Do I RCD protect the oven and hob or not?


S

Sparks

Currently I have a split load consumer unit, boths sides have their own 30mA
RCD
It is split into lighing one side, and everthing else the other.

I am adding a second CU for non-RCD protected things (Alarm, freezers and
feeds to smaller comsomer units in the shed & garage)

Would it be advisable to put the oven and induction hob feeds on this non
RCD CU?

Sparks...
 
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W

waddy

Sparks said:
Currently I have a split load consumer unit, boths sides have their own 30mA
RCD
It is split into lighing one side, and everthing else the other.

I am adding a second CU for non-RCD protected things (Alarm, freezers and
feeds to smaller comsomer units in the shed & garage)

Would it be advisable to put the oven and induction hob feeds on this non
RCD CU?

Sparks...
 
W

waddy

Hi Sparticus,

You should put the hob and oven on an rcd protective device if one is
available, obviously if they are not on rcd it will still comply with
the iee 16th ed regs (excluding outside/garden barbecues/sockets, etc),
though if you have a circuit available with rcd protection for the
hob/oven then use it.

You shouldn't really put lighting circuits on rcd protective circuits,
hence the idea of a split consumer unit, as a trip of the lighting
causes a hazard in itself, also alarm circuits i.e. fire/intruder
(without outlets should be dedicated circuits) should also not be rcd
proctected for similar reasons.

Regs Alan
 
F

Fred

waddy said:
Hi Sparticus,
You shouldn't really put lighting circuits on rcd protective circuits,
hence the idea of a split consumer unit, as a trip of the lighting
causes a hazard in itself, also alarm circuits i.e. fire/intruder
(without outlets should be dedicated circuits) should also not be rcd
proctected for similar reasons.

Regs Alan
I have always been amazed in this day and of implied safety, you're still
allowed to have bare connectors associated with light fittings without any
protection at 230V AC.

What do you think will be in the 17th Edition?
 
S

Sparks

They don't need RCD protecting, and oven elements can cause
Another thing I should have said, or asked, What type of earthing
system do you have? If it's a TT system, you can't normally have
any non-RCD protected circuits (except possibly for some low
current ones if you can prove the earth fault loop impedance is
OK for them). This might be the reason you have all circuits RCD
protected (although some of them should be at >= 100mA).
The house is a TN-S (Supplied by the electricity company's cable)

Incedently, this earth wire from the head to the CU seems to be about 4mm or
6mm - is this normal, or should it be replaced with heavier cable?

If so, do I ask the electricity company, as it is sealed in the lower part
of the cable head?

Sparks...
 
S

Sparks

waddy said:
Hi Sparticus,

You should put the hob and oven on an rcd protective device if one is
available, obviously if they are not on rcd it will still comply with
the iee 16th ed regs (excluding outside/garden barbecues/sockets, etc),
though if you have a circuit available with rcd protection for the
hob/oven then use it.

You shouldn't really put lighting circuits on rcd protective circuits,
hence the idea of a split consumer unit, as a trip of the lighting
causes a hazard in itself, also alarm circuits i.e. fire/intruder
(without outlets should be dedicated circuits) should also not be rcd
proctected for similar reasons.

So, for the fridge and freezer, should these be hard wired, so not having a
socket on an unprotected circuit?

Sparks...
 
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S

Stefek Zaba

Sparks said:
Would it be advisable to put the oven and induction hob feeds on this non
RCD CU?
My preference would be to put those fixed loads on the non RCD side. The
Regs certainly don't require them to be RCDed; and the older your oven
and grill elements get (also radiant and 'sealed' hotplates, but not
induction plates as you have) the more they pass a small leakage
current, especially when cold and a little damp (e.g. after a steamy
baking session as the elements cool down). Putting these on a shared RCD
predisposes that RCD to nuisance tripping.

But if you prefer the added reassurance that slopping salty spud-boiling
water about will cut the supply should it drip where it shouldn't,
there's nothing deeply bad about putting it on the RCD side. You could
always (assuming enough slack at the CU end) start off with it on the
RCD side, and move it across to the non-RCD CU if you get nuisance trips
which sort-of tie in with turning the cooker on.

