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Johnaldo

Flex cable size

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I know this topic has come up before on this and other forums, but there seems to be disagreement on the size of flex to use … some say 1.5mm and others say 2.5mm … but which is it, or doesn’t it matter?

 

Supplementary question - out of the hundreds of pieces of flex in my “never-throw-away-a-bit-of-wire” box, how do I know which is, say, 1.5mm?  Or if I look in the van, how do I know what the manufacturer used ?

 

For instance, this piece looks right, but how can I be sure?

 

6915E37A-F132-4945-B62B-8D37426EB065.thumb.jpeg.a3686e9fc906343d8645aebac985380e.jpeg
 

John

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1.5 for lights and light power draw items.

2.5 for sockets and heavy power draw items.

 

Use a micrometer to measure the cable core size.

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You're right - it is debatable whether to use 1.5 or 2.5 flexible for caravan power points.   When I've fitted any new power point in my van, I've used 2.5 simply because that's what Avondale used when they built the van.

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How many of you have a (factory made) 2.5mm cabled 13a extension lead??

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At least in a caravan, you are unlikely to have more than 16A in use.  Houses used to have one fuse or MCB for the upstairs sockets and one for downstairs sockets.  Now we might have four or more double 13A sockets in the reception rooms and two in each bedroom.  it's always going to be better to oversize cable than to scrimp.  proper installation cable,twin-core plus earth is better and cheaper than 'flex' which is more for extensions and appliances.  I don't know what cable is required by code for caravans.

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Not twin and earth.  There is a perfectly valid reason flex is used. 

52 minutes ago, Johnaldo said:

I know this topic has come up before on this and other forums, but there seems to be disagreement on the size of flex to use … some say 1.5mm and others say 2.5mm … but which is it, or doesn’t it matter?

 

Supplementary question - out of the hundreds of pieces of flex in my “never-throw-away-a-bit-of-wire” box, how do I know which is, say, 1.5mm?  Or if I look in the van, how do I know what the manufacturer used ?

 

For instance, this piece looks right, but how can I be sure?

 

6915E37A-F132-4945-B62B-8D37426EB065.thumb.jpeg.a3686e9fc906343d8645aebac985380e.jpeg
 

John

The cable size should be embossed on the outer sheath John. 

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Posted (edited)

Normally 1.5mm cross section wire for lighting and 2.5mm cross section wire for sockets.

 

In houses etc. where the cables are not subject to flexing, solid core cable is normally used.

In caravans and motor-homes where the cables are subjected to movement then multi-strand core cable should be used as it tolerates flexing (within reason), the more strands per core the more flexible the wire.

 

Use the chart below to convert between wire square mm and diameter mm:

Electrical wire is measured by it's 'cross section', if the cable sheathing is printed with2.5mm, the diameter of the conductor wire(s) will be 1.8mm.

Measure the conductor wire alone, not the conductor wire and the insulation.

 

Note the difference between cross section and cable diameter.

 

                         Wire

1.5 mm2 = 1.4mm Diameter

2.5mm 2  = 1.8mm Diameter

6mm 2       = 2.8mm Diameter

 

EDIT: I am informed that I should try to elaborate further on the cross sectional 'Area' aspect and it's relationship to the diameter of the wire.

I tried to insert a table explaining this but was unable to export or paste a table to this post.

 

I hope someone else can clarify better than I have :blush:

 

 K :Thankyou:

Edited by Sea&Sand

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My sockets in my Caravan are protected by a 10 mcb, so a 1.5mm cable can take roughly 14 amps, in a situation like this 1.5mm would suffice

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Posted (edited)

I don’t own a micrometer … so, following Clairndaves’s suggestion I found the following stamped on the insulation … 

 

3183 Y   H05VV-F   3GO.75MM   300/500V   EN50525-2-11   Eca CE   2018

 

… perhaps someone could interpret that for me?

 

John

 

Hang on - I’ve just spotted what is possibly 0.75mm amongst all that, and holding a ruler against the cable core it’s definitely less than 1mm … so I need something chunkier, I think?

 

E659B43B-096C-417E-8DE3-B13180C0EA8C.thumb.jpeg.036d0ab30c3008a2c489d15e13e409c8.jpeg

 

Edited by Johnaldo

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3 hours ago, kelper said:

I don't know what cable is required by code for caravans.

The only cable that is allowed to be used in a caravan is multicore flex.

Standard Twin and Earth is NOT permitted

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Posted (edited)

1.5mm cross section multi-strand cable:

https://www.builderdepot.co.uk/1-5mm-3-core-flex-cable-white-50m-drum-3183y

 

2.5mm cross section multi-strand cable:

https://www.builderdepot.co.uk/1-5mm-3-core-flex-cable-white-50m-drum-3183y 

 

As I mentioned earlier, 1.5mm for lighting & 2.5mm for sockets.

