I ended up buying a Wylex NH series. Cheap, big (15 ways), fairly well
made. Comes with a 100A switch and two 83A 30mA RCDs for split-
loading per 17th Ed.

Cost another 30 quid to fit a double-pole 100mA RCD instead of the
supplied main switch (They offered 16th Ed RCD incomers, but not yet a
17th Ed triple-split for TT use). The two workshop feeds need to avoid
the 30mA RCDs, and as it's a TT (overhead) supply I can't simply run
them from the main switch, no matter what their cable (inside the
workshops are their own CUs). No RCBOs planned as yet.

I'm plannning to run the kitchen cooker / oven circuit from the 100mA
side too. I can protect the cable so as to not need a 30mA RCD from
that aspect.

One thing I'm not certain about is discrimination between the incomer
RCD and the 30mAs, in terms of their times (When it's wired up though
I can time them, with my new Shiny 8-) ) I've been "assured" that
it's OK, but...

So, does this fly?

Andy Dingley wrote:
I ended up buying a Wylex NH series. Cheap, big (15 ways), fairly well
made. Comes with a 100A switch and two 83A 30mA RCDs for split-
loading per 17th Ed.

Cost another 30 quid to fit a double-pole 100mA RCD instead of the
supplied main switch (They offered 16th Ed RCD incomers, but not yet a
17th Ed triple-split for TT use). The two workshop feeds need to avoid
the 30mA RCDs, and as it's a TT (overhead) supply I can't simply run
them from the main switch, no matter what their cable (inside the
workshops are their own CUs). No RCBOs planned as yet.

I'm plannning to run the kitchen cooker / oven circuit from the 100mA
side too. I can protect the cable so as to not need a 30mA RCD from
that aspect.

One thing I'm not certain about is discrimination between the incomer
RCD and the 30mAs, in terms of their times (When it's wired up though
I can time them, with my new Shiny 8-) ) I've been "assured" that
it's OK, but...

So, does this fly?

The 100mA RCD needs to be time delayed.

--
Adam

On 4 Nov,
"ARWadsworth" wrote:

Andy Dingley wrote:
I ended up buying a Wylex NH series. Cheap, big (15 ways), fairly well
made. Comes with a 100A switch and two 83A 30mA RCDs for split-
loading per 17th Ed.

Cost another 30 quid to fit a double-pole 100mA RCD instead of the
supplied main switch (They offered 16th Ed RCD incomers, but not yet a
17th Ed triple-split for TT use). The two workshop feeds need to avoid
the 30mA RCDs, and as it's a TT (overhead) supply I can't simply run
them from the main switch, no matter what their cable (inside the
workshops are their own CUs). No RCBOs planned as yet.

I'm plannning to run the kitchen cooker / oven circuit from the 100mA
side too. I can protect the cable so as to not need a 30mA RCD from
that aspect.

One thing I'm not certain about is discrimination between the incomer
RCD and the 30mAs, in terms of their times (When it's wired up though
I can time them, with my new Shiny 8-) ) I've been "assured" that
it's OK, but...

So, does this fly?

The 100mA RCD needs to be time delayed.

If all circuits are RCD protected why is the 100ma RCD needed? It's only
protecting the short amount of cable /within/ the cu that is effectively a
continuation of the meter tails beyond the isolator.

AIUI two seperate 30ma protected CUs fed from a henley would be acceptable.

--
B Thumbs
Change lycos to yahoo to reply

ARWadsworth wrote:
Andy Dingley wrote:
I ended up buying a Wylex NH series. Cheap, big (15 ways), fairly well
made. Comes with a 100A switch and two 83A 30mA RCDs for split-
loading per 17th Ed.

Cost another 30 quid to fit a double-pole 100mA RCD instead of the
supplied main switch (They offered 16th Ed RCD incomers, but not yet a
17th Ed triple-split for TT use). The two workshop feeds need to avoid
the 30mA RCDs, and as it's a TT (overhead) supply I can't simply run
them from the main switch, no matter what their cable (inside the
workshops are their own CUs). No RCBOs planned as yet.

I'm plannning to run the kitchen cooker / oven circuit from the 100mA
side too. I can protect the cable so as to not need a 30mA RCD from
that aspect.

One thing I'm not certain about is discrimination between the incomer
RCD and the 30mAs, in terms of their times (When it's wired up though
I can time them, with my new Shiny 8-) ) I've been "assured" that
it's OK, but...

So, does this fly?

The 100mA RCD needs to be time delayed.


