Cutler Hammer Split Bus?

[rkenney]

Circa 1974 or thereabouts. Who has an explanation for this crazy wiring?

Third double breaker on left side, identified only as 'Main'

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[Marc]

Split bus.

I've seen with my own eyes only one in all my life and I identified it promptly because I saw it here.

Marc

[Jim Katen]

The leads from the lighting main are spot welded to the bus. Very common in my area.

Is that the part that's "crazy" or is it something else?

[hausdok]

Yeah,

Pre-1984 split bus. See 'em on virtually every pre-1984 house I see that's built between the 60's and 80's.

OT - OF!!!

M.

[Chad Fabry]

Fairly common panel in this neck of the woods.

[rkenney]

Is that the part that's "crazy" or is it something else?

What's the point. Can't for the life of me see how this is any more efficient, economical or achieves any real purpose.

So, the explanation i was really seeking is what purpose did it serve, the logic behind design as it were, and if it was any good (safe) why'd they stop building them this way.

[kurt]

Big questions that can't be answered here. How can anyone peer into the void to determine why a multinational company does anything? I assume because it's a more complicated expensive method, so it had to be eliminated......much easier to screw clamp a wire to a cheap plastic component that snaps onto the bus.

I've seen them occasionally over the years; seemed fine to me. What exactly might be the problem in integrally bonding the cable to the bus?

[Jim Katen]

Is that the part that's "crazy" or is it something else?

What's the point. Can't for the life of me see how this is any more efficient, economical or achieves any real purpose.

So, the explanation i was really seeking is what purpose did it serve, the logic behind design as it were, and if it was any good (safe) why'd they stop building them this way.

I'm still not understanding the root of your question. Are you asking about split bus panels in general or the spot welded connections?

[Marc]

Is that the part that's "crazy" or is it something else?

What's the point. Can't for the life of me see how this is any more efficient, economical or achieves any real purpose.

So, the explanation i was really seeking is what purpose did it serve, the logic behind design as it were, and if it was any good (safe) why'd they stop building them this way.

The purpose of the spot weld is to make a connection. The purpose of the split panel is to keep the maximum # of main breakers to 6 so you don't have to buy that expensive single main breaker. It's brilliant. Firemen just pull the meter these days anyway so what's the problem with 6 cheap 2-pole breakers instead of one expensive breaker? Saves money.

Marc

[John Kogel]

Is that the part that's "crazy" or is it something else?

What's the point. Can't for the life of me see how this is any more efficient, economical or achieves any real purpose.

So, the explanation i was really seeking is what purpose did it serve, the logic behind design as it were, and if it was any good (safe) why'd they stop building them this way.

The purpose of the spot weld is to make a connection. The purpose of the split panel is to keep the maximum # of main breakers to 6 so you don't have to buy that expensive single main breaker. It's brilliant. Firemen just pull the meter these days anyway so what's the problem with 6 cheap 2-pole breakers instead of one expensive breaker? Saves money.

Marc

Nice theory, Marc. But we have split bus panels in Canada, where a main breaker or disconnect is always required, no 6 breaker rule here.

I suppose you will say that panels intended for the US market ended up this side of the border. Ok that's possibly it. The only split bus panels I see here are very old 50's units.

[Carson2006]

Explanation of split-bus panels by a senior electrician, Al Hildenbrand and why you may find them in electrical systems (mostly dwelling units). Hope this helps.

?In the decades around the Code driven transition from 60 Amp minimum service size to 100 Amp, the split bus panel was a way to side step the quantum jump in cost of a single 100 Amp fuse pull out or circuit breaker as the single service disconnect.

The single panel enclosure had two separate bus systems in it. The service entrance conductors landed on lugs directly connected to the first bus system. This first bus system usually came with one service disconnect installed, commonly a 60 Amp, that disconnected the feeder to the second bus system. The second bus system was designed to hold the bulk of the branch circuits installed in the occupancy.

As noted, the first bus system could have up to six service disconnects (assuming there weren't others in the grouping just outside the panel), so this is where the larger loads, say the central AC, electric range, electric hot water heater, etc., were installed.

As a result of the split bus, no service disconnect needed to be larger than 60 Amp for a 125 Amp rated service center. There was a certain economy realized . . .

The service entrance conductors were sized for the load calculation at the time of installation, plus any "room to grow" the designer deigned to add."

[Rhudi]

I just discovered this in my home. I about freaked out, thinking the previous owner had just stuffed the wires under the bus bars. I couldn't see they had been spot welded.

[:-monkeyd

My question is this: What is that large 100Amp Double Pole breaker suppose to be used for? There is nothing on it. Can I use the space it's blocking, so I can move my Dryer (the 2nd Double Pole breaker on the left)?

That way, I can reduce the load on the "Main" 60Amp that supplies the lower bus.

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[Jim Katen]

You might want to remove the 100-amp breaker, move both of the lower 2-pole breakers up there, and move the two single-pole breakers down to the lower section.

[mjr6550]

I think the answer about cost savings is correct. The lower amperage main lighting breaker is less expensive. I recently bought 60 and 100 ampere circuit breakers and there was a significant price difference.

[Rhudi]

You might want to remove the 100-amp breaker, move both of the lower 2-pole breakers up there, and move the two single-pole breakers down to the lower section.

Thank yoiu. That makes complete sense to me. I wonder how many of these panels are out there scaring the wits out of other people. I was scheduled for this Monday to spend $4700 to have the entire thing gutted and replaced.[:-crazy]

No, it's just vacuum the panel and move a couple of breakers.

[Marc]

You might want to remove the 100-amp breaker, move both of the lower 2-pole breakers up there, and move the two single-pole breakers down to the lower section.

Thank yoiu. That makes complete sense to me. I wonder how many of these panels are out there scaring the wits out of other people. I was scheduled for this Monday to spend $4700 to have the entire thing gutted and replaced.[:-crazy]

No, it's just vacuum the panel and move a couple of breakers.

I've seen a few. They've been outlawed I'm told, but it's a brilliant concept and I wish I had one.

Send me yours if you ever swap it out. I'll rearrange the wiring a little to accommodate the power plant in my workshop. It powers my house when the hurricanes come.

Marc