I did a test and inspection on a domestic premises and noticed the RCBO's installed were type C, these have a much lower Zs value than the type B, apart from that i always assumed type C's were for circuits with equipement that had a high start up current. Are type C RCBO's acceptable in domestic installations?.
type C rcbo's
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They are not a problem so long as the Zs is ok.
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Absolute rubbish.
Where on do earth have you got this drivel from - if you exceed the tabulated value for efli you must carry out design CALCS to ensure that you still meet the requirements for thermal constraint with regards short circuit protection.
Once you deviate from the OSG you can longer use it as an excuse for any lack of relevant design knowledge.
I`ve had a bad day ....
In most cases it would meet the requirements.
......Just Sayin.........
......Just Sayin.........
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Steve3948,
I'm not saying you, or Schneider are wrong, but...
What about protection against small overloads of long duration?
Not giving an answer, just promoting debate.
I'm not saying you, or Schneider are wrong, but...
What about protection against small overloads of long duration?
Not giving an answer, just promoting debate.
sparkytim
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I am sorry you have had a bad day.
Perhaps you could explain how Thousands of TT installs can comply with a Zs of 200 ohms and more?
And yes I often deviate from the OSG as it is only a guide.
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I did say in most cases :innocent :innocent:innocent:coat
All to do with the trip curve apparently ......Just sayin.........
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Thing is Steve, this could be interpreted as not in any case, as any circuit is capable of being overloaded by a small amount for a long duration!... :innocent
I've looked into this before, BS7671 does allow protection against indirect contact to be provided by an RCD device on a TN system. Its incredably shoddy design practice to design in this way and shows a lack of regard for the basic principles of circuit design!
Well Ok then in "Professionals case" hahaThing is Steve, this could be interpreted as not in any case, as any circuit is capable of being overloaded by a small amount for a long duration!... :innocent
My understanding was that the principle operation of the device was equal to or better than a non rcd type, hence why on a TT system it's the only acceptable way, however it will interesting to hear other views because if it's not OK, then all these TT systems out there are in serious trouble.
....Just sayin......
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How many TT systems use type C breakers ??
I had a similar question a few weeks ago. A type C rcbo protecting a shower circuit.
I rang the NAPIT technical advice line. They advised me to measure the line earth loop,AND the neutral earth loop, then compare the readings with the 'corrected' Zs figure in the on site guide for type C breakers/rcds. The overcurrent protection is relevant !! Not just the 'earth leakage' fault protection. The circuit was a short run in 10mm t & e cable.The circuit did comply, but by just .02 ohm !
Best wishes,
Speedster.
---------- Post Auto-Merged at 21:46 ---------- Previous post was made at 21:39 ----------
Its getting late. That should have read, Line Earth loop AND Line Neutral loop ! The rest is the same .
Hope it hasn't caused too much confusion !!!!!
Speedster.
I had a similar question a few weeks ago. A type C rcbo protecting a shower circuit.
I rang the NAPIT technical advice line. They advised me to measure the line earth loop,AND the neutral earth loop, then compare the readings with the 'corrected' Zs figure in the on site guide for type C breakers/rcds. The overcurrent protection is relevant !! Not just the 'earth leakage' fault protection. The circuit was a short run in 10mm t & e cable.The circuit did comply, but by just .02 ohm !
Best wishes,
Speedster.
---------- Post Auto-Merged at 21:46 ---------- Previous post was made at 21:39 ----------
Its getting late. That should have read, Line Earth loop AND Line Neutral loop ! The rest is the same .
Hope it hasn't caused too much confusion !!!!!
Speedster.
Nicky Tesla
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AND the neutral earth loop Why?
Line Neutral loop Still Why?
Line Neutral loop Still Why?
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Use your design knowledge ....
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well Im thinking these are SP RCBOs, so whoever uses them on a TT needs shot!
SP disconnection is NOT adequate for TT. IMHO
they are probably type C cos that was what the wholesaler had in stock, and thats the only reason,
and the installer was a muppet and didnt know any difference,
bit like folks saying if you have 30mA protection you can have 1666 ohms Zs ! utter nonsense, you could probably get that through the fabric of the building without any cpc's
SP disconnection is NOT adequate for TT. IMHO
they are probably type C cos that was what the wholesaler had in stock, and thats the only reason,
and the installer was a muppet and didnt know any difference,
bit like folks saying if you have 30mA protection you can have 1666 ohms Zs ! utter nonsense, you could probably get that through the fabric of the building without any cpc's
Steps, they are single module not singe pole, you still have the neutral monitored through the RCBO ?:|
Steve,
Not many are double pole, most are single pole, solid Neutral, in single module, check the spec sheets, both Steps & I have, mind we do disagree over some aspects of the compliance.
Not many are double pole, most are single pole, solid Neutral, in single module, check the spec sheets, both Steps & I have, mind we do disagree over some aspects of the compliance.
Ok, but it still discriminates N-E fault, which is the point of the RCBO, no need for double pole, you don't get that with standard single pole mcb so why would this make a difference.
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