Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8
PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I
asked if he could firt an 100mA RCD for now, but as he didn't have one
with him, and we need people to be able to work, he is going to replace
the RCD with an isolator "At our request"

My question is, is it against the regs to install this whole
installation RCD in this situation in the first place?

He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to protect
this.

I basically want to know if we should use him to replace the CU with a
new 17th edition one, probably with RCBO's, or we need to find another
electrician.

Thanks!

--
Toby...
Remove your pants to reply

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

On 09/11/2015 10:57, Toby wrote:
Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8
PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I
asked if he could firt an 100mA RCD for now, but as he didn't have one
with him, and we need people to be able to work, he is going to replace
the RCD with an isolator "At our request"

My question is, is it against the regs to install this whole
installation RCD in this situation in the first place?

Its certainly a deprecated way of designing things, and probably not
really meeting the requirement to maintain discrimination (i.e. limiting
the effects of a fault in one part of an installation on other unrelated
circuits)

He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to protect
this.

Easiest for him perhaps...

I basically want to know if we should use him to replace the CU with a
new 17th edition one, probably with RCBO's, or we need to find another
electrician.

Assuming his quality of workmanship is ok, then he ought to be able to
do an all RCBO install since there is not much in the way of decision
making ;-)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article ,
Toby wrote:
In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8
PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I
asked if he could firt an 100mA RCD for now, but as he didn't have one
with him, and we need people to be able to work, he is going to replace
the RCD with an isolator "At our request"

Just how much office equipment is there in this small office? Things like
computers and peripherals?

But the most likely things to trip an RCD are water heaters or anything
with a 'solid' heating element. These can leak to ground.

My question is, is it against the regs to install this whole
installation RCD in this situation in the first place?

He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to protect
this.

I basically want to know if we should use him to replace the CU with a
new 17th edition one, probably with RCBO's, or we need to find another
electrician.

I'd certainly not fancy having the one RCD protecting everything. Whether
you'd need to go to the expense of RCBOs, I dunno. Being commercial
premises the regs may be different.

--
*A clear conscience is the sign of a fuzzy memory.

Dave Plowman London SW
To e-mail, change noise into sound.

On 09/11/15 13:52, Chris Hogg wrote:
On Mon, 9 Nov 2015 10:57:44 +0000, Toby
wrote:

Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8
PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I
asked if he could firt an 100mA RCD for now, but as he didn't have one
with him, and we need people to be able to work, he is going to replace
the RCD with an isolator "At our request"

My question is, is it against the regs to install this whole
installation RCD in this situation in the first place?

He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to protect
this.

I basically want to know if we should use him to replace the CU with a
new 17th edition one, probably with RCBO's, or we need to find another
electrician.

Thanks!

IANA electrician, but following advice from various better-qualified
contributors to this NG, when I had my CU upgraded from wire fuses to
a split way unit with MCP's, I also had a 100A, 100mA time-delayed
whole-house RCD fitted at the front end, i.e. whole house. This was
because we have a TT supply, i.e. overhead cables, and apparently with
a TT supply this level of protection is implied by the regs, if not
actually spelled out in as many words.

Having a 100mA time-delayed unit does two things: it doesn't trip when
experiencing small current imbalances, where a 30mA trip would trip,
and being time-delayed, it allows the 30mA RCD in the CU to trip
first, isolating the ring mains, which is where the current-imbalance
fault is most likely to occur, but leaving the light circuit still
live, so you can still see where you're going at night. Cooker,
immersion, lights etc. are not on the 30mA RCD, but do have MCB's (as
do the ring mains on the 30mA RCD).


But it will not actually qualify as a device offering protection against
accidental contact on the non 30mA RCD circuits, so you still need
either a split way board with twin RCDs or RCBOs if you wish all the
circuits to be protected.

In either case the delayed RCD has no value outside of TT systems.

On 09/11/2015 13:38, Dave Plowman (News) wrote:
In article ,
Toby wrote:
In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8
PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I
asked if he could firt an 100mA RCD for now, but as he didn't have one
with him, and we need people to be able to work, he is going to replace
the RCD with an isolator "At our request"

Just how much office equipment is there in this small office? Things like
computers and peripherals?

9 x PC's (I forgot one)
2 servers (via a UPS)
13 monitors (1 is an old CRT)
1 x MFD (Copier)
2 x Printers
1 x Fax
1 x PoE Network switch
2 x desktop Ethernet switches
2 x Routers
1 x Firewall
1 x Wireless Access point
1 x Time attendance RFID reader
1 x Phone System
1 x Shredder
1 x Franking machine
1 x Intruder alarm
1 x Fire alarm
1 x Boiler with an external pump and a wireless thermostat receiver
2 x Small over-sink hot water boilers (Stored water, 13A connections)
1 x Dishwasher


But the most likely things to trip an RCD are water heaters or anything
with a 'solid' heating element. These can leak to ground.

