What Calculations are required by an Engineer when Replacing Panels and Breakers?

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Installer

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  1. We need to replace about 4 power panels completely and various circuit breakers in other Panels at this old remote Facility that we have to keep in service.
  2. What Calculations are required to be submitted when (1) Replacing Panels Completely and (2) Replacing Individual Breakers in other Panels? I found this in my old notes.
  3. Is their a Code or Practice that specifies the specific calculations or does Good Engineering Practice apply?
  4. I was trained as an electrical engineer many years ago but have been doing other things and have not been practicing. I only understand rough concepts now.
Thank you in Advance
Respectfully
Installer

Load-Panel BoardLoad on each panelboard per
NEC to determine panel,
circuit, and transformer size
Software Spreadsheets,, hand calculations
Short CircuitAvailable fault current at each
bus to determine equipment
short circuit/interrupting
ratings
Software
Circuit Breaker sizing/settingTables, hand calculations
Protective
device
coordination
To minimize outages to
smallest portion of system
possible
Arc-flashTo label gear regarding arc flash hazard and PPE
required. NEC requires label,
not calculations. Reference NFPA 70E and IEEE 1584.
Software
 
Installer said:
  1. We need to replace about 4 power panels completely and various circuit breakers in other Panels at this old remote Facility that we have to keep in service.
  2. What Calculations are required to be submitted when (1) Replacing Panels Completely and (2) Replacing Individual Breakers in other Panels? I found this in my old notes.
  3. Is their a Code or Practice that specifies the specific calculations or does Good Engineering Practice apply?
  4. I was trained as an electrical engineer many years ago but have been doing other things and have not been practicing. I only understand rough concepts now.
Thank you in Advance
Respectfully
Installer

Load-Panel BoardLoad on each panelboard per
NEC to determine panel,
circuit, and transformer size
Software Spreadsheets,, hand calculations
Short CircuitAvailable fault current at each
bus to determine equipment
short circuit/interrupting
ratings
Software
Circuit Breaker sizing/settingTables, hand calculations
Protective
device
coordination
To minimize outages to
smallest portion of system
possible
Arc-flashTo label gear regarding arc flash hazard and PPE
required. NEC requires label,
not calculations. Reference NFPA 70E and IEEE 1584.
Software
Click to expand...

There are many equations/formulae, codes, standards, conditions and methods that would need to be considered when performing a short-circuit analysis, protective device coordination and arc-flash hazard analysis - too many to fully explain or summarize in a single forum post to be useful.

Generally, industry recognized/certified software handles these kinds of calculations to comply with the latest applicable codes and standards. Most project specifications prohibit engineers from doing manual calculations when determining fault currents; however, manual calculations are often done when developing settings in protective device coordination.

I highly recommend studying the IEEE Violet book as a starting point since this will open the door to some of the other standards and hence calculation methods. The NEC is also a very important resource for establishing minimum and maximum requirements for device ratings/settings. For arc-flash hazard analysis, you can reference IEEE 1584-2018.

Don’t expect to find all the information you need in one convenient/concise location. Power system engineering is a huge topic which takes several years to an entire career to master. You may be better off hiring a professional for your project. Many state statutes require a competent professional engineer perform this type of analysis.

Btw. If you need training on this I could probably spend some time with you one-on-one. Send me a private message if you’re interested.
 
Last edited:
Thank you very much. I passed the P.E. but I never got to use it. During the hardest part of the crisis last year, I reopened my books and a lot came back. I'm close to 60 now and I'm hope to keep my mind sharp.
 
For a direct replacement with no tripping breakers prior to the replacement, the only things I am going to look at is the available fault current at the panels, check the existing conductor sizes to verify that they are not undersized for the rating of the breakers that they are connected to, and do the calculations for arc flash labels at the panels.
 
I don't think any calculations are required at all as long as nothing much has changed since the original calculations were done. You are just replacing stuff not adding loads.
 
this is an incredible loaded subject. you will find the spectrum goes from "replace in kind-no calculations" to "new arc flash, short circuit and coordination study" depends on your risk tolerance and fee

There are many new rules throughout the years so what might have been accepted when that stuff was installed may no longer be. those types of cases are usually outliers though. arc flash/coordination/short circuit is one of those subjects.

in reality, you will be altering the dynamic impedance of the system under fault conditions and there will be ramifications. someone needs to determine what those are and demonstrate it complies with the NEC. it doesn't have to be you, necessarily, but it does have to be part of your project IMO. by that I mean you can specify that the contractor perform an arc flash/short circuit/coordinations study, adjust breaker settings accordingly and provide report to owner.

16015 is a common spec that has this stuff.

eaton has a really basic one available.
@electrical/documents/content/16015a.pdf

another one in a public bid
 
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