SCCR For Elevator

Strathead said:
Everything you say here I agree with except the POCO part. Any job that I am currently referring to will have a dedicated Utility transformer. As such Utility transformer size and generic impedance ratings can and IMO should be used for equipment sizing. In today's hurry up society, it is generally not feasible to wait for accurate AFC information prior to ordering equipment. Lastly, have you ever seen an elevator controller that had an SCCR higher than 5000A?
Click to expand...
I have several, but then I made sure it was in the spec and I reviewed the submittals
 
jim dungar said:
I have sat in meetings with electrical contractors owners were trying to get our company to pay for the SCCR fiasco and overruns. During the discussion it was pointed out the EC project manager never provided installed equipment data sheets and conductor data to the power study engineer. They never told us about all of the value engineering and changes they had implemented. This is why EC firms are usually not allowed to do these studies in house, on large projects.
Click to expand...
BTW, I don't expect PE's here to be less that stellar, but I have certainly dealt with some. That is specifically the issue with the job for the study I posted. The HVAC equipment that failed the study, was as specified at bid time by the Engineering firm that provided both mechanical and electrical plans and specs.
 
Strathead said:
Why would I be in any way responsible (as an EC) to review, approve or supply the information about value engineered items by others?
Click to expand...
In several of the situations I have been involved with the items, with improper SCCR, were purchased by the EC or the specs called for them to be coordinated with the SC study provided through the EC.

In no case do I ever remember seeing a different trade responsible for the solution. Often this was because the EC did not share the preliminary SC study with all concerned parties in a timely manner.
 
Strathead said:
THIS is where the rubber mees the road in my post. The Electrical and the Mechanical Engineers work for the same company. The specified HVAC units doesn't meet the AIC requirements of the design ON THE PERMIT Plans and Specs. The mechanical contractor supplies the equipment as specified, the electrical contractor installs the system per plans and specifications. Who is responsible when the Short Circuit Study report comes out and looks like the one I attached above?
Click to expand...
When I was an electrician in the field, some of the worst coordinated plans I ever saw were from the MEP firms. Seems like they never talked to each other. The engineering firm I am at now, the mechanical guys get angry when we tell them that their equipment needs a higher SCCR.
 
jim dungar said:
In several of the situations I have been involved with the items, with improper SCCR, were purchased by the EC or the specs called for them to be coordinated with the SC study provided through the EC.
Click to expand...
I am not being argumentative on this part (that is to follow), what equipment? Motor control center with electronics and maybe UPS's or a large emergency inverter are the only things that come to my mind that we supply with any regularity. What other equipment that SCCR would be a concern do we supply regularly?
jim dungar said:
In no case do I ever remember seeing a different trade responsible for the solution. Often this was because the EC did not share the preliminary SC study with all concerned parties in a timely manner.
Click to expand...
See post #26. Frankly, at the risk of irritating you, that is a cop out from the engineering firm meaning electrical and mechanical together. If the electrical engineer doesn't do preliminary calculations, which would usually be close enough to base SCCR on, to the ME then the ME, who went to school for years to learn his trade, should either insist on them or put in a high SCCR, which is obviously not wise, so right back to they should insist on AFC for their equipment from the Electrical Engineer, period. The only time the electrical contractor should be held responsible is if we VE something that has an affect on AFC. Any SCCR should have a enough fudge factor to account for reasonable changes like slight decrease in wire resistance due to higher ampacity (copper to aluminum switch) or shorter distance. Basically I am saying the the EC's short circuit study should not be necessary to determine SCCR for ordering mechanical equipment etc. It should merely confirm the Electrical Engineer's preliminary calculations. Give me one good reason why the designing Engineer is incapable of providing an order of magnitude AFC study.
 
Strathead said:
Basically I am saying the the EC's short circuit study should not be necessary to determine SCCR for ordering mechanical equipment etc.
Click to expand...
I wish it were so, but the circuit conductor choice and routing can have a very large impact on branch circuit fault currents. More than once, I have had to reccommend rerunning conductors to increase the impedance and lower the fault current. The design plans rarely show the actual branch circuit runs, leaving those details to the EC at install time, and which trade got there first.

I agree it is not fair everything is pushed to the EC, but as long as Certificates of Ocuppancy are denied due to electrical issues, GCs are going to make the solution the EC's problem.
 
Strathead said:
…so it is pretty easy for the Electrical Engineer to ensure no more than 5000 amps is available.
Click to expand...
Ensure? How would they do that? By adding a 240V transformer of less than 75kVA dedicated to the elevator circuit? Seems wasteful if you ask me. All they need to do is coordinate with the other disciplines to require that the equipment vendors provide panels that are listed for the appropriate values of SCCR. It’s NOT DIFFICULT to attain higher SCCR values, it takes minimal effort on the part of whomever picks out the components. As long as these equipment vendors are not held accountable, they will continue to keep doing the minimum cheapest thing.
 