I will get the hot water boilers checked, I think only one is on anyway.

My question is, is it against the regs to install this whole
installation RCD in this situation in the first place?

He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to protect
this.

I basically want to know if we should use him to replace the CU with a
new 17th edition one, probably with RCBO's, or we need to find another
electrician.

I'd certainly not fancy having the one RCD protecting everything. Whether
you'd need to go to the expense of RCBOs, I dunno. Being commercial
premises the regs may be different.


Ta.

--
Toby...
Remove your pants to reply

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

On 09/11/2015 10:57, Toby wrote:
Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8
PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I
asked if he could firt an 100mA RCD for now, but as he didn't have one
with him, and we need people to be able to work, he is going to replace
the RCD with an isolator "At our request"

My question is, is it against the regs to install this whole
installation RCD in this situation in the first place?

He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to protect
this.

I basically want to know if we should use him to replace the CU with a
new 17th edition one, probably with RCBO's, or we need to find another
electrician.

Thanks!

I think a single RCD protection is ok as long as you have emergency
lighting.

Given your setup and the potential loss of data etc when a trip occurs,
I wouldn't have any hesitation to have a full RCBO setup.

In theory he should be able to test insulation of your boiler, and a PAT
check on your other items if need be.

I have known PC PSUs to cause nuisance trips. In reality after
investigating and ruling out the obvious boiler, it could be anything!

On 09/11/2015 14:43, Toby wrote:

But the most likely things to trip an RCD are water heaters or anything
with a 'solid' heating element. These can leak to ground.

I will get the hot water boilers checked, I think only one is on anyway.

Unless its a double pole isolator a leak from the neutral can trip a
RCD. Most fused spurs are only single pole.

On Monday, 9 November 2015 10:55:27 UTC, Toby wrote:
He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to protect
this.

He could have put a RCD FCU on the supply to the lighting circuit if that was all he was worried about.

And I think the fire alarm panel (if it's a commercial panel system) MUST NOT be on an RCD circuit but should be on a protected cable like MICC or Fireproof which does not need RCD protection, connected as close as possible to the origin of the installation.

If he's taken your fire alarm installation out of its BS compliance then there may be costs to correct this at the next annual inspection, and insurance implications meantime.

Anyone putting a single RCD on an installation with 12 circuits these days needs their understanding of the Regs questioned.

Owain

On Mon, 9 Nov 2015 14:43:01 +0000, Toby
wrote:

On 09/11/2015 13:38, Dave Plowman (News) wrote:
In article ,
Toby wrote:

Just how much office equipment is there in this small office? Things like
computers and peripherals?

9 x PC's (I forgot one)
2 servers (via a UPS)
13 monitors (1 is an old CRT)
1 x MFD (Copier)
2 x Printers
1 x Fax
1 x PoE Network switch
2 x desktop Ethernet switches
2 x Routers
1 x Firewall
1 x Wireless Access point
1 x Time attendance RFID reader
1 x Phone System
1 x Shredder
1 x Franking machine


That should be more than enough noise filters to make an RCD wobbly.

On Monday, 9 November 2015 10:55:27 UTC, Toby wrote:
Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8
PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I
asked if he could firt an 100mA RCD for now, but as he didn't have one
with him, and we need people to be able to work, he is going to replace
the RCD with an isolator "At our request"

My question is, is it against the regs to install this whole
installation RCD in this situation in the first place?

He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to protect
this.

I basically want to know if we should use him to replace the CU with a
new 17th edition one, probably with RCBO's, or we need to find another
electrician.

Thanks!

--
Toby...
Remove your pants to reply

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

You can determine the cause by leaving items turned off one by one until the problem stops.
Start with stuff that only runs intermittently.

All your portable equipment should be PAT tested anyway.

In article ,
harry wrote:
On Monday, 9 November 2015 10:55:27 UTC, Toby wrote:
Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8
PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I
asked if he could firt an 100mA RCD for now, but as he didn't have one
with him, and we need people to be able to work, he is going to replace
the RCD with an isolator "At our request"

My question is, is it against the regs to install this whole
installation RCD in this situation in the first place?

He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to protect
this.

I basically want to know if we should use him to replace the CU with a
new 17th edition one, probably with RCBO's, or we need to find another
electrician.

Thanks!

--
Toby...
Remove your pants to reply

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

You can determine the cause by leaving items turned off one by one until
the problem stops. Start with stuff that only runs intermittently.

