Pring Arc Flash Analysis

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aelectricalman

aelectricalman

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Location
KY
So, now that I have been formally trained in how to perform an industral arc flash analysis, I have no idea what to charge. I have a customer that is interested in the service and I have walked the facility. I know it is a 250,000 sq ft facility. For anyone how has performed one, is there a book or words of advice you can give on how to charge per piece, per square foot, per machine, ect.... The study will entail using a software (SKM) to create one lines, along with breaking down the study on all equipment all the way up to the customer owned transformer down to smallest panels and switches. I will include only the required 208 voltage equipment, not all of it. I foget the minimal sized transformer feed but everythign above that. Anyhow, thanks for any advise on how to cost estimate this. I don't want to underestimate it and kill myself. haha. If you dont feel comfortable talking to me about pricing in an open forum, please feel free to speak to me in a message. I understand we all need to protect our pricing methodology. Im in KY by the way.
 
Writing a report and creating an engineering model, can be done on a per point basis, especially if you want want to only occasionally make money. Data collection should never be done based on only square ft or number of points, unless you definitely want to loose money in the long term.

How much time and effort is needed to get the fuse data on a 15kV switch? How about for a 4000A 480V services entrance switch? What about a 60A switch on a busduct over a row of machine tools?

How much time is needed to model a breaker from 1950 that isn't in the SKM library? How many different scenarios are you going to run in order to recommend the 'best' mitigation strategies? How much time do you plan to spend deciding on how to deal with the inevitable assumptions?

Why are you only going to do a partial workscope? Yes, NFPA 70E says there are some items that do not need to be analyzed, however they still need to be documented and labeled so that workers know what PPE to wear when interacting with them.
 
Jim,


Thanks for the thourogh advise. I am providing a full analysis. Maybe I misspoke. I am logging and including on the one-lines, all the equipment but only catergorizing what is neccessary. I guess I could include everything but it would add substaintal cost that can not be justified. I really just mean that for anything less than 240 volts thats fed from a transformer less than 125kVA, there are no arc flash hazards. Per IEEE 1584 that is.

The 15kV "stuff" can be received from the POCO, and all the others can be a bear. I agree there's a point of diminished return when it comes to estimating versus guesstimating. Are there reasonable assumptions that can be made?
 
As a ballpark strictly wild a.. guess, "SWAG", how long should I expect to work on this project (given a fair amount of hurdles)? Its roughly 250,000 sqft with approximately 340 pieces, 4 large gear with 20 (1000amp) panels for equipment (not forgetting about all the other stuff). The building is only 8 years old.
 
aelectricalman said:
I really just mean that for anything less than 240 volts thats fed from a transformer less than 125kVA, there are no arc flash hazards. Per IEEE 1584 that is.
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For these small systems, PPE is still required, both voltage and arc flash. IEEE 1584, just says they do not need to be analyzed. NFPA 70E still requires their risk to be assessed.
 
jumper said:
I thought it was 112.5 kVA @240V and that it is not that there is not any arc flash hazards, it is just that the equipment need not be part part of the analysis.
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The transformer limit is 125kVA, which leaves the 112.5kVA as the practical cut off limit as that is the nearest, but not over, 'standard' design.
The voltage limit is <240V, so 208V becomes the largest nominal voltage.
 
I don't know of any guidelines or standards for estimating arc flash studies. The estimates for arc flash studies I have performed have been pretty much pulled out of my a## - well they have been educated guesses anyway. By far, the area I tend to underestimate is the data collection effort. Occasionally I will have a client that has great documentation of the electrical systems with complete one lines but not very often. So the effort is not only to collect the data but to figure out the one line as well. Put in lots of time for this.

If you can, negotiate a "not to exceed" contract that provides for you to come back to the client and negotiate a change order if you hours are exceeding your estimate by a lot. Nice work if you can get it.

Also, make sure the client understands that to collect certain data or to figure out a one line, you will need a plant electrician to work with you and it may take an equipment outage (verify fuse size is a good example).

I hope that helps.

bilbo336
"still confused but on a higher level and about more important things."
 
The data collection effort will be the most time consuming and costly, therefore people usually underestimate it. Are you doing the data collection yourself in conjunction with a plant electrician? If using plant personnel, make sure that they can be dedicated to spend the time with you.

As far as the engineering portion, that comes with experience. For example, how much time have you spent doing these type of analysis? Just learned the software, first time, then expect it to take a lot longer than someone who has been doing it for awhile.

I have been doing these studies for about 9 years now so I have a good gut feel on how long it will take me and therefore what to charge. I doubt if anyone will give you a concrete dollar amount for per bkr, panel, etc. for a number of reasons primarily not wanting to let confidential bidding info out.
 
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