RCCB, determination of current capacity

GreySquirrel

RCCB, determination of current capacity

Is the current capacity of an RCCB determined by the upstream fuse/MCB or the downstream MCBs?

For example:

upstream fuse/MCB = 63A

Downstream MCB = 20A

RCCB current capacity = ?

Randyleprechaun

It's determined by the total load you expect to pass through it!!!!!

Bruthal

Its determined by its own current interrupt capacity written on the RCCB.
If its a 63 amp 30ma RCCB then it trips at in imballance of 0.03amps(30ma) but is rated to break or interrupt a current of 63 amps.

GreySquirrel

It will be way less than 13 Amps

GreySquirrel

robbie7730 wrote: »

Its determined by its own current interrupt capacity written on the RCCB.
If its a 63 amp 30ma RCCB then it trips at in imballance of 0.03amps(30ma) but is rated to break or interrupt a current of 63 amps.

okily dokily

GreySquirrel

GreySquirrel wrote: »

It will be way less than 13 Amps

No it won't.

Two PCs approx 3 Amps each

Two monitors

1st:

AC input voltage / frequency / current 100 to 240 VAC / 50 or 60 Hz + 3 Hz / 3.0A

Inrush current 120V: 40A (Max.)
240V: 80A (Max.)

Second: ?


So approx 12 Amps.

Randyleprechaun

Randyleprechaun wrote: »

It's determined by the total load you expect to pass through it!!!!!

What I meant here is that you choose one with higher current carrying capacity than your expected load

Randyleprechaun

GreySquirrel wrote: »

It will be way less than 13 Amps

GreySquirrel wrote: »

No it won't.

Two PCs approx 3 Amps each

Two monitors

1st:

AC input voltage / frequency / current 100 to 240 VAC / 50 or 60 Hz + 3 Hz / 3.0A

Inrush current 120V: 40A (Max.)
240V: 80A (Max.)



Second: ?


So approx 12 Amps.

?????

GreySquirrel

Randyleprechaun wrote: »

?????

The monitor? The're the specs from its manual.

But 80 amp in-rush current would trip the MCB would it not?


And I just checked the PSU of one PC. It says Input 12 Amps?!

GreySquirrel

None of the PCs or monitors ever tripped the relevant MCBs.

I've two dedicated radial final circuits for PCs and electronics.

RCCB 30 mA A type followed by an MCB B curve 20A.

Same on second circuit.

I'm looking at Surge Protection Devices and will start another thread about that.

Bruthal

Anything with wire windings will have a higher current at instant of turning on, traditional incandescent light bulbs are the same, they take 10 to 15 times as much at the instant of switching on as they do when running, so a 100 watt bulb could take 5 or 6 amps at the instant of turn on then down to 0.45 amps when on. The inrush is usually so brief that the MCB`s dont trip if the surge is higher than their rating. 3 or 4 times the rating in the case of a b type i think.

2011

If its a 63 amp 30ma RCCB then it trips at in imballance of 0.03amps(30ma) but is rated to break or interrupt a current of 63 amps.

The RCCB described above is rated to safely and indefinitely carry a current of 63A. It is not designed to operate when the current flowing through it exceeds 63A. An RCBO is a combination of an RCD and an MCB, I think that this is what Robbie is referring to.

An RCCB (Residual Current Circuit Breaker) is another name for an RCD (Residual Current Device).

When an RCD is connected to a circuit it will have a live and a neutral conductor connected through it. When this circuit is healthy the current flowing through the live will be equal to the current flowing back through the neutral. In this case the RCD will not operate (trip). In the real world the live (or phase current) and the neutral current will never be exactly equal, there will always be a slight difference. This differential in current is generally reffered to as "I∆n". For most domestic RCDs I∆n is 30mA. This means that if I∆n > 30mA for a particular circuit it will cause the RCD to operate, causing the circuit to be disconnected.

An MCB is a completely different animal. It does not monitor the neutral current at all. Like a fuse, it is designed to operate under short circuit or overlaid conditions.

From what Grey Squirrel has described I do not see him having any issues with circuits tripping.

Anything with wire windings will have a higher current at instant of turning on

+ 1

Bruthal

2011 wrote: »

The RCCB described above is rated to safely and indefinitely carry a current of 63A. It is not designed to operate when the current flowing through it exceeds 63A. An RCBO is a combination of an RCD and an MCB, I think that this is what Robbie is referring to.

Well what i meant/said was the RCCB(RCD) described above has in interrupt capacity of 63 amps, and as such i said it trips at an imballance of 0.03 amps, and upon tripping is rated to interrupt 63 amps. If its rated to interrupt 63 amps then this is its current carrying capacity which was the OP`s question. I did`t actually mean it will trip when the current overloads above 63 amps but it is rated to trip 63 amps on imballance tripping.

The key words i used were its interrupt capacity although this would be way above the actual 63 amp rating which is more its continous carrying capacity alright than its actual breaking capacity.

This rating is written on it anyway. I never mentioned that it does not trip on overload as the OP had referenced the 63 amp fuse before the RCCB(RCD) and the 20 amp after it, so i assumed he knew its not an overload MCB device but just an RCD.

