Split-bus panels

[jeff48356]

When a customer calls you for some electrical upgrades at their house, and you discover that they have an old split-bus panel, would you recommend that they have you upgrade it? I always do because the customer does not have full access to all the amps that the service is rated at. For example, most split-bus panels are rated at 100 amps, with a 50A or 60A breaker being used to power the lower part of the panel (where all the 120V breakers are located). Even though the panel is rated at 100 amps, they would only have access to 50A or 60A for ordinary loads. If I replace the box with a new 100A panel, then they will have access to 100 amps regardless of the loads being used. Also, many split-bus panels are full as far as the lower section, and I need to explain that 120V loads are not allowed in the upper section.

 

[mbrooke]

Unless you have something like Electric heat or a major subpanel on the lower section I would not worry about it.

 

[Cow]

If the panel is in good shape, no, I do not recommend they replace it.

The only wear items are the breakers themselves. And those can be replaced.

 

[480sparky]

The mere fact that they have a split-bus panel won't invoke an upgrade in my book. It would take either a load calculation to show it's overloaded, or the addition of more circuits that would cause it to be overloaded for me to even consider it.

If the 'upgrades' are merely changing lights out to ceiling fans, or adding a few switches or outlets... I wouldn't press the issue.

 

[infinity]

When a customer calls you for some electrical upgrades at their house, and you discover that they have an old split-bus panel, would you recommend that they have you upgrade it? I always do because the customer does not have full access to all the amps that the service is rated at. For example, most split-bus panels are rated at 100 amps, with a 50A or 60A breaker being used to power the lower part of the panel (where all the 120V breakers are located). Even though the panel is rated at 100 amps, they would only have access to 50A or 60A for ordinary loads. If I replace the box with a new 100A panel, then they will have access to 100 amps regardless of the loads being used. Also, many split-bus panels are full as far as the lower section, and I need to explain that 120V loads are not allowed in the upper section.

Is that true?

 

[jeff48356]

Is that true?

It is around here. Local inspectors only allow 240V circuits in the upper sections.

 

[growler]

I need to explain that 120V loads are not allowed in the upper section.

Is that true?

It is around here. Local inspectors only allow 240V circuits in the upper sections.

The reason there is an upper and lower section on a split buss panel is to keep the number of breakers in the upper section at 6 or less. Six switch rule.

If you were to use single pole breakers you could go above six switches.

But if you used a double pole 15 or 20 amp breaker with two 120 volt circuits then the number of breakers would remain at 6 or less.

Infinity was right , in my opinion.

 

[LarryFine]

Even though the panel is rated at 100 amps, they would only have access to 50A or 60A for ordinary loads. If I replace the box with a new 100A panel, then they will have access to 100 amps regardless of the loads being used.

This is not accurate. Unless you're tripping (one of) the 60a breaker(s), you're losing no capacity at all.

If anything a split-but panel makes it easier to over-draw than a main-breaker panel of the same rating.

Also, many split-bus panels are full as far as the lower section, and I need to explain that 120V loads are not allowed in the upper section.

Not accurate either; you're not allowed to exceed six breaker handles, a.k.a. "six throws of the hand".

If you need room, you can move any 2p breakers to the top if possible, and/or install tandem breakers.

 

[jpreed]

How about this question re: Split Bus ?

How about this question re: Split Bus ?

I saw what appears to be a split bus panel with the lower bus "main" breaker wires soldered to the bus? There was a split in the panel, showing bus bars running the whole length of the panel, a 240 volt breaker's wires were soldered to the two bus bars at the split. This breaker was the top breaker on the lower part of the "split bus". (I tried to attach a pic, but can't figure out how to do that) It did not look like this breaker shut off the power to the lower part. Anyhow, this seems quite odd. Is this standard? Seems not. Thanks! John

 

[Dennis Alwon]

I am confused-- you are showing 2 different panels. The CH panel does look like a split buss but I have not ever seen a ch split buss before

 

[LarryFine]

The third pic is of a different panel, and I have seen split-bus CH panels before.

A split-bus panel takes advantage of the six-throws exception to a main breaker.

Yes, they are as described, with the conductors spot-welded to the bus sections.

 

[infinity]

A Larry stated spot welding to the bus is a common practice for these split bus panels and was done by the manufacturer.