Determining amperage on a split bus?

Came across a federal Pacific split bus panel. Not very familiar with split bus style. So basically is everything above the breaker with the yellow wires a main? How do you determine amperage? Thanks for any help with this

or any help with this.

I, typically, used the lesser of the SEC and panel board amperages.

Wire size (ampacity) of feeders.

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Didnt see any visible markings on the main feed and I’m not very good at eyeing up larger size wires for size. Something I need to work on

Shit, I dont have any photos of that :thinking:

Well, don’t guess.


The service amperage was indeterminable but the service entrance conductors size suggest that it is ______ amps.

Or, ago back and get a pic of the panel board label. :smile:


Nah I wont guess. I’ll go back and pop the cover off, lesson learned

Why do you need to know this for a Home Inspection Report to have to go back and pull it apart again?


Not to get confused…, the SEC is not considered a feeder, in case someone reading was not aware. Special rules thus apply to SEC that differ from that of feeders. If this was a remote distribution panel then there would be a feeder from the main, but we wouldn’t use it to size the service (imagine someone installed 200amp remote panel feeding off of 100amp main disconnect).

II. The inspector shall describe:
the main service disconnect’s amperage rating, if labeled; and
the type of wiring observed.

Section 197-5.9 Electrical System
(b). Home inspections shall describe readily accessible and observable portions of:
1. Amperage and voltage rating of the service;

NJ requires us to. Might be different where you’re at, not sure.

That’s true. I meant SEC.

NACHI has no regulative authority.

If not labeled, your guessing.

That is an “Observation” requirement not an “Analysis”.

NACHI SOP: Did you bother to read the whole thing?

IV. The inspector is not required to:

    **insert any tool, probe or device into the main panelboard, sub-panels, distribution panelboards,** or electrical fixtures. SO HOW DO YOU DETERMINE VOLTAGE?
    measure or determine the amperage or voltage of the main service equipment, **if not visibly labeled.**

Bet you’ll find the same in the NY SOP if you look.

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Remember, you asked why would someone need to know this for their HI report… not how they would determine it from the system installed at the house.

If the state is not a licensed state and one puts in their contract that they will follow NACHI’s SOP, the court will hold the inspector to it. That is the service the HI sells to the client. You are correct that NACHI’s SOP does not require one to do more than merely list the amperage as labelled (if labelled) on the main disconnect, if there is one. However, many states, like mine, specifically require you to determine the service ampacity. NY SOP, like I posted, does not merely say list the amps as labelled on the main disconnect.

In fact, if you look up your own state’s HI SOP, you will find it says:

Rule 0780-05-12-.10 (9) Electrical Systems:
(a) The home inspector shall inspect:
3.amperage and voltage ratings of the service
(b) the home inspector shall describe
1.service amperage and voltage

actually, NY SOP instructs the HI to remove the panel covers to examine the insides (of course if safe to do so, and yes without use of putting any tools inside of the panels) and like I posted specifically instructs the HI to get the service ampacity. Nowhere does it say Not Required to “determine the amperage or voltage of the main service equipment” as that would contradict the initial requirement.

Section 197-5.9 Electrical System
(a). Home inspectors shall observe and report upon readily accessible and observable portions of:
3. The main and branch circuit conductors for property over current protection and condition by visual observation after removal of the readily accessible main and sub electric panel covers;

You know, sometimes I wonder why you do this… because I know you’re very knowledgeable when it comes to HVAC and HI in general. How come you don’t know or pretend you don’t what your very own state SOP states? That does confuse me :expressionless:

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Inspecting the inspector :smile:

Maybe because David knows so much about building systems that he spends more attention on the building condition, than on simply describing the building systems, which most anyone can do given enough time.

Note that is not a defense, just a postulation. It can be difficult to determine wire gauge size. There are plenty of inspectors that think their main function is to catalogue and name the differing building components, at least judging by their reports.

Thanks for your input Simon!

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Not being able to determine something is okay… failing to follow SOP is not. Yes, clients want to know the rating of the electrical system because 1) they’re paying money for the information and 2) it can be costly to upgrade the electrical system.

Thanks for your input John!

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It is very relevant information in this area. Many people want to upgrade their evaporative coolers to air conditioning, and that often entails upgrading their electrical service as well, which is an added cost.

Anyone have a guess about the service size? Based on the service entrance conductors in the photo I would guess 100 amps.


Thanks Robert

Did you report on the fact that it’s a federal pacific panel? I know that it is not your question but what I’m getting at is the size of the sec is secondary in nature to the manufacture of the panel. Also wire size is not a 100% effective way to determine service size.

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