5 x Trip 40.4

[MikeB]

GN3 clearly says load to be disconnected.
40ms rcds are rated at 40ms to limit touch voltages from rising above 50 in the event of a fault- as I understand it.
200ms and 300ms rcds won't do this.

 

[xraytek]

GN3 clearly says load to be disconnected.
40ms rcds are rated at 40ms to limit touch voltages from rising above 50 in the event of a fault- as I understand it.
200ms and 300ms rcds won't do this.

Hi Mike,
Its the Zs value of a circuit that limits the touch voltage to below 50, not the disconnection time.
This is the reason why the maximum Zs permitted by BS7671 for a circuit protected by a 30mA RCD is 1667 Ohms, because 1667 Ohms x 30mA= 50.01v.

I think it creates confusion when the regs refer to the different purposes of RCD's because additional protection refers to backup against the failure of basic protection ie insulation being broken and allowing contact with live conductors.

Zs values provide fault protection but offer no basic protection.

Clear as mud eh?

 

[ian.settle1]

So if a RCD trips at 67.3 at x 1 then that would be a fail?

No it's >200mS for the oldertype BS and >300mS for new BSEN types as SES said.

I must ask are you qualified if so GOD HELP US

At 40.4 it has failed as according to the regulations written by my colleagues at the IEE,

 

[electricAl]

No it's >200mS for the oldertype BS and >300mS for new BSEN types as SES said.

I must ask are you qualified if so GOD HELP US

At 40.4 it has failed as according to the regulations written by my colleagues at the IEE,

Interesting that you`d consider that as a fail, Ian
For me, the device has not failed, because when the loads are removed it passes the prescribed test.
However, if you`re saying the cct has failed to comply, i`m inclined to agree with you and other ways of complying must be sought.
Would you agree or otherwise that this distinction should be made?
Or have i misinterpreted your statement?

 

[jackdor]

I was under the impression that you tested RCBO's direct at the RCBO its self with no load and its earth lead dissconnected am i wrong?

 

[MikeB]

thanks xraytek for correcting my very confused post. (I meant to type 30mA, not 40ms)

 

[Des 56]

An RCd has a particular charecteristic,it is this charecteristic that is under test, not this charecteristic and any other items that may be loading the circuit and giving false readings

Failing an installation for 40.4 x 5 would be very harsh and may not reflect the manufactureres declaration of the units conformity,
The RCd tests are after all only functional tests of the operation of the rcd
Who is to say that the test instrument/tester may be the failure .not the unit,