Thread: Feed From Main Panel to Sub Panel

Anybody know what the requirement is for circuits in the main panel feeding the downstream subpanel? Is saw this one yesterday and the circled cables are coming off lugs in the main panel with no breaker disconnect. Is this allowed or should it have a disconnect in the main panel to shut off the sub?

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Nick - If the feeders are rated at or above the main breaker rating on the service equipment panel, which they look like they might be, then the main would protect them, right? That doesn't really answer your question, though. Seems to me there should be a separate disconnect at the service panel for the downstream panel, but I don't know if it's required.

This is an old panel. In a new panel there would not be lugs in the main panel to attach the feed wires for a sub panel and off course tapping the main lugs with a second pair of wires is not allowed. In any sub panel that is not in view of the main panel you have to have a main breaker in the sub panel such as an AC condenser disconnect.

Thats the way I determine it anyway and no I am not going to quote "code". Of course I do not know the age of this panel and would not want to guess on codes from that time. When in doudt refer the matter to an electrician for evaluation. As a matter of fact I have referred this double tapping or feed wires connected to lugs to electricians as I would have the clients consult an electrician even when I see ground wires leading out of an electric panel but I cannot find where they are attached.

Also if there were to be work done on the subpanel or something added to it wouldn't you want to be able to just shut the sub down without disconnecting everything else in the home??????

One good point is that if it is something you have never seen before and have a question have your clients consult an electrician. Better safe than sorry.

Just my point of view.

Thanks guys. There were already other issues in the main and sub panels so an electrician is needed regardless.

Nick - overcurrent protection is required on all branch and feeder conductors at the point where they get their supply. A "main" breaker in a sub-fed panel is often present also, but not required.

Originally Posted by Ted Menelly

Thats the way I determine it anyway and no I am not going to quote "code". Of course I do not know the age of this panel and would not want to guess on codes from that time. When in doudt refer the matter to an electrician for evaluation.

Ted - taking the time to learn code often gets one directly to the correct answer from an authoritative reference. In this case the answer to Nick's question is spelled out clearly in the code.

Originally Posted by 2006 IRC

§RE3605.5 Overcurrent protection required. All ungrounded branch-circuit and feeder conductors shall be protected against overcurrent by an overcurrent device installed at the point where the conductors receive their supply.

If you take the time to think about why the code says what it says, it doesn't matter whether or not that particular code section was in effect when the work was done on the house (since most of us are not doing code compliance inspections). We use the code as a point of reference to determine the current national consensus opinion of subject matter experts regarding what constitutes the minimum acceptable level of safety.

The conductors need to be protected at their source so that if anything goes wrong downstream that would result in a current draw in excess of their rated ampacity, the house doesn't burn down. This is true, no matter what date it made it into the code book or whether or not a particular AHJ enforces it.

An electrician is needed to fix the problem, not to evaluate whether or not there is a problem. The client is paying the HI to make that evaluation.

Sorry, in essence I said what you said to a t. Sometimes I get a little to simplistic. I did in fact tell him I would have an electrician evaluate. I did not find it correct and always do have an electrician evaluate for repairs. When I see that in a home inspection report I do add more to it and get more into detail. No I do not quote code. Code is a wonderful thing that I make my concessis on but I do not claim to any client that I am a code inspector. We are generalists, period. I will not spend a day on one inspection checking every item if there is already an item in concern with a particular system. There were also a lot more questions about his sub panel that were not mentioned and I answered his question in not a complete known item and should have just answered his particular question.

Again, I will try to be more specific in the future. Yes it does not matter what things use to be but I do tell my clients that some particular item may be like this in the past but as you know in a brand new home there will be two main panels and not a sub panel and they will have there own grounds. I answered vaguely and did not mean to. But saying that I still go by when in doubt refer it to a specialist.

Why do I say evaluate???? If there is one item wrong with a particular system I will state that they should have the system, or panels, evaluated for all repairs needed. Specifics, yes, again we are generalists and if the limit is pushed beyond general-ism then we become more a a technically exhaustive inspector and should have spent all day on that item and used testers to follow every ground, pulled the cover off of every receptacles and switch, tested every tiny electrical component in an HVAC system and so on, etc.

If you read my thread On "is IR the future of home inspections" you will see where I am coming from.

If the feeder conductors and the sub-panel is rated for the size of the main breaker then a breaker to the sub-panel is not needed. I see lots of 200 amp service panels with feed-though lugs on the bottom of the panel bus bars that feed 200 amp main lug sub-panels.

First, you would need to look at the wiring schematic for that panel, it would tell you what those lugs are for.

*MOST LIKELY* those lugs are shown as "mains", in which case the only thing they are allowed to be used for at the "mains".

Now, for the purpose of the question ... let's "assume" that those are not specified as "mains".

Those could then be used for "feeders" provided that the "feeder conductors" are rated at or higher than the "main", also, the panel that those are feeding would need to be rated at or above the "main".

Yes, new panels are made with main lugs and with feeder lugs, however, all the ones I've seen have the "mains" and "feeders" at the ends of the bus bars.

Now, though, regarding those feeders to another panel ... 'Houston, we have a problem' ... there is no ground with that (at least not that I can see), which makes the downstream panel(s) non grounded.

My guess it that originally that was the "service entrance cable", in which case all which was needed were the two hots and a neutral/ground. Being as that is now "feeder cable", there needs to be a separate ground, separate from the neutral - and I don't see it there ... am I just missing it?

I'm sure you got the other things in that panel, missing knockout, neutrals and grounds on same bus terminal bars, neutral terminal bars 'may be grounded' (you'd need to check more closely than I can see in that photo), white conductor used as hot, etc.