They're all at it

ricicle · 19 Feb 2008

First it was Part P and now 17th edition - why are all the major tester manufacturers trying to sell their products as though they are something new for the 17th edition - the tolerances might change slightly but the principle of testing stays the same.

Rant over

Dartlec · 20 Feb 2008

The joys of the free market I'm afraid - I remember seeing the first advert for a '17th edition tester' last year sometime and feeling similarly annoyed.

Having said that, given the new requirements for 0.2 second disconnection times in TT installation there are reasons why some new designs of CU may happen, as it seems the standard split load with time delayed RCD will no longer comply.

Pensdown · 20 Feb 2008

Dartlec said:
Having said that, given the new requirements for 0.2 second disconnection times in TT installation there are reasons why some new designs of CU may happen, as it seems the standard split load with time delayed RCD will no longer comply.

That's not strictly true. If the installation conforms to 411.3.1.2 the TN disconnection times of 0.4 can be used.

..and split load boards with a TD RCD never complied with the 16th but hey ho...from time to time we are all guilty of following like sheep......

securespark · 20 Feb 2008

They complied just as much as a "normal" S/L board ever did. Some say they did not comply, either.

Chris.J · 20 Feb 2008

Dartlec said:
The joys of the free market I'm afraid - I remember seeing the first advert for a '17th edition tester' last year sometime and feeling similarly annoyed.

Having said that, given the new requirements for 0.2 second disconnection times in TT installation there are reasons why some new designs of CU may happen, as it seems the standard split load with time delayed RCD will no longer comply.

So with a TT system with slow RCD incomer, and standard one for sockets etc, all modern; will it "pass" a PIR once the 17th come into use?

Pensdown · 20 Feb 2008

securespark said:
They complied just as much as a "normal" S/L board ever did. Some say they did not comply, either.

I think in the early days, SL boards for TN installations were fine because most had just a couple of RF circuits on the RCD side and all other circuits on the non RCD side. So it could be argued they just about complied because in the event of an earth fault on one RF, only one other circuit would be affected.

But as six RCD ways are now common, I think that argument is no longer valid because an earth fault on one circuit should never affect another five circuits. And unless DP MCB’s are used for all RCD circuits it’s very difficult to work on one circuit without tripping the others.

As for SL boards and TT installations I can’t see how they ever complied. As soon as an RCD is used as a mains switch it wont comply with either the 16th or 17th because one earth fault on the non RCD side takes out the whole installation. And if it’s an N-E fault (assuming DP MCB’s are not used) the whole installation stays out until the fault is found.

I agree with ricicle, the 17th edition band wagon is up and running. I would be pretty peed off if I had my house wired to the 17th and the company used one of those so called 17th edition consumer units.

I would have to buy a UPS for my PC to stop it crashing every time a lamp blew up stairs.

RF Lighting · 20 Feb 2008

Pensdown said:
I would have to buy a UPS for my PC to stop it crashing every time a lamp blew up stairs.

Do failing lamps often trip RCDs?

GaryMo · 20 Feb 2008

RF Lighting said:
Pensdown said:

I would have to buy a UPS for my PC to stop it crashing every time a lamp blew up stairs.

Click to expand...

Do failing lamps often trip RCDs?

Not in my experience, only ever the MCB.....

Pensdown · 20 Feb 2008

I'm on TT at home and I would say around one in five lamps used to take out the 100mA TD RCD when they gave up, GU10's being the worst culprits.

The lighting circuits are now fed via DP RCBO's and although they sometimes trip when a lamp goes, I can’t tell if its overload or earth fault.

Dartlec · 20 Feb 2008

Pensdown said:
As for SL boards and TT installations I can’t see how they ever complied. As soon as an RCD is used as a mains switch it wont comply with either the 16th or 17th

Maybe not, but given that it is shown as a standard arrangement in the OSG (Fig 3a - Installing RCDs in a TT Installation) is it really that surprising that people have taken that route?

RCBOs may be the best option, but many clients simply won't wear the extra cost, and with good wiring, RCDs really don't trip that often in my experience - my entire house is running on a 30ma and has not tripped once in over a year - though the 3 pcs I run have crashed repeatedly thanks to Microsoft

Pensdown · 20 Feb 2008

I agree, it's shown as the standard arrangement in many "guides" which is why I said from time to time we are all guilty of following like sheep.

Look on the bright side, at least Microsoft don't make RCD's because if they did, they would probably be the worst RCD's in the world.

Dartlec · 20 Feb 2008

Pensdown said:
I agree, it's shown as the standard arrangement in many "guides" which is why I said from time to time we are all guilty of following like sheep.

Just been watching a MK sponsored video presented by that old stalwart Dave Austin where they show a '17th edition compliant CU' - consisting of a single main switch with two parallel RCD protected circuits. If that is the way everyone goes is it really going to be better I wonder? It will I guess prevent everything tripping at once. But if the lighting is wired on a single circuit in a replacement CU scenario, will it have to be split into two to comply? More work for spanks I guess!

On a serious note, presumably an updated OSG is due along sometime soon to give some guidance on these sort of issues? Surely it would have been better producing it at the same time. The fact they haven't suggests that the 'powers to be' are still working out how to comply in The Real World™

Perhaps there will be a market for CUs with built in emergency lighting

Pensdown said:
Look on the bright side, at least Microsoft don't make RCD's because if they did, they would probably be the worst RCD's in the world.

Not sure about the worst, but they would trip constantly for no reason and take for ever to turn back on - and Apple RCDs would look nicer but cost twice as much

Pensdown · 21 Feb 2008

I doubt if the Apple RCD will be compatable with my CU..

I look forward to seeing how it all pans out and I hope that installers/designers read the red book and question some of the solutions that are being offered - much better than eating grass

GaryMo · 21 Feb 2008

Wylex have a new 17th compliant CU called the high integrity consumer unit (or similar).
It's basically a 100A switch, two unprotected ways for RCBO's (security alarm, smoke alarms etc), 30ma RCD with a number of ways and then another 30ma RCD with yet more ways.
Seems about the best of the bunch but give me an unprotected board and a bunch of RCBO's any day of the week.

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They're all at it

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