Fault currents motor contribution

[hhsting]

My opinion remains that the permitting process is totally unrelated to the installation rules in the NEC. The permitting process is covered by the administrative rules that were, or should have been, adopted, when the code was adopted. These administrative rules should specify all of the documentation that is require to obtain a permit.

The code itself, does not cover the issuing of permits or even the inspection of the work. It only give the installation rules that the AHJ can use for the inspection process.

So we often require grounding electrode system detail main bonding jumper, grounding electrodes, grounding electrode sizing all that in detail for new service equipment. If its not in documentation on website of AHJ then we cannot request it? We have documentation on AHJ for main service grounding and bonding to be provided with drawings. So Issue of short circuit study is Kind of like that a documentation on AHJ website with projects? Am I reading correctly or not?

 

[augie47]

So lets say I request short circuit and motor contribution calculation and engineer provides calculated AIC rating at location X on riser without showing calculation steps and at location X has panelboard interrupt rating Greater than the calculated AIC.

Your saying that if I question the AIC at location X and steps he used if its correct or incorrect then I am liable? What if I dont question the AIC rating steps used to arrive to be correct or incorrect wont department and I be liable then?

A good question for your department's legal authority.
IMO, if you ask a design engineer to confirm his numbers that's all that's necessary. That stamp they use carries a lot of weight (and responsibility)

 

[hhsting]

A good question for your department's legal authority.
IMO, if you ask a design engineer to confirm his numbers that's all that's necessary. That stamp they use carries a lot of weight (and responsibility)

Confirm as in confirm with designer what shown on riser are the calculated worse case short circuit with motor contribution fault currents in compliance with 110.10 and 110.9?

 

[MyCleveland]

My opinion remains that the permitting process is totally unrelated to the installation rules in the NEC. The permitting process is covered by the administrative rules that were, or should have been, adopted, when the code was adopted. These administrative rules should specify all of the documentation that is require to obtain a permit.

The code itself, does not cover the issuing of permits or even the inspection of the work. It only give the installation rules that the AHJ can use for the inspection process.

Thanks Don

 

[augie47]

To me all this is an inner-departmental question. What does your supervisor expect ?
In the agencies where I worked , the engineered drawings were the "bible". Our plans review folks would assure all areas had been addressd and if they or one of the inspectors had questions, the plans were marked acordingly and the design engineer was notifed.
During the inspection process, Code issues are brought to the attention of the contractor and the engineers are brought in when necessary. They are normally way higher on the food chain than plans review personnel.

 

[jim dungar]

Your saying that if I question the AIC at location X and steps he used if its correct or incorrect then I am liable? What if I dont question the AIC rating steps used to arrive to be correct or incorrect wont department and I be liable then?

Of course you are allowed to question the data provided to you.
However, unless your governmental agency has rules as to which specific methods must be employed it is unlikely you are allowed to question the methodology employed to create that data.

Have you had specific training in electrical design and calculations? Are you required to maintain some type of certification or take continuing education similar to those that are providing the plans to you?

 

[hhsting]

Of course you are allowed to question the data provided to you.
However, unless your governmental agency has rules as to which specific methods must be employed it is unlikely you are allowed to question the methodology employed to create that data.

Have you had specific training in electrical design and calculations? Are you required to maintain some type of certification or take continuing education similar to those that are providing the plans to you?

Our government agency does Not have any rules as to which specific method to use.

I am P.E. computer, power but I still cannot tell which method to use to the designer. Government agency has no rule which method to use

 

[petersonra]

Wrong. If the utility says the AFC is 25-kA, but the design documents specify equipment rated 65-kA. No calculation necessary.

Besides it was already stated the power system study is typically done after the work has started. I don’t think you have any reason to be demanding fault calculations unless it’s standard protocol for your plan submittal process.

I have yet to see anybody specify control panels to have anything other than 65KA short circuit current rating. It seems to be the default if they specify anything. Most times I don't see them specify anything but if they do I've seen nothing other than 65 KA. And that makes a lot of sense because there are very few places you would install an industrial control panel where the short circuit current available would exceed 65 kA.

