EHU cable length

[Anseo]

Not exactly Technical, so if posted in wrong area, perhaps the mods can move it please.

As general guide, what total length of EHU cable should I be carrying to allow for some hook up points that might be some distance from the pitch.

I know it's a "how long is a piece of string" kind of question , just looking for a general guide.

I have 2 cables, total length is around 25 metres.

Thanks folks.

 

[WoodlandsCamper]

Standard length you can buy is 25m. Both main clubs say that is adequate for their site. The longer the lead the more voltage drop you get.

 

[PaulT]

I agree, normal length is 25 mtrs but I have been to a few sites where I've needed 30 mtrs so I usually carry 2 lengths of 25 mtrs.

 

[Dwarfer]

If I remember rightly the wiring regs state that caravan EHU cables must be 25m. I think this is to reduce the chances of anyone unplugging the wrong cable and working on something they think is isolated when its actually plugged into the next point down and still live.

 

[chrisbee1]

If you caravan in Europe you are very likely to come across sites where you will be pitched more than 25mtrs from the EHU bollard. I've also visited a CL where the best view entailed pitching more than 25mtrs from the supply. I carry 2x25 and 1x10 lengths but have only ever needed to use a combination of 2 cables.

 

[Jaydug]

During the summer I stayed on a lovely CL with a grand view over the Exe estuary and even in August site fees were only £12 per night. The site did however have only one electric bollard which was situated on pitch No.1. My pitch was No 5 but my dismay turned to relief when I saw that the site owner had provided two extra cables. One at 15mtrs and the other 30mtrs. That one together with my own 25mtr cable worked well.

 

[pitpony]

Years ago we went to Clifford Park at Walmer nr Deal, and ended up using Three EHU cables, two of my own and a third one I had to hire for the week from the site office obviously a problem because they had plenty,

 

[Dustydog]

Standard length you can buy is 25m. Both main clubs say that is adequate for their site. The longer the lead the more voltage drop you get.

I've been on two CLs where the owner provided an extra 25 metre cable making 50 in all.
Never noticed any voltage drop and it was the winter.

 

[Martin24]

Only once needed more than 25m and then a longer cable was provided by the owner of the CL on arrival.

 

[JamesH]

I have two 25M cables but one has an increased conductor size to compensate for the volt drop at the caravan. The coupling between the two leads is watertight to BS4343 (not splash proof).
I have a plug in voltage indicator due to having problems in the past with the supply tripping out due to the unbelievable low voltage of the site supply. Now if the site supply is showing a low voltage I can adjust my caravan load accordingly.

 

[KeefySher]

Y not plug one of these:
eBay item 222155348481

into the next caravan and share the load?? :evil: :evil:

A splitter can be used on the water tap too

Oh and connect to their gas bottle too :evil:

Save you carrying too much weight off the precious little payload, and helps the nose weight too.

Just takes a bit of lateral (out of the [strike]box[/strike] caravan) thinking :evil: :evil:

 

[Anseo]

A few points I noted in the replies makes me comment:

1. As I said I have 2 cables, I fitted waterproof (I would not regard them as submersible ) plugs and sockets, and now I am very happy that I did just that.
I did not take into consideration that linked up cables could inadvertently be misidentified by users thereby creating a potential safety issue, point taken thanks.

2. I had not thought of increased conductor size on cables to account for voltage drop, or voltage indicators.

3. I would have thought it a nice gesture if all sites had a few extension cables free for use for those who either forgot to bring their own or find that travel distances to hook up points were beyond say 20 metres, if cables were to be hired by site owners then I understand that there is a cost to this, purchase and PAT testing etc., but if they were to be on a hire basis then it should only be on the basis of 1 20th of purchase cost per week of hire and lesser increments based on number of days and based on standard plant hire profit margins.

Camp hire sites that ' give a fair deal' would always have my repeat business and or recommendations, same applies to all other business services I use.

John

 

[ProfJohnL]

I have two 25M cables but one has an increased conductor size to compensate for the volt drop at the caravan. The coupling between the two leads is watertight to BS4343 (not splash proof).
I have a plug in voltage indicator due to having problems in the past with the supply tripping out due to the unbelievable low voltage of the site supply. Now if the site supply is showing a low voltage I can adjust my caravan load accordingly.

I'm intrigued by your contention that low voltage caused your system to trip out.
Exactly what tripped please?

 

[chrisbee1]

If I remember Ohm's law correctly from my younger days for a given wattage, the lower the voltage the higher the Amps. If James was using appliances totalling say 15 amps @ 230volts all would be well but if the site supply was only 210v it would be over 16 amps, possibly enough to trip the bollard? Of course, I could be way off the mark.

 

[saint-spoon]

The longer the lead the more voltage drop you get.

Whilst this is true WC the voltage drop will be negligible even when you have higher loads.

 

[WoodlandsCamper]

If I remember Ohm's law correctly from my younger days for a given wattage, the lower the voltage the higher the Amps. If James was using appliances totalling say 15 amps @ 230volts all would be well but if the site supply was only 210v it would be over 16 amps, possibly enough to trip the bollard? Of course, I could be way off the mark.

Yes, you are off. Ohm's law says Volts = Amps x Resistance, re-written this is Volts/Resistance = Amps. The Resistance of an appliance is relatively constant, so if Volts drop then Amps will drop also, NOT increase. Hence the prof's comment earlier.

