ECN Forum Forums Safety Discussion and News Occupational Safety Discussion Split buss panelboards

Yes, the split bus panel - three phase above, single below- does exist. One of my customers has one in his restaurant.

You need to look a wee bit closer at the lables. They don't simply say 'no single phase circuits.' Rather, they describe the distribution systems for which the panel is approved; for the 'delta' distribution systems they'll say they're approved as power panels only, or not approved as lighting panels.

In other words, the panel neglects to include the 240/120 delta as one of the approved applications.

I'll see if I can find such a lable and post a pic. Heck, even when younger I needed a magnifyer to read the blessed things!

That's interesting Reno. I've seen single phase loads in
probably every Delta panel I've been in. I guess I'm guilty of not reading the ol fine print and I sure do miss my good eyesight!! I'm thinking that the labeling is a liability related move by the manufacturer since someone could inadvertently overvolt equipment with the stinger. What other reason do you see for a single phase restriction? I don't get it.

I couldn't agree more ... as soon as they make something 'idiot proof,' they come out with a better idiot.

Ironically, I only noticed this fine print myself when a service call brought me to an industrial rental space that had some electrical problems- including some 208V receptacles. Gee, I wonder how that might have happened

The gent there was so confident that 'electrric work wasn't rocket science' and that 'electricians charge too damn much' that -naturally- he couldn't bother to learn anything before trying to do it .... let alone read the fine print on the panel.

IMO, if you know enought about the trade to even understand tha lable, you already know enough to identify and avoid the high leg. The lable isn't the most absurd that I've seen, but it's on the list!

Still, in this day of third party inspections and hungry lawyers, it's only a matter of time before this little detail hits the inspection seminar circuit.

As I see it, that leaves us with two code-compliant ways to address 240/120 delta systems: 'sister' a single phase panel (fed from the three phase panel), or use a split buss panel.

Reno:
In the split buss, delta panel, was the top (3 phase) section barriered from the neutral buss?? I personally have not seen a split buss panel in many years.

I recall coming upon a attempt at 120 volts, from a 3 phase 240 delta, 3 wire, by a rocket scientist using the ground for a neutral, as this was 'power panel' only!

If you see a panel without a neutral buss, you can be sure it was intended as a 'power only' panel. Remember that in the days before the 2008 NEC, there was a distinction between panel types, with the 'lighting and appliance' panel being defined as having a large number of neutral-served circuits, and then went on to limit the number of circuits allowed.

In 2008, that distinction -and limit- went away.

In a split buss panel, there is a split between the two halves - but you might not be able to see it without removing the breakers. Typically, all of the busses are separate, with the single phase part fed from a breaker in the three phase part.

Though I need to be careful as to what I claim is 'typical.' I haven't seen that many split-buss panels- and all of them were old enough that the 'neutral buss' was a plate at the top, where you had to wrap each wire around a screw.

There is no barrier separating the sections, and wires commonly pass through the 'other' part of the panel.

Thanks Reno.

Yes, I remember the old screw/wrap neutral blocks. Now, that's an old panel.

Reaching into memories, the split buss had a cb in the 'power' section that fed the GP section via factory conductors to lugs on the lower buss. The ones I remember were FPE Stab-Loc. No 'Main' OCP, and utilized the six switch rule, until some hack made modifications.

New Jersey (in my day) was full of split-bus panels, mostly FPE and Murray, 60 amp "lighting" main for the sub section.

The DC metro area also had them quite frequently, especially in total-electric homes since 200A main breaker panels were still fairly expensive back in the 80's.

I remember some of the larger ones even having two sub-sections, thus limiting the mains section to only four disconnects. We would often find all single-pole circuits in one sub-section and heating/AC loads in the other, leaving the dryer, range, water heater, etc. breakers as
mains.

No matter the location, hack jobs almost always resulted in single-pole breakers ending up in the mains section or <gasp> some Harry Homeowner managing to cram twin breakers in those spaces. Ah yes, those were the days.....