Neher McGrath Calculation

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RickyG.

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Pueblo, Colorado, United States of America
I need help on a Neher McGrath Calculation. I tried to purchase a software program, so I can do it myself, but have had no luck or response from them on how to purchase the software. Any ideas on a company or a person who may be interested in doing this Calculation for me? It is for my own personal knowledge about a project that I do not believe the secondaries should be derated, but they have them derated, and their reasoning was because Neher McGrath Calculation. With the research I have done and the examples I have seen I am calling "B.S." It is a typical commercial building with a small server room and nothing near a Data Center. Any help?
 
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Hv&Lv

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RickyG. said:
I need help on a Neher McGrath Calculation. I tried to purchase a software program, so I can do it myself, but have had no luck or response from them on how to purchase the software. Any ideas on a company or a person who may be interested in doing this Calculation for me? It is for my own personal knowledge about a project that I do not believe the secondaries should be derated, but they have them derated, and their reasoning was because Neher McGrath Calculation. With the research I have done and the examples I have seen I am calling "B.S." It is a typical commercial building with a small server room and nothing near a Data Center. Any help?
Click to expand...

This may or may not help, but it is interesting reading. It also has an excel spreadsheet, although I can't open it to check it out.(I'm on an ipad at the moment...)
http://www.electrician2.com/articles/ampacity.htm
 
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pgonski

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RickyG. said:
I need help on a Neher McGrath Calculation. I tried to purchase a software program, so I can do it myself, but have had no luck or response from them on how to purchase the software. Any ideas on a company or a person who may be interested in doing this Calculation for me? It is for my own personal knowledge about a project that I do not believe the secondaries should be derated, but they have them derated, and their reasoning was because Neher McGrath Calculation. With the research I have done and the examples I have seen I am calling "B.S." It is a typical commercial building with a small server room and nothing near a Data Center. Any help?
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I've done these for data centers using ETAP's add-on for duct banks. It's pricey ($4-5k), and only economical to use on larger jobs.
You need to know all the soil information, duct bank layouts, burial depths, etc.............

If you have the secondary side of the transformer, with potentially multiple phases, they will heat each other inside the ductbank. One of the jobs I used this on, the frost depth was deep, so the cables were buried pretty far in the ground. The affect was given the soil, the cables were derated as the cables get hotter the deeper you bury.

I'd say it might be worthwhile to ask them for the calculation?
 
don_resqcapt19

don_resqcapt19

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retired electrician
pgonski said:
... One of the jobs I used this on, the frost depth was deep, so the cables were buried pretty far in the ground. The affect was given the soil, the cables were derated as the cables get hotter the deeper you bury. ....
I
Click to expand...
This an issue that many miss, however it is interesting to note that the NEC does not address this in mandatory code language for systems under 2001 volts. It is addressed for 2001 through 35kV in mandatory code language. It is also addressed in Informational Annex B for under 2001 volt systems, but that is not code language..just information.
 
kingpb

kingpb

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SE USA as far as you can go
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Engineer, Registered
don_resqcapt19 said:
This an issue that many miss, however it is interesting to note that the NEC does not address this in mandatory code language for systems under 2001 volts. It is addressed for 2001 through 35kV in mandatory code language. It is also addressed in Informational Annex B for under 2001 volt systems, but that is not code language..just information.
Click to expand...

I think because too many use the NEC as a design guide when it is not intended for that purpose.
 
don_resqcapt19

don_resqcapt19

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Illinois
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retired electrician
kingpb said:
I think because too many use the NEC as a design guide when it is not intended for that purpose.
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That is true, but they are telling us what the conductor ampacity is for systems of less than 2001 volts without giving the restrictions like they do for systems of 2001 through 35, 000 volts. They don't even address the issue of underground duct banks for the lower voltage systems.
 
Besoeker

Besoeker

Senior Member
Location
UK
RickyG. said:
I need help on a Neher McGrath Calculation. I tried to purchase a software program, so I can do it myself, but have had no luck or response from them on how to purchase the software. Any ideas on a company or a person who may be interested in doing this Calculation for me? It is for my own personal knowledge about a project that I do not believe the secondaries should be derated, but they have them derated, and their reasoning was because Neher McGrath Calculation. With the research I have done and the examples I have seen I am calling "B.S." It is a typical commercial building with a small server room and nothing near a Data Center. Any help?
Click to expand...

This any help?

http://www.electrician2.com/articles/ampacity.htm
 
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