I am installing a new built-in oven and hit the usual problem of the
horrible connectors they always seem to come with. However this one
seems even worse than usual and I'm a bit stumped as to how to do a
proper job of connecting it.

I have a dedicated 32 amp MCB for the oven and (electric, induction)
hob and it has a 6sq mm cable running to the kitchen units.

However there is absolutely no way that one can connect 6sq mm cable
to the oven. The connection block is too small. The only cable that
I think I can reasonably connect to it is 2.5sq mm because the screw
terminals are such that only single, solid wire can be reliably
connected to it.

There's not enough room for any sort of termination on the cable.
I've tried and I have a wide variety of crimps in many shapes and
sizes, while you can terminate a cable with a 'ring' that will fit
under the screw the body of the crimp is too fat to fit through the
slot provided for the cable.

The oven is rated 2.3kw so 2.5sq mm is perfectly adequate, the problem
is that it's not ideal for allowing the oven to be slid in and out and
it's not properly protected by the 32amp MCB.

What options do I have? I suppose I could have a local FCU for the
oven but it seems a bit overly complex and discrimination might be a
problem. I can't see *any* way to connect flexible cable to the oven
so I think it's stuck with at least a short length of 2.5sq mm. The
best I can do at present is to take the short length of 2.5sq mm to a
junction box (or terminal block) on the back of the oven and run a
more flexible cable from there. Can one get high temperature 2.5sq mm
cable with solid conductors that I could rate at 32 amps? That would
be be the neatest solution I guess.

Or maybe I should take the back off the oven and replace their crap
connector!

--
Chris Green

wrote:
I am installing a new built-in oven and hit the usual problem of the
horrible connectors they always seem to come with


The oven is rated 2.3kw so 2.5sq mm is perfectly adequate, the problem
is that it's not ideal for allowing the oven to be slid in and out and
it's not properly protected by the 32amp MCB.

There is a very good chance the 2.5 T&E will be adequately protected by the
32A MCB.


However I now suspect that you have just unleashed the pillock from
Birmingham and we can now expect a load of ranting and ******** about the
dangers (made up ones) of installing unfused spurs using 2.5 T&E on a 32A
circuit.

Our only hope is that he is in his straight jacket or that nursie has
heavily sedated him tonight to stop him going again out without permission
armed with a hair drier, hi viz jacket and a clipboard. (Last time he went
out it took 3 nurses to pry him off the speed camera he was making love to,
and then they had to presure wash the camera post clean after they had done
so)

PS Are you sure you cannot get 2.5m flex to fit (maybe with a bootlace
ferrule on the end of the flex)
--
Adam

ARWadsworth wrote:
wrote:
I am installing a new built-in oven and hit the usual problem of the
horrible connectors they always seem to come with


The oven is rated 2.3kw so 2.5sq mm is perfectly adequate, the problem
is that it's not ideal for allowing the oven to be slid in and out and
it's not properly protected by the 32amp MCB.

There is a very good chance the 2.5 T&E will be adequately protected by the
32A MCB.

I was wondering if that might be so, it'll be a very short piece of
2.5 T&E.


[snip]

PS Are you sure you cannot get 2.5m flex to fit (maybe with a bootlace
ferrule on the end of the flex)

Pretty sure yes, for two reasons:-

The bootlace ferrule's "shoulder" almost certainly won't fit
through the space provided.

It won't locate safely under the screw terminal anyway, there's no
washer or anything. The only way one can make 2.5 T&E secure is
by pre-forming a U in the end of the wire and wrapping that round
the terminal screw.

--
Chris Green

On Apr 19, 2:13*pm, "ARWadsworth"
wrote:
wrote:
I am installing a new built-inovenand hit the usual problem of the
horrible connectors they always seem to come with
Theovenis rated 2.3kw so 2.5sq mm is perfectly adequate, the problem
is that it's not ideal for allowing theovento be slid in and out and
it's not properly protected by the 32amp MCB.

There is a very good chance the 2.5 T&E will be adequately protected by the
32A MCB.

However I now suspect that you have just unleashed the pillock from
Birmingham and we can now expect a load of ranting and ******** about the
dangers (made up ones) of installing unfused spurs using 2.5 T&E on a 32A
circuit.

Our only hope is that he is in his straight jacket or that nursie has
heavily sedated him tonight to stop him going again out without permission
armed with a hair drier, hi viz jacket and a clipboard. (Last time he went
out it took 3 nurses to pry him off the speed camera he was making love to,
and then they had to presure wash the camera post clean after they had done
so)

PS Are you sure you cannot get 2.5m flex to fit (maybe with a bootlace
ferrule on the end of the flex)
--
Adam

The worst thing is that nursie probably has to clean his horrible
connector.

On 2012-04-19, ARWadsworth wrote:

wrote:
I am installing a new built-in oven and hit the usual problem of the
horrible connectors they always seem to come with


The oven is rated 2.3kw so 2.5sq mm is perfectly adequate, the problem
is that it's not ideal for allowing the oven to be slid in and out and
it's not properly protected by the 32amp MCB.

There is a very good chance the 2.5 T&E will be adequately protected by the
32A MCB.


However I now suspect that you have just unleashed the pillock from
Birmingham and we can now expect a load of ranting and ******** about the
dangers (made up ones) of installing unfused spurs using 2.5 T&E on a 32A
circuit.

I'm not looking for an argument (or even a good session of
contradiction), but I was under the impression that 2.5 T&E wasn't
rated for 32 A in any situation, and that you ought to use
heat-resistant (rather than "ordinary") cable coming into an oven.
I'd like to know why those notions are wrong.