All your portable equipment should be PAT tested anyway.

However, a PAT test won't necesarily show up a fault which is either
intermittent or takes time to develop.

--
Please note new email address:

On 09/11/15 13:52, Chris Hogg wrote:
On Mon, 9 Nov 2015 10:57:44 +0000, Toby
wrote:

Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8
PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I
asked if he could firt an 100mA RCD for now, but as he didn't have one
with him, and we need people to be able to work, he is going to replace
the RCD with an isolator "At our request"

My question is, is it against the regs to install this whole
installation RCD in this situation in the first place?

He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to protect
this.

I basically want to know if we should use him to replace the CU with a
new 17th edition one, probably with RCBO's, or we need to find another
electrician.

Thanks!

IANA electrician, but following advice from various better-qualified
contributors to this NG, when I had my CU upgraded from wire fuses to
a split way unit with MCP's, I also had a 100A, 100mA time-delayed
whole-house RCD fitted at the front end, i.e. whole house. This was
because we have a TT supply, i.e. overhead cables, and apparently with
a TT supply this level of protection is implied by the regs, if not
actually spelled out in as many words.

Having a 100mA time-delayed unit does two things: it doesn't trip when
experiencing small current imbalances, where a 30mA trip would trip,
and being time-delayed, it allows the 30mA RCD in the CU to trip
first, isolating the ring mains, which is where the current-imbalance
fault is most likely to occur, but leaving the light circuit still
live, so you can still see where you're going at night. Cooker,
immersion, lights etc. are not on the 30mA RCD, but do have MCB's (as
do the ring mains on the 30mA RCD).

I think this is in many ways the best solution, A 100mA slo blo is good
for the hole house as some gross issues will cause it to trip, but RCBOs
on specialised mains - stuff that goes outside, or maybe kicthen and
workshop - is well worth it


--
the biggest threat to humanity comes from socialism, which has utterly
diverted our attention away from what really matters to our existential
survival, to indulging in navel gazing and faux moral investigations
into what the world ought to be, whilst we fail utterly to deal with
what it actually is.

On 09/11/15 16:59, Chris Hogg wrote:
On Mon, 9 Nov 2015 14:12:37 +0000, Tim Watts
wrote:

On 09/11/15 13:52, Chris Hogg wrote:
On Mon, 9 Nov 2015 10:57:44 +0000, Toby
wrote:

Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8
PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I
asked if he could firt an 100mA RCD for now, but as he didn't have one
with him, and we need people to be able to work, he is going to replace
the RCD with an isolator "At our request"

My question is, is it against the regs to install this whole
installation RCD in this situation in the first place?

He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to protect
this.

I basically want to know if we should use him to replace the CU with a
new 17th edition one, probably with RCBO's, or we need to find another
electrician.

Thanks!

IANA electrician, but following advice from various better-qualified
contributors to this NG, when I had my CU upgraded from wire fuses to
a split way unit with MCP's, I also had a 100A, 100mA time-delayed
whole-house RCD fitted at the front end, i.e. whole house. This was
because we have a TT supply, i.e. overhead cables, and apparently with
a TT supply this level of protection is implied by the regs, if not
actually spelled out in as many words.

Having a 100mA time-delayed unit does two things: it doesn't trip when
experiencing small current imbalances, where a 30mA trip would trip,
and being time-delayed, it allows the 30mA RCD in the CU to trip
first, isolating the ring mains, which is where the current-imbalance
fault is most likely to occur, but leaving the light circuit still
live, so you can still see where you're going at night. Cooker,
immersion, lights etc. are not on the 30mA RCD, but do have MCB's (as
do the ring mains on the 30mA RCD).


But it will not actually qualify as a device offering protection against
accidental contact on the non 30mA RCD circuits, so you still need
either a split way board with twin RCDs or RCBOs if you wish all the
circuits to be protected.

In either case the delayed RCD has no value outside of TT systems.

When you say it won't qualify as a device offering protection against
accidental contact on the non 30mA RCD circuits, do you man according
to the regs?

Yes - 30mA, 40mS trip time or lower/faster. I can't quote the reg number
off the top of my head.

Try electrical.theiet.org/wiring-matters/15/insp-test-rcd.cfm?type=pdf

which has a list of regs against RCD types.

As it offers whole-house protection, it must offer some
protection to the non 30mA RCD circuits, although it will obviously be
a bit less sensitive.

It offers ADS (automatic disconnection of supply) fault protection
(which is why you have it with a TT installation as your Live-Earth loop
impedance is not low enough to trip a breaker or the main fuse in the
required times because it cannot generate a high enough fault current.


