JEuriech Posted August 6, 2011 Report Posted August 6, 2011 I inspected a 30 year old house with a GE 200 amp split panel. It had 5 main disconnects with one of the breakers feeding the bottom half of the panel. My question is related to the 6 disconnect rule. Can the combined rating of all the main disconnect breakers exceed the rating of the panelboard? The 5 breakers in this panel totaled 230 amp which could draw more amps than the panel rating of 200 amps. If I use the 2006 IRC as a guideline, E3606.3 would indicate that the breakers cannot exceed the rating of the panel. However reading under E3503.3.1 the exception would tend to indicate that you could exceed the ampacity of the service conductors. Now I'm confused. Am I mixing apples and oranges? Jeff Click to Enlarge 46.03 KB
Marc Posted August 6, 2011 Report Posted August 6, 2011 A panel with one main breaker cannot be rated any less than the size of that main breaker. If there's more than one main breaker then the rating of the panel must be adequate for the loads on it, as revealed by the load analysis. This calculation is detailed in the codes and is usually performed by the electrician. In installations having more than one main, it's common for the numerical sum of the main breaker ratings to exceed the rating of the panel. Marc
Jim Katen Posted August 6, 2011 Report Posted August 6, 2011 I inspected a 30 year old house with a GE 200 amp split panel. It had 5 main disconnects with one of the breakers feeding the bottom half of the panel. My question is related to the 6 disconnect rule. Can the combined rating of all the main disconnect breakers exceed the rating of the panelboard? Yes. With split bus panels, the sum of the main breakers nearly always exceeds the rating of the panel. It's probably fine. If you want to know for sure, do a load calc.
John Kogel Posted August 7, 2011 Report Posted August 7, 2011 Jerry, I think you got your answer. It is OK if we assume load calcs were done and the total does not exceed the rating for those service conductors. But I see why you would question it. The hazard there is if the load is increased, there is no safety built in to protect the conductors. So if there have been recent additions to the house, I think it would be wise to have that service checked out. BTW, that setup is not permitted in Canada. The CEC allows only one main disconnect. A panel with one main breaker cannot be rated any less than the size of that main breaker. Say what?If there happens to be a 200 amp main breaker in your panel, but it is fed by a 100 amp breaker from another panel, then how do you rate the panel?
Marc Posted August 7, 2011 Report Posted August 7, 2011 A panel with one main breaker cannot be rated any less than the size of that main breaker. Say what? If there happens to be a 200 amp main breaker in your panel, but it is fed by a 100 amp breaker from another panel, then how do you rate the panel? If a main breaker is fed by another breaker then this 'main breaker' isn't technically the main breaker for that electrical installation. Marc
Greg Booth Posted August 7, 2011 Report Posted August 7, 2011 If a main breaker is fed by another breaker then this 'main breaker' isn't technically the main breaker for that electrical installation. Marc "technically" correct, but practically........... a home served by a (sub)panel with a 200A breaker, fed from a 100A breaker at a meter bank..........that 200A breaker will be considered the "main". I see this exact set-up in manufactured home communities often. The community operator generally will not allow "their" breaker to be used as a disconnect by the homeowner/service folks. ..........Greg
John Kogel Posted August 7, 2011 Report Posted August 7, 2011 If a main breaker is fed by another breaker then this 'main breaker' isn't technically the main breaker for that electrical installation. Marc "technically" correct, but practically........... a home served by a (sub)panel with a 200A breaker, fed from a 100A breaker at a meter bank..........that 200A breaker will be considered the "main". I see this exact set-up in manufactured home communities often. The community operator generally will not allow "their" breaker to be used as a disconnect by the homeowner/service folks. ..........Greg I wish the electrician would write the true service size on those panels. I don't know how many times I've seen undersized wiring coming into a mobile home panel. The buyer sees a 100 amp breaker and doesn't realize the service is only 50 or 60 amps.I had to break the bad news to an older lady who was planning to replace the old oil furnace in the mobile with an new electric unit. Sorry, this is not really a 100 amp service. "But it says it is". [:-bigeyes
Marc Posted August 8, 2011 Report Posted August 8, 2011 If a main breaker is fed by another breaker then this 'main breaker' isn't technically the main breaker for that electrical installation. Marc "technically" correct, but practically........... a home served by a (sub)panel with a 200A breaker, fed from a 100A breaker at a meter bank..........that 200A breaker will be considered the "main". I see this exact set-up in manufactured home communities often. The community operator generally will not allow "their" breaker to be used as a disconnect by the homeowner/service folks. ..........Greg It's misleading to refer to a feeder breaker as a main breaker, though I can understand how some people might make that mistake. Marc
John Kogel Posted August 8, 2011 Report Posted August 8, 2011 Thanks. Marc. If you called the main breaker a service disconnect, it would be less confusing. I know we are just hashing over different terms for the same thing. I knew what you meant, but it could be interpreted wrong if someone confused the main breaker in a service panel with a 'main' breaker in a subpanel. In a condo or a mobile home, we generally in my area will call the feeder breaker a main.
Marc Posted August 8, 2011 Report Posted August 8, 2011 Agreed. 'Service disconnect' is a better term for it. Marc
Jim Baird Posted August 9, 2011 Report Posted August 9, 2011 Nitpicking as usual, I'd point out that the "six" rule applies to motions, not discos. Grouped discos are usually found in commercial applications, not houses, unless it is split panel.
Jim Katen Posted August 10, 2011 Report Posted August 10, 2011 Nitpicking as usual, I'd point out that the "six" rule applies to motions, not discos. The only time it applies to motions is with multiwire circuits. Otherwise, it does, indeed, refer to breakers or switches. Heck, I can turn off 40 individual breakers with one "motion" or, to use the code term, "operation of the hand." Check out 230.71(A): General. The service disconnecting means for each service permitted by 230.2, or for each set of service-entrance conductors permitted by 230.40, Exception No. 1, 3, 4, or 5, shall consist of not more than six switches or sets of circuit breakers, or a combination of not more than six switches and sets of circuit breakers, mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard. There shall be not more than six sets of disconnects per service grouped in any one location.
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