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Old October 23rd 13, 10:50 PM posted to uk.d-i-y
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Posts: 1,154
Default Thoughts on fitting RCBOs

Hi all, especially the knowledgeable electricians on here.

What are your thoughts on me replacing all of the MCBs in my CU with
RCBOs? At present I have 14 MCBs all protected by one 30mA RCD main
switch. Over the last few years I've had tripping problems from a
trapped L to E fault in a metal clad light unit, it too 10 years before
this became a problem! Water blowing into an extractor fan, water in an
outside light and the big issue of too many switch mode PSUs in the
house. While some of the genuine faults were a pain and time
consuming to locate the SMPSUs are something I have to live with and
they are taking my overall leakage too near the 30mA limit on the CU.

This has been brought to a head by a few trips this evening, no one
circuit being the culprit, leave any 2 or 3 MCBs off and it is happy,
just not happy with all on, I'm assuming something is leaking a bit more
than normal and has taken the main RCD to it's limit. I've left one
circuit off that has a number of SMPSUs on it and so far all is stable
again.

Yes I will turn everything off and check the trip current of the1 RCD in
case it has become overly sensitive, but NOT tonight!

So my thought was to replace the main switch/RCD with a simple switch
and then all of the MCBs with RCBOs, everything will be protected and in
the event of a real problem I don't lose the whole darn house, just the
one errant circuit.

So is it a practical idea? I think so, but would welcome any thoughts,
good or bad about doing it. I know the 17th edition suggests a split
load CU, but that would still leave me with a 50/50% split and a gamble
as to what worked and what didn't.

Yes I am competent to do it, just nervous that I may have missed a
fundamental flaw in the idea.

If it matters the CU is a Crabtree Starbreaker with a single 80A
switch/30mA RCD and 14 MCBs and a DIN mount bell transformer.



Apart from the cost, am I crazy?
--
Bill
( A different one )

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Old October 23rd 13, 11:20 PM posted to uk.d-i-y
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First recorded activity by DIYBanter: Aug 2013
Posts: 223
Default Thoughts on fitting RCBOs

On 23/10/2013 22:50, Bill wrote:
Hi all, especially the knowledgeable electricians on here.

What are your thoughts on me replacing all of the MCBs in my CU with
RCBOs? At present I have 14 MCBs all protected by one 30mA RCD main
switch. Over the last few years I've had tripping problems from a
trapped L to E fault in a metal clad light unit, it too 10 years before
this became a problem! Water blowing into an extractor fan, water in an
outside light and the big issue of too many switch mode PSUs in the
house. While some of the genuine faults were a pain and time
consuming to locate the SMPSUs are something I have to live with and
they are taking my overall leakage too near the 30mA limit on the CU.

This has been brought to a head by a few trips this evening, no one
circuit being the culprit, leave any 2 or 3 MCBs off and it is happy,
just not happy with all on, I'm assuming something is leaking a bit more
than normal and has taken the main RCD to it's limit. I've left one
circuit off that has a number of SMPSUs on it and so far all is stable
again.

Yes I will turn everything off and check the trip current of the1 RCD in
case it has become overly sensitive, but NOT tonight!

So my thought was to replace the main switch/RCD with a simple switch
and then all of the MCBs with RCBOs, everything will be protected and in
the event of a real problem I don't lose the whole darn house, just the
one errant circuit.

So is it a practical idea? I think so, but would welcome any thoughts,
good or bad about doing it. I know the 17th edition suggests a split
load CU, but that would still leave me with a 50/50% split and a gamble
as to what worked and what didn't.

Yes I am competent to do it, just nervous that I may have missed a
fundamental flaw in the idea.

If it matters the CU is a Crabtree Starbreaker with a single 80A
switch/30mA RCD and 14 MCBs and a DIN mount bell transformer.



Apart from the cost, am I crazy?



I have done exactly what you propose.

I previously had a MK metal clad CU with split rails.

there were 2 off 6A MCBs feeding two lighting circuits (up and down) and
4 MCBS fed from a 30mA RCD. the 4 MCBs were for cooker, immersion, left
hand side ring main, right hand side ring main.

I basically ended up replacing the entire CU with a Curve Unit. You can
get them from Denmans. I have a double pole on-off switch and can have
up to 19 RCBO's I took the opportunity to split some circuits and add
new ones.

I now have:

outside & garage lighting
ground floor lighting
first floor lighting
loft lighting
smoke, heat, CO detectors and intruder alarm
boiler & immersion
garage & outside sockets
front left sockets
front right sockets
Rear left sockets
Rear right sockets
loft sockets
Kitchen sockets
cooker

and I have 5 spare ways for the future.

since doing it, I have not had a single trip. Prior to all this, I had
all the problems you describe.


