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?