Is there any practical way of modifying a Crabtree Starbreaker CU from
6+6 split to 8+4? Ideally I want to move two of the circuits
(immersion heater and air conditioner) to the non-RCD-protected side,
to reduce nuisance trips. There are no spare positions.

Richard.
http://www.rtrussell.co.uk/

On 14 June, 15:57, Richard Russell wrote:
Is there any practical way of modifying a Crabtree Starbreaker CU from
6+6 split to 8+4? *Ideally I want to move two of the circuits
(immersion heater and air conditioner) to the non-RCD-protected side,
to reduce nuisance trips. *There are no spare positions.

I have no idea about your Crabtree, on an MK it is simple but you
would have to replace one of the copper bus bars with a longer one and
cut the other down.
If my immersion heater was tripping the RCD I would not call it a
nuisance trip, I would want to investigate the problem and correct it.

On 14 June, 16:41, pcb1962 wrote:
I have no idea about your Crabtree, on an MK it is simple but you
would have to replace one of the copper bus bars with a longer one and
cut the other down.

I haven't managed to find a longer busbar for the Crabtree. I know MK
boxes are easy to modify but replacing the entire unit isn't really an
option for me (and even if I did, wouldn't I have to do it to the 17th
edition regs?).

If my immersion heater was tripping the RCD I would not call it a
nuisance trip, I would want to investigate the problem and correct it.

It's not (in fact it's switched off, so it can't), but the FAQ says an
immersion heater should be on the non-RCD-protected side.

Richard.
http://www.rtrussell.co.uk/

"Richard Russell" wrote in message
...
On 14 June, 16:41, pcb1962 wrote:
I have no idea about your Crabtree, on an MK it is simple but you
would have to replace one of the copper bus bars with a longer one and
cut the other down.

I haven't managed to find a longer busbar for the Crabtree. I know MK
boxes are easy to modify but replacing the entire unit isn't really an
option for me (and even if I did, wouldn't I have to do it to the 17th
edition regs?).

If my immersion heater was tripping the RCD I would not call it a
nuisance trip, I would want to investigate the problem and correct it.

It's not (in fact it's switched off, so it can't), but the FAQ says an
immersion heater should be on the non-RCD-protected side.

Richard.
http://www.rtrussell.co.uk/

Moving any circuit from the RCD side to the non RCD side may be against the
17th edition regulations. If it works and is not tripping your RCD then
leave it where it is.

Cheers

Adam

On 14 June, 17:14, "ARWadsworth"
wrote:
Moving any circuit from the RCD side to the non RCD side may be against the
17th edition regulations. If it works and is not tripping your RCD then
leave it where it is.

When the air conditioner was installed (recently) they wanted to put
it on the non-RCD side, but there wasn't a spare position. I can't
believe it would be "against the regs" to move it to where the
installers wanted to put it in the first place! It's a largish
'inverter' type with no doubt a substantial EMC filter, potentially
resulting in a significant leakage to earth.

The situation is that we suffer rare but annoying nuisance trips.
It's not surprising because there are lots of items with Switch Mode
Power Supplies that are usually left on standby (computers, microwave
oven etc.) on the RCD-protected circuits, so it's probably close to
tripping all the time. I have no reason to think any single item of
equipment is faulty, it's just the cumulative effect of all those EMC
filters. Moving things which *should* be on the non-RCD side would be
a practical step which might mitigate the problem.

Richard.
http://www.rtrussell.co.uk/

"Richard Russell" wrote in message
...
On 14 June, 17:14, "ARWadsworth"
wrote:
Moving any circuit from the RCD side to the non RCD side may be against
the
17th edition regulations. If it works and is not tripping your RCD then
leave it where it is.

When the air conditioner was installed (recently) they wanted to put
it on the non-RCD side, but there wasn't a spare position. I can't
believe it would be "against the regs" to move it to where the
installers wanted to put it in the first place! It's a largish
'inverter' type with no doubt a substantial EMC filter, potentially
resulting in a significant leakage to earth.

I said "could" not "would" be against the regs! If the cable is surface
mounted or armoured then it would not be against the 17th regs.