As the items connected to the non 30mA RCD circuits are permanently
wired in, they're less likely to be a hazard than items plugged into
ring-main sockets, that are frequently plugged/unplugged and moved
around. At least, that was the thinking (not mine) for having the
set-up as I have. Probably not appropriate for the OP though, given
his particular situation.


Please note that I am NOT saying a 30mA RCD is required on all circuits
in a commercial installation. What I am saying is: please don't confuse
a 100mA RCD as offering " slightly less" protection than a 30mA/40mS RCD
as regards protection against accidental (human) contact. It provides no
recognised protection. So it is effectively pointless (unless you have a
TT earth).

Cheers,

Tim

In article om,
dennis@home wrote:
Unless its a double pole isolator a leak from the neutral can trip a
RCD.

Most fused spurs are only single pole.

Really? How far back are you going?

--
*I didn't like my beard at first. Then it grew on me.*

Dave Plowman London SW
To e-mail, change noise into sound.

"dennis@home" wrote in message
eb.com...
On 09/11/2015 14:43, Toby wrote:

But the most likely things to trip an RCD are water heaters or anything
with a 'solid' heating element. These can leak to ground.

I will get the hot water boilers checked, I think only one is on anyway.

Unless its a double pole isolator a leak from the neutral can trip a RCD.
Most fused spurs are only single pole.

Are you making this up?



--
Adam

"Toby" wrote in message
...
Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.


Then he is either a prick, a cowboy or just following instructions from the
client for the cheapest possible job (lets assume the later is not true).

An all RCBO or High integrity CU is the the way forward.

http://wiki.diyfaq.org.uk/index.php/...Consumer_Units

may help - you will have to juggle the circuits from the domestic approach
given to those setups to suit your needs (eg the computers need to be on
their own RCBO).

--
Adam

On 09/11/15 18:31, ARW wrote:
"Toby" wrote in message
...
Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.


Then he is either a prick, a cowboy or just following instructions from
the client for the cheapest possible job (lets assume the later is not
true).

An all RCBO or High integrity CU is the the way forward.

http://wiki.diyfaq.org.uk/index.php/...Consumer_Units

may help - you will have to juggle the circuits from the domestic
approach given to those setups to suit your needs (eg the computers need
to be on their own RCBO).


I'll just add that all the refurbs in universities seem to regard RCD
protected power circuits as "undesirable". The trend there seems to be
no RCD protection at circuit level and sockets with inbuilt RCDs in
certain vulnerable places - eg seminar rooms were students are likely to
jack in.

On 09/11/2015 17:56, Dave Plowman (News) wrote:
In article om,
dennis@home wrote:
Unless its a double pole isolator a leak from the neutral can trip a
RCD.

Most fused spurs are only single pole.

Really? How far back are you going?


Well most of the trade packs on screwfix don't say they are DP.
Only the crabtree and MK do.
Which ones do you think the electrician is going to buy if the customer
doesn't specify?

"dennis@home" wrote in message
web.com...
On 09/11/2015 17:56, Dave Plowman (News) wrote:
In article om,
dennis@home wrote:
Unless its a double pole isolator a leak from the neutral can trip a
RCD.

Most fused spurs are only single pole.

Really? How far back are you going?


Well most of the trade packs on screwfix don't say they are DP.
Only the crabtree and MK do.
Which ones do you think the electrician is going to buy if the customer
doesn't specify?


Give a link to one that you think is single pole.

--
Adam

"harry" wrote in message
...
On Monday, 9 November 2015 10:55:27 UTC, Toby wrote:
Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8
PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I
asked if he could firt an 100mA RCD for now, but as he didn't have one
with him, and we need people to be able to work, he is going to replace
the RCD with an isolator "At our request"

My question is, is it against the regs to install this whole
installation RCD in this situation in the first place?

He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to protect
this.

I basically want to know if we should use him to replace the CU with a
new 17th edition one, probably with RCBO's, or we need to find another
electrician.

Thanks!

--
Toby...
Remove your pants to reply

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

You can determine the cause by leaving items turned off one by one until
the problem stops.
Start with stuff that only runs intermittently.

All your portable equipment should be PAT tested anyway.



That's what all the PAT testers tell you.

PAT testing is a con.


--
Adam

In article , ARW
wrote:
"harry" wrote in message
...
On Monday, 9 November 2015 10:55:27 UTC, Toby wrote:
Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8
PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I
asked if he could firt an 100mA RCD for now, but as he didn't have one
with him, and we need people to be able to work, he is going to
replace the RCD with an isolator "At our request"

My question is, is it against the regs to install this whole
installation RCD in this situation in the first place?

He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to
protect this.

