bphgravity
Senior Member
- Location
- Florida
Anyone know what the little screw is for underneath the sticker near the lug screw on the QO style breakers?
Square D Breaker Screw
- Thread starter bphgravity
- Start date
- Status
bphgravity
Senior Member
- Location
- Florida
Re: Square D Breaker Screw
No ideas? I was informed that it provided an adjustment of some kind, however the Square D bulletin doesn't make a reference to it at all.
No ideas? I was informed that it provided an adjustment of some kind, however the Square D bulletin doesn't make a reference to it at all.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: Square D Breaker Screw
The screw behind the label is the calibration screw.
The screw behind the label is the calibration screw.
bphgravity
Senior Member
- Location
- Florida
Re: Square D Breaker Screw
What calibration? trip time, fault setting, etc...
What calibration? trip time, fault setting, etc...
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: Square D Breaker Screw
The screw is a factory adjustment for the thermal trip element (the magnetic trip is fixed relative to the thermal).
The screw is a factory adjustment for the thermal trip element (the magnetic trip is fixed relative to the thermal).
bphgravity
Senior Member
- Location
- Florida
Re: Square D Breaker Screw
Thanks for the info Jim. So this is definetly something that should not be field adjusted.
Thanks for the info Jim. So this is definetly something that should not be field adjusted.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: Square D Breaker Screw
Definitely do not TAMPER WITH this screw.
Definitely do not TAMPER WITH this screw.
sandsnow
Senior Member
- Location
- Southern California
Re: Square D Breaker Screw
Reference 240.82
It would seem the sticker is there for compliance with this section.
I will have to look at a QO next chance I get.
Reference 240.82
It would seem the sticker is there for compliance with this section.
I will have to look at a QO next chance I get.
bphgravity
Senior Member
- Location
- Florida
Re: Square D Breaker Screw
10 years with my nose stuck in this code book, and I don't ever recall ever reading this section!
I personally never knew the screw was there. I have also found this same arrangement on an older ITE breaker. It also has a small screw located under a sticker.
I just didn't realize an inverse-time trip would have post manufacturing adjustments that can techincally be made in the field.
10 years with my nose stuck in this code book, and I don't ever recall ever reading this section!
I personally never knew the screw was there. I have also found this same arrangement on an older ITE breaker. It also has a small screw located under a sticker.
I just didn't realize an inverse-time trip would have post manufacturing adjustments that can techincally be made in the field.
sandsnow
Senior Member
- Location
- Southern California
Re: Square D Breaker Screw
How did you happen to come across the screw?
bphgravity
Senior Member
- Location
- Florida
Re: Square D Breaker Screw
I was at a meeting which happened to have a few local contractors and other persons in my building department. One of the contractors mentioned that he was having an unusual problem with a circuit that kept tripping for apparently no reason. He eventually exchanged the QO breaker casuing the problem and the new one has never tripped since.
Overhearing the conversation, one of the other contractors jokingly made the comment that he really only needed to give it the "QO tweak". Not knowing what he was talking about, he proceeded to describe the screw and its location. (he assured us that he was only joking) Sure enough, every QO has one.
I looked up every Square D bulletin and literature I could find with no mention of the screw or what it is for, hence the topic.
I was at a meeting which happened to have a few local contractors and other persons in my building department. One of the contractors mentioned that he was having an unusual problem with a circuit that kept tripping for apparently no reason. He eventually exchanged the QO breaker casuing the problem and the new one has never tripped since.
Overhearing the conversation, one of the other contractors jokingly made the comment that he really only needed to give it the "QO tweak". Not knowing what he was talking about, he proceeded to describe the screw and its location. (he assured us that he was only joking) Sure enough, every QO has one.
I looked up every Square D bulletin and literature I could find with no mention of the screw or what it is for, hence the topic.
Re: Square D Breaker Screw
I always promote the taking appart of a junk breaker so you can see the inside and try to identify the parts.
That screw being referred to moves the bimetalic thermal element which if adjusted at the factory during the themal calibration process. However it is common that the magnetic is not calibrated because the pickup setting is in the design of the assembly. Because magnetic trip values are not as critical as the thermal are the magnetic pickups will be most likely the same withing a given group of breakers such as 15-30a, 40-70a, and 80-100a etc.
One would have to look at the trip curves to identify this.
I always promote the taking appart of a junk breaker so you can see the inside and try to identify the parts.
That screw being referred to moves the bimetalic thermal element which if adjusted at the factory during the themal calibration process. However it is common that the magnetic is not calibrated because the pickup setting is in the design of the assembly. Because magnetic trip values are not as critical as the thermal are the magnetic pickups will be most likely the same withing a given group of breakers such as 15-30a, 40-70a, and 80-100a etc.
One would have to look at the trip curves to identify this.
zog
Senior Member
- Location
- Charlotte, NC
Re: Square D Breaker Screw
You can call 1-800-squared for tech support, oh wait that is now a phone sex line, the new number is 1-888-squared
[ January 12, 2006, 08:55 PM: Message edited by: zog ]
You can call 1-800-squared for tech support, oh wait that is now a phone sex line, the new number is 1-888-squared
[ January 12, 2006, 08:55 PM: Message edited by: zog ]
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