The situation is that we suffer rare but annoying nuisance trips.
It's not surprising because there are lots of items with Switch Mode
Power Supplies that are usually left on standby (computers, microwave
oven etc.) on the RCD-protected circuits, so it's probably close to
tripping all the time. I have no reason to think any single item of
equipment is faulty, it's just the cumulative effect of all those EMC
filters. Moving things which *should* be on the non-RCD side would be
a practical step which might mitigate the problem.

Is it the Crabtree Starbreaker with the plug in MCBs that you have? I have
not fitted one for a while but I am sure that they only available in 7, 10
or 15 way versions (with a choice of split between the RCD and Non RCD
sides) There was an older version that did a 6+6 split but was not available
with a choice of split. A photo would help. There is certainly nothing
showing on Crabtrees website that fits what you need.

Cheers

Adam

On 14 June, 17:43, "ARWadsworth"
wrote:
If the cable is surface
mounted or armoured then it would not be against the 17th regs.

Yes, surface mounted.

There was an older version that did a 6+6 split but was not available
with a choice of split.

That will be the one (it was installed in 2007).

There is certainly nothing showing on Crabtrees website that
fits what you need.

That's what I suspected.

As the range of consumer equipment using SMPS technology increases,
nuisance tripping is bound to become a greater problem IMHO. Do you
happen to know whether a standard CU RCD takes account of power factor
(in other words, does it trip just on the imbalance current or is
phase a factor)? Since EMC filter leakage will invariably be
capacitive, whereas a through-the-body circuit is likely to be
primarily resistive, the RCD could in principle discriminate between
them.

Richard.
http://www.rtrussell.co.uk/

"Richard Russell" wrote in message
...
On 14 June, 17:43, "ARWadsworth"
wrote:
If the cable is surface
mounted or armoured then it would not be against the 17th regs.

Yes, surface mounted.

There was an older version that did a 6+6 split but was not available
with a choice of split.

That will be the one (it was installed in 2007).

There is certainly nothing showing on Crabtrees website that
fits what you need.

That's what I suspected.

As the range of consumer equipment using SMPS technology increases,
nuisance tripping is bound to become a greater problem IMHO. Do you
happen to know whether a standard CU RCD takes account of power factor
(in other words, does it trip just on the imbalance current or is
phase a factor)? Since EMC filter leakage will invariably be
capacitive, whereas a through-the-body circuit is likely to be
primarily resistive, the RCD could in principle discriminate between
them.


Just on imbalance AFAIK.

Is there any way you could add a second CU to feed the A/C if needed?

Adam

Richard Russell wrote:
Is there any practical way of modifying a Crabtree Starbreaker CU from
6+6 split to 8+4? Ideally I want to move two of the circuits
(immersion heater and air conditioner) to the non-RCD-protected side,
to reduce nuisance trips. There are no spare positions.

Richard.
http://www.rtrussell.co.uk/
sounds dangerous to me,
immersion heaters mix lots of electrickery and water,
why not add another consumer unit with its own RCD for the trippy circuits
(and why are they tripping)
(2 of mine tripped in the thunderstorms last nght)

[g]

Can you put the immersion on an RCBO?

Reason being immersion elements do breakdown, an IR test would
confirm.
RCBO can be cheap on Ebay at least in pinning down a fault.

On 14 June, 18:21, "ARWadsworth"
wrote:
Is there any way you could add a second CU to feed the A/C if needed?

In fact there already is a second CU which feeds outside circuits
(garden lighting, pond pumps and shed). I suppose it might be
acceptable to connect the A/C there. It would be on an RCD, but there
are no other loads on that CU likely to cause leakage.

Richard.
http://www.rtrussell.co.uk/

Richard Russell wrote:
On 14 June, 16:41, pcb1962 wrote:
I have no idea about your Crabtree, on an MK it is simple but you
would have to replace one of the copper bus bars with a longer one and
cut the other down.

I haven't managed to find a longer busbar for the Crabtree. I know MK
boxes are easy to modify but replacing the entire unit isn't really an
option for me (and even if I did, wouldn't I have to do it to the 17th
edition regs?).

If my immersion heater was tripping the RCD I would not call it a
nuisance trip, I would want to investigate the problem and correct it.

