Add RDC to split load CU

[TonyW2]

Adding an RCD to cover the non-protected circuits looks a fairly easy conversion.
That side includes sockets for a fridge, a freezer, washing machine, dryer and a dishwasher. Presumably they were non RCD protected to avoid tripping from motor start up.
Is there a means to check if the present appliances would be Ok if covered by an RCD?
What spec RCD would be required?
(I am not looking to cause a debate about the rights or wrongs of doing this addition rather than replacing the entire box with an up to date dual version; I just feel that the additional RCD would be a useful but cheap safety improvement)
Secondly, when conducting an EICR prior to a full replacement, what test establishes that existing appliances would not be problematic, and does it follow that an updated unit could not be fitted if old type appliances were present?
Thanks for any input

 

[flameport]

What spec RCD would be required?

30mA, 100A, Type A as a minimum.

Replacing the MCBs with RCBOs would be a much better option.

Presumably they were non RCD protected to avoid tripping from motor start up.

Motors starting will not trip RCDs, and items like dishwashers, washing machines and the like are exactly the ones which should have been covered by RCDs.
The actual reasons for not having them on RCD protected circuits can be known only by whoever installed the consumer unit.

Secondly, when conducting an EICR prior to a full replacement, what test establishes that existing appliances would not be problematic,

None of them - an EICR covers the fixed electrical installation, not appliances.

and does it follow that an updated unit could not be fitted if old type appliances were present?

If you have appliances that will trip an RCD, they are defective and will need to be repaired or replaced.

 

[Murdochcat]

My guess is that they aren’t on the RCD due to existing faults

 

[TonyW2]

Don't think so. It was a new build around 2000.
I thought this was a common set up in those days, with only sockets likely to be accessed by "outside" equipment put on the RCD.

 

[chivers67]

If it's that old can you still purchase a suitable RCD or RCBO?

 

[Murdochcat]

Don't think so. It was a new build around 2000.
I thought this was a common set up in those days, with only sockets likely to be accessed by "outside" equipment put on the RCD.

Not sure I agree with this.

Best advice I can give you is get the CU replaced with one with RCBOs and a SPD

 

[EFLImpudence]

Don't think so. It was a new build around 2000.
I thought this was a common set up in those days, with only sockets likely to be accessed by "outside" equipment put on the RCD.

I think you are correct.

 

[Murdochcat]

I think you are correct.

Not sure I agree with you

Installations circa 2000 are usually all sockets on RCD, everything else not on RCD

 

[ericmark]

None of them - an EICR covers the fixed electrical installation, not appliances.

Not the case for an English rental property EICR, it states it covers non-portable equipment, 18 kg or with wheels makes it portable. I think this is wrong, it should be done as part of the inspection and testing of in service electrical equipment, often called PAT testing, but the law does not say that.

A clamp on ammeter should read the earth leakage, the red/black one is showing 15 mA, but the yellow one is showing 40 mA around the same cables, and the yellow one can't show less than 10 mA so not really suitable.

If the RCD is tripping then we have to use an insulation tester,

however since these test with DC, and we use AC it is not an accurate measure of current flow. 230/Ω=amps, so 25555.56 Ω = 9 mA but in real terms since it is not measuring and inductive or capacitive leaking, 1MΩ is considered the limit.

I replaced the yellow clamp on with the red and black one, as one yellow one only measured in 10 mA increments, and two it would not measure DC. It also seems to have a problem with the jaws, hence high reading.

I have tried to measure DC, the limit with an A type is 6 mA, however with the DC range it uses the hall effect, and it has to be zeroed, and I found in mA range even the slightest movement can cause it to require zeroing again, so not really possible to measure the DC leakage down to 6 mA.

However, using RCBO's then any DC leakage is only affecting that circuit, so although in theory DC can stop the RCBO tripping, the chances of DC freezing the RCD at the same time as it is needed to trip, are much reduced.

We should test the RCD under load conditions, as well as without the load, so the 15 mA test will show if there is excessive leakage, and the 30 mA test will include any DC leakage, but think testing like that would be rare in practice. Also checking if leakage under 9 mA is also rare, if you look at the expensive professional clamp on meters, many are like my cheap yellow one which I bought in Hong Kong before the take-over, so over 25 years old.

Likely if you can get RCD's for the old distribution unit, they will be that expensive, cheaper to fit a new consumer unit.

 

[ericmark]

Installations circa 2000 are usually all sockets on RCD, everything else not on RCD

2004 we only needed to protect circuits likely to be used outside, it was 2008 when we had to protect nearly all circuits.

 

[Murdochcat]

2004 we only needed to protect circuits likely to be used outside, it was 2008 when we had to protect nearly all circuits.

I’ve just emptied my store of 20+ year old CU’s and I can only tell you what reality was

If it was just out door sockets then split load boards simply wouldn’t make sense

 

[TonyW2]

Thanks for so much info; it is what it is and has not been altered to bypass a known fault. All is working
Can 8I conclude that it would be a beneficial change so long as an RCD could be sourced, cheaply and that both old mechanical control working and modern computer electronic type appliances would be compatible with a Type A unit?

 

[ericmark]

In around 1997 my son took his RAE (radio amateurs exam) and I was worried about him playing and making a mistake, so well before we had twin RCD consumer units, I put an adaptable box, and two 30 mA RCD's feeding the two old Wylex fuse boxes (with fuses swapped for MCB's) I don't know if it saved him, he was unlikely to tell me, but it did save me when I hacksawed through a cable in the wall which should not have been there.

However, we would from time to time have one trip, sometimes 4 trips in two weeks, never did find any faults, then it would go two years and no trips. Back then, SPD was not normally fitted, and likely it was a spike which caused it to trip, and my clamp-on would not measure low enough to really know what the background leakage was.

Just before moving here, they tripped, while my wife and I were looking after my mother, result was two freezers of food had to be dumped, I suppose we could have tried to claim, but since not living in the house at the time, it was not really covered.

So on moving here, I decided did not want that again, so went all RCBO's, they were cheaper than two freezers full of food, now living 8 miles from the nearest supermarket, we have three freezers, and they are supplied from two RCD sockets, which are in turn supplied from my solar inverter, and a pair of 3.2 kWh batteries, so even a general power cut, would not stop them working, the one in flat used for BBQ stuff would stop, but not much in that, mainly cakes, which I would not object to gorging myself on.

If one freezer failed, likely insurance would pay out, four I would think would be stretching it. The only item not RCD protected is the central heating. And this was down to solar installers, not me, and I have a compliance certificate to say it is OK.

 

[securespark]

I’ve just emptied my store of 20+ year old CU’s and I can only tell you what reality was

If it was just out door sockets then split load boards simply wouldn’t make sense

In the early 80s, it was common to put an RCD-protected socket next to the front and back doors.

 

[FrodoOne]

Thanks for so much info; it is what it is and has not been altered to bypass a known fault. All is working
Can 8I conclude that it would be a beneficial change so long as an RCD could be sourced, cheaply and that both old mechanical control working and modern computer electronic type appliances would be compatible with a Type A unit?

In this "Day and Age"
it is "preferable" to use RCBOs on all (protected) circuits
rather than use RCDs covering several circuits - with MCBs doing the "overload" protection.

Reason ?
Fault-Finding is much easier if the RCBO "trips" on an individual circuit
and
multiple RCBOs do not (now) cost much more than one RCD, to protect many MCB protected circuits.

(Yes.
I do know that it is not the circuit which is "protected" by a RCD or RCBO - it is the "user".)