 

[chrisbee1]

If I remember Ohm's law correctly from my younger days for a given wattage, the lower the voltage the higher the Amps. If James was using appliances totalling say 15 amps @ 230volts all would be well but if the site supply was only 210v it would be over 16 amps, possibly enough to trip the bollard? Of course, I could be way off the mark.

Yes, you are off. Ohm's law says Volts = Amps x Resistance, re-written this is Volts/Resistance = Amps. The Resistance of an appliance is relatively constant, so if Volts drop then Amps will drop also, NOT increase. Hence the prof's comment earlier.

Sorry, you did not convinced me so I put my quoted figures into http://www.ohmslawcalculator.com/ohms-law-calculator
Have a play

 

[WoodlandsCamper]

If I remember Ohm's law correctly from my younger days for a given wattage, the lower the voltage the higher the Amps. If James was using appliances totalling say 15 amps @ 230volts all would be well but if the site supply was only 210v it would be over 16 amps, possibly enough to trip the bollard? Of course, I could be way off the mark.

Yes, you are off. Ohm's law says Volts = Amps x Resistance, re-written this is Volts/Resistance = Amps. The Resistance of an appliance is relatively constant, so if Volts drop then Amps will drop also, NOT increase. Hence the prof's comment earlier.

Sorry, you did not convinced me so I put my quoted figures into http://www.ohmslawcalculator.com/ohms-law-calculator
Have a play

I've played. I think you are making the mistake to assume the appliance wattage remains constant. It doesn't, as I've stated above because wattage is a function of Amps and Amps will reduce if Voltage is reduced.

 

[JamesH]

Hi Prof.
It was the caravan mcb that tripped out. It wasn't overloaded in the van as we always switch the immersion and/or convector heater off when the elec kettle is on. It was then that I plugged in the voltage indicator, noticed that the supply voltage was very low and assumed that was the reason for it tripping out.
I was working on the assumption that if the supply V was 240V and the appliances were drawing 2400W then that would equal 10A but if the supply voltage was only 215V then that would equal 11A.
When we were away last week the supply voltage occasionally dropped below 215V momently.

One thing that happened that I can't understand is that whilst on site the state of battery charge dial only just managed to stay in the green (with no 12v appliances connected) but on arriving home and connecting to the mains after a couple of hours or so it was showing maximum charge

 

[chrisbee1]

If I remember Ohm's law correctly from my younger days for a given wattage, the lower the voltage the higher the Amps. If James was using appliances totalling say 15 amps @ 230volts all would be well but if the site supply was only 210v it would be over 16 amps, possibly enough to trip the bollard? Of course, I could be way off the mark.

Yes, you are off. Ohm's law says Volts = Amps x Resistance, re-written this is Volts/Resistance = Amps. The Resistance of an appliance is relatively constant, so if Volts drop then Amps will drop also, NOT increase. Hence the prof's comment earlier.

Sorry, you did not convinced me so I put my quoted figures into http://www.ohmslawcalculator.com/ohms-law-calculator
Have a play

I've played. I think you are making the mistake to assume the appliance wattage remains constant. It doesn't, as I've stated above because wattage is a function of Amps and Amps will reduce if Voltage is reduced.

I bow to your greater understanding of the unseen energy. From his comment above it seems James was thinking along the same lines as me.

 

[WoodlandsCamper]

I was working on the assumption that if the supply V was 240V and the appliances were drawing 2400W then that would equal 10A but if the supply voltage was only 215V then that would equal 11A.

Please see my statement above, Wattage is NOT fixed but resistance IS. Wattage depends on the volts applied to the fixed resistance. A reduction in Voltage causes a reduction in Amps, not an increase. Ohm's Law is Volts = Amps x Resistance, wattage is only a calculation from these parameters.

 

[Dustydog]

What a sad bunch we are
I used to use an electric lawnmower with over 50mtrs of cable. It never showed any signs of losing power. So the resistance increase over an extra 25mtrs is negligible .
Even if volts dropped how can the amps increase.

 

[bertieboy1]

Woodlands camper,
You are correct ,
the watt rating changes with voltage,using the square of each voltage -
New voltage squared divided by Rated voltage squared times power rating will give the new power rating -
Using the figures James H used -
215V squared / 240V squared * 2400 Watts = 1920 Watts
So the watt rating reduces to 1920 W at 215 Volts
Current = W/V = 1920/215 = 8.9Amps

 

[WoodlandsCamper]

Woodlands camper,
You are correct ,

Thank you. (I wasn't a Chartered Electrical & Electronic Engineer for nearly 40 years for nothing then. )

Edit - An example of manufacturers acknowledging that the power of their appliances vary with voltage is the label on our Russel Hobbs kettle, which states:

220 - 240 V
2520 - 3000 W

 

[KeefySher]

See thats the thing with you sparkies, same as builders, just not precise enough (there should be the sticky out tongue here, but it don't work, bloody software engineers).

I use the rule of thumb of 220 / Amps to give me the Watts. Or more importantly on a hook up the 220v x the 6,10,16 Amps to give me the power in Watts I can pull. Gives a margin of error to work with, and enables the Mrs to use her hair dryer when she turns the heating power down.

Then I'm CEng FIMechE for my sins (sticky out tongue thing).

I'm also CDM & Bar, which is Cadbury's Dairy Milk & Wine