100 Amp 100mA RCD 4 pole time delayed
- Thread starter Carloss
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Time delayed is referred to as S type.
100ma has no real use any more for fire you require 300ma (see 532.1) and for sockets over 32A in construction sites 500ma (704.411.3.2.1) and for cables buried in walls under 50mm and for sockets under 20A (some places under 32A) it needs 30ma (415.1.1) so the 100ma trip is no longer stipulated for any use so they are really only old stock.
Although in the commercial field you get many variable RCD's these are only permitted to be used by skilled personnel so are not used in domestic.
Why do you want a 100ma RCD?
100ma has no real use any more for fire you require 300ma (see 532.1) and for sockets over 32A in construction sites 500ma (704.411.3.2.1) and for cables buried in walls under 50mm and for sockets under 20A (some places under 32A) it needs 30ma (415.1.1) so the 100ma trip is no longer stipulated for any use so they are really only old stock.
Although in the commercial field you get many variable RCD's these are only permitted to be used by skilled personnel so are not used in domestic.
Why do you want a 100ma RCD?
hi ericmark, with reference to the 100ma rcd, are they no longer of practical use, because the housing company i work for still use the split board 100amp 100ma and 80amp 30ma for tt systems with the time out being on the 100ma rcd, only if we replace the full board do we use a normal two pole mains switch followed by rcbos for all circuits, are the company wrong in just replacing defective 100a/100ma rcds, on some houses ive even seen the old elcb,which if it trips ok we are asked to leave alone, is this right.
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They are still of use for repairs to existing installations which were done to a previous version of BS7671.
The point that ericmark was making is that under the current regs, there is no practical use for them anymore, as you have said, the norm is to install either a dual split or all RCBOs for domestic installations, so there is no need for a 100mA RCD, even on TT supplies.
As for ELCBs, if it is a voltage operated type, it should be replaced as a matter of urgency.
They are rendered useless if there is a paralell path on the earthing system such as main protective bonding, or even the CPC to a central heating boiler.
The test button will still work, but the device will not trip if a real fault exists.
The point that ericmark was making is that under the current regs, there is no practical use for them anymore, as you have said, the norm is to install either a dual split or all RCBOs for domestic installations, so there is no need for a 100mA RCD, even on TT supplies.
As for ELCBs, if it is a voltage operated type, it should be replaced as a matter of urgency.
They are rendered useless if there is a paralell path on the earthing system such as main protective bonding, or even the CPC to a central heating boiler.
The test button will still work, but the device will not trip if a real fault exists.
In a larger TT install with submains you still need something to protect the submains and you probablly don't want to use a 30ma because you will want discrimination with other RCDs downstream.
Doesn't a need for a 4-pole RCD hint that this is probably not a domestic installation?
Yeah, you'd think so wouldn't you 
Those figures are a maximum size - you can use smaller ones if you so wish.
100mA (Selective) devices are still viable for installations such as TT systems where there isn't a sub requirement for a 30mA device.
basically a 3phase supply to the building TT earthing system. sub main feeds hager 3 phase board 30m away. currently a 100mA 4pole rcd not S type. protecting the sub main swa; the rcd is shagged tripping out at 23mA. rcbos fitted on all socket circuits NOT lighting or fixed loads done prior 17th edition. Some faults on these lighting circuits are causing the 100mA to trip out loosing power to everything including gates etc etc..... my plan is to find these faults and upgrade the 60898 breakers to 61009 and install a 100mA s type rcd on the sub main so it has some form of protection. the sub main cable is buried in concrete 25mm 4c swa.
would a 300mA be sufficient enough?
sorry for quick reply and sorry for mistakes or if anything doesn't make sense looking after sprogs.
carlos
would a 300mA be sufficient enough?
sorry for quick reply and sorry for mistakes or if anything doesn't make sense looking after sprogs.
carlos
Did you check the RCD in isolation?
You can use whatever size RCD you wish unless there is a sub requirement i.e. fire protection so long as the Ze (Ra) is sufficiently low that the disconnection times can be met. When you use RCBOs in a TT downstream of another RCD I'd recommend using ones which cut the neutral too.
You can use whatever size RCD you wish unless there is a sub requirement i.e. fire protection so long as the Ze (Ra) is sufficiently low that the disconnection times can be met. When you use RCBOs in a TT downstream of another RCD I'd recommend using ones which cut the neutral too.
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