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Old October 23rd 13, 11:27 PM posted to uk.d-i-y
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First recorded activity by DIYBanter: Mar 2013
Posts: 2,300
Default Thoughts on fitting RCBOs

On 23/10/2013 22:50, Bill wrote:
Hi all, especially the knowledgeable electricians on here.

What are your thoughts on me replacing all of the MCBs in my CU with
RCBOs? At present I have 14 MCBs all protected by one 30mA RCD main
switch. Over the last few years I've had tripping problems from a
trapped L to E fault in a metal clad light unit, it too 10 years before
this became a problem! Water blowing into an extractor fan, water in an
outside light and the big issue of too many switch mode PSUs in the
house. While some of the genuine faults were a pain and time
consuming to locate the SMPSUs are something I have to live with and
they are taking my overall leakage too near the 30mA limit on the CU.

snip
Apart from the cost, am I crazy?

14 MCBs? Jesus H.


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Old October 23rd 13, 11:30 PM posted to uk.d-i-y
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First recorded activity by DIYBanter: Jul 2006
Posts: 1,154
Default Thoughts on fitting RCBOs

In message om, bm
writes
On 23/10/2013 22:50, Bill wrote:
Hi all, especially the knowledgeable electricians on here.

What are your thoughts on me replacing all of the MCBs in my CU with
RCBOs? At present I have 14 MCBs all protected by one 30mA RCD main
switch. Over the last few years I've had tripping problems from a
trapped L to E fault in a metal clad light unit, it too 10 years before
this became a problem! Water blowing into an extractor fan, water in an
outside light and the big issue of too many switch mode PSUs in the
house. While some of the genuine faults were a pain and time
consuming to locate the SMPSUs are something I have to live with and
they are taking my overall leakage too near the 30mA limit on the CU.

snip
Apart from the cost, am I crazy?

14 MCBs? Jesus H.


That isn't including the annexe, which is fed from a separate CU!!




--
Bill
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Old October 23rd 13, 11:46 PM posted to uk.d-i-y
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First recorded activity by DIYBanter: Jul 2006
Posts: 1,154
Default Thoughts on fitting RCBOs

In message om, bm
writes
14 MCBs? Jesus H.



http://s117.photobucket.com/user/G8I...ps287ce74d.jpg
..html

--
Bill


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Old October 24th 13, 12:25 AM posted to uk.d-i-y
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First recorded activity by DIYBanter: Mar 2013
Posts: 2,300
Default Thoughts on fitting RCBOs

On 23/10/2013 23:46, Bill wrote:
In message om, bm
writes
14 MCBs? Jesus H.



http://s117.photobucket.com/user/G8I...ps287ce74d.jpg
.html

LOL

Ahhhh yes, I've blunted many a drill bit in the RS PCB drill
God i'm getting old.

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Old October 24th 13, 01:26 AM posted to uk.d-i-y
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First recorded activity by DIYBanter: Jul 2006
Posts: 22,752
Default Thoughts on fitting RCBOs

On 23/10/2013 22:50, Bill wrote:

Hi all, especially the knowledgeable electricians on here.

What are your thoughts on me replacing all of the MCBs in my CU with
RCBOs? At present I have 14 MCBs all protected by one 30mA RCD main
switch. Over the last few years I've had tripping problems from a
trapped L to E fault in a metal clad light unit, it too 10 years before
this became a problem! Water blowing into an extractor fan, water in an
outside light and the big issue of too many switch mode PSUs in the
house. While some of the genuine faults were a pain and time
consuming to locate the SMPSUs are something I have to live with and
they are taking my overall leakage too near the 30mA limit on the CU.

This has been brought to a head by a few trips this evening, no one
circuit being the culprit, leave any 2 or 3 MCBs off and it is happy,
just not happy with all on, I'm assuming something is leaking a bit more
than normal and has taken the main RCD to it's limit. I've left one
circuit off that has a number of SMPSUs on it and so far all is stable
again.


Your experience adequately illustrates why the "whole house" RCD
arrangement is deprecated - it was never a great idea, and the march of
time (and things with leaky input filters) has only made the limitations
more apparent.

Yes I will turn everything off and check the trip current of the1 RCD in
case it has become overly sensitive, but NOT tonight!

So my thought was to replace the main switch/RCD with a simple switch
and then all of the MCBs with RCBOs, everything will be protected and in
the event of a real problem I don't lose the whole darn house, just the
one errant circuit.

So is it a practical idea?


Practical - yes certainly. Its the "Rolls Royce" solution that gives the
best possible discrimination in the even of an earth fault. Obviously
its more expensive than other options.

I think so, but would welcome any thoughts,
good or bad about doing it. I know the 17th edition suggests a split
load CU, but that would still leave me with a 50/50% split and a gamble
as to what worked and what didn't.


Split load does not have to mean a 50/50 split. Some 17th edition CUs
may have say 4 RCDs and some unprotected (aka "high integrity") ways as
well (for feeding circuits that meet the requirements for not being RCD
protected). You can also arrange the split in various combinations of
ways as suits your application.