I basically want to know if we should use him to replace the CU with a
new 17th edition one, probably with RCBO's, or we need to find another
electrician.

Thanks!

-- Toby... Remove your pants to reply

--- This email has been checked for viruses by Avast antivirus
software. https://www.avast.com/antivirus

You can determine the cause by leaving items turned off one by one
until the problem stops. Start with stuff that only runs
intermittently.

All your portable equipment should be PAT tested anyway.



That's what all the PAT testers tell you.

PAT testing is a con.

PAT testing - because one year is up since the last test IS a con. PAT
testing on a proper risk assessed basis can show up faults - but most are
seen on the visual bit for which you don't need a meter. I have some RED
stickers and I have used them. Once on a piece of brand new kit.

--
Please note new email address:

On 09/11/2015 14:12, Tim Watts wrote:
On 09/11/15 13:52, Chris Hogg wrote:
On Mon, 9 Nov 2015 10:57:44 +0000, Toby
wrote:

Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8
PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I
asked if he could firt an 100mA RCD for now, but as he didn't have one
with him, and we need people to be able to work, he is going to replace
the RCD with an isolator "At our request"

My question is, is it against the regs to install this whole
installation RCD in this situation in the first place?

He said it was done because he fond one of the lighting circuits
upstairs didn't have any earth, and this was the easiest way to protect
this.

I basically want to know if we should use him to replace the CU with a
new 17th edition one, probably with RCBO's, or we need to find another
electrician.

Thanks!

IANA electrician, but following advice from various better-qualified
contributors to this NG, when I had my CU upgraded from wire fuses to
a split way unit with MCP's, I also had a 100A, 100mA time-delayed
whole-house RCD fitted at the front end, i.e. whole house. This was
because we have a TT supply, i.e. overhead cables, and apparently with
a TT supply this level of protection is implied by the regs, if not
actually spelled out in as many words.

Having a 100mA time-delayed unit does two things: it doesn't trip when
experiencing small current imbalances, where a 30mA trip would trip,
and being time-delayed, it allows the 30mA RCD in the CU to trip
first, isolating the ring mains, which is where the current-imbalance
fault is most likely to occur, but leaving the light circuit still
live, so you can still see where you're going at night. Cooker,
immersion, lights etc. are not on the 30mA RCD, but do have MCB's (as
do the ring mains on the 30mA RCD).


But it will not actually qualify as a device offering protection against
accidental contact on the non 30mA RCD circuits, so you still need
either a split way board with twin RCDs or RCBOs if you wish all the
circuits to be protected.

We are probably talking about a pre 17th edition install, where no
direct contact protection on lighting circuits etc would have been the
norm.

In either case the delayed RCD has no value outside of TT systems.

There are times where you want fire and installation protection and
cascaded RCDs - so they still have their uses.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 09/11/2015 18:31, ARW wrote:
"Toby" wrote in message
...
Hi,

In a small commercial office that was covered by a 12 way Wylex fuse
consumer unit (that had been "upgraded" with MCB's), an electrician
installed a whole installation 30mA RCD recently.


Then he is either a prick, a cowboy or just following instructions from
the client for the cheapest possible job (lets assume the later is not
true).

An all RCBO or High integrity CU is the the way forward.

http://wiki.diyfaq.org.uk/index.php/...Consumer_Units

may help - you will have to juggle the circuits from the domestic
approach given to those setups to suit your needs (eg the computers need
to be on their own RCBO).

With that much IT kit, you probably ought to consider high integrity
earthing as well on the computer circuits, since all those mains input
filters will likely contribute to a high non fault leakage current.




--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article ,
Tim Watts wrote:
I'll just add that all the refurbs in universities seem to regard RCD
protected power circuits as "undesirable". The trend there seems to be
no RCD protection at circuit level and sockets with inbuilt RCDs in
certain vulnerable places - eg seminar rooms were students are likely to
jack in.

Fine if you have an unlimited budget, as so many of these places seem to.
IMHO, totally unnecessary for a small office.

--
*"I am " is reportedly the shortest sentence in the English language. *

Dave Plowman London SW
To e-mail, change noise into sound.

On Monday, 9 November 2015 18:47:05 UTC, Tim Watts wrote:
I'll just add that all the refurbs in universities seem to regard RCD
protected power circuits as "undesirable". The trend there seems to be
no RCD protection at circuit level and sockets with inbuilt RCDs in
certain vulnerable places - eg seminar rooms were students are likely to
jack in.

Perhaps partly because they have older distribution boards for which RCBOs aren't available and changing the boards would be A Big Job involving lots of disruption to other users (and a cost to the estates budget rather than the seminar room budget).

