RCD’s x1 X5 etc

[Peter1891]

Hi all
Can someone please explain what I’m missing regarding RCD’s
Here’s what I understand so if you can help me fill in the blanks I’d much appreciate it.
ok so:
X1, X5 40ms 300ms max
RCD for Tn is additional protection
RCD for TT is Fault protection

what is the difference between x1 and X5 and what do they actually mean?
Also on a TN system do you still record highest from both x1 and X5 under the new 18th Edition?
[automerge]1577722417[/automerge]

Hi all
Can someone please explain what I’m missing regarding RCD’s
Here’s what I understand so if you can help me fill in the blanks I’d much appreciate it.
ok so:
X1, X5 40ms 300ms max
RCD for Tn is additional orotection
RCD for TT is Fault protection

 

[bill01803]

one times rated current and five times rated current.
Only need to record the highest result from 5 times test on the latest form.

 

[Peter1891]

one times rated current and five times rated current.
Only need to record the highest result from 5 times test on the latest form.

Hi
Thank you for a swift reply but that’s the bit I don’t get. What is the current? What value? Is it the current the RCD is rated at? Eg 30ma?

 

[Pete999]

Hi
Thank you for a swift reply but that’s the bit I don’t get. What is the current? What value? Is it the current the RCD is rated at? Eg 30ma?

1 x30mA =30mA 5 X 30mA = 150mA or 1X100mA=100mA or 5X100mA =500mA

 

[Peter1891]

1 x30mA =30mA 5 X 30mA = 150mA or 1X100mA=100mA or 5X100mA =500mA

Ah ok yes kind of how I thought then. Thank you so much for clarifying it for me.

 

[Ian1981]

You do not test a 100mA rcd at 5 x it’s rated I delta N.
The 5x I delta N test is purely for testing rcd’s rated upto 30mA for the purpose of additional protection only.

 

[davesparks]

Hi all
Can someone please explain what I’m missing regarding RCD’s
Here’s what I understand so if you can help me fill in the blanks I’d much appreciate it.
ok so:
X1, X5 40ms 300ms max
RCD for Tn is additional protection
RCD for TT is Fault protection

what is the difference between x1 and X5 and what do they actually mean?
Also on a TN system do you still record highest from both x1 and X5 under the new 18th Edition?
[automerge]1577722417[/automerge]

RCDs can be for fault protection and/or additional protection on TN or TT installations, it is up to the designer to establish what purpose RCD protection is required for, where it should be installed and at what ratings.

The limit for the x1 test is 300mS and for a 5x test is 40mS.

 

[stevethesparks]

As I understand it; if for additional protection you record the x5 readings, if for fault protection you record the x1 readings - or so my last NICEIC visit advised. personally I still like to record both regardless.

 

[stevethesparks]

As an addition, if the RCD is the older BS4293 type then the maximum reading should be no more than 200ms for a x1 test.

 

[SJD]

As I understand it; if for additional protection you record the x5 readings, if for fault protection you record the x1 readings - or so my last NICEIC visit advised. personally I still like to record both regardless.

I also had this conversation with my last ELECSA assessor, and it can be confusing which is meant.

The assessor said the schedule of test results is only a minimum, there is no reason why you can't add back the column that got deleted, and have a x1 and x5 column. Then either fill out the appropriate column, or both columns. This assumes, of course, that you have an editable test sheet in Excel or Word etc.

 

[Pretty Mouth]

The 5x I delta N test is purely for testing rcd’s rated upto 30mA for the purpose of additional protection only.

When testing RCDs I always carry out all relevant tests ie X 1/2, X 1, and X 5, plus ramp. However, I read the note to reg 643.8 as saying that the X5 test is the only test required when used for additional protection. Is that correct, or is there something else I've missed (as usual)?

 

[Ian1981]

When testing RCDs I always carry out all relevant tests ie X 1/2, X 1, and X 5, plus ramp. However, I read the note to reg 643.8 as saying that the X5 test is the only test required when used for additional protection. Is that correct, or is there something else I've missed (as usual)?

You are now only required to record one result, so if a 30mA rcd is used then it’s for additional protection so only the 5x test at both 0 and 180 cycles are tested with the highest recorded on the certificate.
It has never been a requirement nor necessary to test an rcd rated above 30mA at 5x it’s rated Idelta N, testing them other than the 1x test would serve zero purpose.
It’s never been a requirement to test an rcd at it’s half rated current but I like probably most people just stick the auto setting on and go through the cycles.

 

[Pretty Mouth]

You are now only required to record one result, so if a 30mA rcd is used then it’s for additional protection so only the 5x test at both 0 and 180 cycles are tested with the highest recorded on the certificate.
It has never been a requirement nor necessary to test an rcd rated above 30mA at 5x it’s rated Idelta N, testing them other than the 1x test would serve zero purpose.
It’s never been a requirement to test an rcd at it’s half rated current but I like probably most people just stick the auto setting on and go through the cycles.

Thank Ian. Why is it not necessary to test at 1/2X and 1X when used for additional protection?

 

[Ian1981]

Thank Ian. Why is it not necessary to test at 1/2X and 1X when used for additional protection?

The regulations have never asked for a half times test to be performed I think it’s more a manufacturer standard product test.
It stands to reason that if the rcd is used for additional protection then the 5x test is the test we need ,to verify for compliance ie disconnection in 40mS or under.

 

[Pretty Mouth]

The regulations have never asked for a half times test to be performed I think it’s more a manufacturer standard product test.
It stands to reason that if the rcd is used for additional protection then the 5x test is the test we need ,to verify for compliance ie disconnection in 40mS or under.

I think you're right, looking now I can't find a reg that specifically requires a 50% test. The procedure in the OSG p118 asks for a 1/2X test, but doesn't link to a reg. Note 2 of 531.3.2 (unwanted tripping) says "RCDs may operate at any value of residual current in excess of 50 % of the rated residual current" but doesn't actually say you must test for this.

What I meant by my previous question is, I know the 5X test =<40ms is required by regulations. But why did the IET decide that particular test and outcome was necessary rather than the 1X =<300ms test?