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View Full Version : single and double circuit breaker !!







kefah
17-01-2014, 09:51 PM
hi
here the electric is 220 volt
usually for cable (line and neutral) we use double circuit breaker

11108

but some electrician here use single circut breaker

11109

for the line conductor

and connect the neutral conductor without breaker
but directly by tape

11110


so what are the advantages and disadvantage of this method

install monkey
17-01-2014, 09:59 PM
jointing a neutral with tape only can result in a loose connection ( a hot joint)
in the uk we dont fuse the neutral
the live is always fused, some american stuff has fuses on live and neutral- if the fuse blew on the neutral then the equipment would be live all the way back to the blown fuse
a doulbe pole mcb would be best as if it tripped it would kill the equipment and prevent any back feed from occuring

chilliwilly
18-01-2014, 12:08 AM
If the joint is twisted together it shouldn't overheat, but ideally it should have a connector/screwit/wirenut/maurrette over the joint to maitain the integrety of the joint.

And yes the American gear sometimes fuses the neutral, only seen it done over here on the primary side of some reduced low voltage systems for some reason, a fellow electrician once tried to tell me it protects both legs on the primary and secondry windings. On a centre tap secondary its understandable, but I always opted for the 110v to earth/ground system. It makes fault finding a lot easier.

Magoo
18-01-2014, 02:58 AM
Hi
you can get two pole breakers with levers pinned so totally isolating field circuit, also there are RCD protection single phase breakers, similar to the one in the pics. Individually switching neutral circuit is illegal here, I have come across two pole breakers and two pole contactors on 3 phase US equipment, a definite death trap.

kefah
18-01-2014, 06:51 AM
sorry for my broken english
what i want to say
220 volt single phase
is
here we use the breaker with hot conductor only
but with neutral conductor we dont use breaker
but connect it directly
by tapes

Peter_1
19-01-2014, 10:10 AM
Don't excuse for your English Kefah, we're happy you post here from a country which came so sadly in the news the last years.
It's better to installa a double pole breaker. The difference in price is very small.
You then can isolate a faulty section completely.
Thé most important reason for me not to tie up al the neutrals togteher is for fault finding.
Search once for a small electrical loss with your meggar when al neutrals are tied together? Much fun
We even install sometimes a 3rd contact aside the breaker connected to an alarm so that the user is warned a breaker is blown.

Frikkie
19-01-2014, 10:37 AM
From an electrical protection point of view a 2-pole circuit breaker should only really be used if the supply arrangement leaves even a remote possiblity that the neutral could ever become at elevated voltage to earth. It's better to use a circuit breaker that provides early break/late make for the live and late break/early make for the neutral, this is know as an SP+N MCB which provides overload protection on the live and only isolation on the neutral.

kefah
20-01-2014, 07:55 PM
ok
thank u all

chilliwilly
20-01-2014, 11:04 PM
If the joint is twisted together it shouldn't overheat, but ideally it should have a connector/screwit/wirenut/maurrette over the joint to maitain the integrety of the joint.

And yes the American gear sometimes fuses the neutral, only seen it done over here on the primary side of some reduced low voltage systems for some reason, a fellow electrician once tried to tell me it protects both legs on the primary and secondry windings. On a centre tap secondary its understandable, but I always opted for the 110v to earth/ground system. It makes fault finding a lot easier. Just to add to my earlier quote, I forgot that the North American 240 v residential/domestic system is a supply derived from 2 phases from a 3 phase system, and doesn't use a grounded/earthed neutral to obtain 240v on domestic/residential supplies. It has a 2 legged live/hot supply with no neutral, 120 v to earth/ground, and 240v between phases If both 120v and 240v are required, then a third wire is used as a neutral, and isn't usually protected. So the fuses and circuit breakers are there to protect both phases, and not neutrals.

Its just when they import to other countries that have a grounded/ pme'd earthed neutral to obtain 220-240v systems, it looks like they fuse the neutral. This is one of my bug bears when I see the
CE mark on any equipment designed, manufactured, and built, outside the UK, and then imported here. It means nothing more than a licence to import into the UK without comply to British Standards

MikeHolm
21-01-2014, 03:31 AM
Just to add to my earlier quote, I forgot that the North American 240 v residential/domestic system is a supply derived from 2 phases from a 3 phase system, and doesn't use a grounded/earthed neutral to obtain 240v on domestic/residential supplies. It has a 2 legged live/hot supply with no neutral, 120 v to earth/ground, and 240v between phases If both 120v and 240v are required, then a third wire is used as a neutral, and isn't usually protected. So the fuses and circuit breakers are there to protect both phases, and not neutrals.

Its just when they import to other countries that have a grounded/ pme'd earthed neutral to obtain 220-240v systems, it looks like they fuse the neutral. This is one of my bug bears when I see the
CE mark on any equipment designed, manufactured, and built, outside the UK, and then imported here. It means nothing more than a licence to import into the UK without comply to British Standards

Well said sir....it would make a lot more sense to have 240 single but that is not what we do. All our "double pole" breakers have the levers tied together. It wouldn't do to have one leg trip now, would it.