Adam Funk wrote:

On 2012-04-19, ARWadsworth wrote:

wrote:
I am installing a new built-in oven and hit the usual problem of the
horrible connectors they always seem to come with


The oven is rated 2.3kw so 2.5sq mm is perfectly adequate, the problem
is that it's not ideal for allowing the oven to be slid in and out and
it's not properly protected by the 32amp MCB.

There is a very good chance the 2.5 T&E will be adequately protected by the
32A MCB.


However I now suspect that you have just unleashed the pillock from
Birmingham and we can now expect a load of ranting and ******** about the
dangers (made up ones) of installing unfused spurs using 2.5 T&E on a 32A
circuit.

I'm not looking for an argument (or even a good session of
contradiction), but I was under the impression that 2.5 T&E wasn't
rated for 32 A in any situation, and that you ought to use
heat-resistant (rather than "ordinary") cable coming into an oven.
I'd like to know why those notions are wrong.

As Adam has pointed out to me, it is a known load, so for that oven,
there is no need for any overload protection.
Clearly, it is sensible to have o/l protection, but not necessary.

The wire input is at the bottom corner (generally) on built-in ovens, so
the cable is unlikely to get much over 30-40 degrees, hence no need for
heat resistant cable.

Alan.
--
To reply by e-mail, change the ' + ' to 'plus'.

On 2012-04-20, A.Lee wrote:

Adam Funk wrote:

I'm not looking for an argument (or even a good session of
contradiction), but I was under the impression that 2.5 T&E wasn't
rated for 32 A in any situation, and that you ought to use
heat-resistant (rather than "ordinary") cable coming into an oven.
I'd like to know why those notions are wrong.

As Adam has pointed out to me, it is a known load, so for that oven,
there is no need for any overload protection.
Clearly, it is sensible to have o/l protection, but not necessary.

Right, but I was thinking more of fault protection (see John Rumm's
reply & my reply to that).


The wire input is at the bottom corner (generally) on built-in ovens, so
the cable is unlikely to get much over 30-40 degrees, hence no need for
heat resistant cable.

Good point.

On 20/04/2012 10:04, Adam Funk wrote:
On 2012-04-19, ARWadsworth wrote:

wrote:
I am installing a new built-in oven and hit the usual problem of the
horrible connectors they always seem to come with


The oven is rated 2.3kw so 2.5sq mm is perfectly adequate, the problem
is that it's not ideal for allowing the oven to be slid in and out and
it's not properly protected by the 32amp MCB.

There is a very good chance the 2.5 T&E will be adequately protected by the
32A MCB.


However I now suspect that you have just unleashed the pillock from
Birmingham and we can now expect a load of ranting and ******** about the
dangers (made up ones) of installing unfused spurs using 2.5 T&E on a 32A
circuit.

I'm not looking for an argument (or even a good session of
contradiction), but I was under the impression that 2.5 T&E wasn't
rated for 32 A in any situation,

You are right its not...

However in this case, we are not designing that part of the installation
to carry 32A, or anything close to it.

This is one of those situations where the responsibility for fault and
overload protection can be split. The fault protection must always be at
the origin of the circuit, and must in the event of a fault ensure that
the circuit is disconnected quickly enough to avoid (possibly further)
cable damage (5 secs typically on a fixed appliance). Overload
protection is also usually at the origin of the circuit and provided by
the same protective device. However in some cases the overload
protection can be placed elsewhere in the circuit, or for that matter
omitted altogehter, if it can be imposed by some other design criterion.

In this circumstance the fault protection for the 2.5mm^2 cable will be
adequately provided by the 32A MCB (much the same situation as applies
with a spur in 2.5mm^2 from a 32A radial wired in 4mm^2 for example).
There is however no need for explicit overload protection since in this
case it is imposed by the design i.e. the oven can only draw a maximum
of 10A, and there is no way for someone to unwittingly add additional
load to the end of its cable.

and that you ought to use
heat-resistant (rather than "ordinary") cable coming into an oven.

Ideally it should be - and high temperature flex would be the cable of
choice. However there are two common problems with that, its not always
easy to buy in the required size[1], and second it won't always fit in
the connector on the oven. This means that in practice many ovens /
cookers etc get wired in T&E. By selecting a size significantly in
excess of that indicated just by the current demand, you also allow for
significant de-rating due to the high ambient temperature. While it gets
warm in the oven enclosure, its unlikely to actually go above the
insulation temperature limit of the "normal" PVC.

[1] Most wholesalers have stock of 2.5mm^2 which will cover pretty much
any oven, however many do not carry the 4.0mm^2 that would be required
for many hobs.

I'd like to know why those notions are wrong.

Your notions are not actually wrong as rules of thumb, its just there is
a little more design finesse one can apply to take into account the
specifics of the situation.

--
Cheers,

John.

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

John Rumm wrote:

In this circumstance the fault protection for the 2.5mm^2 cable will be
adequately provided by the 32A MCB (much the same situation as applies
with a spur in 2.5mm^2 from a 32A radial wired in 4mm^2 for example).
There is however no need for explicit overload protection since in this
case it is imposed by the design i.e. the oven can only draw a maximum
of 10A, and there is no way for someone to unwittingly add additional
load to the end of its cable.

Thanks for this detailed clarification, just what I needed to feel
that the way I have wired it is satisfactory.

--
Chris Green

replying to tinnews , Jeff wrote:
wrote:

Thanks for this detailed clarification, just what I needed to feel
that the way I have wired it is satisfactory.


