SCCR For Elevator

[Strathead]

We are an MEP firm and we always review mechanical submittals for electrical compliance. Mis-coordination is the most common form of engineering errors and omissions.

It would be a pleasure to work with a firm that does that. I refer you to the entirety of this post. In a nut shell. The plans specified HVAC units that were ordered without substitute. The Electrical was installed with equipment locations as drawn but the wire was substituted to Aluminum, so probably minor resistance difference. The short circuit study was commissioned by us, but was not performed until the equipment was already ordered and the cut sheets were given to our PE for his study. The results are as above. WE are "solving" this (at their expense) because the Engineer will not offer any solution OR take any responsibility.

 

[Strathead]

A part of this discussion that nobody has talked about is bidding for Engineering commissions. The follow up studies are never part of the RFP and if we include it in our proposal, we won't be competitive.

I have, on occasion, gotten a commission from a contractor to provide the study that I specified.

THAT is a point to I constantly talk about with my peers. I will defend you PE's to the extent that the Architects and owners aren't willing to pay you enough to do your job well for a couple decades. Then the stuff rolls downhill and we as electricians become responsible to do it instead and we all know that the quality of electricians has also decayed over that same time. Take this SCCR thing, a large swath of "electricians" have zero idea of what we are talking about.

 

[jim dungar]

We are way to pedantic here to say that. NEC definitions:
Interrupting Rating. The highest current at rated voltage that a device is identified to interrupt under standard test conditions
Short-Circuit Current Rating. The prospective symmetrical fault current at a nominal voltage to which an apparatus or system is able to be connected without sustaining damage exceeding defined acceptance criteria.

Based on those definitions the AIC value is part of the SCCR.
During the time a short circuit occurs the OCPD is needs not to fail until the fault is cleared, which means it must have an SCCR. When the OCPD begins to interrupt the fault its AIC rating is important.
You cannot have an AIC without also having an SCCR.

 

[MyCleveland]

A part of this discussion that nobody has talked about is bidding for Engineering commissions. The follow up studies are never part of the RFP and if we include it in our proposal, we won't be competitive.

I have, on occasion, gotten a commission from a contractor to provide the study that I specified.

The IDEA of taking more money for services that should have been provided in any base design...unless the owner was aware and you excluded it in your base fee.

 

[JoeStillman]

The IDEA of taking more money for services that should have been provided in any base design...unless the owner was aware and you excluded it in your base fee.

Please understand that, during the design phase, our SC Calcs can ONLY be based on assumptions. They should be revisited after the POCO has had their way with the design, but our contract is over at that point.

 

[Strathead]

Based on those definitions the AIC value is part of the SCCR.
During the time a short circuit occurs the OCPD is needs not to fail until the fault is cleared, which means it must have an SCCR. When the OCPD begins to interrupt the fault its AIC rating is important.
You cannot have an AIC without also having an SCCR.

But you can have an SCCR without an AIC and this WHOLE thread is about the SCCR not the AIC.

 

[jim dungar]

But you can have an SCCR without an AIC and this WHOLE thread is about the SCCR not the AIC.

The post that first mentioned AIC was basically equating SCCR and AIC. My point has been for all intents this is an acceptable practice, for sure it is a common industry one, but it is context dependent.

 

[MyCleveland]

Help me understand

You gave a thumbs up to #45...what am I missing?

 

[Strathead]

You gave a thumbs up to #45...what am I missing?

I can't even find where I made that statement. It obviously wasn't about post #45, so I can't answer your question.

 

[MyCleveland]

I can't even find where I made that statement. It obviously wasn't about post #45, so I can't answer your question.

Sorry, I added the text "Help me understand" under your tag implying you stated it.

I am asking you to tell me why the agreement with post 45?
Is the issue not that your being made responsible for EE scope of work?
The tired old excuses...utility can't tell me in time, and others, should not be a reason to put this responsibility onto ECs.
Even if true...have the EE of record finish the work when info becomes available...everyone knows at the job start NOTHING gets ordered until completed...at least this takes you away from eating errors that show up late. You should NOT even be able to get a permit, unless conditional, since the entire design is of the power system is incomplete.

 

[Strathead]

Sorry, I added the text "Help me understand" under your tag implying you stated it.

I am asking you to tell me why the agreement with post 45?
Is the issue not that your being made responsible for EE scope of work?
The tired old excuses...utility can't tell me in time, and others, should not be a reason to put this responsibility onto ECs.
Even if true...have the EE of record finish the work when info becomes available...everyone knows at the job start NOTHING gets ordered until completed...at least this takes you away from eating errors that show up late. You should NOT even be able to get a permit, unless conditional, since the entire design is of the power system is incomplete.

Because I understand and accept that the Electrical Engineer is only providing preliminary calculations and that when they require the electrical contractor to provide a coordination and short circuit study, the final results of that will be used to form the basis of actual installation unless they are specifically paid to perform this service, or utilize it. We do a lot of medical in Florida and these studies MUST be part of the record and permit drawings for our medical inspection process (AHCA). For the issues regarding responsibility for errors, I would say there needs to be more education toward Construction Managers and owners about the impact of these studies. For decades, this wasn't even on my radar or, I believe, inspection. Until more recently short circuit studies were rarely even done on a job. I still don't see inspectors scrutinizing the issue. I do feel that the MECHANICAL Engineers need to be more proactive and should NOT approve submittals until they have the short circuit information in hand. That isn't the Electricals' responsibility though. That is why I "liked" Joe's post.

