EHU 2.5mm Mains Leads

[aandncaravan]

My own van has been having an issue for a couple of months getting the Water Hot when set on 230v. Always works fine on Gas, but on mains it only heats up a small portion of the tank before seemingly shutting down.

 

The EHU cable end that plugs into the van had the protecting 'flap' broken in the Winter by someone being a little too enthusiastic removing the lead without releasing the lock.

On Saturday I replaced the end that connects into the van, and dismantled and checked the other end that goes into the Site EHU Bollard.

 

What I found was an eye opener, see photo below.

 

The Live cable core was overheated and burnt away inside the 16A Blue connectors Brass Tube. The cable clamping screw was tight, but clamping down on cable core that was detached from the EHU lead.

 

I fitted a new connector, dismantled and reassembled the other Bollard connector and the Water Heater is working fine. I am guessing that the high current draw of the Water Heater 230v element took it over the top, but I don't understand why everything else seemingly worked perfectly, even the 230v TV which is almost always on.

 

The cable sheath clamp was tight with no signs of any movement and the impression very sharp and clear. It didn't look like the cable had been subject to any Force.

 

This was a 2.5mm 'Fat' cable where the 2.5mm cores would have fitted snug in the 16a Brass screw connector tubes with good connectivity.

Imagine the poor connectivity that will result with a 1.5mm piece of Copper wire inside what is then effectively overlarge screw clamps? The screw may potentially clamp down on just a few strands of Copper.

One undersized 1.5mm EHU cable might get lucky with several Copper strands clamped by the screw, but another might have almost all the Copper strands 'missed' by the tightening of the connector screw.

 

When you buy/use 1.5mm cable, the 16A connectors at each end are the same ones designed for 2.5mm Copper, so far less Copper will be clamped inside the 'screw tube'.

Even when new that will be less than ideal.

 

More photos on our EHU webpage : http://www.aandncaravanservices.co.uk/hookup-leads.php

 

 

[arthur49]

Interesting Allan.

 

I recall quite a few years back being on a CC site with our nearly new van. The bollard kept tripping, no matter which outlet we used.

 

Warden adamant it was a problem with our new van! I found it hard to believe and checked all I could reasonably do but still a problem of tripping.

 

Hadn't thought of checking the new mains cable though. Turned out there was a loose connection. Once fixed, problem cured ..... and apologies to the Warden!

[Charles]

I tinned the ends of my 1.5mm EHU and doubled them up in the hole. Your cable ends look proper knackered, I suppose any size cable will overheat if there's only a few strands connected.

[mgnbuk]

"I tinned the ends of my 1.5mm EHU "

 

Bad move. The one thing we were specifically taught as electrical apprentices NOT to do when wiring to screw connections, as the soft solder flows (slowly) under pressure and the connection will come loose - not "may come loose", but "will come loose" !

 

The correct approach is to terminate the stripped cable with a crimped-on bootlace ferrule to harden the end under the screw. And, as wih all screw terminals, check for tightness regularly.

 

Nigel B

[Derek Uzzell]

I had much the same problem as arthur49 back in the late-1990s at a campsite in France.

 

We (then novice motorcaravanners) had bought an 18-months-old Herald and a UK-norm 25m ‘orange’ EHU cable had been provided by the dealer.

 

I suppose the moral of such stories is to occasionally check the tightness and condition of cable and adapter connectors.

 

 

[plwsm2000]

Those wires exiting the cable jacket seem a bit too short to me and could be a contributing factor.

The overall strain relief clamp should be designed to prevent stresses on the wire as it enters the screw terminal. This type of clamp is not the best as there usually is some flexibility between the clamp and the wire ends. With the tugging and pulling of the cable and connector in normal use, although most of these stresses will be taken by the cable clamp, some maybe be taken by the wire end which will lead to premature failure.

It is good practice to leave the wires slightly longer (5-10mm?) than they need to be. The earth wire should be a bit longer still so that it will be the last one to fail if pulled excessively.

 

The shape of the contact point at the end of the wire screw is important too. It should have a ball end finish so that it does not excessively damage the strands of wire.

 

I agree with Nigel that soldering is not a good idea not only for the reason he mentioned, but also because the solder will tend to wick up the multistranded wire due to capilliar action. This creates a fatigue point just inside the wire jacket that may fail over time if it sees much in the way of vibration. The solder flux residue also cannot be cleaned properly. As suggested, either a bootlace ferrule or a flat blade crimp would be more reliable.

 

 

Phil

 

[Agaric]

Normal practice would be to strip 9mm and twist the core before insertion, most electrical plugs come with a min and max length of wire strip on them or a piece of paper to that effect, or you can look it up online in the manufacturers spec.

[mikejkay]

That is why the individual wires should be twisted together and doubled back.

[aandy]

Derek Uzzell - 2017-05-02 9:02 AM

 

 

I suppose the moral of such stories is to occasionally check the tightness and condition of cable and adapter connectors.

 

 

This I not something I had ever thought to do until reading this thread. Just taken mine apart and found that the earth lead at the 'van end had come adrift.