Good grief don't know what all the fuss is about on this, there are two
options to wire a medium powered fitted hob and a low powered fitted oven.
The medium powered hob is hard wired via 6mm T&E to a 45A cooker control
switch that has a 13A socket outlet, then the 6mm cable runs to the hob,
the 2kW fitted oven is wired with 1.5mm 3 core flex (heat resistance can
be used but not mandatory).
Fit a 13A-fused plug the other end & plug it into the cooker control
switch 13A socket.

The second option is the same for the hob but the oven can be hard wired
to a 13A switch fused spur, the spur unit can be fed with 4mm/6mm cable
from either the cooker control switch or a cooker connection unit but make
sure you have a 45mm mounting box for room, then wire a 1.5mm/2.5mm to the
2kW oven.
You must have easy access to fuses & switches so do not place anything
switched or fused behind fitted ovens, duel cooker connections are also
now available that can take up to 10mm cables.
The golden rule is you must check the power in watts of each appliance &
consider the total wattage for the circuit.
It is paramount that you adhere to the appliance electrical wiring
instructions.
If it states an appliance must have a 13A fuse, then it generally means
there is no internal fuse in the oven to protect the fan & mains input
wiring & components, a 32A cooker circuit fuse would provide unsuitable
protection for the appliance.


--

On 2012-04-20, John Rumm wrote:

On 20/04/2012 10:04, Adam Funk wrote:

I'm not looking for an argument (or even a good session of
contradiction), but I was under the impression that 2.5 T&E wasn't
rated for 32 A in any situation,

You are right its not...

However in this case, we are not designing that part of the installation
to carry 32A, or anything close to it.

This is one of those situations where the responsibility for fault and
overload protection can be split. The fault protection must always be at
the origin of the circuit, and must in the event of a fault ensure that
the circuit is disconnected quickly enough to avoid (possibly further)
cable damage (5 secs typically on a fixed appliance). Overload
protection is also usually at the origin of the circuit and provided by
the same protective device. However in some cases the overload
protection can be placed elsewhere in the circuit, or for that matter
omitted altogehter, if it can be imposed by some other design criterion.

In this circumstance the fault protection for the 2.5mm^2 cable will be
adequately provided by the 32A MCB (much the same situation as applies
with a spur in 2.5mm^2 from a 32A radial wired in 4mm^2 for example).
There is however no need for explicit overload protection since in this
case it is imposed by the design i.e. the oven can only draw a maximum
of 10A, and there is no way for someone to unwittingly add additional
load to the end of its cable.

Right, it's the fault protection that I was thinking of, but (a) I
didn't realize a 32 A MCB was low enough for fault protection on
2.5Â*mm^2, and (b) what about a fault inside the oven that takes it
over 10 A? Do we assume the oven has internal fault protection?


and that you ought to use
heat-resistant (rather than "ordinary") cable coming into an oven.

Ideally it should be - and high temperature flex would be the cable of
choice. However there are two common problems with that, its not always
easy to buy in the required size[1], and second it won't always fit in
the connector on the oven. This means that in practice many ovens /
cookers etc get wired in T&E. By selecting a size significantly in
excess of that indicated just by the current demand, you also allow for
significant de-rating due to the high ambient temperature. While it gets
warm in the oven enclosure, its unlikely to actually go above the
insulation temperature limit of the "normal" PVC.

Good point.

Your notions are not actually wrong as rules of thumb, its just there is
a little more design finesse one can apply to take into account the
specifics of the situation.

Thanks for the explanation.

Adam Funk wrote:
On 2012-04-20, John Rumm wrote:

On 20/04/2012 10:04, Adam Funk wrote:

I'm not looking for an argument (or even a good session of
contradiction), but I was under the impression that 2.5 T&E wasn't
rated for 32 A in any situation,

You are right its not...

However in this case, we are not designing that part of the
installation to carry 32A, or anything close to it.

This is one of those situations where the responsibility for fault
and overload protection can be split. The fault protection must
always be at the origin of the circuit, and must in the event of a
fault ensure that the circuit is disconnected quickly enough to
avoid (possibly further) cable damage (5 secs typically on a fixed
appliance). Overload protection is also usually at the origin of
the circuit and provided by the same protective device. However in
some cases the overload protection can be placed elsewhere in the
circuit, or for that matter omitted altogehter, if it can be
imposed by some other design criterion.

In this circumstance the fault protection for the 2.5mm^2 cable
will be adequately provided by the 32A MCB (much the same situation
as applies with a spur in 2.5mm^2 from a 32A radial wired in 4mm^2
for example). There is however no need for explicit overload
protection since in this case it is imposed by the design i.e. the
oven can only draw a maximum of 10A, and there is no way for
someone to unwittingly add additional load to the end of its cable.

Right, it's the fault protection that I was thinking of, but (a) I
didn't realize a 32 A MCB was low enough for fault protection on
2.5 mm^2, and (b) what about a fault inside the oven that takes it
over 10 A? Do we assume the oven has internal fault protection?


http://wiki.diyfaq.org.uk/index.php?title=MCB

and

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

gives more detail.

It needs 160A to trip a 32A MCB quickly enough to meet fault protection
requirements.

But 160A is NOT the maximum fault current ir is a mimimum current. The fault
current will be much higher than 160A in most cases. A house close to the
substation could have a very low ELI and well over 1000A could pass through
the cable in the event of a fault (even on a 6A lighting circuit).

If the manufacturer of the oven specifies a 13A fuse needs to be fitted then
you must fit one.

Can you suggest a way that a 3kW oven could fail and allow greater than a
27A current (the maximum 2.5 T&E can carry) for any length of time?