 

[hhsting]

To me it would make much more sense to provide fault current study with plan conservative one for complex projects like high rise, hospitals and be done with computer software with PE sign and seal no hand written calcs so that reviewers can verify that what is installed comply with installation rules provided in 110.9 and 110.10

So all of you are saying fault current study is required for sure to verify the install comply per NEC 2017 section 110.9 and 110.10 but NEC 2017 section 110.9 and 110.10 does not state that fault current study be provided with plans, or if not with plans then to inspecting authority meaning to inspectors if not to reviewers

In our department permitting agency their is no rule provided to submit fault current calculation study with plans, which method to use nor their is rule to provide fault current study to inspectors.

In our department permitting agency Inspectors do Not verify AIC ratings downstream of main service equipment. Of course main service equipment Available fault currents are verified because I am guessing NEC 2017 section 110.24(A)

This creates problems. Now problems:

a. lets say fault current study is done then our inspecting authority would not verify it downstream of main service equipment. Reviewers cannot ask for it during review time.
So then who is responsible if something goes wrong checking if fault current study is provided and how is 110.10 and 110.9 rules be enforced or checked?


b. Lets say fault current study is Not done reviewers cannot ask for the study during review time. Whose to see if the required fault current study is done? So then who is responsible if something goes wrong checking if fault current study is provided and how is 110.10 and 110.9 rules be enforced or checked?

c. Is their Anywhere in NEC 2017 that requires fault current study be provided to AHJ, reviewers, inspectors, inspecting authority, to verify the installation rules of 110.10 and 110.9 are complied?

 

[don_resqcapt19]

So we often require grounding electrode system detail main bonding jumper, grounding electrodes, grounding electrode sizing all that in detail for new service equipment. If its not in documentation on website of AHJ then we cannot request it? We have documentation on AHJ for main service grounding and bonding to be provided with drawings. So Issue of short circuit study is Kind of like that a documentation on AHJ website with projects? Am I reading correctly or not?

You only get the documentation that your administrative rules require the permit requester to give you.
You can request additional documentation, but the question whether you can deny the permit if they don't supply the requested additional documentation becomes a legal question.

The code itself does not require any thing to be provided as part of getting a permit. That whole process is outside of the scope of the NEC.
There are a few sections in the code that do require some documentation be made available to the AHJ, but the short circuit study is not one of those.

 

[xptpcrewx]

To me it would make much more sense to provide fault current study with plan conservative one for complex projects like high rise, hospitals and be done with computer software with PE sign and seal no hand written calcs so that reviewers can verify that what is installed comply with installation rules provided in 110.9 and 110.10

So all of you are saying fault current study is required for sure to verify the install comply per NEC 2017 section 110.9 and 110.10 but NEC 2017 section 110.9 and 110.10 does not state that fault current study be provided with plans, or if not with plans then to inspecting authority meaning to inspectors if not to reviewers

In our department permitting agency their is no rule provided to submit fault current calculation study with plans, which method to use nor their is rule to provide fault current study to inspectors.

In our department permitting agency Inspectors do Not verify AIC ratings downstream of main service equipment. Of course main service equipment Available fault currents are verified because I am guessing NEC 2017 section 110.24(A)

This creates problems. Now problems:

a. lets say fault current study is done then our inspecting authority would not verify it downstream of main service equipment. Reviewers cannot ask for it during review time.
So then who is responsible if something goes wrong checking if fault current study is provided and how is 110.10 and 110.9 rules be enforced or checked?


b. Lets say fault current study is Not done reviewers cannot ask for the study during review time. Whose to see if the required fault current study is done? So then who is responsible if something goes wrong checking if fault current study is provided and how is 110.10 and 110.9 rules be enforced or checked?

c. Is their Anywhere in NEC 2017 that requires fault current study be provided to AHJ, reviewers, inspectors, inspecting authority, to verify the installation rules of 110.10 and 110.9 are complied?

First, the Engineer of Record is responsible for his design and owns the liability for any errors/omissions in his/her work. It’s their legal duty to ensure that all elements of the submittal to the building official or public authority are compatible, coordinated and provide a logical and comprehensive document.