Time-delayed = "selective" and may have an icon on the front with an S
in a squa

non-selective:
http://www.tlc-direct.co.uk/Images/P...M100SLASH2.JPG

selective:
http://www.tlc-direct.co.uk/Images/P...T100SLASH2.JPG

wrote:
On 4 Nov,
"ARWadsworth" wrote:

Andy Dingley wrote:
I ended up buying a Wylex NH series. Cheap, big (15 ways), fairly
well made. Comes with a 100A switch and two 83A 30mA RCDs for
split- loading per 17th Ed.

Cost another 30 quid to fit a double-pole 100mA RCD instead of the
supplied main switch (They offered 16th Ed RCD incomers, but not
yet a 17th Ed triple-split for TT use). The two workshop feeds need
to avoid the 30mA RCDs, and as it's a TT (overhead) supply I can't
simply run them from the main switch, no matter what their cable
(inside the workshops are their own CUs). No RCBOs planned as yet.

I'm plannning to run the kitchen cooker / oven circuit from the
100mA side too. I can protect the cable so as to not need a 30mA
RCD from that aspect.

One thing I'm not certain about is discrimination between the
incomer RCD and the 30mAs, in terms of their times (When it's wired
up though I can time them, with my new Shiny 8-) ) I've been
"assured" that it's OK, but...

So, does this fly?

The 100mA RCD needs to be time delayed.

If all circuits are RCD protected why is the 100ma RCD needed? It's
only protecting the short amount of cable /within/ the cu that is
effectively a continuation of the meter tails beyond the isolator.

AIUI two seperate 30ma protected CUs fed from a henley would be
acceptable.

Not all the circuits are RCD protected. The CU is divisible into 3 sections,
the first of which has no RCD protection.
--
Adam

On 04/11/2010 21:16, John Rumm wrote:

A way round it would be to retain the main switch and add a pair of
RCBOs to the non RCD positions (or not use those positions)

Another point to bear in mind with TT is that isolation must be all-pole
(double-pole in a single-phase installation). Hence normal MCBs and
RCBOs with solid neutrals can't be considered to provide isolation for
individual final circuits. Groups of circuits fed via 2-pole RCDs can
be isolated using the relevant RCD, but to isolate circuits in the
'unprotected' section of a 17th ed. rig requires use of the main switch,
which the designer might (or might not) consider fails to meet the
'division for convenience' requirement.

Another option is to use double-pole MCBs (and a board that will accept
them), but they're not so readily available in the UK.

I'm wondering whether an option for Andy is just to retain the original
main switch - 2-RCD split (with no unprotected ways or RCBOs). Group
sockets and anything else needing 30 mA protection on one side and put
everything else on the 100 mA side (assuming surface wiring).

A further option, e.g. to keep lighting separate, is to take the incomer
thro' a separate isolator then split the 'tails' to two separate CUs,
perhaps a single-RCD one for lighting and a 2-RCD one for power.

--
Andy

On Nov 4, 9:16*pm, John Rumm wrote:
On 04/11/2010 16:19, Andy Dingley wrote:

I ended up buying a Wylex NH series. Cheap, big (15 ways), fairly well

Plastic rather than metal clad I take it?

Yes, as I understand this to be a requirement with a TT system.
Incidentally, I've got a few feet of meter tail going into this
(across the width of the cupboard under the stairs), what's adequate
protection for this between the isolator and the CU?

Specifically, it's one of these (although from TLC locally)
http://www.discount-electrical.co.uk...-80a-30ma-rcds

Something else I don't understand is what this "High Integrity"
version is about:
http://www.discount-electrical.co.uk...-80a-30ma-rcds

Apart from being £150 rather than £60, I can't see what the difference
is. The one I've got supports triple busbars too. There's no problem
in hanging breakers off the main switch, and I still need to swap that
supplied switch disconnect for an RCD incomer.



made. *Comes with a 100A switch and two 83A 30mA RCDs for split-
loading per 17th Ed.
Cost another 30 quid to fit a double-pole 100mA RCD instead of the
supplied main switch (They offered 16th Ed RCD incomers, but not yet a

That sounds a bit cheap for a time delayed RCD to me...

That is I think the problem. I asked TLC for the delayed RCD incomer
and was told I didn't need it. I think they're wrong, and despite the
damned thing being £50 quid more (How much?! Just for time delay?) I
think I need to take it back and swap it. 50 mile round trip I don't
often have the chance to do, something else I really don't need.

If the 100mA RCD is a normal non time delayed one, then nope - you won't
get discrimination on any earth faults that result from leakages
exceeding both trip thresholds.

One rather wonders what good the stock 100mA double pole RCD is
then... Is the need for discrimination by time as well as by current
really that crucial?

In other penny-pinching news, MK's delayed RCD is 20 quid cheaper and
also a rail mount. Anyone know if they're compatible?


