- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
I would say it might be appropriate for equipment built before the 60's with withstand ratings in the area of 30kA for 30 cycles. Field testing, is usually destructive, unless you get lucky.
Documenting and testing overcurrent devices for series rating 240.86(A)
- Thread starter Tainted
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I'd say (B) is only used by manufacturers getting new gear listed.
Say we have service gear by one manufacturer, say manufacturer A, that is rated for the greater than 10ka available fault current (AFC) of the incoming service.
Then say we need to replace a feeder panel, and we want to go with one from manufacturer B for whatever reason.
The new panel will have typical 10k branch breakers but these are not tested with manufacturer A so 240.86(B) is not met. Then we go to Tainted who has a brand new subscription to SKM or some such software that decides if it will work. And if it does 240.86(A) is met.
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- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
There is no standard software, like SKM, that can determine series ratings between manufacturers. The last time I used this type of software it could only give results based on publicized manufacture submitted testing.
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mayanees
Senior Member
- Location
- Westminster, MD
- Occupation
- Electrical Engineer and Master Electrician
My experience with 240.86 (A) is that the devices must be existing and must be listed together. Following is a chart for Cutler-Hammer
Even with the equipment evaluation module? (That is a feature that is purchased separately if you have Powertools.)
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
My understanding is no one has been able to come with a way to accurately model two OCPDs in series.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Not even then. I believe the manufactures use their proprietary empirical data rather than what they give to companies like SKM
The SKM evaluation module may not do what you think it does. It basically just looks at the manufacturer's supplied catalog data and compares it to its fault current module output. The engineering group I worked for created our own Excel spreadsheet that did the same thing.
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mayanees
Senior Member
- Location
- Westminster, MD
- Occupation
- Electrical Engineer and Master Electrician
SKM is effective for determining areas to scrutinize for equipment failures. When equipment fails SKM's "Equipment Evaluation" module, then it's on the study doer to evaluate relative to 240.86
SKM's Equipment Evaluation module flags areas where 240.86 must be investigated. I've worked with models where my predecessor failed millions of dollars' worth of electrical equipment because SKM said it failed. I was given the project to remediate the failed equipment condition and determined there were substation fuses installed that series-rated with the breakers to meet the fault current requirements. This occurred more than once!
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