Is my RCD spur socket working

[burmesterbob67]

I have just connected a Volex VT1092 Fused Spur to my outside garden sockets. All seems to be working OK, but the instructions are not very clear, there is a red indicator light in the centre which is always on. The seperate 'test' indicator is just about red, and goes to black when I press the test button, the other main red indicator goes out until I press the reset button. I have used the sockets and tested voltage with a meter, but i am worried that the instruction say the test light should show as red, but should it be brighter ?

 

[PrenticeBoyofDerry]

The question you should be really asking, is the RCD tripping in the regulated times and without testing this, using the approved test equipment, who would you know?
Other than that it is red on/black off. It would be difficult to say whether it bright enough, without seeing in real life.
Have you measured the supply voltage?

 

[burmesterbob67]

Thanks for response, I have tested the supply voltage and it is correct. I was just worried that the red test light was barely visible before the testing the rcd, but it does cut the power when tested, so i can only assume it is ok. I already have RCD in consumer unit, so this was just extra protection for the extenal socket. I would remove it again if I am not 100% sure it is working

 

[JohnW2]

Thanks for response, I have tested the supply voltage and it is correct. I was just worried that the red test light was barely visible before the testing the rcd, but it does cut the power when tested, so i can only assume it is ok. I already have RCD in consumer unit, so this was just extra protection for the extenal socket. I would remove it again if I am not 100% sure it is working

As you've been told, only proper testing with equipment you won't have would prove for certain that the RCD is working as intended. However, everything you've said suggests that it is working satisfactorily, and is probably as close as a consumer/end-user is going to be able to get.

The fact that it is only a 'secondary' RCD obviously adds to re-assurance - even if the RCD FCU failed to trip, the CU one would. There's nothing wrong with the sort of 'belt and braces' approach you've adopted, but I presume you realise that it's quite likely that both RCDs (or possibly just one, either, of them) would trip in the event of a fault (or current passing through a person).

Kind Regards, John

 

[PrenticeBoyofDerry]

I have tested the supply voltage and it is correct. I was just worried that the red test light was barely visible

I have fitted one or two of this brand before, I recall that the light was not of a great brightness, but was easily visible.

but it does cut the power when tested, so i can only assume it is ok.

You can only assume though! If you are trying to increase the level of protection to the required amount, the device should be tested for trip times. This can only be done using the correct equipment.

I already have RCD in consumer unit, so this was just extra protection for the extenal socket. I would remove it again if I am not 100% sure it is working

As you already have RCD protection and if that is rated at 30mA? Then you did not really require this extra device. As John has mentioned it could well be, that under an earth leakage fault, that this device would not operate any quicker than that one at the consumer unit. And even under test, it could well be that the RCD tester would trip the device at the CU first.

 

[JohnW2]

As you already have RCD protection and if that is rated at 30mA? Then you did not really require this extra device. As John has mentioned it could well be, that under an earth leakage fault, that this device would not operate any quicker than that one at the consumer unit. And even under test, it could well be that the RCD tester would trip the device at the CU first.

All true. However, given that we are told that a substantial proportion of RCDs in service are actually 'faulty' (I can never remember whether it is 7% or '1 in 7' that gets quoted), I would never criticise someone for adopting a 'belt and braces' approach.

Kind Regards, John

 

[stillp]

we are told that a substantial proportion of RCDs in service are actually 'faulty' (I can never remember whether it is 7% or '1 in 7' that gets quoted)

The figure often quoted is 7%. However this was based on a fairly small sample, a long time ago, in Italy. A proportion of the "faulty" RCDs in that survey were actually functioning correctly but did not respond to their test button.
In reality, the proportion of RCDs of reputable manufacture that are faulty must be far, far smaller than the 7% that, as you say, is often quoted.

 

[JohnW2]

The figure often quoted is 7%. However this was based on a fairly small sample, a long time ago, in Italy. A proportion of the "faulty" RCDs in that survey were actually functioning correctly but did not respond to their test button.

Thanks. Do I take it that "functioning correctly but did not respond to the test button" means that the test button/switch istelf was actually faulty?

In reality, the proportion of RCDs of reputable manufacture that are faulty must be far, far smaller than the 7% that, as you say, is often quoted.

One would certainly hope so. On a number of occasions I've asked (here and elsewhere) what proportion of RCDs electriciuans test 'fail' significantly, but have never really got an answer. The question, of course, is what percentage of 'faulty in service' one would regard as acceptable. Anything approaching 7% would IMO not be, but what would - 1%, 0.1%, or what?

It's the MCBs which are perhaps more worrying - given that they are effectively untestable in service, one wonders how many of them out there are in a condition/state to do 'what it says on the tin' if/when called to.

Kind Regards, John

 

[PrenticeBoyofDerry]

All true. However, given that we are told that a substantial proportion of RCDs in service are actually 'faulty' (I can never remember whether it is 7% or '1 in 7' that gets quoted), I would never criticise someone for adopting a 'belt and braces' approach.

I don't disagree with the belt and braces being worn.
But if they were to worn correctly, then surly belt/braces would then suggest, correct test procedures.

