[Autolycus[_2_]]

The (gas) boiler is around 8ft from the area where all the control
wiring is to be brought together, in a different room.

The supply to its fcu will be surface-run behind some fixed furniture,
then in trunking for the last 4ft to the boiler, and will be in 2.5 t&e.
No problem so far.

Is there a presumption against running 4-core flex directly from the
boiler's control side, through the trunking, and thence to the controls,
as against using a shorter length of flex, then connecting to 3+e cable,
as far as the controls? Pro: avoids the need for a flex outlet box /
box with a choc block in; Cons: I suppose the flex is less mechanically
protected than cable (extra protection where it goes through walls?); it
somehow seems wrong to use flex for "fixed" wiring. The boiler fcu will
be fused at 3A, the controls are all 240v, and there will be plenty of
room for either in the trunking.


--
Kevin Poole
**Use current month and year to reply (e.g. )***

[Andrew Gabriel]

In article ,
"Autolycus" writes:
The (gas) boiler is around 8ft from the area where all the control
wiring is to be brought together, in a different room.

The supply to its fcu will be surface-run behind some fixed furniture,
then in trunking for the last 4ft to the boiler, and will be in 2.5 t&e.
No problem so far.

Is there a presumption against running 4-core flex directly from the
boiler's control side, through the trunking, and thence to the controls,
as against using a shorter length of flex, then connecting to 3+e cable,
as far as the controls? Pro: avoids the need for a flex outlet box /
box with a choc block in; Cons: I suppose the flex is less mechanically
protected than cable (extra protection where it goes through walls?); it
somehow seems wrong to use flex for "fixed" wiring. The boiler fcu will
be fused at 3A, the controls are all 240v, and there will be plenty of
room for either in the trunking.

There's no prohibition against using flex for fixed wiring.
It just usually isn't as convenient or cheap to do so.
FWIW, I've got a 7 core flex running from my boiler to its
control centre.

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

[Dave Liquorice]

On Wed, 23 Jan 2008 07:41:02 -0000, Autolycus wrote:

The (gas) boiler is around 8ft from the area where all the control
wiring is to be brought together, in a different room.

The supply to its ...

The boiler?

... fcu will be surface-run behind some fixed furniture, then in
trunking for the last 4ft to the boiler, and will be in 2.5 t&e.

If so the boiler does not need a FCU as the *whole* CH/HW control system
will have a requirement to a single mains feed from DP switched (to
provide proper isolation for maintenance, a SP fuse or an MCB is not
suffcient) fused at 3A connection unit. Look at the ratings for
thermostats, motorised valves, programmers etc as well for the 3A
requirement.

All the boiler needs is a flex outlet, so run the T&E from the wiring
centre to the flex outlet adjacent to the boiler and flex from there into
the boiler.

--
Cheers
Dave. pam is missing e-mail

[David Hansen]

On Wed, 23 Jan 2008 07:41:02 -0000 someone who may be "Autolycus"
wrote this:-

The (gas) boiler is around 8ft from the area where all the control
wiring is to be brought together, in a different room.

The supply to its fcu will be surface-run behind some fixed furniture,
then in trunking for the last 4ft to the boiler, and will be in 2.5 t&e.

Seems a trifle large and I doubt if it comes in three core and earth
format.

Is there a presumption against running 4-core flex directly from the
boiler's control side, through the trunking, and thence to the controls,

There is a fair presumption against it, but I can't recall a
prohibition.

As you are DIYing it you have the opportunity to do it to a higher
standard than someone doing it for a living. If you have the cheaper
three core and earth 1.0mm cable anyway then I would run this to a
suitable point. At that point I would put either a triple pole "fan"
isolator, or a standard cord outlet (with the additional wire
connected via a terminal block inside). From there I would run
suitable flex to the boiler. This gives a place to disconnect near
the boiler which can be useful, for example if the flex is damaged
one just has to replace a short length of flex.




--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

[Autolycus[_2_]]

"David Hansen" wrote in message
news
On Wed, 23 Jan 2008 07:41:02 -0000 someone who may be "Autolycus"
wrote this:-

The (gas) boiler is around 8ft from the area where all the control
wiring is to be brought together, in a different room.

The supply to its fcu will be surface-run behind some fixed furniture,
then in trunking for the last 4ft to the boiler, and will be in 2.5
t&e.

