electrical (posted by Mike Smith)

[ASKNACHI]This question was posted on AskNACHI.org by Mike Smith (from Arkadelphia,Ar). [/ASKNACHI]What is the best way to determine electrical service size and amps?

If you know how to be safe around electricity, you can look in the electrical service panel and check the service entrance conductor size, the main breaker size, and the the service panel rating.

**Calculating available amperage

**In many cases the listing information about a home is incorrect about the service amperage, due to the broker or owner relying solely on the size of the main breaker or fuse. Many people are also mistakenly under the impression that the available amperage is the total of the individual breakers or fuses in the service panel.

The correct way to determine the available amperage is to determine the ampacity of the lowest rated of the following components:

  • Service supply

  • Electric meter & socket

  • Service entrance conductors

  • Service disconnect

  • Distribution panel
    Here are a couple of examples:

  • A 200 amp service lateral, a 200 amp meter and base, a 175 amp rated SEC, a 150 amp rated panel, and a 125 amp service disconnect. = A 125 amp reportable service supply.
    *]A 150 amp service drop, a 60 amp meter and base, a 150 amp SEC, a 100 amp rated panel, and a 100 amp service disconnect. = A 60 amp reportable service supply.

Please follow these basic safety rules when inspecting live electrical components.

  • Wear protective eye-wear
  • Wear electricians **gloves **(600 volt rated)
  • Do **NOT **wear nylon or polyester clothing
  • Do NOT allow your client to get between you and live components
  • Visually inspect the panel before removing the dead front
  • Do NOT open a panel that is either very rusted or shows signs of moisture
  • Do NOT open any panel that is buzzing or arcing
  • If you decide to remove the dead front, test for stray voltage with the back of your right hand, or use a voltage tic
  • Do **NOT **insert any probes or tools into the service panel
    *]NEVER put ladders up under the service drop

Best way is to watch my sizing a service video on www.theelectricalguru.com

Very nice video Paul. Very good work. On a side note…Do you happen to know John Mills? I’m pretty sure he has also taught for Mike Holt before.

I dont know him personally…and I do believe he has. I dont actually teach for Mike Holt, I own my own consulting business and use his material and sit on his expert panels for the making of his DVD products but thats about it.

Ahh I see. Ok. Just thought maybe you guys had met sometime. John happens to be one of the sharpest electricians I’ve met. I call him the walking, talking Code Book…lol.


I like what you did with your website!! Keep up the good work!

I agree Paul.
Great site, and free of charge.


I enjoy your site. Good work and thanks for the access.