Jraef said:
Ensure? How would they do that? By adding a 240V transformer of less than 75kVA dedicated to the elevator circuit? Seems wasteful if you ask me. All they need to do is coordinate with the other disciplines to require that the equipment vendors provide panels that are listed for the appropriate values of SCCR. It’s NOT DIFFICULT to attain higher SCCR values, it takes minimal effort on the part of whomever picks out the components. As long as these equipment vendors are not held accountable, they will continue to keep doing the minimum cheapest thing.
Click to expand...
Someone has pointed out that the major elevator manufacturers do provide controllers with a higher SCCR than 5000A so, that may not be necessary. Kone specifically indicated to me that 5000 was it. They were probably lying. But your transformer assumes no feeder, in many cases, the branch circuit offers significant impedance, and yes, if the manufacturer doesn't provide equipment with an adequate SCCR, then it is the Engineer's responsibility to provide a design that minimizes the AFC, or require different equipment. My point is that it isn't the Electrical Contractor's responsibility.

And I didn't say cheap, I said easy.
 
JoeStillman said:
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.
Click to expand...
Please tell me why that is the Electrical Contractor's responsibility though? Early on there were a couple posts that pointed the finger at the EC. This is what has my back up, if that information isn't available then the EC certainly can't acquire a Coordination study in a timely fashion.
 
Strathead said:
Early on there were a couple posts that pointed the finger at the EC.
Click to expand...
If the building is not allowed to be occupied whose fault is it? Who does GC blame? Who doesn't get paid?
The engineer performing the electrical power system study? Really they have no input they are simply part of the building 'checks and balances'
The engineer doing the MEP design? Their work may have occurred months or years before any equipment is purchased.
The general contractor or other prime contractor? Aren't they ultimately responsible for coordinating the work of all trades and the material purchased under their contract.

But it still typically comes down to the Inspector red tagging the electrical work, even if the violation was not caused by the EC.
 
Strathead said:
Please tell me why that is the Electrical Contractor's responsibility though?
Click to expand...
Our specifications call for a short circuit study to be completed before ordering any gear. If I get a submittal for switchgear before the study is done (which is the usual sequence) I send it back without approval.

Often we are done and off the job before the utility company even starts making any plans. That's why our specs turn over relations with the utility to the contractors. Nobody hires us to babysit a job all the way through construction.

If you can buy a switchboard with lower AIC's than my conservative estimate, why wouldn't you? I've never had an owner ask for a credit for that.
 
Strathead said:
Please tell me why that is the Electrical Contractor's responsibility though? Early on there were a couple posts that pointed the finger at the EC. This is what has my back up, if that information isn't available then the EC certainly can't acquire a Coordination study in a timely fashion.
Click to expand...
I have argued this topic to exhaustion that the design engineer should be the provider of equipment ratings and all necessary calculations required.
I have tried engineering boards, state board building officials with no success.
Some ECs boosted how great it was because they were able to make a profit on the mark up for the power study adder. Must never have had one of many a$# aches discussed on the forum.
This will never end until someone finds a way. Here is maybe a new suggestion…with your next bid that requires the EC to provide engineering services, provide it as a line item and offer a line cost + 15% credit if the owner or GC will hire the second engineer and take on the responsibility themselves. If nothing else the owners will become aware that their engineer of record passed a large piece of the design to someone else.
 
JoeStillman said:
Our specifications call for a short circuit study to be completed before ordering any gear. If I get a submittal for switchgear before the study is done (which is the usual sequence) I send it back without approval.
Click to expand...

You are talking about gear, this entire discussion has been about SCCR, of which gear is generally 200,000, so rarely an issue. You don't approve mechanical equipment. If your firm is both mechanical and electrical, do you review mechanical submittals for electrical compliance?
JoeStillman said:
If you can buy a switchboard with lower AIC's than my conservative estimate, why wouldn't you? I've never had an owner ask for a credit for that.
Click to expand...
On top of the fact that this thread is about SCCR, I have never read a spec in Florida or California (the states I have worked in) that stated we could reduce the AIC of the gear because our study allows a lower AIC. On occasion we HAVE offered a VE to reduce the AIC.
 
Strathead said:
On top of the fact that this thread is about SCCR...
Click to expand...
AIC and SCCR are the same thing, like conductors and cabe are the same.

The AIC of a device is immaterial if the SCCR of the equipment it is mounted in is not sufficient.

For some 50 years, NEC 110.09 said OCPD must be rated to interrupt the amount of bolted fault amps at their line side terminals. Over the same time 110.10 has said all electrical equipment must be able to tolerate/withstand the amount of short circuit current that exists, at that part of the circuit, until an upstream OCPD operates.
 
MyCleveland said:
If nothing else the owners will become aware that their engineer of record passed a large piece of the design to someone else.
Click to expand...
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.
 
jim dungar said:
AIC and SCCR are the same thing, like conductors and cabe are the same.

The AIC of a device is immaterial if the SCCR of the equipment it is mounted in is not sufficient.

For some 50 years, NEC 110.09 said OCPD must be rated to interrupt the amount of bolted fault amps at their line side terminals. Over the same time 110.10 has said all electrical equipment must be able to tolerate/withstand the amount of short circuit current that exists, at that part of the circuit, until an upstream OCPD operates.
Click to expand...
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.
 
You must log in or register to reply here.
Top