converting DB to comply with 17th edition

[netblindpaul]

Wylex NHXSBS type RCBO is single pole solid neutral not switched, as are 90+% of those in the market place.
There are VERY, VERY few double pole or single pole switched neutral RCBO's.
SPSN = Single Pole Solid Neutral, NOT Single Pole Switched Neutral.

 

[Plonker 3]

What would be the point of making any changes to the distribution board, since in four months time, it wouldn’t comply again?

It will comply exactly the same in years time as it does right now, he is on about swappong a RCD for a main switch not swappping the whole DB.

 

[leep82]

What would be the point of making any changes to the distribution board, since in four months time, it wouldn’t comply again?

forgive my ignorance but what will be happening in four months time?

 

[telectrix]

New years eve pi$$ up, followed by heavy metal CUs.

 

[leep82]

Done a little research and read that 100ma time delayed rcd acting as a main switch on a TT system is no longer required providing that all circuits are 30ma protected and the DB is of an all insulated material

 

[leep82]

New years eve pi$$ up, followed by heavy metal CUs.

ha ha, i was aware about the consumer unit changes

 

[richy3333]

Ok, I've skip read and drunk the best part of a bottle of wine but something doesn't bode well with the op's questions

 

[davesparks]

.
SPSN = Single Pole Solid Neutral, NOT Single Pole Switched Neutral.

Depends which manufacturer you look at, they seem to use the acronym SPSN interchangeably

 

[davesparks]

Done a little research and read that 100ma time delayed rcd acting as a main switch on a TT system is no longer required providing that all circuits are 30ma protected and the DB is of an all insulated material

But if it's there already why remove it? You will only be removing an additional layer of protectection

 

[leep82]

at the minute any problems, nuisance tripping with that and the whole installation goes off

But removing it removes the backup fault protection it provides when the 30mA fails to trip.
By removing it you are making the installation less safe than when you found it.

i would be installing a 30ma rcd to protect the lighting curcuits currently protected by a 100ma rcd. Does this make the system any less safe? Removing the 100ma rcd and replacing with a main switch would also allow the installation to be divided better so in the event of a single fault the whole installation would not be lost

 

[davesparks]

i would be installing a 30ma rcd to protect the lighting curcuits currently protected by a 100ma rcd. Does this make the system any less safe? Removing the 100ma rcd and replacing with a main switch would also allow the installation to be divided better so in the event of a single fault the whole installation would not be lost

Yes it makes it less safe, the 100mA RCD would provide a second level of fault protection if left in place. Being time delayed it will only trip if the 30mA RCD fails to trip due to being faulty.
If the 30mA RCD works correctly then the 100mA RCD will not trip

 

[Andy78]

i would be installing a 30ma rcd to protect the lighting curcuits currently protected by a 100ma rcd. Does this make the system any less safe? Removing the 100ma rcd and replacing with a main switch would also allow the installation to be divided better so in the event of a single fault the whole installation would not be lost

The time delay on the 100mA RCD should take care of any discrimination issues. As Dave says, leave it in. It won't cause inconvenient tripping, the 30mA RCDs should be able cause enough nuisance while being left well alone by the main RCD.

 

[leep82]

So we are effectively saying that if we had a new install, TT system, we could use a dual 30ma rcd, fully insulated board, all acceptable to current regs but this isnt as safe as the scenario ive described?

 

[davesparks]

So we are effectively saying that if we had a new install, TT system, we could use a dual 30ma rcd, fully insulated board, all acceptable to current regs but this isnt as safe as the scenario ive described?

Exactly
Compliance with the regulations is a minimum standard, not an absoloute

 

[leep82]

Thinking of using an rcbo after all. Question now though is do i need a double pole device? Been searching for similar threads and it seems its open to debate, maintaining the 100ma time delay rcd would give me an isolation point that isolates all live conductors ( as required in a TT), but this isolates the whole of the installation and not individual circuits?

 

[Leesparkykent]

Thinking of using an rcbo after all. Question now though is do i need a double pole device? Been searching for similar threads and it seems its open to debate, maintaining the 100ma time delay rcd would give me an isolation point that isolates all live conductors ( as required in a TT), but this isolates the whole of the installation and not individual circuits?

The problem you have if you don't use a double pole or single pole switched neutral RCBO is in the event of a neutral earth fault on the circuit the 100ma "S" type RCD will still see the neutral earth fault and trip taking out everything because the neutral of the circuit hasn't been disconnected when the RCBO has tripped.

Edit: from post #21 I'm not sure if Wylex make a single pole switched neutral RCBO without looking.

 

[telectrix]

Done a little research and read that 100ma time delayed rcd acting as a main switch on a TT system is no longer required providing that all circuits are 30ma protected and the DB is of an all insulated material

the reason that the 100mA RCD was installed on a TT system was to provide fault protection when all circuits were not RCD protected ( 16th). if all circuits have RCD protection, it's no longer required, but useful as a back up if the 30mA tripe was liable to not tripping on a fault due to being gummed up from never having the test button pressed.

 

[leep82]

Thanks for tour replys guys, things have changed once again with regards to this job. Customer now wants switch moving in dining room ( downstairs lighting circuit ). Now thinking of using the 80a 30ma rcd i have to protect the two lighting circuits i intend to work on but as mentioned leaving the 100ma time delay rcd main switch in place. Checked wylex catalogue and as thought there double pole rcbo's are two module, now im working on both lighting circuits i havnt got the room to fit these.

 

[7029 dave]

What ra are you measuring.? (out of interest) Leave the s type 100ma rcd in situ IMO.

 

[leep82]

Yeah i am going to leave it in place