Depending on the age of the building universities are more likely to have been properly wired in the first place in steel conduit or in dado trunking systems, ie no buried unprotected cables.

Owain

On 10/11/15 11:13, Dave Plowman (News) wrote:
In article ,
Tim Watts wrote:
I'll just add that all the refurbs in universities seem to regard RCD
protected power circuits as "undesirable". The trend there seems to be
no RCD protection at circuit level and sockets with inbuilt RCDs in
certain vulnerable places - eg seminar rooms were students are likely to
jack in.

Fine if you have an unlimited budget, as so many of these places seem to.
IMHO, totally unnecessary for a small office.


What on earth are you on about?

The sum total of RCD sockets in my place is a few % at most of all sockets.

I did say: certain common/accessible areas. I did not say every office,
lecture room, corridor.

It's certainly cheaper to do what they did than upgrade the circuit
(bearing in mind then they'd have to test the circuit possibly with
dozens of sockets, and these are commercial breaker panels so I expect
RCBOs will cost a little more than domestic ones).

On 10/11/15 12:38, wrote:
On Monday, 9 November 2015 18:47:05 UTC, Tim Watts wrote:
I'll just add that all the refurbs in universities seem to regard RCD
protected power circuits as "undesirable". The trend there seems to be
no RCD protection at circuit level and sockets with inbuilt RCDs in
certain vulnerable places - eg seminar rooms were students are likely to
jack in.

Perhaps partly because they have older distribution boards for which RCBOs aren't available and changing the boards would be A Big Job involving lots of disruption to other users (and a cost to the estates budget rather than the seminar room budget).

Depending on the age of the building universities are more likely to have been properly wired in the first place in steel conduit or in dado trunking systems, ie no buried unprotected cables.

Owain


That too...

In article ,
Tim Watts wrote:
On 10/11/15 11:13, Dave Plowman (News) wrote:
In article ,
Tim Watts wrote:
I'll just add that all the refurbs in universities seem to regard RCD
protected power circuits as "undesirable". The trend there seems to be
no RCD protection at circuit level and sockets with inbuilt RCDs in
certain vulnerable places - eg seminar rooms were students are likely to
jack in.

Fine if you have an unlimited budget, as so many of these places seem
to. IMHO, totally unnecessary for a small office.


What on earth are you on about?

The sum total of RCD sockets in my place is a few % at most of all
sockets.

Then you must have many with no RCD protection. To give the same degree of
protection, they'd all have to be RCD outlets. And have you looked at the
cost of them? At least four times that of a non RCD outlet.

I did say: certain common/accessible areas. I did not say every office,
lecture room, corridor.

It would be a very brave person who would guarantee there was never a need
for RCD protection on some sockets, while accepting it was needed on
others. In any form of public building.

--
*I am a nobody, and nobody is perfect; therefore I am perfect*

Dave Plowman London SW
To e-mail, change noise into sound.

On 10/11/15 15:14, Dave Plowman (News) wrote:

Then you must have many with no RCD protection. To give the same degree of
protection, they'd all have to be RCD outlets. And have you looked at the
cost of them? At least four times that of a non RCD outlet.


If you read back, my point was that universities DON'T tend to have RCD
protection on all sockets - very few IME out of a small sample set.


I did say: certain common/accessible areas. I did not say every office,
lecture room, corridor.

It would be a very brave person who would guarantee there was never a need
for RCD protection on some sockets, while accepting it was needed on
others. In any form of public building.

There'd seem to be a lot of brave people then... Remember, it's not a
domestic environment, nor one deemed to have vulnerable people.

In article ,
Dave Plowman (News) wrote:
In article ,
Tim Watts wrote:
On 10/11/15 11:13, Dave Plowman (News) wrote:
In article ,
Tim Watts wrote:
I'll just add that all the refurbs in universities seem to regard RCD
protected power circuits as "undesirable". The trend there seems to be
no RCD protection at circuit level and sockets with inbuilt RCDs in
certain vulnerable places - eg seminar rooms were students are likely to
jack in.

Fine if you have an unlimited budget, as so many of these places seem
to. IMHO, totally unnecessary for a small office.


What on earth are you on about?

The sum total of RCD sockets in my place is a few % at most of all
sockets.

Then you must have many with no RCD protection. To give the same degree of
protection, they'd all have to be RCD outlets. And have you looked at the
cost of them? At least four times that of a non RCD outlet.

I did say: certain common/accessible areas. I did not say every office,
lecture room, corridor.

It would be a very brave person who would guarantee there was never a need
for RCD protection on some sockets, while accepting it was needed on
others. In any form of public building.

Our local authority, in the case of village halls says "sockets on stage"
must be RCD protected.