A way round it would be to retain the main switch and add a pair of
RCBOs to the non RCD positions (or not use those positions)

I need to use these to supply two outgoing feeds to the workshop.
There are devices in the workshop that are incompatible with 30mA
RCDs: Specifically a kiln (high leakage current) and also large motors
and welders with inrush currents that are a problem for domestic
circuit breakers.

AFAIK, I can't get 100mA RCBOs and as it's TT I have to RCD protect
everything, so I think I do need a 100mA RCD incomer.

Andy Dingley wrote:
On Nov 4, 9:16 pm, John Rumm wrote:
On 04/11/2010 16:19, Andy Dingley wrote:

I ended up buying a Wylex NH series. Cheap, big (15 ways), fairly well
Plastic rather than metal clad I take it?

Yes, as I understand this to be a requirement with a TT system.
Incidentally, I've got a few feet of meter tail going into this
(across the width of the cupboard under the stairs), what's adequate
protection for this between the isolator and the CU?

As meter tails are insulated and sheathed, they don't need protecting
unless you do a risk assessment and can identify a risk that says they
specifically do. In which case it is usual to put them in 50 x 50
plastic trunking with open ends (no need to derate for temperature)


Specifically, it's one of these (although from TLC locally)
http://www.discount-electrical.co.uk...-80a-30ma-rcds

Something else I don't understand is what this "High Integrity"
version is about:
http://www.discount-electrical.co.uk...-80a-30ma-rcds

Apart from being £150 rather than £60, I can't see what the difference
is. The one I've got supports triple busbars too. There's no problem
in hanging breakers off the main switch, and I still need to swap that
supplied switch disconnect for an RCD incomer.

Dunno. This document:

http://www.electrium.co.uk/Wylex17th%20Edition.pdf

suggests that the difference is that yours is a two-busbar and the high
integrity is a three-busbar design.

You sure they sent you the right one, cos it sounds like you got the
high-integrity one?



made. Comes with a 100A switch and two 83A 30mA RCDs for split-
loading per 17th Ed.
Cost another 30 quid to fit a double-pole 100mA RCD instead of the
supplied main switch (They offered 16th Ed RCD incomers, but not yet a
That sounds a bit cheap for a time delayed RCD to me...

That is I think the problem. I asked TLC for the delayed RCD incomer
and was told I didn't need it. I think they're wrong, and despite the
damned thing being £50 quid more (How much?! Just for time delay?) I
think I need to take it back and swap it. 50 mile round trip I don't
often have the chance to do, something else I really don't need.

If the 100mA RCD is a normal non time delayed one, then nope - you won't
get discrimination on any earth faults that result from leakages
exceeding both trip thresholds.

One rather wonders what good the stock 100mA double pole RCD is
then... Is the need for discrimination by time as well as by current
really that crucial?

Yes. If there is a 100mA fault on the 30mA circuit, both will see a
fault current worthy of tripping. If the 100mA RCD is not time-delayed,
then either the 30 or the 100 or both will trip. If the 100 is time
delayed, then only the 30 will trip.


In other penny-pinching news, MK's delayed RCD is 20 quid cheaper and
also a rail mount. Anyone know if they're compatible?


Probably.


A way round it would be to retain the main switch and add a pair of
RCBOs to the non RCD positions (or not use those positions)

And yet another way around it would be to buy the MK time-delayed, put
it in a separate enclosure and put it between the isolator and the CU.

http://www.tlc-direct.co.uk/Products/MK5502.html or even the 4-way one,
which strangely is cheaper still.


I need to use these to supply two outgoing feeds to the workshop.
There are devices in the workshop that are incompatible with 30mA
RCDs: Specifically a kiln (high leakage current) and also large motors
and welders with inrush currents that are a problem for domestic
circuit breakers.

AFAIK, I can't get 100mA RCBOs and as it's TT I have to RCD protect
everything, so I think I do need a 100mA RCD incomer.


As it's TT, you either need a 100mA time-delayed RCD protecting the
whole installation, or every final circuit has to be protected by an RCD
somehow. It would be cheaper to put RCBO's in your three-busbar consumer
unit and keep the non-RCD main switch. If you need a 100mA protected
circuit for the kiln, put an MCB in the consumer unit and an external
2-pole 100mA RCD adjacent to the CU (you have one of these already!).

If you have a potential problem with 100mA of leakage, then you need to
further sub-divide your installation using Henley blocks and put a 100mA
time-delayed on each outgoing way on the Henley blocks.

I think I'm going to end up back with two CUs.

