Fault currents motor contribution

Status
Not open for further replies.
I see no issue with you rejecting the plans based on incomplete information and requiring a revised set of plans that show the required SSCR and AIC ratings.

But even that could be an issue where the administrative rules do not require the submission of plans with the permit application.

Well yea we have admin rule to submit plans alright PE stamp sign and seal with permit application but don’t see no admin rule saying to provide SSCR and AIC rating. Admin rule says electrical plans comply with NEC 2017 and local chapter 17 which does not have no rule to submit SSCR and AIC rating.

So thats the problem how does one solve this if they don’t provide AIC rating at all and no SSCR panel schedules, meter stacks schedule?

It has to be approved conditionally with note all AIC ratings comply with short circuit study with motor contribution?
 
again, what is wrong with putting a note "AIC to be verified in field"? The inspectors look at all the write ups on the plans, thats what they do.
Most plans I see are given that direction, mostly put burden on EC via a single sentence while the larger firms call for a study….via EC contract…and submit when completed.

Liability has been washed away.
 
Most plans I see are given that direction, mostly put burden on EC via a single sentence while the larger firms call for a study….via EC contract…and submit when completed.

Liability has been washed away.

Liability has not been washed away. If the contractor installs overdutied equipment it’s on them to rip it out and install equipment that is adequate when it fails inspection. The study is a means to approve equipment being proposed for the project. If the study is not done, the contractor is simply taking a risk. The requirement to have adequate equipment is still there, the means of determining if said equipment is adequate is what is not specified.
 
I see no issue with you rejecting the plans based on incomplete information and requiring a revised set of plans that show the required SSCR and AIC ratings.

But even that could be an issue where the administrative rules do not require the submission of plans with the permit application.

Good luck. Speaking from the other side of the table it’s just not that easy. You will not get that much detail on the equipment often until it is received and inspected. It is unrealistic to expect to have say make/model and rating if everything. With process equipment even if you did often motors have to be changed a little.
 
Liability has not been washed away. If the contractor installs overdutied equipment it’s on them to rip it out and install equipment that is adequate when it fails inspection. The study is a means to approve equipment being proposed for the project. If the study is not done, the contractor is simply taking a risk. The requirement to have adequate equipment is still there, the means of determining if said equipment is adequate is what is not specified.
I was implying the designer of plans has removed liability, not the EC…or whoever that “verified in field” party is.
 
Explosion due to overduty equipment can cause high rise to fall you know. Worse someone getting hurt.

An explosion resulting from overdutied equipment will not cause the building to fall. However, it may cause a fire, extensive damage or injure nearby personnel.
 
All electrical room walls are 2 hours rated.

I’m not down playing the severity of overdutied equipment, but it might be a stretch to say the building would collapse. I think several layers of engineering and administrative controls would have to fail to get to that point. In a short-circuit analysis, “prospective” bolted fault currents are calculated under worst case conditions; i.e. maximum fault generation from the utility, all motors running simultaneously, worst-case switching configuration, fault occurring at the zero-voltage-crossing, etc. The likely hood for a fault to occur and be near the calculated fault duty and come apart when interrupting a fault is slim, especially when devices have additional safety factors built-in. A funny trick manufacturers pull is a lot of equipment on the market is already rated 65-kA, but the manufacturer provides labels with lower ratings and gets you to pay more if you want the 65-kA label.
 
What about plan reviewers liability? Gone or not?

There’s no such thing as no liability. Everyone plays a role in this process. Even if you didn’t have any legal liability, it doesn’t mean you wouldn’t have any other kind of responsibility. You should talk to a lawyer, but even then I’m sure it’s going to be another grey area.
 
I’m not down playing the severity of overdutied equipment, but it might be a stretch to say the building would collapse. I think several layers of engineering and administrative controls would have to fail to get to that point. In a short-circuit analysis, “prospective” bolted fault currents are calculated under worst case conditions; i.e. maximum fault generation from the utility, all motors running simultaneously, worst-case switching configuration, fault occurring at the zero-voltage-crossing, etc. The likely hood for a fault to occur and be near the calculated fault duty and come apart when interrupting a fault is slim, especially when devices have additional safety factors built-in. A funny trick manufacturers pull is a lot of equipment on the market is already rated 65-kA, but the manufacturer provides labels with lower ratings and gets you to pay more if you want the 65-kA label.
There is another thread going on right now on this topic:


It has interesting how AIC has become such a "critical" characteristic in the last few decades despite the chances of problems being very small and probably very few actual cases.
 
Don't worry... if you end up in court just tell the judge you got your advice here....
Judges need a good laugh occasionally.
 
Don't worry... if you end up in court just tell the judge you got your advice here....
Judges need a good laugh occasionally.

Joke? Seriously. Everyone is off the hook designer and EC but the reviewers? Judge might asks why you didnt check study? If its not provided why didnt I ask one.
 
There is another thread going on right now on this topic:


It has interesting how AIC has become such a "critical" characteristic in the last few decades despite the chances of problems being very small and probably very few actual cases.

Like most incident driven code rules, extensive damage resulting from overdutied equipment at one point was a serious recurring issue that eventually became less and less prevalent as the industry and equipment safety standards evolved.
 
EE punts to plan review, to EC, to EI.
What documentation, calculations per 110.24A are you providing the EI ?

Do you think the EI will know how to interpret a study or any of the calculations presented in it? The EI only needs to know that it was done and/or get certification from the EE that the installation complies with 110.9, 110.10, and 110.24(A). It’s really that simple. If the EI has additional questions, or wants to spot check the equipment ratings fine.
 
Status
Not open for further replies.
Top