[Dustin89]

hi everyone, I'm new here and I was searching for solutions online when I came across this website. I find it very interesting.
I'm a student in electrical electronics engineering, @ 500 level.
in a double pole 100 ampere main breaker, split busbar 240volt at 50hertz supply,
if the current carrying capacity of the sub circuit breakers in either busbars exceed 100amp will the main breaker trip?

or if the current carrying capacity of the the sub circuit breakers in both busbar combine exceed 100amp?

DUSTIN 89
"he who ask is a fool for a short time, he who never ask is a fool forever "

 

[poiihy]

I am pretty sure that the breaker will trip when either pole exceeds the rating. Same with any double pole breaker. Because a double pole breaker is basically just two breakers attached together and interconnected so they trip together.

 

[rjniles]

Depends. If the current exceeds the capacity of the branch circuit breaker, that breaker will trip. If the sum total of all the branch circuits exceed 100 amps (without exceeding the capacity of any branch circuit breaker), the main will trip.

 

[Oso954]

I wouldn't try to answer the question as it it not a North American power question. While I've looked at 240v 50hz systems in various countries, I've never seen a 2 pole main on a split bus panel. It is probably a commercial service rather than residential.

Since he didn't specify the "exceed 100 amps" in quanity or time, and we don't have trip curves for his equipment, we don't know how long or if it would trip at x amps above 100amps.

 

[Jump-start]

DIN rail consumer unit or North American load center?

 

[Tom738]

This is what data sheets are for. Or calling the manufacturer. Or testing in a lab.

 

[joed]

You help with your homework?

if the current carrying capacity of the sub circuit breakers in either busbars exceed 100amp will the main breaker trip?

It's possible but for sure. It all depends on the actual load not the breaker rating.

 

[micromind]

I think what the OP is getting at is 'will an overload on either pole trip the breaker?'

The answer is yes, if one pole is loaded to 2 amps while the other is loaded to 200 amps, the breaker will trip. And if it is a factory assembled 2 pole unit, it'll trip both poles even though only one is overloaded.

Rob

 

[Dustin89]

what I really mean by the questions is
if the actual load of the sub circuit breakers in either busbar exceed 100amp or if the sum the total load of all the sub circuit breakers in both busbar combine exceed 100amp?
can I safely load each side of the busber to 100amp each?

thanks for the reply.

 

[joed]

can I safely load each side of the busber to 80% each?

yes you can

If the current on either bus bar exceeds 100amps the breaker will trip. Do not add the two bus currents.

 

[Dustin89]

thank you Joed.
so I can safely load the two sides to 80% each.
but I feel like if I load the two busbar to 100amp each is like I'm loading 200amp in a double pole 100amp main breaker

 

[poiihy]

You can draw up to 200 amps of 120 volts from a 2-pole 100 amp breaker. Or you can draw 100 amps of 240 volts.
You might be surprised about drawing twice the current but actually you are getting the same amount of power (watts).

 

[Jump-start]

thank you Joed.
so I can safely load the two sides to 80% each.
but I feel like if I load the two busbar to 100amp each is like I'm loading 200amp in a double pole 100amp main breaker

NEC load calc, but usually adding circuits to a home panel will not cause a problem as most dwelling services are already over sized. Also consider that adding the breaker handles up mean nothing. A 100 amp panel can have over 400 amps worth the breakers.

 

[Dustin89]

actually in my country here the supply voltages are;
phase to phase 420 to 440 volt

phase to neutral 220 to 240 volt

50 Hz 220 volt supply and not 60 Hz 120 volt supply

 

[poiihy]

actually in my country here the supply voltages are;
phase to phase 420 to 440 volt

phase to neutral 220 to 240 volt

50 Hz 220 volt supply and not 60 Hz 120 volt supply

Wow I did not know houses there have two phases; I thought they only had 220 volts.
That 440 volt power supply would make a good electric rat trap. :biggrin2:

 

[Dustin89]

actually it is Nigeria in West Africa.
the supply voltage here is
220 volt line to neutral and
440 volt phase to phase

 

[Jump-start]

actually in my country here the supply voltages are;
phase to phase 420 to 440 volt

phase to neutral 220 to 240 volt

50 Hz 220 volt supply and not 60 Hz 120 volt supply

So your 3 phase system is high leg delta? Or homes are split phase? Im confused.

 

[Dustin89]

I mean one phase and a neutral here is 220/240 volt supply
in my country we don't use 120 volt supply here.

 

[Oso954]

Nigeria lists 2 commercial service voltages. 220/380 off the 11kv system or 230/400 off of the 15kv system.

So it sounds like 2 phases (of 3) at 120 degrees.

 

[Dustin89]

you are correct.