In my direct experience of this, with a whole-house RCD (as used to be
the fashion), young kids (so making me keen on keeping the whole-house
RCD until they were past the fingerpoken age - 85, isn't it? ;-), a
coupla 'emergency' lights which came on if the power failed, and a
growing number of switched-mode-PSU computers and mains-filtered
appliances, *oh* and an RCD which on test showed it'd trip at under
14mA! - it was still only rare that turning on the cooker ring/grill
would make the RCD trip immediately; rather, it'd pop a minute or two
after you'd started to use the cooker. Maybe an element had to expand a
little first to bring a live conductor close enough to the earthed
casing to leak enough... maybe it was just pixies at work ;-)

HTH - Stefek
 
D

Dave Jones

Sparks said:
Currently I have a split load consumer unit, boths sides have their own
30mA RCD
It is split into lighing one side, and everthing else the other.

I am adding a second CU for non-RCD protected things (Alarm, freezers and
feeds to smaller comsomer units in the shed & garage)

Would it be advisable to put the oven and induction hob feeds on this non
RCD CU?

Sparks...
Why have you got 2 RCD's are you sure they are both RCD's? If so I'd remove
the one supplying the lighting and add the other circuits to it, if you have
room and don't overload the cu!

If the oven switch has a 13 amp outlet on it then it must be rcd protected,
otherwise up to u.
 
S

Sparks

Stefek Zaba said:
It will have been compliant when installed - maybe, say 14th Edn of
t'Regs. Theze Dayz it'd be 16mmsq or so. Not sure there's a *vast* benefit
in getting the supply co out to upgrade - they may then want you (or at
least suggest you should) up the rest of your own bonding to
10mmsq/16mmsq, and/or PMEify you...
So, if it was compliant at some point, it would still pass an inspection
now?

If that is that case. surely that is a bit stupid, as if the regulations
have changed, the older ones must now be deemed unsafe?

Sparks...
 
A

Andrew Gabriel

Currently I have a split load consumer unit, boths sides have their own 30mA
RCD
It is split into lighing one side, and everthing else the other.

I am adding a second CU for non-RCD protected things (Alarm, freezers and
feeds to smaller comsomer units in the shed & garage)

Would it be advisable to put the oven and induction hob feeds on this non
RCD CU?
They don't need RCD protecting, and oven elements can cause
tripping whilst not presenting any significant electrocution
risk which means it's not a brilliant idea to have them sharing
an RCD with anything else. So normally, they go on the non-RCD
protected side.
 
A

Andrew Gabriel

They don't need RCD protecting, and oven elements can cause
tripping whilst not presenting any significant electrocution
risk which means it's not a brilliant idea to have them sharing
an RCD with anything else. So normally, they go on the non-RCD
protected side.
Another thing I should have said, or asked, What type of earthing
system do you have? If it's a TT system, you can't normally have
any non-RCD protected circuits (except possibly for some low
current ones if you can prove the earth fault loop impedance is
OK for them). This might be the reason you have all circuits RCD
protected (although some of them should be at >= 100mA).
 
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P

Peter Parry

It comes down to which is the greater danger, being plunged into
darkness or being electrocuted...
That one is a complete no brainer.

The number of people killed or severely injured by electrocution in
domestic accidents the UK each year is very small. Even if you
include accidents which are not electrocution but attributable to it
(such as falling off a ladder after touching a live cable) the
numbers involved in domestic accidents are still small, about 25
deaths and 2000 injuries of all severities (compare this with 70
deaths and 40,000 injuries caused by DIY!). Those figures have not
reduced since whole house RCD's started to be used but are expected
to rise with Part P dissuading people from installing extra sockets
and increasing the use of extension leads.

The total number of people killed in accidents in the home each year
is about 4,000, of this roughly half are due to falls and about 1,000
due to falls down stairs.

The number of people killed or injured in house fires is also
depressingly large, many times greater than those killed by
electrocution. Typically 500 people die and 18,000 are seriously
injured each year by fire in the home. Of these deaths about 20 are
attributable to electrical fires some of which an RCD might have
prevented. The remainder are caused by non-electrical ignition.

