?
wirenut1980
Senior Member
- Location
- Plainfield, IN
Re: Nuisance tripping of 80 amp CB?
Mustang, sounds like you found the culprit. Have everyone focus their intellectual firepower on that cooling tower. One question is do the voltage sags still occur when the cooling tower is taken offline?
Mustang, sounds like you found the culprit. Have everyone focus their intellectual firepower
on that cooling tower. One question is do the voltage sags still occur when the cooling tower is taken offline?Re: Nuisance tripping of 80 amp CB?
Not much firepower there...
The sags happen randomly over several hours but the tower was only down for about a day. I didn't record any sags below 440 (vice the 330) during that time but I would guess the sags are still upstream from there (my opinion) and that we would have seen the 330 vac sags if given enough time with the tower down. Maybe that unit didn't like the sags either. Now there is a bunch of people who are "NEC" experts fighting over the 125 amp breaker on 6 awg wire. I showed them the previously mentioned tables but to no avail...
Not much firepower there...
The sags happen randomly over several hours but the tower was only down for about a day. I didn't record any sags below 440 (vice the 330) during that time but I would guess the sags are still upstream from there (my opinion) and that we would have seen the 330 vac sags if given enough time with the tower down. Maybe that unit didn't like the sags either. Now there is a bunch of people who are "NEC" experts fighting over the 125 amp breaker on 6 awg wire. I showed them the previously mentioned tables but to no avail...
Re: Nuisance tripping of 80 amp CB?
I would have to agree with wirenut. It could very well be a chaffed wire inside a conduit. It may be worth the time to take a look in any condulet fittings if there are any in that line. These things can drive you absolutely nuts. How long has your cooling tower been there?
I would have to agree with wirenut. It could very well be a chaffed wire inside a conduit. It may be worth the time to take a look in any condulet fittings if there are any in that line. These things can drive you absolutely nuts. How long has your cooling tower been there?
charlie tuna
Senior Member
- Location
- Florida
Re: Nuisance tripping of 80 amp CB?
musty,
how does the power get to this panel??? is it by bus duct? sounds like there are now three different issues with trips?? a insulation break on a wire inside a raceway doesn't last long -- it welds itself to the raceway!
musty,
how does the power get to this panel??? is it by bus duct? sounds like there are now three different issues with trips?? a insulation break on a wire inside a raceway doesn't last long -- it welds itself to the raceway!
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