For all that it costs I would not skimp on the cable sizes\current rating.


 

Edited by Sea&Sand

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8 hours ago, Johnaldo said:

I don’t own a micrometer … so, following Clairndaves’s suggestion I found the following stamped on the insulation … 

 

3183 Y   H05VV-F   3GO.75MM   300/500V   EN50525-2-11   Eca CE   2018

 

… perhaps someone could interpret that for me?

 

John

 

Hang on - I’ve just spotted what is possibly 0.75mm amongst all that, and holding a ruler against the cable core it’s definitely less than 1mm … so I need something chunkier, I think?

 

E659B43B-096C-417E-8DE3-B13180C0EA8C.thumb.jpeg.036d0ab30c3008a2c489d15e13e409c8.jpeg

 

Yes John that is 0.75 so not suitable.   

 

1.5 is rated high enough.   

 

2.5 is used for most hookup cables due to the length.  

 

Most domestic extension leads are 1.5 yet most have a maximum load rating advised if they have more than one socket.

 

*Your ideal option is to match what is already used in the van. It's not ideal to mix and match cable sizes.  Even if it's up sizing to 2.5.   

A future owner could then add on from that and "potentially" cause issues. 

 

 

 

 

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As clairndave above  says 1.5mm is rated 16A according to the latest IET regs so is perfectly acceptable for caravan use.

 

The factors that come into play are voltage drop - which can be ignored - and heating of the cable. Given the cable is in free air the MCB will go long before the cable can get to any sort of temperature.

 

2.5mm Arctic cable is used for the EHU so that (1) the voltage drop under full load is not excessive and (2) as it is physically stronger it will more easily survive is run over by vehicles.

 

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9 hours ago, Sea&Sand said:


S&S, both links point to the same product 🙂

John

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On a similar note, site to caravan hookup cable is also a mine field.  A quick look on Amazon and you will see a lot of them are 1.5mm cross sectional area, not the preferred 2.5.  Some of the adds simply state such as "Caravan / Camping Hook up Extension Lead Cable with 16 amp Blue Plug and Socket" which in my experience is 1.5 mm area with 16A connectors.

Buyer beware.

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1 hour ago, ChrisUK said:

  A quick look on Amazon and you will see a lot of Caravan Hookup cables are 1.5mm cross sectional area, not the preferred 2.5.  Some of the adds simply state such as "Caravan / Camping Hook up Extension Lead Cable with 16 amp Blue Plug and Socket

 

If you look around on Continental caravan sites, you'll see many European caravanners using hookup cables which are nothing more than a standard extension cable reel.

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15 hours ago, clairendave said:

How many of you have a (factory made) 2.5mm cabled 13a extension lead??

You make an excellent point.  I have one with four sockets and it's only rated at 10 Amps.  A second one is 50m and it is rated at 13A but only when fully unreeled.  I can't read its cable size.

 

Anyway, it must be a good idea to clarify the difference between CSA (cross-section area) and diameter so people reading the thread are clear on the matter.

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Posted (edited)
18 minutes ago, Jaydug said:

 

If you look around on Continental caravan sites, you'll see many European caravanners using hookup cables which are nothing more than a standard extension cable reel.

Just because that's what they use doesn't actually mean that they are safe.

 

 

Edited by matelodave

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35 minutes ago, Jaydug said:

 

If you look around on Continental caravan sites, you'll see many European caravanners using hookup cables which are nothing more than a standard extension cable reel.

 

Only OK if the site supply is 6 amps, which is quite common in Europe, but so many of them plug into the bollard first and then unreel the cable, but that's also an error made in the UK.

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1 hour ago, matelodave said:

Just because that's what they use doesn't actually mean that they are safe.

 

Nowhere did I say that they were safe.   I posted the comment simply to add to what Chris said about Amazon selling them.  

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Hi

In response to your question  it really depends on the current being drawn from appliances. With that said 2.5mm  is the preferred option, however I have used 4mm2 on certain applications. On inspection you can see that 2.5  is a thicker cable. 

Hope this helps

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19 hours ago, clairendave said:

How many of you have a (factory made) 2.5mm cabled 13a extension lead??

I have a 50 metre x 2.5mm lead similar to the one below, except that the outer sheath is orange.

NB: I have had it for probably 30 years and it is always fully extended before use if heavy loads are employed.

image.png

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8 minutes ago, Sea&Sand said:

 

Sorry Johnaldo, hopefully this is the correct link to the 2.5mm cable:

 

https://www.builderdepot.co.uk/2-5mm-3-core-flex-cable-white-50m-drum-3183y


Thanks S&S - it wasn’t a complaint, more to help anyone else following the thread 👍.

John

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