Previous research published in Italy indicated that electromechanical RCDs had an average failure rate of 7.1%. However, if the RCDs were operated regularly by means of the integral test button, this figure fell to 2.8%, indicating that RCD reliability improved if they had been operated regularly
From the available evidence, the primary mode of failure on electromechanical RCDs was ingress of fine particles of dust and moisture causing the moving components to stick or to operate more slowly than intended

http://www.esc.org.uk/industry/poli...search/in-service-reliability-of-rcds-report/

Our tests were carried out on a total of 607 RCDs in properties owned by four Housing Associations and Local Housing Authorities in the UK. All the devices tested were of the electromechanical (voltage independent) type.

The tests were made on the load side of the RCD, as close as practicable to the device. Occupiers were asked to turn off all appliances such as washing machines, TVs and computers for the duration of the test.

Although it could not be guaranteed that all loads had been disconnected prior to the RCD tests, there was no indication from subsequent analysis of the results that the tests would have been affected by any capacitive loads that had inadvertently remained energized.
The initial test for the first 172 devices was carried out in alternate properties at one times (30 mA) and five times (150 mA) the rated operating current. This was to determine whether or not the magnitude of the initial test current had any significant effect on the failure rate.

For the remainder of the tests, each RCD was tested at the rated operating current of the RCD (30 mA) three times during the positive and negative half cycles of the supply waveform. The tests were then repeated at five times the rated operating current (150 mA).
Functional testing of the integral push button was carried out last..........
Of the 607 RCDs tested, a total of 23 failures were recorded, giving an overall failure rate of:

3.8% - including the six RCDs that had been shorted out.
2.8% - excluding the shorted out RCDs.

http://www.esc.org.uk/fileadmin/user_upload/documents/industry/rcd_research/Final_Report.pdf

 

[JohnW2]

I don't disagree with the belt and braces being worn. But if they were to worn correctly, then surly belt/braces would then suggest, correct test procedures.

Yes, but some realism is needed here, isn't it? Are you seriously suggesting that every householder should (or would) get an electrician in every few months (or whatever) to undertake 'correcttest procedures'on their RCDs?

Previous research published in Italy indicated that electromechanical RCDs had an average failure rate of 7.1%. However, if the RCDs were operated regularly by means of the integral test button, this figure fell to 2.8%, indicating that RCD reliability improved if they had been operated regularly

If those figures are generally applicable, it would suggest that the in service 'faulty' rate is probably nearer 7.1% than 2.8%, since I imagine that the proportion of people who 'test' their RCDs regularly is very low. The only member of my family (other than myself!) who, to the best of my knowledge, has ever done it was one of my daughters, and she has now sworn 'never to touch an RCD test button again' after (as reported here) last time she did it the RCD blew up and covered her in black soot!

Kind Regards, John

 

[riveralt]

I should point out that the RCD provides 'Additional protection'.
That level of protection can of course be tested either mechanically by the householder or by someone like me with the appropriate equipment.
I don't have any test equipment to check the primary method of protection though!

 

[JohnW2]

I should point out that the RCD provides 'Additional protection'.

Whilst that is true in terms of regulatory terminology, I think it's potentially misleading, particularly to non-electricians. It does, indeed (in a TN installation) only provide 'Additional Protection' in terms of ADS (i.e. in response to low impedance L-E faults) but for the person who unfortunately finds themselves as the (much higher impedance) path from L to earth, the RCD represents the only protection. Of course, in a TT installation, the RCD again is effectively the 'only protection', even in terms of ADS.

That level of protection can of course be tested either mechanically by the householder or by someone like me with the appropriate equipment.
I don't have any test equipment to check the primary method of protection though!

Quite so. As I wrote above:

It's the MCBs which are perhaps more worrying - given that they are effectively untestable in service, one wonders how many of them out there are in a condition/state to do 'what it says on the tin' if/when called to.

Kind Regards, John

 

[PrenticeBoyofDerry]

Yes, but some realism is needed here, isn't it? Are you seriously suggesting that every householder should (or would) get an electrician in every few months (or whatever) to undertake 'correct test procedures'on their RCDs?

I am suggesting they are tested on installation and they are functionally tested as per instruction on tin and periodical trip time tested at least every 2 years.
I don't think that is beyond the of realms of realism!

 

[JohnW2]

I am suggesting they are tested on installation and they are functionally tested as per instruction on tin and periodical trip time tested at least every 2 years. I don't think that is beyond the of realms of realism!

All three are very reasonable and desirable, and the first is realistic if its installed by an electrician (but, whatever people might say/think, not 'realistic' {even though highly desirable} in the vast majority of cases of installation by a non-electrician). As for how realistic the second and third are, as I've said, I doubt that a very high proportion of householders ever go near the test button, and I certainly doubt that many, if any, householders have even thought of getting an electrician to test their RCDs anything like as frequenly as every two years - so, I suppose, not very 'realistic'!

Kind Regards, John

 

[ban-all-sheds]

I am suggesting they are tested on installation and they are functionally tested as per instruction on tin and periodical trip time tested at least every 2 years.
I don't think that is beyond the of realms of realism!

Depends on whether you think an average of around 28,500 tests per day in England alone is realistic or not.

FWIW, I tend towards "not".