--
Adam (But not Adam Funk)

On 20/04/2012 15:15, Adam Funk wrote:
On 2012-04-20, John Rumm wrote:

On 20/04/2012 10:04, Adam Funk wrote:

I'm not looking for an argument (or even a good session of
contradiction), but I was under the impression that 2.5 T&E wasn't
rated for 32 A in any situation,

You are right its not...

However in this case, we are not designing that part of the installation
to carry 32A, or anything close to it.

This is one of those situations where the responsibility for fault and
overload protection can be split. The fault protection must always be at
the origin of the circuit, and must in the event of a fault ensure that
the circuit is disconnected quickly enough to avoid (possibly further)
cable damage (5 secs typically on a fixed appliance). Overload
protection is also usually at the origin of the circuit and provided by
the same protective device. However in some cases the overload
protection can be placed elsewhere in the circuit, or for that matter
omitted altogehter, if it can be imposed by some other design criterion.

In this circumstance the fault protection for the 2.5mm^2 cable will be
adequately provided by the 32A MCB (much the same situation as applies
with a spur in 2.5mm^2 from a 32A radial wired in 4mm^2 for example).
There is however no need for explicit overload protection since in this
case it is imposed by the design i.e. the oven can only draw a maximum
of 10A, and there is no way for someone to unwittingly add additional
load to the end of its cable.

Right, it's the fault protection that I was thinking of, but (a) I
didn't realize a 32 A MCB was low enough for fault protection on
2.5 mm^2, and

Yup, fault protection (i.e. short circuits L to N or L to E) is a *very*
different ball game from overload protection. You are dealing with very
high instantaneous currents way in excess of the normal duty rating of
the conductors. Hence you need enough fault current to cause the
protective device to open quickly, and you need the cable conductors to
survive long enough to ensure that happens when subjected to adiabatic
heating (i.e. so fast you can't take into account any losses to the
surroundings).

So with a 32A MCB:

http://wiki.diyfaq.org.uk/images/d/d...e-MCBTypeB.png

The table shows that a current of 160A or more is needed to cause it to
operate in its "instantaneous" mode (i.e. its magnetic rather than its
thermal response).

Say you take a fault scenario of the insulation on the oven element
breaking down completely and the element shorts to earth. Say this
presents a total Earth Loop Impedance of 0.8 ohms at the fault position.
That ELI would give rise a fault current of around 230/0.8 = 290A. So
enough to open the MCB in a nominal 0.1 secs. The weak link of the chain
with T&E is the earth conductor which is only 1.5mm^2 in this case. You
can check that it will survive long enough to clear the fault with the
adiabatic check:

s = sqrt( i^2 x t ) / k

Where s is the cross sectional area of earth conductor required, i the
fault current, t the time to clear the fault, and k a factor empirically
derived to factor in the physical response of the cable.

So you get:

s = sqrt( 290^2 x 0.1 ) / 115

(where 115 is the k factor for PVC cable, see table [1])

s = 0.8mm^2

So we known that the 1.5mm^2 in the T&E is = s, hence it is adequate.

(b) what about a fault inside the oven that takes it
over 10 A?

Here is where you need to be careful with language... if you really mean
fault, then its covered by the above - as in my example.

However you also need to assess the risk of overload - i.e. a sustained
period drawing more current than the circuit was designed for.

In this case, while there are a number of fault current scenarios that
may occur in the oven, there are no realistic scenarios where the oven
could start drawing current significantly in excess of its design
current for an extended period of time. There is also no way for a user
to easily do anything that could add to its load.

(there are additional failure modes for things like ovens that result in
excess earth leakage, but only at very low current levels rather than
fault levels)

Do we assume the oven has internal fault protection?

No, not in general. (Although as a general rule, if an appliance needs
additional protection beyond that expected for its supply conductors
then it should include it).

[1]
http://wiki.diyfaq.org.uk/index.php?...abatic _Check

--
Cheers,

John.

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

wrote:

I am installing a new built-in oven and hit the usual problem of the
horrible connectors they always seem to come with. However this one
seems even worse than usual and I'm a bit stumped as to how to do a
proper job of connecting it.

I have a dedicated 32 amp MCB for the oven and (electric, induction)
hob and it has a 6sq mm cable running to the kitchen units.

However there is absolutely no way that one can connect 6sq mm cable
to the oven. The connection block is too small. The only cable that
I think I can reasonably connect to it is 2.5sq mm because the screw
terminals are such that only single, solid wire can be reliably
connected to it.

You need to separate the oven and hob, and have 2 switches, one for
each. I presume that 32A is enough for the both?

You spur off the 6mm cable with a 13A FCU to supply the oven. You can
run 4mm cable from a connector box/joint to the FCU if you cannot
terminate the 6mm in a normal FCU.
You dont need heat resistant cable, it doesnt get very hot at the back
of the oven. 2.5mm from the FCU to the oven is fine.

--
To reply by e-mail, change the ' + ' to 'plus'.

"A.Lee" wrote in message
.. .
wrote:

I am installing a new built-in oven and hit the usual problem of the
horrible connectors they always seem to come with. However this one
seems even worse than usual and I'm a bit stumped as to how to do a
proper job of connecting it.

I have a dedicated 32 amp MCB for the oven and (electric, induction)
hob and it has a 6sq mm cable running to the kitchen units.

However there is absolutely no way that one can connect 6sq mm cable
to the oven. The connection block is too small. The only cable that
I think I can reasonably connect to it is 2.5sq mm because the screw
terminals are such that only single, solid wire can be reliably
connected to it.