GreySquirrel

robbie7730 wrote: »

Well what i meant/said was the RCCB(RCD) described above has in interrupt capacity of 63 amps, and as such i said it trips at an imballance of 0.03 amps, and upon tripping is rated to interrupt 63 amps. If its rated to interrupt 63 amps then this is its current carrying capacity which was the OP`s question. I did`t actually mean it will trip when the current overloads above 63 amps but it is rated to trip 63 amps on imballance tripping.

The key words i used were its interrupt capacity although this would be way above the actual 63 amp rating which is more its continous carrying capacity alright than its actual breaking capacity.

This rating is written on it anyway. I never mentioned that it does not trip on overload as the OP had referenced the 63 amp fuse before the RCCB(RCD) and the 20 amp after it, so i assumed he knew its not an overload MCB device but just an RCD.

The RCD is an RCCB. And yes I am aware it is not an overload device.

The RCD is a 25 A, I delta n 0.03 A. Checking the "small print" is difficult. I need new glasses. It says Im 1500 A and in a little rectangle "6000". The 6000 I take to be the breaking capacity. I am not sure what "Im" stands for. Maximum current? Of what? Surge current?

Also A (type?) with a little rectangle with a sine wave over what I call the "pair of breasts symbol", or to be PC "the two hump camel sign". No disrespect to any any camels lurking about.

2011 wrote: »

The RCCB described above is rated to safely and indefinitely carry a current of 63A. It is not designed to operate when the current flowing through it exceeds 63A. An RCBO is a combination of an RCD and an MCB, I think that this is what Robbie is referring to.

An RCCB (Residual Current Circuit Breaker) is another name for an RCD (Residual Current Device).

When an RCD is connected to a circuit it will have a live and a neutral conductor connected through it. When this circuit is healthy the current flowing through the live will be equal to the current flowing back through the neutral. In this case the RCD will not operate (trip). In the real world the live (or phase current) and the neutral current will never be exactly equal, there will always be a slight difference. This differential in current is generally reffered to as "I∆n". For most domestic RCDs I∆n is 30mA. This means that if I∆n > 30mA for a particular circuit it will cause the RCD to operate, causing the circuit to be disconnected.

An MCB is a completely different animal. It does not monitor the neutral current at all. Like a fuse, it is designed to operate under short circuit or overlaid conditions.

From what Grey Squirrel has described I do not see him having any issues with circuits tripping.


+ 1

I understand that the RCBO is a combined RCCB and MCB. The confusion here is a B type. Does it refer to the RCCB bit or the MCB bit? Both have B types, although for the MCB, curve and type are used interchangably.

Surge protection is now looming. There seems to be more lightning strikes per year than before. Also I don't remember snow and lightning together like during the recent snow.

Hager have some interesting literature on lightning and SPDs, but it seems to have been translated from the French who use all TT systems and all their protective devices are double pole.

Some of Hager's diagrams are contradictory and also show SPDs with Neutral to Earth connections. The 4th edition Rules say a TN-C-S system does not need an N to earth connection.

The Rules also have a great labeled diagram for SPDs in a TN-C-S system but don't explain the labels.

And I am amazed with continental prices compared to ours. Less than half in some cases.


By the way, this is a great forum with Knowledgable and interesting posts.

2011

robbie7730 wrote: »

Well what i meant/said was the RCCB(RCD) described above has in interrupt capacity of 63 amps, and as such i said it trips at an imballance of 0.03 amps, and upon tripping is rated to interrupt 63 amps. If its rated to interrupt 63 amps then this is its current carrying capacity which was the OP`s question. I did`t actually mean it will trip when the current overloads above 63 amps but it is rated to trip 63 amps on imballance tripping.

The key words i used were its interrupt capacity although this would be way above the actual 63 amp rating which is more its continous carrying capacity alright than its actual breaking capacity.

This rating is written on it anyway. I never mentioned that it does not trip on overload as the OP had referenced the 63 amp fuse before the RCCB(RCD) and the 20 amp after it, so i assumed he knew its not an overload MCB device but just an RCD.

+ 1
Agree 100%

In general (not from you) there seems to be quite a bit of confusion regarding RDCs, MCBs RCBOs etc....

Bruthal

GreySquirrel wrote: »

The RCD is an RCCB. And yes I am aware it is not an overload device.

Yes i assumed that from your post so i did`t mention its not a 63amp overload which the 63amp refers to.

B type is to do with MCB`s and is the factor above the MCB`s rating which will cause it to trip straight away.

A 20 amp one could stay on a long time at 25 amps, a B type could take 50 or 60 amps to cause a fast trip. This allows motors to start etc.

2011

The confusion here is a B type. Does it refer to the RCCB bit or the MCB bit?

This refers to the MCB part.

Bruthal

2011 wrote: »

+ 1
Agree 100%

In general (not from you) there seems to be quite a bit of confusion regarding RDCs, MCBs RCBOs etc....

