Campsite Electric Hook-up connection

[dunny1234]

Looking at a job on a farm campsite. They require hookup's for 18 touring caravans in a field thats 85m long (9 caravans up one side, and then 9 caravans down the other) . An approx. calculation is that i need 250m of 16mm swa cable. I'm looking at using 16a 2way hookup unit/rcbo's for every 2 caravans. Not done anything like this before, any advice would be great. Do you think 16mm swa is enough. Thanks

 

[telectrix]

assuming a 10A supply for each caravan that's 90A without diversity. 10mm XLPE SWA is rated at 81A ( AEI Cable Finder Wizard ) so should be sufficient ( and a hell of a lot easier to install). volt drop could be an issue here though.

 

[dunny1234]

Thanks teletrix. I suppose 10mm swa would be cheaper too, the farmer would like that. But, volt drop over 250 metres is a concern. I told the farmer roughly what 16mm swa would cost and he seemed okay. Might as well be safe. What do you reckon? Thanks again

 

[telectrix]

are you doing it in 1 run or 2? i would either run 2 radials, 9 vans each, or make a ring.

 

[Engineer54]

I reckon you should do the calc's required for this installation, especially those regarding ''volt drop''

The farmers incoming supply is almost certainly going to be PME/TNC-S, so it's gong to have to be TT systems. Maybe linking them all up on each line of caravan pitches will give you decent Ra values that you can work with....

 

[dunny1234]

I was thinking a ring as the farmer is digging trenches for a water connection in the same areas needed for a suitable ring.

 

[telectrix]

I reckon you should do the calc's required for this installation, especially those regarding ''volt drop''

The farmers incoming supply is almost certainly going to be PME/TNC-S, so it's gong to have to be TT systems. Maybe linking them all up on each line of caravan pitches will give you decent Ra values that you can work with....

i,m just wondering how to calc. volt drop on an install like this. assuming 1 or 2 radial circuits, the load is taken at varying points, i.e. the load at the end of a run is not the total load. (only 10A if each van has a 10A supply) so would you use 10A for the full cable length, and calculate say at 50% of the length at say 30A ( allowing na bit of diversity)

 

[sparks1234]

I recently did a similar job although in a boating marina, its amazing the distance and volt drop. We allowed about 8 -10 amps per boat over 230 mtrs and ended up putting 25mm in. Our incomer was a TN-S system but due to the distances and the fact the hook up posts each had RCD built in we TT'd every post and also we protected the SWA with a 300ma time delay RCD

 

[Engineer54]

Remember, if direct burial the correct trench depths, and correct materials are used for back filling. DON'T let the farmer back-fill with just the excavated earth from the trenches!!! Better to duct the cables, but then costs go up!!

 

[dunny1234]

I'm struggling with how much diversity / calcs on this cable design. Taking full whack (which isn't going to happen) 18 x 16A = 288A and cable size for that is 95mm2 plus! The farmers going to have a heart attack when i tell him how much thats going to cost. surely thats not right

 

[Engineer54]

i,m just wondering how to calc. volt drop on an install like this. assuming 1 or 2 radial circuits, the load is taken at varying points, i.e. the load at the end of a run is not the total load. (only 10A if each van has a 10A supply) so would you use 10A for the full cable length, and calculate say at 50% of the length at say 30A ( allowing na bit of diversity)

On a radial circuit, your biggest loading is at the first point, 9 x caravans at 10a =90A. Second Point 8 x 10A =80A , and so on. To conduct a diversity exercise you will need some experience of such caravan installations, which i'm sorry to say i don't have. Maybe someone here on the forum, will be able to help on that score for you....

The volt drop calculation is similar to those or a row of lights so distance x load at each point along the circuit then combine the totals

 

[telectrix]

as a rule of thumb, i would apply 50% diversity, as i can't imagine average load for 9 caravans > 5A average at any one time. that's mt guesstimate. someone might prove me wrong. it's something i've not come across before, except one site where 4 caravan pitches were taken from the car park lighting which was on a 10A MCB. he wanted me to sort out the"nuisance tripping" of the MCB. FFS.

 

[grantr37]

The farmer will have loads of rolls of the ducting needed to bury the cable in, so wont need to buy more, its something pretty much all farmers keep a large stock of, and he will probably have his own digger as well, so he will be able to sort out any trenches that need digging....

 

[Mikehull]

Just wondering doesn't each socket outlet at the caravan pitch need individual overcurrent protection? so would not be able to do it in a ring or radial?

 

[thekingiam]

Just wondering doesn't each socket outlet at the caravan pitch need individual overcurrent protection? so would not be able to do it in a ring or radial?

Correct me if ime wrong but I thought the discussion was ring or radials feeding a rcd,mcb connection points to each pitch with maybe metering included? That's what I thought would be required? Although as you say hasn't been mentioned.

 

[Engineer54]

Just wondering doesn't each socket outlet at the caravan pitch need individual overcurrent protection? so would not be able to do it in a ring or radial?

How do you know if these Caravan supply units don't incorporate an MCB, as well as the RCD?? Personally i don't know, but i would assume that they will!!! Maybe a DP RCBO even....lol!!!

 

[Mikehull]

Just checked over the regs i think i read it wrong i thought it meant each socket had to be on a seperate circuit/cable. my bad lol.

 

[thekingiam]

I would like some bright spark to explain the volt drop equation for me in this circumstance, basicly if each point is rcd,mcb etc protected then isn't it just a bunch of sub mains connected together?

 

[Engineer54]

Yep, something like a rising main in a high rise building, but on a smaller scale ...lol!!!

 

[thekingiam]

Yep, something like a rising main in a high rise building, but on a smaller scale ...lol!!!

Or a ring mains with everything using 13amps at every socket, but on a bigger scale!

Trippy!!!