armoured cable for cooker?

30 Mar 2003
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United Kingdom
we have a house which has got solid floors on the ground floor.
Can someone please tell me if we first ran internally, an "armoured" cable from the CU (under the stairs) up a side wall via a boxed in soil pipe ducting (which is already there) then running it along the upstairs joists and then back down the outside of the house and then back into the kitchen(approx full length 20m) what cable size do i need?.... and can i even run an armoured cable for this purpose? the rating of the oven is yet to be decided, but will be of a typical standard rating say 2.3kw (eg.baumatic B0600BL). thanks in advance.
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Not sure why you would need armoured cable for this? Its only necessary underground really....
because i will be going outside of the house... down the side wall. exposed to the elements!
The first question i'd ask is do you actually need to do this? What are the existing major loads on the ring? Normally it's ok to put single ovens on the ring though it can be pushing it if there are too many other heavy loads (heaters, washing machines, driers, dishwashers etc) on the ring.

As for cable type you could use SWA but it is a pain to terminate. Personally i'd suggest using singles in PVC conduit.

As for cable size 2.5mm shuld suffice for pretty much all single ovens. However personally if I was running in a new cooker circuit on an awkward route I wouldn't use anything less than 10mm², it's overkill for a single oven but peoples choice of cooking appliances tends to change over time.
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I would not recommend singles in conduit. Conduit yes, but not singles. You would need to construct a conduit system the entire route then.

For that oven, 2.5mm Twin and Earth from the consumer unit , through conduit outside (using terminal boxes top and bottom).

It would be better to consider running 4 or 6mm for a larger oven, should this be required in the future.
Possibly! I have not got the Green Bible with me so cannot read the appendix.
The appendix is concerned with heavy loads for prologed periods such as immersion heaters and cookers etc.

A dynamic load like a kettle will not be a problem.

Why haven't you got your regs with you Simon? You should have a copy with you at all times.
Because SWA in one of the cables where RCD protection is not required for the cable when buried in a wall or ceiling there are times when using it makes a lot of sense.

My parents kitchen has SWA from under stairs running outside to a sub-consumer unit in the kitchen which then supplies all the kitchen appliances.

A lot of thought went into the converting of the kitchen including the ability of my mother in a wheel chair to reset any of the RCBO's should they trip.

However remote from the job it is hard to work out if this is the best method for you. There is a lot missing it seems from the post as to why a kitchen which has been a kitchen likely for years needs a new supply?

In my parents case it was mainly to comply with today's regulations all the new sockets needed RCD protection but the house wiring was in a state and to try and RCD protect the whole of the house would likely result in it tripping on a regular basis and my mother could not access the existing CU to reset a RCD should it trip.

It was not ideal but the best compromise I could get the council to do. But it did need some thought as to how to earth the SWA when using a plastic box outside with careful positioning of the CU and trunking so the SWA terminated outside with just the inner three cores going though the wall back into the house.

Much also depends on the make of SWA used. Some the inner cores are in a material which offers very little protection and will crumble away others use a much tougher material.

For a scheme member electrician this whole exercise is easy as he knows if he will pass his own work. But for DIY where the LABC or Scottish equivalent has to inspect and decide if to pass it then to my mind it's far too much work to do and wait with baited breath to see if it passes.

So either a conventional approach or detail exactly what you intend when applying to council so they have the option to reject anything they don't like before you even start.

Personally I took a third approach I let a scheme registered electrician do the whole job.

As to cable size I would not want to go to all that trouble and then have to do it again so I would ensure it was big enough to in the future take what ever cooker hob and oven I fitted so likely 6mm sq thermosetting. But first job is to measure the loop impedance one can't start calculating what is required without knowing the loop impedance figures and max load.

With 1.5 mm cables thermosetting clipped direct one could consider using a MCB or RCBO of around 20A. But not sure if you can really say it's clipped direct but from your description likely you could use a 16A MCB/RCBO on 1.5mm SWA without a problem. Use thermoplastic and it may still comply but with either type at 29 mV/A/m at 20 meters at 16A = 9.28 volts which is within the 11.5 volts allowed but at 20A just fails.