 

[Knightryder12]

If it takes more than a week to ten days to get this information from a POCO you all have some terrible POCO's. I can usually get this information in a week or less with our POCO's here in Florida.

 

[MyCleveland]

Because I understand and accept that the Electrical Engineer is only providing preliminary calculations and that when they require the electrical contractor to provide a coordination and short circuit study, the final results of that will be used to form the basis of actual installation unless they are specifically paid to perform this service, or utilize it. We do a lot of medical in Florida and these studies MUST be part of the record and permit drawings for our medical inspection process (AHCA). For the issues regarding responsibility for errors, I would say there needs to be more education toward Construction Managers and owners about the impact of these studies. For decades, this wasn't even on my radar or, I believe, inspection. Until more recently short circuit studies were rarely even done on a job. I still don't see inspectors scrutinizing the issue. I do feel that the MECHANICAL Engineers need to be more proactive and should NOT approve submittals until they have the short circuit information in hand. That isn't the Electricals' responsibility though. That is why I "liked" Joe's post.

Accepting isn't the case is it, you really have no choice in the matter if you want to bid the project. Are the EE documents labeled "Preliminary" ?. Even if that is or is not the case, how does a permit get placed in your hand based on "Preliminary" documents?
I understand the position you are left with, my argument is this should never be allowed.
Regarding the ME issue, the project EE of record is responsible for passing on the calculated SCC at each piece of equipment to project ME. If the ME changes equipment selection, the cycle starts all over...new equip spec -> EE, check calc -> inform ME if SCC holds or revised to "X". If the SCC calcs have been passed on to the EC, NOW the coordination falls into your lap.

 

[Jraef]

You cannot have an AIC without also having an SCCR.

And vice-versa... You are not going to get a reasonable SCCR unless there is a circuit protective device somewhere, which will need an AIC rating. While they are not exactly the SAME thing, they are integral and inseparable to one another.

It's just important to understand though that having a circuit protective device with an appropriate AIC rating is NOT by itself adequate in terms having an SCCR. The SCCR of an assembly is limited by the LOWEST rated device in the power circuit, so even if you have a breaker rated for 65kAIC, that does not mean the entire PANEL is rated for that, and if there are devices in that panel that are only rated for only 5kA, then the entire panel is rated only 5kA. Devices MIGHT have a higher tested and listed SERIES SCCR with that breaker, which is very common and why it is not difficult to attain a higher value with just a small amount of effort on component selection. But for equipment suppliers to not bother and just slap on the "courtesy" 5kA listing, is just, in my opinion, lazy and a little disrespectful of the EC who has to deal with it in the field...

OK, putting my soapbox away again.

 

[binwork91]

I think this 2 page UL article might help understand SCCR and Aic.

https://japan.ul.com/wp-content/uploads/2014/04/ul_PanelboardShortCircuitRatings.pdf

 

[Strathead]

If it takes more than a week to ten days to get this information from a POCO you all have some terrible POCO's. I can usually get this information in a week or less with our POCO's here in Florida.

This, I find true AFTER the job has been permitted and the customer has started negotiation with the POCO, not before.

 

[Knightryder12]

This, I find true AFTER the job has been permitted and the customer has started negotiation with the POCO, not before.

Not true at all. When I get a design that will entail any scope of work that has to be coordinated with the POCO or if I need information from the POCO, I can either start a work permit on-line or call. Never had it take more that 2 to 3 days for the POCO field engineer to call me back and no more then 3 to 5 days for them to get me the info I need. Our POCO also publishes a white paper that has a lot of the information it that we can use regarding transformers and the max fault at the secondary side.

 

[WD40]

Sometimes we work in North Jersey where the POCO uses an area network. We've had AFC's from them that are north of 100kA, and you don't get the info from them until 6 months after the GC signs on the Electrician.

I was contacted by an old boss about signing back on for a big project he bid in north Jersey, he ended up putting some conditions in the bid because he could not get sufficient RFI from the POCO or the EE, he said it happens often and just not worth the headache anymore hes close to retirement. Someone else took the job without the info, when I ask about all the money he lost doing the bid, he said "better to let someone else get sued"

I have, on occasion, gotten a commission from a contractor to provide the study that I specified.

Probably my old boss LOL, he always had someone from the engineering firm checking this and that, the firm usually sent a kid who was very green, we called him "the kid" just out of school and never seen a job. But that kid did get the numbers, and worked with our suppliers. My boss said he cost 1/2 of a foreman and was 2x as valuable. the kid also made "as built" plans for the owners, assisted with panel schedules a helped deal with the L&I.

 

[hmspe]

Not true at all. When I get a design that will entail any scope of work that has to be coordinated with the POCO or if I need information from the POCO, I can either start a work permit on-line or call.

You should feel fortunate. Where I work most power companies won't do anything without a signed contract, and it generally takes 6 weeks or more for any response. If you have contacts at the POCO you can usually get preliminary information, but it is as risky to use that information as it is to follow phone advice from the IRS.

 

[JoeStillman]

Probably my old boss LOL, he always had someone from the engineering firm checking this and that, the firm usually sent a kid who was very green, we called him "the kid" just out of school and never seen a job. But that kid did get the numbers, and worked with our suppliers. My boss said he cost 1/2 of a foreman and was 2x as valuable. the kid also made "as built" plans for the owners, assisted with panel schedules a helped deal with the L&I.

Often I can do it for a lot less than the distributors quote because I've already done one with estimated POCO AFC. All I have to do is update it for the actual AFC, then generate a fancy PDF and some stickers.