Put the switch incomer back into the 15 way Wylex and run it as a
straight-up 17th Ed split load with two 30mA RCDs. Take the 100mA fast
RCD back to TLC

Buy an extra MK 100mA delayed RCD and couple of MCBs in a simple 4-way
housing. Connect up via the Henley block (This is already in, as I
have old & new CUs in place during the switchover).

Workshop CUs have their existing switch incomers and 30mA RCBOs on the
socket circuits, plain MCBs otherwise (surface conduit wiring, so I
don't need to RCD it to protect the cabling).

Everything is protected, although the low-risk and the high-leakage
circuits in the workshop are only on the RCD in the house.


Pour a new floor in the workshop to take heavy machinery
Get the 3-phase workshop supply re-instated. This is really awkward
and could cost too much, owing to a pole issue. I'd also need to
remove the single phase feed, to avoid multi-phase in the same
building issues (they're being awkward over that).

Andy Dingley wrote:
On Nov 4, 9:16 pm, John Rumm wrote:
On 04/11/2010 16:19, Andy Dingley wrote:

I ended up buying a Wylex NH series. Cheap, big (15 ways), fairly
well

Plastic rather than metal clad I take it?

Yes, as I understand this to be a requirement with a TT system.
Incidentally, I've got a few feet of meter tail going into this
(across the width of the cupboard under the stairs), what's adequate
protection for this between the isolator and the CU?

Specifically, it's one of these (although from TLC locally)
http://www.discount-electrical.co.uk...-80a-30ma-rcds

Something else I don't understand is what this "High Integrity"
version is about:
http://www.discount-electrical.co.uk...-80a-30ma-rcds

Apart from being £150 rather than £60, I can't see what the difference
is. The one I've got supports triple busbars too. There's no problem
in hanging breakers off the main switch, and I still need to swap that
supplied switch disconnect for an RCD incomer.



made. Comes with a 100A switch and two 83A 30mA RCDs for split-
loading per 17th Ed.
Cost another 30 quid to fit a double-pole 100mA RCD instead of the
supplied main switch (They offered 16th Ed RCD incomers, but not
yet a

That sounds a bit cheap for a time delayed RCD to me...

That is I think the problem. I asked TLC for the delayed RCD incomer
and was told I didn't need it. I think they're wrong, and despite the
damned thing being £50 quid more (How much?! Just for time delay?) I
think I need to take it back and swap it. 50 mile round trip I don't
often have the chance to do, something else I really don't need.

If the 100mA RCD is a normal non time delayed one, then nope - you
won't get discrimination on any earth faults that result from
leakages exceeding both trip thresholds.

One rather wonders what good the stock 100mA double pole RCD is
then... Is the need for discrimination by time as well as by current
really that crucial?

In other penny-pinching news, MK's delayed RCD is 20 quid cheaper and
also a rail mount. Anyone know if they're compatible?


A way round it would be to retain the main switch and add a pair of
RCBOs to the non RCD positions (or not use those positions)

I need to use these to supply two outgoing feeds to the workshop.
There are devices in the workshop that are incompatible with 30mA
RCDs: Specifically a kiln (high leakage current) and also large motors
and welders with inrush currents that are a problem for domestic
circuit breakers.

AFAIK, I can't get 100mA RCBOs and as it's TT I have to RCD protect
everything, so I think I do need a 100mA RCD incomer.

I'll have a look in my stores over the weekend. I had a couple of 100mA
Wylex main switches knocking about. If one of them is time delayed then you
can have it.

--
Adam

On Nov 5, 4:52*am, John Rumm wrote:
On 05/11/2010 03:09, Andy Dingley wrote:

I'd also need to
remove the single phase feed, to avoid multi-phase in the same
building issues (they're being awkward over that).

I wonder why - it would just mean you has a second "copy" of one of the
phases....

Allegedly it's because I might then bond the single phase live to its
counterpart from the three phase supply, without noticing, then years
later they re-phase the supplies on the external poles (two different
poles too) without telling me, and then there's a 400V bang that
neither party was expecting.

On Nov 5, 4:47*am, John Rumm wrote:
On 05/11/2010 00:38, Andy Dingley wrote:

I need to take it back and swap it. *50 mile round trip I don't
often have the chance to do, something else I really don't need.

TLC deliver!

One way perhaps, but I don't fancy trying to haggle a return by post.


Could you for example add an additional small CU dedicated to the
outbuilding feeds, and put your 100mA "normal" RCD in that - might be
cheaper than the type S RCD!

I think I'd still need the delayed 100mA. The workshops have two CUs
with a mix of 30mA protection (mostly RCBOs), but not on the lights
(protected cable) or kiln radial (round blue socket). However that
still needs a bare minimum of protection from something, as it's TT,
so it's either a single upstream 100mA with discrimination (as
suggested), or lots more RCBOs all round.