What I would do if you insist on DIY is make sure you say exactly what you intend to do. The LABC ask for a lot of money for you to DIY so why make it easy for them. Once the work is completed it's easy to use a loop impedance tester and say pass or fail. Before the work is started it takes a lot more effort to work out volt drop and prospective loop impedance before saying "yes go ahead" or "no it will fail".

I would also check they will accept your signature on the forms. Even with a C&G 2391 I have seen the LABC refuse to accept a signature saying they wanted a scheme member to do the work.
Even if you run in thermosetting (XLPE) SWA you still have to rate it using PVC current carrying capacities unless the accesories are rated for 90°C terminations.
Even if you run in thermosetting (XLPE) SWA you still have to rate it using PVC current carrying capacities unless the accesories are rated for 90°C terminations.

If I'm reading your post correctly I'm struggling to understand what the terminations have to do with the insulation type?
XLPE insulated cables are permitted to carry higher currents than their PVC counterparts due to their different insulation characteristics, however, there working temperature is therefore increased from 70degC to 90degC, and so when terminating the cable, you need to ensure your accessory is rated to this temperature.
Or, if your accessories are not rated for 90° operation, you cannot allow the cable to reach 90° which means that it no longer has its native XLPE CCC and you have to use the rating for PVC cable, which assumes a maximum temperature of 70°C
Useful take on the regs as well as suitability of push fit connectors as Maintainance Free as per Ammendment 1.

In reponse to your questions here is some information about the Wagobox Junction Box System, Wago connectors and the MF Logo

What is the MF logo?
The MF logo was introduced in BS5733:2010 "General Requirements for electrical accessories" as a marking that can be used on accessories to indicate that the accessory doesn't require further inspection, testing or maintenance after installation.

What is BS5733:2010?
BS5733 is a British Standard which specifies tests to check the safety in normal use of electrical accessories not covered by other specific British standards.

Is the MF logo mentioned in BS7671: Requirements for Electrical Installations?
Yes, the MF logo is mentioned in BS7671 Amendment No. 1. 2011 in Section 526.3 (vi).

Section 5 deals with the Selection and Erection of Equipment.
Subsection 526. Electrical Connections:
Requirement 526.3 Every connection shall be accessible for inspection, testing and maintenance except for the following:
526.3(vi) Equipment complying with BS5733 for a maintenance free accessory and marked with the symbol MF and installed in accordance with the manufacturers instructions.

How has this changed from the previous edition of BS7671?
In the previous edition of BS7671 the regulation 526.3(v) was "A joint forming part of the equipment complying with the appropriate product standard."

This was widely accepted as a BSEN60670-22 junction box with maintenance free terminals as this is indicated in Appendix 15 of BS7671: Ring and Radial final circuit arrangements: "A junction box to BSEN60670-22 with screw terminals must be accessible for inspection, testing and maintenance or alternatively use maintenance free terminals."

The Wagobox and Wago terminals are still Maintenance Free, that hasn't changed. It's BS7671 that has changed and now requires an accessory to use terminals tested to BS5733 Maintenance Free screwless terminals.

So is BSEN60670-22 not an applicable junction box standard anymore?
BSEN60670-22 is still the applicable standard for junction boxes and continues to be referenced in many places within BS7671.

What does the MF mark mean?
The MF mark indicates that an accessory "does not require further inspection, testing or maintenance after installation in a circuit and incorporates screwless terminals (re: 14.5 Terminals for use within maintenance free accessories) and cable clamps to secure associated cables" (From section 3.31 BS5733:2010).

Section 14.5 within the BS5733:2010 details a number of tests that need to be performed on the screwless terminals to establish that they are appropriate for use in a MF marked accessory.

Can the Wagobox have the MF mark?
In order to put an MF mark on the Wagobox we must use terminals which satisfy the tests set out in BS5733 for maintenance free screwless terminals.