You need to separate the oven and hob, and have 2 switches, one for
each. I presume that 32A is enough for the both?

You spur off the 6mm cable with a 13A FCU to supply the oven. You can
run 4mm cable from a connector box/joint to the FCU if you cannot
terminate the 6mm in a normal FCU.
You dont need heat resistant cable, it doesnt get very hot at the back
of the oven. 2.5mm from the FCU to the oven is fine.

This sounds much better than what ARW said.
I would go with what Mr Lee says.

dennis@home wrote:
"A.Lee" wrote in message
.. .
wrote:

I am installing a new built-in oven and hit the usual problem of
the horrible connectors they always seem to come with. However
this one seems even worse than usual and I'm a bit stumped as to
how to do a proper job of connecting it.

I have a dedicated 32 amp MCB for the oven and (electric,
induction) hob and it has a 6sq mm cable running to the kitchen
units. However there is absolutely no way that one can connect 6sq mm
cable to the oven. The connection block is too small. The only
cable that I think I can reasonably connect to it is 2.5sq mm
because the screw terminals are such that only single, solid wire
can be reliably connected to it.

You need to separate the oven and hob, and have 2 switches, one for
each. I presume that 32A is enough for the both?

You spur off the 6mm cable with a 13A FCU to supply the oven. You
can run 4mm cable from a connector box/joint to the FCU if you
cannot terminate the 6mm in a normal FCU.
You dont need heat resistant cable, it doesnt get very hot at the
back of the oven. 2.5mm from the FCU to the oven is fine.

This sounds much better than what ARW said.
I would go with what Mr Lee says.

How do you know what I said? You claim you do not read my posts?

Have you invented a time machine so that you can see posts from the future?
That means you can claim that you were replying to a post of mine by seeing
another posters reply (by someone that you do not claim to blacklist) to my
post?

All it takes is someone that you have not blacklisted to reply to my post
with the words "dennis you are a bell end" to make the future come true

Any volunteers to make this post?

--
Adam

A.Lee wrote:
wrote:

I am installing a new built-in oven and hit the usual problem of the
horrible connectors they always seem to come with. However this one
seems even worse than usual and I'm a bit stumped as to how to do a
proper job of connecting it.

I have a dedicated 32 amp MCB for the oven and (electric, induction)
hob and it has a 6sq mm cable running to the kitchen units.

However there is absolutely no way that one can connect 6sq mm cable
to the oven. The connection block is too small. The only cable that
I think I can reasonably connect to it is 2.5sq mm because the screw
terminals are such that only single, solid wire can be reliably
connected to it.

You need to separate the oven and hob, and have 2 switches, one for
each. I presume that 32A is enough for the both?

You spur off the 6mm cable with a 13A FCU to supply the oven. You can
run 4mm cable from a connector box/joint to the FCU if you cannot
terminate the 6mm in a normal FCU.
You dont need heat resistant cable, it doesnt get very hot at the back
of the oven. 2.5mm from the FCU to the oven is fine.

Yes, that is one option I suppose, just rather 'messy'. (It was a
possibility I mentioned)

--
Chris Green

On 19/04/2012 18:37, wrote:
I am installing a new built-in oven and hit the usual problem of the
horrible connectors they always seem to come with. However this one
seems even worse than usual and I'm a bit stumped as to how to do a
proper job of connecting it.

I have a dedicated 32 amp MCB for the oven and (electric, induction)
hob and it has a 6sq mm cable running to the kitchen units.

No need if it can only draw 2.3kw peak...

However there is absolutely no way that one can connect 6sq mm cable
to the oven. The connection block is too small. The only cable that
I think I can reasonably connect to it is 2.5sq mm because the screw
terminals are such that only single, solid wire can be reliably
connected to it.

There's not enough room for any sort of termination on the cable.
I've tried and I have a wide variety of crimps in many shapes and
sizes, while you can terminate a cable with a 'ring' that will fit
under the screw the body of the crimp is too fat to fit through the
slot provided for the cable.

The oven is rated 2.3kw so 2.5sq mm is perfectly adequate, the problem
is that it's not ideal for allowing the oven to be slid in and out and
it's not properly protected by the 32amp MCB.

It will be adequately protected by the 32A MCB - since in this
application you are only concerned about fault current protection.

What options do I have? I suppose I could have a local FCU for the
oven but it seems a bit overly complex and discrimination might be a

You could use a FCU. A 13A fuse would normally discriminate with a 32A
MCB upstream. However the chances of it ever operating are slim anyway.

problem. I can't see *any* way to connect flexible cable to the oven
so I think it's stuck with at least a short length of 2.5sq mm. The

If you can get 2.5mm^2 T&E into the terminals then you are likely to be
able to get a 2.5mm^2 heat resistant flex in there as well.

Note however if you were to fit a FCU, then you could reduce your flex
size to 1.5mm^2:

http://www.tlc-direct.co.uk/Products...Q3slash50.html

best I can do at present is to take the short length of 2.5sq mm to a
junction box (or terminal block) on the back of the oven and run a
more flexible cable from there. Can one get high temperature 2.5sq mm
cable with solid conductors that I could rate at 32 amps? That would
be be the neatest solution I guess.

Sounds like you are over thinking this one ;-)


--
Cheers,

John.

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

John Rumm wrote:
On 19/04/2012 18:37, wrote:
I am installing a new built-in oven and hit the usual problem of the
horrible connectors they always seem to come with. However this one
seems even worse than usual and I'm a bit stumped as to how to do a
proper job of connecting it.

I have a dedicated 32 amp MCB for the oven and (electric, induction)
hob and it has a 6sq mm cable running to the kitchen units.