Of the 4,000 people killed in both falls and fires each year there is
no easily available breakdown of contributory factors. However some
police and fire reports do give further information. Of these I have
seen only a very small number from one area, however within these
there were a significant minority, probably about 10-20 which
mentioned that lights were out and could not be turned back on from
the light switch when the emergency services arrived. Only one or
two of these, usually fire service reports, specifically mention
RCD's having tripped. Nonetheless it is reasonable to infer even
from this imperfect data that the number of people killed in falls
and fires in which tripped RCD's were the cause or a major
contributory factor is significantly higher than the number of people
protected by them _in the home_. In the garden or garage is quite
another matter.
FWIW our lighting circuits are RCD protected and are staying like it ;)
I suggest you invest in a book on basic risk assessment.
 
S

Stefek Zaba

Sparks said:
The house is a TN-S (Supplied by the electricity company's cable)

Incedently, this earth wire from the head to the CU seems to be about 4mm or
6mm - is this normal, or should it be replaced with heavier cable?

If so, do I ask the electricity company, as it is sealed in the lower part
of the cable head?
It will have been compliant when installed - maybe, say 14th Edn of
t'Regs. Theze Dayz it'd be 16mmsq or so. Not sure there's a *vast*
benefit in getting the supply co out to upgrade - they may then want you
(or at least suggest you should) up the rest of your own bonding to
10mmsq/16mmsq, and/or PMEify you...
 
D

Dave Plowman (News)

Would it be advisable to put the oven and induction hob feeds on this
non RCD CU?
Yes. There's no point in RCD protecting permanently connected devices like
this - and since they may well have mineral insulated heating elements
might cause nuisance tripping.
 
D

Dave Plowman (News)

I have always been amazed in this day and of implied safety, you're
still allowed to have bare connectors associated with light fittings
without any protection at 230V AC.
I tend to agree. I know the arguments about a blown bulb plunging the
house into darkness - but think the hazards of Joe Bloggs replacing a bulb
on a possibly live circuit more of a risk. IMHO.
 
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R

raden

Lee said:
Just because we chose one slight benefit over a possible risk does not
mean that we are unaware that risk.

We are unlikely to fall down stairs we don't have, for instance...
But for those of us with real stairs ...

No I'm not going there,

what are the upright bits of a bannister called, and where can you buy
them

Off to book my holiday to Indonesia, prolly safer
 
S

Stefek Zaba

Sparks said:
If that is that case. surely that is a bit stupid, as if the regulations
have changed, the older ones must now be deemed unsafe?
No - there's every difference between 'unsafe' and 'not to latest
standards for a new installation'. There's no obligation to keep an
installation continually updated in line with Regs changes (though I bet
the NICEIC would *lurv* such a principle to be established). There's a
specific category for 'not in line with latest Regs but not presenting
any problem' on the standard Periodic Inspection form (scrabbles for
OSG: ah yes, here it is.) There's a 4-level "recommendation" scale,
thus: "1 - requires urgent attention; 2 - requires improvement; 3 -
requires further investigation; 4 - does not comply with BS 7671:2001
amended to <date>. This does not imply that the electrical installation
inspected is unsafe."

HTH - Stefek
 
T

The Natural Philosopher

Sparks said:
Currently I have a split load consumer unit, boths sides have their own 30mA
RCD
It is split into lighing one side, and everthing else the other.

I am adding a second CU for non-RCD protected things (Alarm, freezers and
feeds to smaller comsomer units in the shed & garage)

Would it be advisable to put the oven and induction hob feeds on this non
RCD CU?

Sparks...
No idea what regs apply, but I personally like a BIG RCD - 100mA - for
the whole house, and 30mA RCBO's for where the regs say its needed.

Cookers aint it though. I do not believe there is a requirement to RCD them

I believe the philosophy is where portable appliances have cables whose
earth may become cut or disconnected and/or the appliance may become damp.
 
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A

Andrew Gabriel

I have always been amazed in this day and of implied safety, you're still
allowed to have bare connectors associated with light fittings without any
protection at 230V AC.
When doing portable appliance testing and checking for IP2X
(fingers can't access live parts), lampholders is the one
exception allowed there. (The usual causes for failures on
this test are old electric fires with the grill guard spacing
large enough to poke a finger through.)
 

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