The Wagobox and Wagobox - Light boxes are designed to be used with the Wago 773, 222 and 224 ranges of screwless terminals. These terminals are already tested compliant with BSEN90998-1 (Connecting devices for low voltage circuits for household and similar purposes), as well as:

Mechanical Tests
* Pull-Out Test to IEC/EN 60947-7-1, IEC/EN 60998-2-2, IEC/EN 60999-1
* Shock Test to IEC/EN 60068-2-27, 60068-2-30; Railway Applications IEC/EN 61373
* Vibration Test to IEC/EN 60068-2-6; Shipbuilding GL, LR, DNV; Railway Applications EN 61373

Electrical Tests
* Temperature-Rise Test to IEC/EN 60947-7-1, IEC/EN 60998-1, IEC/EN 1-61984
* Derating Curve to IEC/EN 60512-5-2
* Voltage Drop Test to IEC/EN 60947-7-1
* Short-Time Withstand Current Test (Short-Circuit Withstand Capacity) to IEC/EN 60947-7-1
* Insulation Parameters to IEC/EN 60664-1
* Power-Frequency Withstand Voltage Test to IEC/EN 60998-1
* Rated Impulse Withstand Voltage Test to IEC/EN 60664-1
* IP Ratings for Electrical Equipment to IEC/EN 60529

Material Tests
* Needle Flame Test to IEC/EN 60695-2-2
* Glow-Wire Test to IEC/EN 60998-1, IEC/EN 60695-2-11

Environmental Tests
* Temperature Cycling Test to IEC/EN 60947-7-1, IEC/EN 60998-2-2
* Industrial Atmospheres to EN ISO 6988, IEC 60068-2-42, IEC/EN 60068-2-60
* Salt Spray Test to IEC/EN 60068-2-11, Marine Applications GL, LR, DNV
* Quick Change of Temperature to IEC/EN 60068-2-14
* Damp Heat, Cyclic (12 + 12 Hour Cycle) to IEC/EN 60068-2-30, Marine Applications GL, LR, DNV as a wide range of Mechanical, Electrical, Material and environmental tests.

They have also been extensively tested and approved by many safety standards (e.g. UL,KEMA EUR, DVE, CSA etc) for use in different geographic areas around the world.

Incredibly, BS5733:2010 only references one (Vibration Test to IEC/EN 60068-2-6) of the above internationally recognised tests. All the other MF terminal tests in BS5733 are neither documented or used in any other internationally recognised product standard.
Despite all of the above and the flawless operation of billions of Wago 773, 222 and 224 terminals around the world, these new tests will still need to be performed on the Wago 773, 222 and 224 terminals before we can consider putting an MF symbol on the Wagobox or Wagobox-Light for the UK market.

These tests are being done and when we have had verification that the Wago terminals comply with the MF terminal requirements set out in BS5733 we will then be able to mark the Wagobox system with an MF.

Why is it taking so long?
Wago are a large multinational company with an excellent safety record that has spent millions of Euros developing and testing their products to internationally recognised product standards. BS5733 is not a product standard and the MF terminal tests detailed in BS5733 are not required anywhere else other than in BS7671 which is a UK standard. The new tests include very long duration tests which take an extended period to complete and are consequently very expensive. This additional need for further tests on a product already in production has taken some considerable commitment and effort by Wago in Germany to include this further testing into their scheduled program of work.

How does this effect my past installations?
It doesn't. Standards are never applied retrospectively.

What about installations I've done recently?
Please refer to 511.2 in BS7671. At this stage it's a case of the designer of the installation being satisfied that the use of the product offers the same degree of safety as afforded by compliance.

I used Wago extensively in my rewire, I struggled to get more than 2 6mm cables into the box though, were really tight although that forms the strain relief.

These items are extensively tested for short current as well as the other bits and bobs listed above; lots of carp on forums about shorts damaging terminals etc when they actually meet requirements.

Edit: Worth adding the following from the last page:

Well I had my NICEIC Approved annual assessment today and the assessor had with him the director of the NICEIC who was there to watch the assessment being done with the use of an iPad.
I thought it an ideal opportunity to mention what the OP had mentioned in his post regarding the Wago Box.

The reply I had was that he hoped an assessor had not advised a rework of the installation and felt that incorrect.
He mentioned to his knowledge only one manufacturer had been able to use the MF logo, but it was early days and he was sure the rest would follow in due course including Wago.
Adding that if the designer of the installation and manufacturer are of the opinion it's MF then it meets the requirement or words to that affect.

So the NICEIC are not enforcing they are not to be used and are ok with them and feel sure that they will carry the MF logo in due course.
He did mention that another similar product may not be, but Wago are fine.

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