Thread: Main disconnect rating

Not used to seeing the main disconnect in the electrical panel being a combination of 2 double breakers like this. Is this disconnect rating 100 Amps? I know the ratings of the meter, panel and conductors and what to make sure I'm using the correct rating of the disconnect to determine the service rating.

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It is a 100 amp service. For each bus, the current is divided equally across two 50 amp breakers, so it can reach 100 amps total before the breaker trips.

The problem is that there is no tie bar joining the two legs.
It should be repaired, IMO. If one side trips or is manually tripped, the other bus will still be energized. That's a shock hazard, and some 240 volt equipment could be damaged as well.

The tiebar should be marked '100' to eliminate confusion.

Some doofus pulled the OEM main breaker. The only way to have a 100A main is to use a 100A 2-pole breaker in the center two poles & filler plates on the outside spaces, but if the line conductors are only rated for 100A, replacement of the panel would be the best bet, 150A is likely the smallest OEM main avail. w/o a panel replacement.

What is the size of the conductors feeding the panel? Is it service equipment or a subpanel? These questions could change things, but the existing main is not acceptable as-is.

BTW, that is a 1970's I-T-E panel, they were the 1st to use the 4-pole wide breaker for a residential 150-200A main breaker, Cutler-Hammer & GE also used that type in later years.

This is the service panel being fed by 3/0 aluminum conductors which should be rated at 175 amps. The panel and meter are rated at 200 amps. Not sure the best way to state the issues in the report, but for sure I will recommend the panel be evaluated by an electrician.

If I am understanding the question correctly you want to know the service capacity? Well first of all, you determine the lowest rating of all the different components and use that one as your max service rating. Then you must work off of the premise that your main disconnect can be shut off with up to six hand movements. So while what you see is not Ideal, it does not appear to be "per se'" wrong. imo.

Originally Posted by George Hallaron

If I am understanding the question correctly you want to know the service capacity? Well first of all, you determine the lowest rating of all the different components and use that one as your max service rating. Then you must work off of the premise that your main disconnect can be shut off with up to six hand movements. So while what you see is not Ideal, it does not appear to be "per se'" wrong. imo.

Hello George. It is wrong because, as Rollie pointed out, it is not original equipment.

That 6 hand rule does not apply here. At least, it would be wrong to use that rule here, because any 240 volt circuit needs to be shut off by one hand movement. If it takes two movements to completely disengaged the power to that circuit, it is wrong.

We can't say why this setup was used in the first place. Maybe the original main breaker failed. That is an unknown, but if a fire ever occurs in this panel now that it has been altered, good luck to the home owner.

Thanks to all for your help. I will write it up as deficient because there is no tie bar joining the two legs and if one leg trips or is manually tripped, power to the other leg with 220 volt equipment would be a safety hazard as well as could damage such equipment. I'll also recommend the panel be evaluated by a qualified electrician.