Yes there does alright, would you say the 63 amp rating is the actual contact rating also, to be rated to repeatedly break 63 amps, we know it could probalby interupt a very high fault current, thousands of amps possibly,,, but the 63 amps could perhaps be seen as the contacts rating also.

Bruthal

Overall it would have to be seen as the continous current the RCD can carry anyway, not much doubt about that.

M cebee

a 25amp type A rccb/rcd and a 20amp B type mcb for each final circuit

is that what he has-sounds ok:)

you can buy an rcbo with the A+B protection( leakage and trip curve) afaik
for circuits with rectifiers etc.

the 'current rating' needed will be the maximum sustained load current determined by the mcbs+diversity 'downstream' i would think

GreySquirrel

M cebee wrote: »

a 25amp type A rccb/rcd and a 20amp B type mcb for each final circuit

is that what he has-sounds ok:)

Yep

25amp type A rccb/rcd and a 20amp B type mcb

M cebee

http://www.chnphx.com/products/Residual-Current-Device-246315.html
going by that i'd say that your 1500 and 6000

are prob the 'breaking capacity' and 'rated short-circuit current' respectively

Im (1500 here)is the making/breaking capacity

your 6000 is prob the L-N short circuit current the device can safely handle

GreySquirrel

M cebee wrote: »

http://www.chnphx.com/products/Residual-Current-Device-246315.html
going by that i'd say that your 1500 and 6000

are prob the 'breaking capacity' and 'rated short-circuit current' respectively

Im (1500 here)is the making/breaking capacity

your 6000 is prob the L-N short circuit current the device can safely handle

thanks for the link. Very informative.

Bruthal

Imagine standing beside that with 6000 amps goin through it:eek:

GreySquirrel

robbie7730 wrote: »

Imagine standing beside that with 6000 amps goin through it:eek:

And on a wet floor :eek:

My brother lives in America. He showed me his basement. It was like a submarine what with all the pipes and ducting. He opened the distribution box. It was full of bare copper busbars shaped like those shower rails you hold onto for support. And a concrete floor. Gave me the willies just looking at it.

Bruthal

GreySquirrel wrote: »

And on a wet floor :eek:

My brother lives in America. He showed me his basement. It was like a submarine what with all the pipes and ducting. He opened the distribution box. It was full of bare copper busbars shaped like those shower rails you hold onto for support. And a concrete floor. Gave me the willies just looking at it.

Yea i remember in dublin airport we had to put a timer on the fuel pumps that fill the trucks to refuel the planes. Originally they just had to connect the hose and press start and leave the pumps going and go off and have tea etc. We made up a timer setup so after a few minutes a light would flash and if the flashing button was not pressed within a minute it would shut down, so it would have to be attended.

But the panel with the contactors we had to incorporate the timer wiring into had big exposed bus bars and the fella i was workin with dropped a short piece of wire in by accident blowing 150 amp fuses i think they were. The flash left his arm nicely burnt but it was not immediately apparent. By the next day it showed up with bad burns, amazing the damage a brief flash from a large short can cause.

Seen it in intel as well when a fella let a ratchet thing hit main bus bars, it was like a bomb went off in the panel.

GreySquirrel

robbie7730 wrote: »

Yea i remember in dublin airport we had to put a timer on the fuel pumps that fill the trucks to refuel the planes. Originally they just had to connect the hose and press start and leave the pumps going and go off and have tea etc. We made up a timer setup so after a few minutes a light would flash and if the flashing button was not pressed within a minute it would shut down, so it would have to be attended.

What! No tea. Spoilsport.

Was reading somewhere recently, that although they have some idea what to do to set up voltages and get current to flow, they really have no idea why electricity works.

Reading about lightning at the moment. An average bolt of positive lightning carries an electric current of about 300 kA and 5,000 megajoules of energy. Now that would really boil the lads' tea.

Also lightning strikes produce x-rays so maybe your mate got radiation burns.

Bruthal

GreySquirrel wrote: »

What! No tea. Spoilsport.

Was reading somewhere recently, that although they have some idea what to do to set up voltages and get current to flow, they really have no idea why electricity works.

We only have to ask 3 or 4 questions about electricity based on the answer given to each question before know one knows the answer.

Reading about lightning at the moment. An average bolt of positive lightning carries an electric current of about 300 kA and 5,000 megajoules of energy. Now that would really boil the lads' tea.

Also lightning strikes produce x-rays so maybe your mate got radiation burns.

Could of actually been burns from vaporised copper possibly. All the UV rays etc should be present in electric arc welding but that does not seem to be too severe, but an explosive short circuit has flying metal particles so maybe thats it.

GreySquirrel

robbie7730 wrote: »

We only have to ask 3 or 4 questions about electricity based on the answer given to each question before know one knows the answer.




Could of actually been burns from vaporised copper possibly. All the UV rays etc should be present in electric arc welding but that does not seem to be too severe, but an explosive short circuit has flying metal particles so maybe thats it.

There's a utube video going around. it's a train in what looks like India. There is a guy on the roof threatening to touch the overhead cable. He does. Poof. Gruesome.

Bruthal

Yea i seen that one, 25kv i think them lines are. It would be rare to survive contact with them.