No need if it can only draw 2.3kw peak...

The induction hob is 7.5kW (if we get the one we're thinking about
getting).

The oven is rated 2.3kw so 2.5sq mm is perfectly adequate, the problem
is that it's not ideal for allowing the oven to be slid in and out and
it's not properly protected by the 32amp MCB.

It will be adequately protected by the 32A MCB - since in this
application you are only concerned about fault current protection.

I did wonder about this, maybe I am being a bit paranoid! :-)

What options do I have? I suppose I could have a local FCU for the
oven but it seems a bit overly complex and discrimination might be a

You could use a FCU. A 13A fuse would normally discriminate with a 32A
MCB upstream. However the chances of it ever operating are slim anyway.

problem. I can't see *any* way to connect flexible cable to the oven
so I think it's stuck with at least a short length of 2.5sq mm. The

If you can get 2.5mm^2 T&E into the terminals then you are likely to be
able to get a 2.5mm^2 heat resistant flex in there as well.

Yes, but the terminals won't hold flex properly. They are just
round[ish] head screws with a plastic guard around them, no washers or
anything, if you put flex under them it just squeezes out. The only
reason that 2.5sq mm works is because a pre-formed U stays under the
screw.


Note however if you were to fit a FCU, then you could reduce your flex
size to 1.5mm^2:

http://www.tlc-direct.co.uk/Products...Q3slash50.html

best I can do at present is to take the short length of 2.5sq mm to a
junction box (or terminal block) on the back of the oven and run a
more flexible cable from there. Can one get high temperature 2.5sq mm
cable with solid conductors that I could rate at 32 amps? That would
be be the neatest solution I guess.

Sounds like you are over thinking this one ;-)

Could be!

--
Chris Green

On 19/04/2012 22:03, wrote:
John wrote:
On 19/04/2012 18:37, wrote:
I am installing a new built-in oven and hit the usual problem of the
horrible connectors they always seem to come with. However this one
seems even worse than usual and I'm a bit stumped as to how to do a
proper job of connecting it.

I have a dedicated 32 amp MCB for the oven and (electric, induction)
hob and it has a 6sq mm cable running to the kitchen units.

No need if it can only draw 2.3kw peak...

The induction hob is 7.5kW (if we get the one we're thinking about
getting).

The hob won't be on the reduced capacity cable feeding the oven though...

Still if you do the sums:

7.5 + 2.3kW = 9,800W = theoretical max combined load of 42A

Now apply diversity: 10A + 30% of remaining 32A = 19.6A

(assuming no socket on the cooker switch, around 25A if there is).

In reality, not a big load.

The oven is rated 2.3kw so 2.5sq mm is perfectly adequate, the problem
is that it's not ideal for allowing the oven to be slid in and out and
it's not properly protected by the 32amp MCB.

It will be adequately protected by the 32A MCB - since in this
application you are only concerned about fault current protection.

I did wonder about this, maybe I am being a bit paranoid! :-)

When you think that you routinely run more powerful devices, on longer
and thinner flexes without concern...

What options do I have? I suppose I could have a local FCU for the
oven but it seems a bit overly complex and discrimination might be a

You could use a FCU. A 13A fuse would normally discriminate with a 32A
MCB upstream. However the chances of it ever operating are slim anyway.

problem. I can't see *any* way to connect flexible cable to the oven
so I think it's stuck with at least a short length of 2.5sq mm. The

If you can get 2.5mm^2 T&E into the terminals then you are likely to be
able to get a 2.5mm^2 heat resistant flex in there as well.

Yes, but the terminals won't hold flex properly. They are just
round[ish] head screws with a plastic guard around them, no washers or
anything, if you put flex under them it just squeezes out. The only
reason that 2.5sq mm works is because a pre-formed U stays under the
screw.

Either twist the strands together and loop it round, or stick a bootlace
ferrule on the end, which will make it substantially the same as T&E
solid core to terminate. (on 1.5mm^2 there ought to be space to spare!)

Note however if you were to fit a FCU, then you could reduce your flex
size to 1.5mm^2:

http://www.tlc-direct.co.uk/Products...Q3slash50.html

best I can do at present is to take the short length of 2.5sq mm to a
junction box (or terminal block) on the back of the oven and run a
more flexible cable from there. Can one get high temperature 2.5sq mm
cable with solid conductors that I could rate at 32 amps? That would
be be the neatest solution I guess.

Sounds like you are over thinking this one ;-)

Could be!


--
Cheers,

John.

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

John Rumm wrote:
The oven is rated 2.3kw so 2.5sq mm is perfectly adequate, the problem
is that it's not ideal for allowing the oven to be slid in and out and
it's not properly protected by the 32amp MCB.

It will be adequately protected by the 32A MCB - since in this
application you are only concerned about fault current protection.

I did wonder about this, maybe I am being a bit paranoid! :-)

When you think that you routinely run more powerful devices, on longer
and thinner flexes without concern...

But not with just 32 amp circuit protection surely? There will be a
13 amp fuse in the plug to protect the cable.

--
Chris Green

wrote in message ...
John Rumm wrote:
On 19/04/2012 18:37, wrote:
I am installing a new built-in oven and hit the usual problem of the
horrible connectors they always seem to come with. However this one
seems even worse than usual and I'm a bit stumped as to how to do a
proper job of connecting it.

I have a dedicated 32 amp MCB for the oven and (electric, induction)
hob and it has a 6sq mm cable running to the kitchen units.

No need if it can only draw 2.3kw peak...

The induction hob is 7.5kW (if we get the one we're thinking about
getting).