Seems a trifle large and I doubt if it comes in three core and earth
format.

David and Dave: sorry if it wasn't clear: the 2.5 t&e is the 16A
RCD-protected radial circuit supplying the boiler fcu, and an adjacent
socket. The fcu will be fused at 3A and will protect and provide
isolation for the boiler and all its controls.


Is there a presumption against running 4-core flex directly from the
boiler's control side, through the trunking, and thence to the
controls,

There is a fair presumption against it, but I can't recall a
prohibition.

As you are DIYing it you have the opportunity to do it to a higher
standard than someone doing it for a living. If you have the cheaper
three core and earth 1.0mm cable anyway then I would run this to a
suitable point. At that point I would put either a triple pole "fan"
isolator, or a standard cord outlet (with the additional wire
connected via a terminal block inside). From there I would run
suitable flex to the boiler. This gives a place to disconnect near
the boiler which can be useful, for example if the flex is damaged
one just has to replace a short length of flex.

I'd prefer to avoid another switch, as it might one day lead to
confusion as to which one isolates the boiler. Unfused, unswitched cord
outlets aren't so easy to find, unless one goes to a cooker outlet,
which I'd guess has rather large terminals to hold a bit of 0.75 flex.

I liked Andrew's re-assurance: I'll go with flex, but leave a small loop
somewhere so that if the end is ever damaged someone could re-address
this problem for themselves. B&Q want £8.48 for 5m of 4-core 0.75 flex,
so I don't think I'll buy it there.

Thanks to all.


--
Kevin Poole
**Use current month and year to reply (e.g. )***

[David Hansen]

On Thu, 24 Jan 2008 08:11:04 -0000 someone who may be "Autolycus"
wrote this:-

Unfused, unswitched cord outlets aren't so easy to find,

There have been two of these beside my boiler since December.
http://www.tlc-direct.co.uk/Main_Index/Wiring_Accessories_Menu_Index/White_Mk_Accessories/Flex_Outlets_Plates/index.html

One takes the supplies (switched live and "permanent" live) to the
boiler. The other takes the supply from the boiler to the boiler
pump.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

[Dave Plowman (News)]

In article ,
Autolycus wrote:
I'd prefer to avoid another switch, as it might one day lead to
confusion as to which one isolates the boiler. Unfused, unswitched cord
outlets aren't so easy to find, unless one goes to a cooker outlet,
which I'd guess has rather large terminals to hold a bit of 0.75 flex.

Some grid switch systems include a cord outlet option.

--
*If horrific means to make horrible, does terrific mean to make terrible?

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

[Dave Liquorice]

On Thu, 24 Jan 2008 08:11:04 -0000, Autolycus wrote:

David and Dave: sorry if it wasn't clear: the 2.5 t&e is the 16A
RCD-protected radial circuit supplying the boiler fcu, and an adjacent
socket.

So the boiler is fed from one source of mains and the controls from
another? *VERY* bad practice, the switched mains from the controls could
or be live when the boiler is "off"...

Confused, yes I am.

The fcu will be fused at 3A and will protect and provide isolation for
the boiler and all its controls.

A FCU does not provide isolation the fuse is only single pole. A DP
switched, fused, connection unit does provided the contact gap when off is
3mm.

--
Cheers
Dave. pam is missing e-mail

[Autolycus[_2_]]

"Dave Liquorice" wrote in message
ll.net...
On Thu, 24 Jan 2008 08:11:04 -0000, Autolycus wrote:

David and Dave: sorry if it wasn't clear: the 2.5 t&e is the 16A
RCD-protected radial circuit supplying the boiler fcu, and an
adjacent
socket.

So the boiler is fed from one source of mains and the controls from
another?

No: all controls, including timeswitch, motorised valves, and the
receiver for an rf thermostat, are (electrically-speaking) downstream of
the boiler.

*VERY* bad practice, the switched mains from the controls could
or be live when the boiler is "off"...

Exactly, which is why I've done it as I have.

Confused, yes I am.

Hmmm.


The fcu will be fused at 3A and will protect and provide isolation
for
the boiler and all its controls.

A FCU does not provide isolation the fuse is only single pole. A DP
switched, fused, connection unit does provided the contact gap when
off is
3mm.

I have checked that the connection unit I've used is DP, but I'll have
to rely on the makers about the contact gap.


--
Kevin Poole
**Use current month and year to reply (e.g. )***