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Use Of Cable Ferrules

Former Community Member over 4 years ago

Morning gentlepeople of the IET forum.

I'm just throwing this out there to try a get some opinions on cable ferrules and if people use them and where.

From my understanding, they are mainly used during panel builds, IT equipment and even on flexible cables. However, I recently went to a domestic property to perform an EICR and every cable connected to the RCBOs (ignore the earth fly lead which already comes crimped from the manufacturers) had ferrules clamped on the ends.

Clamped on every cable with the exception of the cooker and garage supply, which from memory i believe were both 6mm cables.

in hindsight, i should have taken a picture and shared this, but i didnt, so I failed you all!

To be fair, the electrician who did this, I can see committed to being very neat and tidy. One of the nicest installs i have seen in a while.

I personally have never done this with T+E so just found the ferrule thing a bit strange and wondered if it's something others do, and maybe this could or should be a future reg!?? Pro's and Con's i suppose.

My thinking was that it does protect the copper cable inside the ferrule, allowing for a better connection too i suppose!?

0 gkenyon over 4 years ago
Ferrules are mainly intended for use on Class 5 (flexible) and Class 6 (extra-flexible) cables to:
Help reduce the risk of "dropping strands" or accidental shorting between terminals (one reason for their use in control panels, especially "hot swap", as Class 5 conductors are often used in this type of equipment).

Help prevent damage to strands in maintenance, testing and fault-finding (another reason for their use in control panels)

"Convert" the Class 5 or Class 6 stranded conductor into a "solid" conductor for terminals that are unsuitable for Class 5 and Class 6 conductors.

Whilst I can see that ferrules may be of use for stranded conductors (Class 2), and these are not precluded, I don't believe any manufacturer of ferrules expresses their suitability for solid conductors with less than 7 strands.
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0 Zoomup over 4 years ago

Joe-not-exotic:

Morning gentlepeople of the IET forum.

I'm just throwing this out there to try a get some opinions on cable ferrules and if people use them and where.

From my understanding, they are mainly used during panel builds, IT equipment and even on flexible cables. However, I recently went to a domestic property to perform an EICR and every cable connected to the RCBOs (ignore the earth fly lead which already comes crimped from the manufacturers) had ferrules clamped on the ends.

Clamped on every cable with the exception of the cooker and garage supply, which from memory i believe were both 6mm cables.

in hindsight, i should have taken a picture and shared this, but i didnt, so I failed you all!

To be fair, the electrician who did this, I can see committed to being very neat and tidy. One of the nicest installs i have seen in a while.

I personally have never done this with T+E so just found the ferrule thing a bit strange and wondered if it's something others do, and maybe this could or should be a future reg!?? Pro's and Con's i suppose.

My thinking was that it does protect the copper cable inside the ferrule, allowing for a better connection too i suppose!?

In electrical installation work I do not use ferrules on large solid copper conductors in consumer units. There simply is no need. The copper is best made to "fill" the terminal. I normally double over the ends of single copper wires such as 1.0 and 1.5mm2. Or if there are two or three ends I just insert them parallel into one terminal. With ring final circuits I just place two or three 2.5mm2 wires into the terminal without doubling over the ends. 4.0mm2 and 6mm2 wires can take care of themselves. With cage clamp type terminals I try to insert stranded wire as flat (untwisted at the end) as possible to give equal grip to all strands. My methods are tried and tested over many years and work well.

Z.
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0 Helios over 4 years ago

I have seen one domestic installtion use them , and very presentable and clean installtion it looked too , and it was new build , but as you say pretty rare , on the kits for the bootlace type , there is a difference in quality , so look at tools and kit first , and reading GKenyons useful guide post is probebly the sort of place more likely , and seen them on 4 core three phase from transformers and on transformers and tool to clamp them,looks like a pair of boltcutters
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0 Gerrard Wilson over 4 years ago

To avoid inappropriate separation or spreading of individual wires of fine wire conductors, suitable terminals shall be used or ends treated. (BS 7671-526.9.1)

The photographs below show what happens when fine wire conductors are inadequately captured in the terminals of a 20-amp double pole switch.

In some cases, it has taken more than five years for the effects to reach maturity.

Demonstrating this, the photograph below has two types of wiring, with the same cross-sectional area installed into a 20-amp double pole switch.

Twin and earth supply the switch and heat resistant flex is used as a means of final connection to a water heater.

The T&E being single solid cores is happy to supply without failure or objection to the load.

Capturing all the strands of a fine wire conductor in a terminal of this type is very difficult to achieve.

Multiple outlets were discovered with the same fault, which could have been easily avoided.

An indicator is cracking of the faceplate caused by excessive heat. Over time it will eventually turn brown.

Not all terminals are loose!
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0 Former Community Member over 4 years ago

I work all over Europe on electro-technical systems and the national regulations (All CENELEC based), in some countries, locally require that ANY flexible cable in a terminal not specifically designed for flex (Such as a Wago connector) is terminated in a ferrule.

The logic goes (so I have read in those regulations) that flexible stranded cables are more prone to the strands spreading under the terminal screw when subject to movement or resonance and the use of a ferrule reduces the risk of increased contact resistance and consequently fire. They certainly seem to maintain tightness better under long term inspection tests of cables from hire stocks that I have been involved in testing..

It is certainly good practice to put ferrules on flex, and does improve the mechanical connection under a screw terminal. I use ferrules on all the work I do with flex where it would help, that way we keep compliance in any jurisdiction, and it results in a far better job for almost no cost.

We also crimp the ferrules before inserting. I have seen some just pushed on and tightened under the screw.

They are so cheap and easy to use it is a no-brainer to use them on flex, and anyone who takes pride in their work appreciated the better look of the install.

Quite a lot of connectors (Such as Phoenix connectors or Powercon connectors) have a small metal shim between the screw and the cable and are specifically intended for use with flex and do not require a ferrule in those jurisdictions. I haven't found any detriment to putting ferrules on those connectors.

I can't see any reason to use a ferrule on a solid core cable other than cosmetic reasons, although maybe under extreme misuse (such as gross overtightening of the terminal screw) it may help.
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Use Of Cable Ferrules

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