Trunking

[manbey1]

Hi can you tell me is it acceptable to put 6mm cooker cable in the same trunking as 2 lots of 2.5mm t&e? Someone recommended I do this, even though it's quite a tight fit.
Many thanks

 

[JohnD]

1) it must not be a tight fit

2) you have to apply de-rating factors for bunched cables and probably end up having to buy larger cable sizes at great expense.

More trouble than it's worth.


p.s. do you really mean trunking or do you mean conduit or mini-trunking; like 25mm x 16mm?

 

[manbey1]

Thanks for getting back to me, yes it's mini trunking (25mmx16mm). The cooker is 5.485kw and the cable run is 17m, hence 6mm cable. So shall I remove the cable and clip it to the wall?

 

[davy_owen_88]

Someone recommended I do this, even though it's quite a tight fit.

Write the guys name down and remember to never ask for his advice again.

The general rule of thumb is conduit/trunking should not have more than 45% of its area taken up by cables (including their insulation). Also as JohnD has mentioned, there are de-rating factors to be applied to these cables (even if the 45% rule is stuck to). Run another length of the trunking for the cooker cable or clip it directly to the wall.

 

[securespark]

Or bigger trunking.

As has been mentioned cables have to be derated when trunked.

6mm² drops to 38A when trunked, as opposed to 46A clipped direct.

 

[KingboyD]

What does 10mm² drop to when "snugly" trunked??

 

[davy_owen_88]

63A down to 52A when correct spacing is used. If you crammed the cable in then a fair bit below 52A because the heat can't escape as easily.

 

[manbey1]

I'll take it out, and put it back on the wall . Can I tell my friend that his suggestion was unsafe or was it just unconventional?
The 2x 2.5mm t&e is fine in the mini trunking isn't it, just double checking....
Can I just ask one other non related question.... Is it ok to have a 2 way switched light with one switch being on a dimmer and the other being a standard ie one light, 2 switches: one dimmer one standard
thanks yet again guys

 

[securespark]

You cannot have two standard dimmers on the same switching circuit.

 

[manbey1]

You cannot have two standard dimmers on the same switching circuit.

So can one be a dimmer and the other be a standard switch, therefore not 2 dimmers controlling the same light

 

[Spark123]

Yes, you can have one bog standard 2 way dimmer switch and a normal 2 way switch on the same light.

For info, you can also get some fancy master/slave dimmer arrangements if you want to be able to control the dim from various positions, you'd need to check that the installed wiring is suitable before buying these type.

 

[manbey1]

Thanks alot guys, for your help; and I had such fun removing my kitchen units (yet again) to take the 6mm cable out of the trunking and put it BACK on the wall. Oh how I laughed

With regards to the 6mm cable that is above the work surface and going to the CCU can I just have this in a channel and clip it in place, then plaster over it (channeling out is about 10cm wide and has the in and out 6mm in it). Or do I have to put it in suitable conduit before plastering. The whole run is only about 30cm up from the TOB and 20cm across to CCU. This in and out 6mm had also been put into one piece of mini truncking by my friend, and obviously broke the 45% rule.

 

[davy_owen_88]

Yes, you can just plaster over cables. It's beneficial to put some plastic capping over it to protect the cable from the trowel during plastering but it isn't essential.

Are you aware of the safe zones for running concealed cables?

 

[manbey1]

Regulation 522-06-06
A cable concealed in a wall or partition at a depth of less than
50 mm from the surfaces of the wall or partition shall:
(i) incorporate an earthed metallic covering which complies with
the requirements of these Regulations for a protective
conductor of the circuit concerned, the cable complying with
BS 5467, BS 6346, BS 6724, BS 7846, BS EN 60702-1 or
BS 8436, or
(ii) be of insulated concentric construction complying with
BS 4553-1, BS 4553-2, or BS 4553-3, or
(iii) be enclosed in earthed conduit, trunking or ducting satisfying
the requirements of these Regulations for a protective
conductor, or be mechanically protected sufficient to prevent
penetration of the cable by nails, screws and the like, or
(iv) be installed in a zone within 150 mm from the top of the
wall or partition or within 150 mm of an angle formed by two
adjoining walls or partitions. Where the cable is connected to
a point, accessory or switchgear on any surface of the wall or
partition, the cable may be installed in a zone either
horizontally or vertically, to the point, accessory or switchgear.
Where the location of the accessory, point or switchgear can
be determined from the reverse side, a zone formed on one
side of a wall of 100 mm thickness or less or partition of
100 mm thickness or less extends to the reverse side.


Is this what you mean?

 

[davy_owen_88]

be installed in a zone within 150 mm from the top of the
wall or partition or within 150 mm of an angle formed by two
adjoining walls or partitions. Where the cable is connected to
a point, accessory or switchgear on any surface of the wall or
partition, the cable may be installed in a zone either
horizontally or vertically, to the point, accessory or switchgear.
Where the location of the accessory, point or switchgear can
be determined from the reverse side, a zone formed on one
side of a wall of 100 mm thickness or less or partition of
100 mm thickness or less extends to the reverse side.

Yes. No additional protection is required when the cables are run within these zones.