Terminology

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GerryB

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woodbridge, ct. USA
This will be a stupid question for many. I was reading a post and the term "split phase panel " was used. I used to think that referred to old panels I've seen with apparently two main breakers, one top and another lower, maybe to separate lighting from other loads. But actually the standard resi panel with two hots and a neutral is a "split phase panel", correct? I've always called them and heard them called single phase. We normally call our breakers for this panel single pole or double pole (or 2 pole), not single phase and two phase, (or split phase). Any comments?
 
GerryB said:
This will be a stupid question for many. I was reading a post and the term "split phase panel " was used. I used to think that referred to old panels I've seen with apparently two main breakers, one top and another lower, maybe to separate lighting from other loads. But actually the standard resi panel with two hots and a neutral is a "split phase panel", correct? I've always called them and heard them called single phase. We normally call our breakers for this panel single pole or double pole (or 2 pole), not single phase and two phase, (or split phase). Any comments?
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Split phase is single phase. 120/240 residential is not two phase. Split phase refers to single phase, usually with a center tapped transformer, to provide both 120 and 240 volts. So yes, a resi panel with two hots and a neutral is a split phase panel. It is also a single phase panel.

Poles and phases are not synonymous.
 
GerryB said:
I used to think that referred to old panels I've seen with apparently two main breakers, one top and another lower, maybe to separate lighting from other loads.
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That's a split bus panel, and the purpose was to use six 2p breakers instead of a single main breaker, using the "six throws of the hand" allowance.
 
GerryB said:
I used to think that referred to old panels I've seen with apparently two main breakers, one top and another lower, maybe to separate lighting from other loads.
Click to expand...
The historic "split bus panel" was developed as a way to get 100, or even 125 Amp service entrance conductors connected to a set of branch circuits while never paying for the 100 or 125 Amp service disconnect breaker.

The 100 or 125 Amp bus was split into two sections. The upper section had space for multiple service disconnects (up to six) all 60 Amps or less in size. One of these service disconnects (60 Amp) supplied the power to the lower section of bus and this lower section was generally known as the "Lighting Section".

The remaining service disconnects supplied major loads, such as the range, electric water heater, electric clothes dryer, central air, electric furnace, etc.

The service conductors were sized by the load calculation, and, most of the time, had an added capacity for some growth, but not always.

ETA: Larry is right. The split bus panels were very popular Sixties into the Eighties.
 
Some split-bus panels had two lower sections, supplied through two 60a "main" breakers. I've made generator-ready panels from SqD QO panels, using the QO interlock rocker.

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Yes, Cutler-Hammer and others made a double split panel (3 total buss sections). The top section could hold 6 2 pole Breakers and I believe the middle and bottom sections could hold 12 to 16 breakers ea.. The bottom bus bars had perhaps 2 gauge copper soldered on, and they were pre bent to go into the 2 pole breakers in the top part of the panel, usually in spots 5 / 7 and 9/11.

The other four spaces up top are usually the range, the dryer, the water heater, and the air conditioning/HVAC or baseboard heat.

Old FPE (Flawed Piece of Equipment) Stab-Lock had a split buss with two mains. They had a very funky buss arrangement, you could not put a 2 pole breaker just anywhere, and the numbers were not consecutive or consistent.
 
K8MHZ said:
Split phase is single phase. 120/240 residential is not two phase. Split phase refers to single phase, usually with a center tapped transformer, to provide both 120 and 240 volts. So yes, a resi panel with two hots and a neutral is a split phase panel. It is also a single phase panel.
Click to expand...
On that basis, hexaphase would have to be called three-phase. Three centre tapped windings after all.
Yes, I know..............
 
JFletcher said:
Yes, Cutler-Hammer and others made a double split panel (3 total buss sections). The top section could hold 6 2 pole Breakers and I believe the middle and bottom sections could hold 12 to 16 breakers ea.. The bottom bus bars had perhaps 2 gauge copper soldered on, and they were pre bent to go into the 2 pole breakers in the top part of the panel, usually in spots 5 / 7 and 9/11.

The other four spaces up top are usually the range, the dryer, the water heater, and the air conditioning/HVAC or baseboard heat.

Old FPE (Flawed Piece of Equipment) Stab-Lock had a split buss with two mains. They had a very funky buss arrangement, you could not put a 2 pole breaker just anywhere, and the numbers were not consecutive or consistent.
Click to expand...

Pushmatic was popular to have two bus sections with 100 amp main on each section - common main lugs to accept ~200 amp conductor.

Quite a few of the old fuse panels with two 60 amp pull outs and four plug fuses were actually 100 amp rated - the two 60 amp pullouts were both connected directly to main lugs. The "main" killed the four plug fuses and feed thru lugs, the "range" was still live when the "main" was pulled.
 
kwired said:
Non military people and maybe even younger military people - that is a can opener. Otherwise it is a P-38.:happyyes:
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I knew it as a P-38 back when I was a teenager, and I'll be 63 in one month. That's how I knew to look for a pic of it.
 
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