Yes I am competent to do it, just nervous that I may have missed a
fundamental flaw in the idea.

If it matters the CU is a Crabtree Starbreaker with a single 80A
switch/30mA RCD and 14 MCBs and a DIN mount bell transformer.


Without checking I don't know if you can get single module wide RCBOs
for this enclosure (and if so if there is really enough space to wire
them). You may find you need to replace the enclosure as well.

Apart from the cost, am I crazy?


No, although you probably ought to look at some pragmatic options. You
may find a combination of several RCDs covering a two or three circuits
each, plus a smaller number of RCBOs would make for a system that is
equally effective, but also leave more money to spend on improving other
aspects of the system.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/
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Old October 24th 13, 01:30 AM posted to uk.d-i-y
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Posts: 22,752
Default Thoughts on fitting RCBOs

On 23/10/2013 23:30, Bill wrote:
In message om, bm
writes
On 23/10/2013 22:50, Bill wrote:
Hi all, especially the knowledgeable electricians on here.

What are your thoughts on me replacing all of the MCBs in my CU with
RCBOs? At present I have 14 MCBs all protected by one 30mA RCD main
switch. Over the last few years I've had tripping problems from a
trapped L to E fault in a metal clad light unit, it too 10 years before
this became a problem! Water blowing into an extractor fan, water in an
outside light and the big issue of too many switch mode PSUs in the
house. While some of the genuine faults were a pain and time
consuming to locate the SMPSUs are something I have to live with and
they are taking my overall leakage too near the 30mA limit on the CU.

snip
Apart from the cost, am I crazy?

14 MCBs? Jesus H.


That isn't including the annexe, which is fed from a separate CU!!


I was about to say, 14 sounds a bit restrictive ;-)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/
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Old October 24th 13, 07:35 AM posted to uk.d-i-y
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First recorded activity by DIYBanter: Jul 2011
Posts: 4,454
Default Thoughts on fitting RCBOs

On Wednesday 23 October 2013 22:50 Bill wrote in uk.d-i-y:

Hi all, especially the knowledgeable electricians on here.

What are your thoughts on me replacing all of the MCBs in my CU with
RCBOs? At present I have 14 MCBs all protected by one 30mA RCD main
switch. Over the last few years I've had tripping problems from a
trapped L to E fault in a metal clad light unit, it too 10 years before
this became a problem! Water blowing into an extractor fan, water in an
outside light and the big issue of too many switch mode PSUs in the
house. While some of the genuine faults were a pain and time
consuming to locate the SMPSUs are something I have to live with and
they are taking my overall leakage too near the 30mA limit on the CU.

This has been brought to a head by a few trips this evening, no one
circuit being the culprit, leave any 2 or 3 MCBs off and it is happy,
just not happy with all on, I'm assuming something is leaking a bit more
than normal and has taken the main RCD to it's limit. I've left one
circuit off that has a number of SMPSUs on it and so far all is stable
again.

Yes I will turn everything off and check the trip current of the1 RCD in
case it has become overly sensitive, but NOT tonight!

So my thought was to replace the main switch/RCD with a simple switch
and then all of the MCBs with RCBOs, everything will be protected and in
the event of a real problem I don't lose the whole darn house, just the
one errant circuit.

So is it a practical idea? I think so, but would welcome any thoughts,
good or bad about doing it. I know the 17th edition suggests a split
load CU, but that would still leave me with a 50/50% split and a gamble
as to what worked and what didn't.


I have 100% RCBOs (glad I did with the nusiance trips I had the other day!)

I have Hager. Crabtree are (or were) a good brand.

I would advise not putting all the larger RCBOs (32A rings, heaters) next to
each other - apparantly localised heat build up is a problem. I left a 1
module gap every 2-3 on mine and the middle RCBO is a low current one
(lights).

You'll probably need 1 module RCBOs - they are a lot taller than an MCB.

Is your CU tidy inside?

In the worst case, you could replace your CU with a bigger one to give you
more space.

--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

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Old October 24th 13, 08:05 AM posted to uk.d-i-y
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Posts: 3,157
Default Thoughts on fitting RCBOs

In article , Tim Watts
wrote:

[Snip]

Is your CU tidy inside?


In the worst case, you could replace your CU with a bigger one to give
you more space.


The trouble with replacing the enclosure is that you have the incoming live
& neutral to deal with. You can only isolate them by removing the
"compnay" fuse. Years ago, before 'privatisation', I needed to repace my
CU and arranged for someone to come and remove the company fuse. I said to
him that I estimated it was a two hours job, if he came back and and
reconnected me then, I could put the kettle on. He came back as suggested.
Would that work these days?

--
From KT24

Using a RISC OS computer running v5.18



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