It's not (in fact it's switched off, so it can't),

If something is switched off only on the live wire then it could trip an
RCD if theres a leakage from neutral to earth

but the FAQ says an
immersion heater should be on the non-RCD-protected side.


The FaQ says an imemersion heater should have no RCD?

http://wiki.diyfaq.org.uk/index.php?...on_Heaters#top
says the RCD wll trip on insulation breakdown or a split element -
which is a reason to put them on an RCD.

Richard.
http://www.rtrussell.co.uk/

js.b1 wrote:
Can you put the immersion on an RCBO?

Reason being immersion elements do breakdown, an IR test would
confirm.
RCBO can be cheap on Ebay at least in pinning down a fault.

I put a link here some months back of a TV programme investigating cheap
RCBOs which didnt have the correct circuits in them , one exploded!

beware!

[g]

On 14 June, 18:40, "george [dicegeorge]"
wrote:
If something is switched off only on the live wire then it could trip an
RCD if theres a leakage from neutral to earth

Depending on the neutral-earth voltage, yes, but IME it requires a low-
impedance connection like a dead short for that to happen. Anyway,
the immersion heater switch is double-pole (Hamilton).

The FaQ says an imemersion heater should have no RCD?

"Immersion Heaters are run off the non-RCD side.
Immersion Heaters are a common cause of earth leakage, and can thus
make an installation unreliable if on an RCD":

http://wiki.diyfaq.org.uk/index.php?..._for_Beginners

http://wiki.diyfaq.org.uk/index.php?...on_Heaters#top
says the RCD wll trip on insulation breakdown or a split element -
which is a reason to put them on an RCD.

DIY FAQ being inconsistent again!

Richard.
http://www.rtrussell.co.uk/

On Jun 14, 6:43*pm, "george [dicegeorge]"
wrote:
js.b1 wrote:
Can you put the immersion on an RCBO?

Reason being immersion elements do breakdown, an IR test would
confirm.
RCBO can be cheap on Ebay at least in pinning down a fault.

I put a link here some months back of a TV programme investigating cheap
RCBOs which didnt have the correct circuits in them , one exploded!

Cheap = "Boxed New" from genuine sellers with good feedback :-)

Recalls do happen.
Wylex/Crabtree MCB have had recent recall.
MK/MG/Schneider RCBO/RCD had a recall for 2003-2004 product.

There are also intentionally counterfeit devices.
BS1361 house-sized HRC fuses without sand, this one is obvious due to
the weight and they ain't arf going to go with a bang.
Counterfeit MCB which were in fact a continuous link, this one was
rather odious since it could result in damaged wiring or ejection of
material from steam generation (cable overheating). Chester just had
an underground cable blowup in a street today causing flash damage &
ejecting material.

I am wondering when the bad caps issue or similar hits RCD/RCBO in the
future, since I am rather dubious about product quality these days re
hidden outsourcing from lousy screws to electronic components. I have
two RCBO fail on me in 6yrs.

xxxx

The FaQ says an imemersion heater should have no RCD?

"Immersion Heaters are run off the non-RCD side.
Immersion Heaters are a common cause of earth leakage, and can thus
make an installation unreliable if on an RCD":

http://wiki.diyfaq.org.uk/index.php?..._for_Beginners

IEE Wiring regulations 17th edition says:
554.1.2 The supply to the electrode water heater or electrode boiler
shall be controlled by a linked circuit breaker arranged to disconnect
the supply from all electrodes simultaneously and provided with an
overcurrent protective device in each conductor feeding an electrode

[g]

On Tue, 15 Jun 2010 00:19:38 +0100, wibbled:

On 14 Jun,
"george [dicegeorge]" wrote:

554.1.2 The supply to the electrode water heater or electrode boiler
shall be controlled by a linked circuit breaker arranged to disconnect
the supply from all electrodes simultaneously and provided with an
overcurrent protective device in each conductor feeding an electrode

An electrode water heater is *not* an immersion heater. It is where the
current is passed through the water in order to heat it. Many years ago
I used to operate a pair of 3 phase electrode boilers used off peak for
a heatbank for space heating. Earthing has to be well up to spec, and
earth leakage *is* expected. I can't imagine that single phase ones are
permitted.