The oven is rated 2.3kw so 2.5sq mm is perfectly adequate, the problem
is that it's not ideal for allowing the oven to be slid in and out and
it's not properly protected by the 32amp MCB.

It will be adequately protected by the 32A MCB - since in this
application you are only concerned about fault current protection.

I did wonder about this, maybe I am being a bit paranoid! :-)

What options do I have? I suppose I could have a local FCU for the
oven but it seems a bit overly complex and discrimination might be a

You could use a FCU. A 13A fuse would normally discriminate with a 32A
MCB upstream. However the chances of it ever operating are slim anyway.

problem. I can't see *any* way to connect flexible cable to the oven
so I think it's stuck with at least a short length of 2.5sq mm. The

If you can get 2.5mm^2 T&E into the terminals then you are likely to be
able to get a 2.5mm^2 heat resistant flex in there as well.

Yes, but the terminals won't hold flex properly. They are just
round[ish] head screws with a plastic guard around them, no washers or
anything, if you put flex under them it just squeezes out. The only
reason
that 2.5sq mm works is because a pre-formed U stays under the screw.

I'd solder the stranded copper solid where it goes under the screw.

Corse you may not have access to a decent soldering iron.

Note however if you were to fit a FCU, then you could reduce your flex
size to 1.5mm^2:

http://www.tlc-direct.co.uk/Products...Q3slash50.html

best I can do at present is to take the short length of 2.5sq mm to a
junction box (or terminal block) on the back of the oven and run a
more flexible cable from there. Can one get high temperature 2.5sq mm
cable with solid conductors that I could rate at 32 amps? That would
be be the neatest solution I guess.

Sounds like you are over thinking this one ;-)

Could be!

--
Chris Green

Rod Speed wrote:

Yes, but the terminals won't hold flex properly. They are just
round[ish] head screws with a plastic guard around them, no washers or
anything, if you put flex under them it just squeezes out. The only
reason
that 2.5sq mm works is because a pre-formed U stays under the screw.

I'd solder the stranded copper solid where it goes under the screw.

Corse you may not have access to a decent soldering iron.

I certainly could do that (and I'm reasonably skilled at soldering
having started my career in the electronics industry in the late
1960s). However there are lots of dire warnings hereabouts that the
solder creeps and the wire fails at the solder/non-solder interface.

--
Chris Green

wrote
Rod Speed wrote

Yes, but the terminals won't hold flex properly. They are just
round[ish] head screws with a plastic guard around them, no washers or
anything, if you put flex under them it just squeezes out. The only
reason
that 2.5sq mm works is because a pre-formed U stays under the screw.

I'd solder the stranded copper solid where it goes under the screw.

Corse you may not have access to a decent soldering iron.

I certainly could do that (and I'm reasonably skilled at soldering
having started my career in the electronics industry in the late 1960s).

However there are lots of dire warnings hereabouts that the solder creeps

Cant see that that is going to happen in this particular situation.

and the wire fails at the solder/non-solder interface.

And that isnt going to happen either.

You arent using normal flex, just a few strands of copper
with the terminal not stopping the strands from escaping
from under the head as the screw is tightened.

And why, if the terminal does allow you bend the
copper in a U works fine, why cant you use a crimp
terminal on the wire, which goes where the U goes ?

On 20/04/2012 09:02, wrote:
Rod wrote:

Yes, but the terminals won't hold flex properly. They are just
round[ish] head screws with a plastic guard around them, no washers or
anything, if you put flex under them it just squeezes out. The only
reason
that 2.5sq mm works is because a pre-formed U stays under the screw.

I'd solder the stranded copper solid where it goes under the screw.

Corse you may not have access to a decent soldering iron.

I certainly could do that (and I'm reasonably skilled at soldering
having started my career in the electronics industry in the late
1960s). However there are lots of dire warnings hereabouts that the
solder creeps and the wire fails at the solder/non-solder interface.

It would also not meet the wiring regs requirement of selection of
appropriate termination techniques, since it would not allow for the
creep of the solder under screw tension.

(it might be ok if you could actually solder the wire to the terminal)


--
Cheers,

John.

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

En el artículo ,
escribió:

However there are lots of dire warnings hereabouts that the
solder creeps and the wire fails at the solder/non-solder interface.

Yes, it's a bad idea to tin wire ends where they will be secured by a
screw. The solder, being soft, "creeps" and a loose connection
eventually develops.

Woddles is talking ****, as usual. http://tinyurl.com/883xp7v

--
(\_/)
(='.'=)
(")_(")

In article ,
"Rod Speed" writes:

I'd solder the stranded copper solid where it goes under the screw.

In which case, you'd generate an overheating join as the solder
creeps and the connection pressure is lost, solder creeps more,
etc, which is why this is forbidden.

If the terminal is not designed to take stranded copper,
the right way to do it is to crimp on a bootlace ferrule,
or an appropriate insulated crimp connector to mate with
the terminal (such as a ring, open ring, flat tab, i.e.
whatever matches the terminal design).

Corse you may not have access to a decent soldering iron.

Soldering is also a skilled job (including knowing when you
should, or shouldn't use it). Crimping is less skilled
provided you have a reasonable quality ratchet crimper
and the right size crimps for it ans the conductors.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Andrew Gabriel wrote
Rod Speed wrote

I'd solder the stranded copper solid where it goes under the screw.

In which case, you'd generate an overheating join as the solder
creeps and the connection pressure is lost, solder creeps more, etc,

Fantasy.

which is why this is forbidden.

Fantasy.