--
Please note new email address:

replying to charles , westom wrote:
charles wrote:
Our local authority, in the case of village halls says
"sockets on stage" must be RCD protected.
--

Nothing should fault at even 2 milliamps. If something is tripping a 100
ma RCD, then an appliance or some household wiring has a major defect.
Find and fix that serious human safety issue. Never cure symptoms - ie
blame an RCD. Find and fix a human safety defect.


--

"charles" wrote in message
...
In article ,
Dave Plowman (News) wrote:
In article ,
Tim Watts wrote:
On 10/11/15 11:13, Dave Plowman (News) wrote:
In article ,
Tim Watts wrote:
I'll just add that all the refurbs in universities seem to regard
RCD
protected power circuits as "undesirable". The trend there seems to
be
no RCD protection at circuit level and sockets with inbuilt RCDs in
certain vulnerable places - eg seminar rooms were students are
likely to
jack in.

Fine if you have an unlimited budget, as so many of these places seem
to. IMHO, totally unnecessary for a small office.


What on earth are you on about?

The sum total of RCD sockets in my place is a few % at most of all
sockets.

Then you must have many with no RCD protection. To give the same degree
of
protection, they'd all have to be RCD outlets. And have you looked at the
cost of them? At least four times that of a non RCD outlet.

I did say: certain common/accessible areas. I did not say every office,
lecture room, corridor.

It would be a very brave person who would guarantee there was never a
need
for RCD protection on some sockets, while accepting it was needed on
others. In any form of public building.

Our local authority, in the case of village halls says "sockets on stage"
must be RCD protected.


What do you mean by local authority?


--
Adam

On 10/11/15 21:44, westom wrote:
replying to charles , westom wrote:
charles wrote:
Our local authority, in the case of village halls says
"sockets on stage" must be RCD protected. --

Nothing should fault at even 2 milliamps. If something is tripping a 100
ma RCD, then an appliance or some household wiring has a major defect.
Find and fix that serious human safety issue. Never cure symptoms - ie
blame an RCD. Find and fix a human safety defect.

work out what the leakage current of 30 PC RFI units with 15nF caps from
live and neutral to earth is.

Well over 30 mA IIRC





--
the biggest threat to humanity comes from socialism, which has utterly
diverted our attention away from what really matters to our existential
survival, to indulging in navel gazing and faux moral investigations
into what the world ought to be, whilst we fail utterly to deal with
what it actually is.

replying to The Natural Philosopher , westom wrote:
tnp wrote:
work out what the leakage current of 30 PC RFI units with 15nF caps from
live and neutral to earth is.

Maximum that any should leak is 100 microamps. PCs typically leak 60
microamps or less. That is 1.8 milliamps maximum. In other venues, an
RCDs trips on 5 ma - because no appliances all grouped together should
never leak even 5 milliamps.

That 100 milliamp RCD has detected a potentially serious human safety
problem.



--

In article , ARW
wrote:
"charles" wrote in message
...
In article , Dave Plowman (News)
wrote:
In article , Tim Watts
wrote:
On 10/11/15 11:13, Dave Plowman (News) wrote:
In article , Tim Watts
wrote:
I'll just add that all the refurbs in universities seem to regard
RCD protected power circuits as "undesirable". The trend there
seems to be no RCD protection at circuit level and sockets with
inbuilt RCDs in certain vulnerable places - eg seminar rooms were
students are likely to jack in.

Fine if you have an unlimited budget, as so many of these places
seem to. IMHO, totally unnecessary for a small office.


What on earth are you on about?

The sum total of RCD sockets in my place is a few % at most of all
sockets.

Then you must have many with no RCD protection. To give the same
degree of protection, they'd all have to be RCD outlets. And have you
looked at the cost of them? At least four times that of a non RCD
outlet.

I did say: certain common/accessible areas. I did not say every
office, lecture room, corridor.

It would be a very brave person who would guarantee there was never a
need for RCD protection on some sockets, while accepting it was needed
on others. In any form of public building.

Our local authority, in the case of village halls says "sockets on
stage" must be RCD protected.


What do you mean by local authority?

Borough Council who are responsible for issuing licences to such premises.

--
Please note new email address:

In article ,
The Natural Philosopher wrote:
On 10/11/15 21:44, westom wrote:
replying to charles , westom wrote:
charles wrote:
Our local authority, in the case of village halls says
"sockets on stage" must be RCD protected. --

Nothing should fault at even 2 milliamps. If something is tripping a 100
ma RCD, then an appliance or some household wiring has a major defect.
Find and fix that serious human safety issue. Never cure symptoms - ie
blame an RCD. Find and fix a human safety defect.

work out what the leakage current of 30 PC RFI units with 15nF caps from
live and neutral to earth is.