I've seen electric showers in China (these have a small tank that
requires preheating as most people's supplies wouldn't manage a 9-11kW
instantaneous device) based on electrode heating. That scared me.
Especially as RCDs are only recently appearing on new builds (ironically
the new build I looked at for fun was RCBOs on all circuits - talk about
extremes!).

However, after noting exactly where the socket for the shower was mounted
(in the shower, albeit at ceiling height) I stopped worrying so much
about the electrode heaters :-|



--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.

"Richard Russell" wrote in message
...
The FaQ says an imemersion heater should have no RCD?

"Immersion Heaters are run off the non-RCD side.
Immersion Heaters are a common cause of earth leakage, and can thus
make an installation unreliable if on an RCD":

http://wiki.diyfaq.org.uk/index.php?..._for_Beginners

http://wiki.diyfaq.org.uk/index.php?...on_Heaters#top
says the RCD wll trip on insulation breakdown or a split element -
which is a reason to put them on an RCD.

DIY FAQ being inconsistent again!

Or outdated. But the wiki also says-
NOTE - The current set of IEE Wiring Regulations, the 17th Edition are more
onerous in the requirements to install RCD (or RCBO) protection than the
previous 16th Edition. In general, ANY cable which is less than 50mm below
the wall surface AND is NOT mechanically protected as defined by the IEE
Regulations (which generally means armoured cable [SWA], pyro cable [MICC,
mineral insulated copper clad], cable in steel heavy guage conduit or a
limited use of highly specialised cables incorporating an earthed foil
screen MUST HAVE a 30mA non timed delayed RCD protecting that circuit, in
addition to all other requirements. Such circuit protection may be derived
from either an RCD protecting several circuits, or individual RCD/RCBOs on
each circuit. This statement and it's implications now overrides anything
else in this article which was written to the 16th Edition, pending more
detailed updates to this article.

Adam

"Richard Russell" wrote in message
...
On 14 June, 18:21, "ARWadsworth"
wrote:
Is there any way you could add a second CU to feed the A/C if needed?

In fact there already is a second CU which feeds outside circuits
(garden lighting, pond pumps and shed). I suppose it might be
acceptable to connect the A/C there. It would be on an RCD, but there
are no other loads on that CU likely to cause leakage.

Richard.
http://www.rtrussell.co.uk/

Well as there is nothing on the Crabree website to change a 6+6 split to
anything else (all the other CUs on their site have different busbars to
alter the split) then could have a 3rd CU? I am still not sure that the
immersion need to be RCD protected unless it causing you problems (ie is it
usually off when you get a nuisance trip). I have not checked yet but you
might be able to change the bus bar and then use RCBOs for the circuits that
you want RCD protection on. Please sit down before looking at the prices on
Crabtree RCBOs.

Adam

On 15 June, 14:06, "ARWadsworth"
wrote:
you might be able to change the bus bar and then use RCBOs for the
circuits that you want RCD protection on. Please sit down before looking
at the prices on Crabtree RCBOs.

I would consider that option (the price isn't a concern) but I'm not
even sure there's a non-split busbar available for my CU. It would
need to be a Main Switch + 15, and that doesn't seem to be listed.

Richard.
http://www.rtrussell.co.uk/

"Richard Russell" wrote in message
...
On 15 June, 14:06, "ARWadsworth"
wrote:
you might be able to change the bus bar and then use RCBOs for the
circuits that you want RCD protection on. Please sit down before looking
at the prices on Crabtree RCBOs.

I would consider that option (the price isn't a concern) but I'm not
even sure there's a non-split busbar available for my CU. It would
need to be a Main Switch + 15, and that doesn't seem to be listed.

Richard.
http://www.rtrussell.co.uk/

There is not a bus bar that would fit. I have had it straight from the
horses mouth (I called their tech department for something else but I asked
for you whilst on the phone). I was imformed that the 6+6 load Starbreaker
was a specially built/imported CU for a big customer in Scotland to fit a
certain sized box. The CU became a good seller and no other varients to the
6+6 split were ever made. If you look on the web site it is the only 412
list no for their CUs. Feeding a new CU from one on the non RCD slots is a
viable option.

And just to make you feel better the Wylex team also disappointed me (well
my customer) with my tech enquiry.

Cheers

Adam