If the terminal is not designed to take stranded copper,
the right way to do it is to crimp on a bootlace ferrule,

He already said that wont work and that
only a U in the solid conductor works.

or an appropriate insulated crimp connector to mate
with the terminal (such as a ring, open ring, flat tab,
i.e. whatever matches the terminal design).

He did say that that isnt viable and I'm
too lazy to check why he said it wasn't.

Corse you may not have access to a decent soldering iron.

Soldering is also a skilled job

Not when doing something as simple as that it isnt.

(including knowing when you should, or shouldn't use it).

You clearly don't.

Crimping is less skilled provided you have
a reasonable quality ratchet crimper and
the right size crimps for it ans the conductors.

He did say that that isnt viable and I'm
too lazy to check why he said it wasn't.

Andrew Gabriel wrote:
I'd solder the stranded copper solid where it goes under the screw.

In which case, you'd generate an overheating join as the solder
creeps and the connection pressure is lost, solder creeps more,
etc, which is why this is forbidden.

Exactly my thoughts about tinning stranded wire to do this.

If the terminal is not designed to take stranded copper,
the right way to do it is to crimp on a bootlace ferrule,
or an appropriate insulated crimp connector to mate with
the terminal (such as a ring, open ring, flat tab, i.e.
whatever matches the terminal design).

I don't think the terminal is 'designed' to take anything! :-(

Any sort of bootlace ferrule or insulated crimp on the end of the wire
to be connected prevents the wire from entering the terminal correctly
as there's a very narrow slot where the wire goes in. As I said I
think the only wire which can be reliably fixed under these terminal
screws is solid 2.5 sq mm (1.5 sq mm would probably be OK too).


Corse you may not have access to a decent soldering iron.

Soldering is also a skilled job (including knowing when you
should, or shouldn't use it). Crimping is less skilled
provided you have a reasonable quality ratchet crimper
and the right size crimps for it ans the conductors.

I have all sorts of insulated crimps and decent ratchet crimp tools, I
also have a load of ferrules and uninsulated crimps for sizes from 0.5
sq mm up to much larger than needed for this oven. I can solder too.
However this oven really stumped me. I hate to think what horrible
bodges get hidden inside oven housings with connection blocks like
this one.

--
Chris Green

En el artículo ,
escribió:

Yes, but the terminals won't hold flex properly. They are just
round[ish] head screws with a plastic guard around them, no washers or
anything, if you put flex under them it just squeezes out.

When that has happened to me in the past, I've added another washer
under the screw head. That prevents the stranded wire from squeezing
out as the additional washer doesn't turn with the screw head.

--
(\_/)
(='.'=)
(")_(")

On Apr 19, 6:37*pm, wrote:
I have a dedicated 32 amp MCB for the oven and (electric, induction)
The oven is rated 2.3kw so 2.5sq mm is perfectly adequate

Do you have something like an MK 32A cooker switch & 32A cord outlet
behind units, ie, originally for a conventional standalone electric
oven?

32A cord outlet supplies units...
Cord outlet - 6mm FTE - Jn-Box
.... Jn-Box - 6mm FTE - hob
.... Jn-Box - 4mm FTE - FCU - 1.5mm Flex - oven

2.3kW oven cable...
- 1.5mm Flex in Butyl / 90oC PVC
- Commonly used for storage heaters, immersions etc.

NkW hob cable...
- 6.0mm FTE - 60oC PVC (or 90oC 6242BH off Ebay)
- 6.0mm Flex - Butyl, High Temp PVC, Silicone (CPC, Farnell, Conrad)

TLC do a good range of junction boxes, 6mm cut length, 4mm cut length,
1.5mm high temp flex.

Check what spec cable the hob requires, that may make things a bit
more interesting.

Easy. Done. What you moan'n about. Your cat is eating the children
whilst you are thinking about it :-)))

js.b1 wrote:
On Apr 19, 6:37Â*pm, wrote:
I have a dedicated 32 amp MCB for the oven and (electric, induction)
The oven is rated 2.3kw so 2.5sq mm is perfectly adequate

Do you have something like an MK 32A cooker switch & 32A cord outlet
behind units, ie, originally for a conventional standalone electric
oven?

32A cord outlet supplies units...
Cord outlet - 6mm FTE - Jn-Box
... Jn-Box - 6mm FTE - hob
... Jn-Box - 4mm FTE - FCU - 1.5mm Flex - oven

2.3kW oven cable...
- 1.5mm Flex in Butyl / 90oC PVC
- Commonly used for storage heaters, immersions etc.

As I've said in a previous reply flexible cable simply won't stay
under the terminal screws on the oven.


NkW hob cable...
- 6.0mm FTE - 60oC PVC (or 90oC 6242BH off Ebay)
- 6.0mm Flex - Butyl, High Temp PVC, Silicone (CPC, Farnell, Conrad)

I've actually got *loads* of 90 degree flex which I use on our boat.


Thanks for all the advice everyone. I think maybe I'll go for my
current solution:-

Short length of 2.5 T&E connected to oven terminals.

connecting to

Junction box fixed to oven

connecting to

6sqmm cable (which will be properly strain relieved at both ends)

--
Chris Green

En el artículo ,
escribió:

The oven is rated 2.3kw

At that rating, I would have expected it to come with a flex and plug to
be plugged into a standard 13A socket.

--
(\_/)
(='.'=)
(")_(")

Mike Tomlinson wrote:
En el artÃ*culo ,
escribió:

The oven is rated 2.3kw

At that rating, I would have expected it to come with a flex and plug to
be plugged into a standard 13A socket.

Quite, but it doesn't, it's designed for permament connection.

--
Chris Green