Second, the building official is charged with the administration and enforcement of building codes. Note: you are not the building official, you are authorized staff directed to enforce provisions of “adopted codes and ordinances” by regulating and controlling the design, construction, use, location, energy conservation, and maintenance of all buildings, structures and other improvements within the jurisdiction.

Third, Let’s not forget, “This Code is not intended as a design specification or an instruction manual for untrained persons.”

At the end of the day, if there was an accident because of overdutied equipment (resulting form a design error), the Engineer of Record would be implicated. His lawyer could always argue at the time of plan submission, no such administrative procedure existed to perform a fault study, and the plan reviewer even approved the plans.

If you demand additional information without having a code/ordinance to fall back on, and then approve the plans once documentation is provided, your liability in the matter has just increased and your qualifications to evaluate such information could be called into question (several liability).

If you reject plans, you must have references to codes/ordinances and provide sound technical facts as to where the deficiency lies. If they are not legitimate or legal reasons for rejecting a design, expect to get pushback.

Also, not sure why some of you think short-circuit “calculations” are required in the NEC. There is no such language.

 

[MyCleveland]

Does not 110.24A state calculations required….
How can AFC current labels be provided for main, hvac, industrial control panels, elevator, etc, etc, if no calls are required ?

110.24A seems to comport with Don’s argument that this get addressed in the field, apparently. If you agree that inspector does include plan reviewer.

Can we at least agree this is GRAY…when it should be crystal clear.

 

[hhsting]

You only get the documentation that your administrative rules require the permit requester to give you.
You can request additional documentation, but the question whether you can deny the permit if they don't supply the requested additional documentation becomes a legal question.

The code itself does not require any thing to be provided as part of getting a permit. That whole process is outside of the scope of the NEC.
There are a few sections in the code that do require some documentation be made available to the AHJ, but the short circuit study is not one of those.

And these admin rules are usually on AHJ website stating what documents are require for plan review?

 

[hhsting]

Does not 110.24A state calculations required….
How can AFC current labels be provided for main, hvac, industrial control panels, elevator, etc, etc, if no calls are required ?

110.24A seems to comport with Don’s argument that this get addressed in the field, apparently. If you agree that inspector does include plan reviewer.

Can we at least agree this is GRAY…when it should be crystal clear.

2017 Code Language:

110.24 Available Fault Current.

(A) Field Marking. Service equipment at other than dwelling units shall be legibly marked in the field with the maximum available fault current. The field marking(s) shall include the date the fault-current calculation was performed and be of sufficient durability to withstand the environment involved. The calculation shall be documented and made available to those authorized to design, install, inspect, maintain, or operate the system.



Seems to me that IS required and says to provide to person inspecting. Fault currents at the switchboard service also depend upon down stream motor contribution Don.

Just based on that I can request fault current calculation with motor study


See link below for explanation:

110.24 Available Fault Current.

There are many programs to determine the available fault current at a given location but most just provide the final AFC value, not the math to back it up. What would be the available fault current at the service if the service entrance conductors are only 80 feet?

www.electricallicenserenewal.com

 

[xptpcrewx]

Does not 110.24A state calculations required….
How can AFC current labels be provided for main, hvac, industrial control panels, elevator, etc, etc, if no calls are required ?

110.24A seems to comport with Don’s argument that this get addressed in the field, apparently. If you agree that inspector does include plan reviewer.

Can we at least agree this is GRAY…when it should be crystal clear.

110.24(A) is with reference to the service equipment only. This information is provided by the utility company. No calculation necessary unless you are trying to demonstrate a lower fault duty resulting from cable impedance when selecting lower rated devices, or if the utility doesn’t provide data (to which an infinite bus approach is employed). One purpose of this rule is for compliance with NFPA 70E. See informational notes.

If there are sufficient motor contributions then that would be the only good reason to demand a calculation. But this would only be for the service equipment.

 

[hhsting]

110.24(A) is with reference to the service equipment only. This information is provided from the utility company. No calculation necessary unless you are trying to demonstrate a lower fault duty resulting from cable impedance when selecting lower rated devices. See informational notes. The main purpose of this rule is for compliance with NFPA 70E.