Well over 30 mA IIRC

But surely in good nick those present a balanced load to both line and
neutral?

--
*If you can't see my mirrors, I'm doing my hair*

Dave Plowman London SW
To e-mail, change noise into sound.

In article s.com,
westom wrote:
replying to charles , westom wrote:
charles wrote:
Our local authority, in the case of village halls says
"sockets on stage" must be RCD protected.
--

Nothing should fault at even 2 milliamps. If something is tripping a 100
ma RCD, then an appliance or some household wiring has a major defect.
Find and fix that serious human safety issue. Never cure symptoms - ie
blame an RCD. Find and fix a human safety defect.

Willing to bet in the OP's case it is one of his water heaters.

--
*Some days you're the dog, some days the hydrant.

Dave Plowman London SW
To e-mail, change noise into sound.

On Tue, 10 Nov 2015 23:44:01 +0000, westom
wrote:

replying to The Natural Philosopher , westom wrote:
tnp wrote:
work out what the leakage current of 30 PC RFI units with 15nF caps from
live and neutral to earth is.

Maximum that any should leak is 100 microamps. PCs typically leak 60
microamps or less. That is 1.8 milliamps maximum. In other venues, an
RCDs trips on 5 ma - because no appliances all grouped together should
never leak even 5 milliamps.

Where do you get 100uA from? A class1 piece of equipment to IEC 950
(Information Technology Equipment), a PC for example, can have up to
3.5mA of earth leakage current. Moreover an RCD will eventually trip
if continuously subjected to a current imbalance of half its rated
value, so 15mA will eventually trip an RCD. Given a worse case but
compliant leakage it would require only 5 pieces of Class 1 (earthed)
IT equipment to eventually trip a 30mA RCD.

replying to Peter Parry , westom wrote:
peter wrote:
On Tue, 10 Nov 2015 23:44:01 +0000, westom
Where do you get 100uA from? A class1 piece of equipment to IEC 950
(Information Technology Equipment), a PC for example, can have up to
3.5mA of earth leakage current.

We design this stuff. Maybe 1 milliamp is acceptable in some undeveloped
nations. But other standards demand well under 100 microamps.
Furthermore, leakage that low is easy. Some venues must have numerous
equipment on the same circuit that would trip at 5 milliamps. 3.5 mA
leakage from any appliance is a serious design or manufacturing flaw.
Especially when microamps are so easily achieved.

I have never seen a standard that permits a leakage that large. A PC
leaking 3.5 ma would cause circuit tripouts in many nations - completely
unacceptable when a computer must be designed for all world power systems.
Those milliamps approach currents that can kill. In many venues, a 5
milliamp leakage would trip RCDs.

If a 100 milliamp RCD is tripping, then the building contains a serious
human safety defect. Fix the defect. Many, instead, want to blame the
RCD.


--

"charles" wrote in message
...
In article , ARW
wrote:
"charles" wrote in message
...
In article , Dave Plowman (News)
wrote:
In article , Tim Watts
wrote:
On 10/11/15 11:13, Dave Plowman (News) wrote:
In article , Tim Watts
wrote:
I'll just add that all the refurbs in universities seem to regard
RCD protected power circuits as "undesirable". The trend there
seems to be no RCD protection at circuit level and sockets with
inbuilt RCDs in certain vulnerable places - eg seminar rooms were
students are likely to jack in.

Fine if you have an unlimited budget, as so many of these places
seem to. IMHO, totally unnecessary for a small office.


What on earth are you on about?

The sum total of RCD sockets in my place is a few % at most of all
sockets.

Then you must have many with no RCD protection. To give the same
degree of protection, they'd all have to be RCD outlets. And have you
looked at the cost of them? At least four times that of a non RCD
outlet.

I did say: certain common/accessible areas. I did not say every
office, lecture room, corridor.

It would be a very brave person who would guarantee there was never a
need for RCD protection on some sockets, while accepting it was needed
on others. In any form of public building.

Our local authority, in the case of village halls says "sockets on
stage" must be RCD protected.


What do you mean by local authority?

Borough Council who are responsible for issuing licences to such premises.


Just wondered as I this year I have electrically tested a few village halls
for insurance purposes. The LA had no specific requirements other than a
NICIEC EICR saying the electrics were safe. BTW I would put a lack of RCD on
stage sockets as a code 1.

I failed all of them for various reasons - the main failure at two of them
was an incredibly high Ze to the properties. As they were both tested within
two days of each other I questioned the calibration of test case I was
using. Both were, when double checked, DNO faults.

--
Adam