Andy Dingley wrote:
On Nov 5, 4:47 am, John Rumm wrote:
On 05/11/2010 00:38, Andy Dingley wrote:

I need to take it back and swap it. 50 mile round trip I don't
often have the chance to do, something else I really don't need.

TLC deliver!

One way perhaps, but I don't fancy trying to haggle a return by post.


Could you for example add an additional small CU dedicated to the
outbuilding feeds, and put your 100mA "normal" RCD in that - might be
cheaper than the type S RCD!

I think I'd still need the delayed 100mA. The workshops have two CUs
with a mix of 30mA protection (mostly RCBOs), but not on the lights
(protected cable) or kiln radial (round blue socket). However that
still needs a bare minimum of protection from something, as it's TT,
so it's either a single upstream 100mA with discrimination (as
suggested), or lots more RCBOs all round.


I have found one in my stores. 100A 100mA WRMT 100/2 S.

So email me with your details and I'll get it into the post for you.

Cheers

--
Adam

Andy Wade wrote:
On 04/11/2010 21:16, John Rumm wrote:

A way round it would be to retain the main switch and add a pair of
RCBOs to the non RCD positions (or not use those positions)

Another point to bear in mind with TT is that isolation must be
all-pole (double-pole in a single-phase installation). Hence normal
MCBs and RCBOs with solid neutrals can't be considered to provide
isolation for individual final circuits. Groups of circuits fed via
2-pole RCDs can be isolated using the relevant RCD, but to isolate
circuits in the 'unprotected' section of a 17th ed. rig requires use
of the main switch, which the designer might (or might not) consider
fails to meet the 'division for convenience' requirement.

Another option is to use double-pole MCBs (and a board that will
accept them), but they're not so readily available in the UK.

I'm wondering whether an option for Andy is just to retain the
original main switch - 2-RCD split (with no unprotected ways or
RCBOs). Group sockets and anything else needing 30 mA protection on
one side and put everything else on the 100 mA side (assuming surface
wiring).
A further option, e.g. to keep lighting separate, is to take the
incomer thro' a separate isolator then split the 'tails' to two
separate CUs, perhaps a single-RCD one for lighting and a 2-RCD one
for power.

I think I would be tempted to keep the main switch, use some RCBOs on the
non protected side for some of the house circiuts (paid for buy not buying a
second CU) use one of the 30mA RCDs for the rest of the house circuits and
replace the other 30mA RCD with a 100mA one for the outbuildings

Cheers

--
Adam

On 5 Nov,
Andy Dingley wrote:


One way perhaps, but I don't fancy trying to haggle a return by post.

I got an incorrect item from them once and they emailed a label (postage
paid) to return the wrong item. The required item arrived next morning.
Another time (low value item) they just sent replacements. Generally they are
quite reliable and any problems easily sorted.

--
B Thumbs
Change lycos to yahoo to reply

Dave Osborne wrote:

If you have a potential problem with 100mA of leakage, then you need
to further sub-divide your installation using Henley blocks and put a
100mA time-delayed on each outgoing way on the Henley blocks.

Or wire each outbuilding as seperate TT supplys with individual earth rods.


--
Adam

Andy Dingley wrote:
On Nov 4, 9:16 pm, John Rumm wrote:
On 04/11/2010 16:19, Andy Dingley wrote:

I ended up buying a Wylex NH series. Cheap, big (15 ways), fairly
well

Plastic rather than metal clad I take it?

Yes, as I understand this to be a requirement with a TT system.
Incidentally, I've got a few feet of meter tail going into this
(across the width of the cupboard under the stairs), what's adequate
protection for this between the isolator and the CU?

Specifically, it's one of these (although from TLC locally)
http://www.discount-electrical.co.uk...-80a-30ma-rcds

Something else I don't understand is what this "High Integrity"
version is about:
http://www.discount-electrical.co.uk...-80a-30ma-rcds

Apart from being £150 rather than £60, I can't see what the difference
is. The one I've got supports triple busbars too. There's no problem
in hanging breakers off the main switch, and I still need to swap that
supplied switch disconnect for an RCD incomer.

The only difference is the expensive CU has fixeds bus bars. Ie they are set
at 4, 6 and 5 ways

Your CU is one of these

http://s428.photobucket.com/albums/qq6/adamko2020/?action=view&current=WestGroveWylexUnit.jpg

and allows you to put the no of RCD and non RCD ways as you see fit.

NOTE this is a work in progress picture as some of the MCBs are now RCBOs

--
Adam