Agree the part that 110.24(A) is for service equipment only at other than dwelling units. Well the high rise I have is combination their is one assembly area A commercial, one B business and rest are dwelling units. Service equipment that feeds A and B occupancy group require what 110.24(A) says but then that service equipment also serves dwelling units so would 110.24(A) apply or not?

Now Where is the language that utility fault currents is what is requested in 110.24(A)? It says available fault currents calculated.

Lets say utility fault currents are provided and they are X.

Do you agree or disagree that motor contribution fault currents Y would also add to utility fault currents to the service equipment so now available fault currents at service equipment would be X+Y so then you agree or disagree that fault current calculation is needed for service with motor contribution per NEC 2017 section 110.24(A)?

 

[hhsting]

110.24(A) is with reference to the service equipment only. This information is provided by the utility company. No calculation necessary unless you are trying to demonstrate a lower fault duty resulting from cable impedance when selecting lower rated devices, or if the utility doesn’t provide data (to which an infinite bus approach is employed). One purpose of this rule is for compliance with NFPA 70E. See informational notes.

If there are sufficient motor contributions then that would be the only good reason to demand a calculation. But this would only be for the service equipment.

Good god what has NEC 2017 section 110.24(A) done. Not only motor contributions but ATS too at service equipment. ATS if its make before break etc depending upon configuration you now either open closed transition then it may also contribute from generator as well as utility then what? You don’t take that into account at service equipment fault currents 110.24(A)?

Is plan reviewers actually suppose to take math behind this too and all that for 110.24(A). NEC 2017?

 

[MyCleveland]

110.24(A) is with reference to the service equipment only. This information is provided by the utility company. No calculation necessary unless you are trying to demonstrate a lower fault duty resulting from cable impedance when selecting lower rated devices, or if the utility doesn’t provide data (to which an infinite bus approach is employed). One purpose of this rule is for compliance with NFPA 70E. See informational notes.

If there are sufficient motor contributions then that would be the only good reason to demand a calculation. But this would only be for the service equipment.

As much as I disagree, I can see your logic, but how then do you provide labels on items downstream mentioned with no calc, or are we back to it’s all done after the permit process.

 

[hhsting]

First, the Engineer of Record is responsible for his design and owns the liability for any errors/omissions in his/her work. It’s their legal duty to ensure that all elements of the submittal to the building official or public authority are compatible, coordinated and provide a logical and comprehensive document.

Second, the building official is charged with the administration and enforcement of building codes. Note: you are not the building official, you are authorized staff directed to enforce provisions of “adopted codes and ordinances” by regulating and controlling the design, construction, use, location, energy conservation, and maintenance of all buildings, structures and other improvements within the jurisdiction.

Third, Let’s not forget, “This Code is not intended as a design specification or an instruction manual for untrained persons.”

At the end of the day, if there was an accident because of overdutied equipment (resulting form a design error), the Engineer of Record would be implicated. His lawyer could always argue at the time of plan submission, no such administrative procedure existed to perform a fault study, and the plan reviewer even approved the plans.

If you demand additional information without having a code/ordinance to fall back on, and then approve the plans once documentation is provided, your liability in the matter has just increased and your qualifications to evaluate such information could be called into question (several liability).

If you reject plans, you must have references to codes/ordinances and provide sound technical facts as to where the deficiency lies. If they are not legitimate or legal reasons for rejecting a design, expect to get pushback.

Also, not sure why some of you think short-circuit “calculations” are required in the NEC. There is no such language.

If the lawyer argues at the time of plan submission, no such administrative procedure existed to perform a fault study, and the plan reviewer even approved the plans then Plan reviewer would also be liable no?

 

[MyCleveland]

it remains my opinion that where the inspection authority wants to see this type of information, they need to have something in there permit process that requires such information to be submitted will the plans and specs.

Don
Going through Ohio Building Code, 2017.

Chapter 1 Administration
106.1.1 Information on construction documents
List of 17 items…number 17, Additional information required by the building official to determine compliance. Seems open ended where a SCC study could be requested.