Proposed Caravan Site

[chrish_1977]

I know, before anyone asks Im thinking the same.

Anyway, I have been asked by a customer (on the phone) how much to convert an old farm building into a caravan site for approx 14 pitches, from what i have gathered there is a TT supply feeding a 100A fuse from the DNO. I have yet to see this install yet, asked the customer to email me some pics as this is up north from me, and want to see if its worth my while to start with.

I digress, sorry. Am I right in thinking that they may have to upgrade to a 3 phase supply to allow for the pitches and main building (which has about 5 individual C/U within the property). Or could I get away (bad term im sorry) with just derateing everything to 80A?

I'm just picking brains until I get the pictures from him.

Many thanks in advance

Chris

 

[Sparky Ninja]

what's the demand from the proposed new design?

from my experience with what these mobile homes come with these days I think it's safe to assume that a 3phase system may be required..

 

[chrish_1977]

Unknown at the moment, When i mentioned 3 phase they said "would a caravan really use that much?", I did say that if you have 14 pitches and the entire house then you may have too.

But anyway, havent asked too many questions until i get the piccies, if they are worth looking at i will post them too

 

[J@mes]

Most caravan sites have a 10Amp supply to each pitch, for touring caravans anyway - are they touring or permanent? Obviously if permanent they will need more. If they are touring, you could have some that are 16A, some which are 10A and some which are 6A and the owner could charge different amounts, this could help keep the demand down and mean that a 3P is not required.

It's probably going to involved a fair amount of discussion over what the owner wants from his site and for the house. If he is planning to possibly expand to tents and wants a toilet/shower/dishwash block in the future too then this would also require the additional load of extra hand driers/ lighting/ sockets/ power showers etc.

If it is 14 Static caravans then I think there is no chance you will get it all on the current supply

 

[Guest123]

14 pitches with say, a standard 16A outlet = 224A. Obviously diversity will play a big factor here as not all pitches will be drawing 16A, nor will they be in use at the same time all year round etc etc. Will there be a toilet/shower block also???

A 100A single phase supply for these and the existing/new buildings will not be anywhere near enough IMO and detailed thought will need to be given when you have more info.

 

[chrish_1977]

Thanks j@ames, thats pretty much what i was thinking, but like i said until i get the pics, i wasn't going to worry about it too much, just have to break out the brb i think. I think it will be touring caravans and not static. Am i right in thinking that i could wire them all off the same supply (max demand permitting of course)with just the hookups at each pitch

 

[Sparky Ninja]

Well it's a bigger size site, but I have done a lot of work on a site that had approx 70 pitches. It had an office, and a bungalow for the warden. The existing installation is PME TP&N, which supplied a couple of load centres. Needless to say, with these mobiles homes these days requiring more demand than council houses, all the cables are undersized.

I guess you need to find out more about the use of the site... is it a 'mobile home' type setup or a typical 'caravan'?

 

[chrish_1977]

14 pitches with say, a standard 16A outlet = 224A. Obviously diversity will play a big factor here as not all pitches will be drawing 16A, nor will they be in use at the same time all year round etc etc. Will there be a toilet/shower block also???

A 100A single phase supply for these and the existing/new buildings will not be anywhere near enough IMO and detailed thought will need to be given when you have more info.

Thanks Lenny, this was exactly what i was thinking, but i guess i will just wait and see if he sends the pics

 

[J@mes]

Personally I'd try and split it up so that if the main breaker for the circuit trips the whole site isn't affected.

2-3 outlets of RCBO/ MCB/RCD and then have individual CU's at each pitch with an RCBO of the required size and a site-socket attached.

 

[chrish_1977]

Cool, thanks for all your help guys

 

[nickblake]

Having done a few small caravan site in fact installed a hookup today in the rain nice,up to my knees in mud , if you have 14 hookups then you are looking at max demand of 140 amps if you supply 10 amps per hook up , but you may find that some areas will require higher current demand so work out on max 16 amp per hook up , what i would do is work from this and allow for diversity , it may need a seperate feed from the DNO as widdler has mentioned then the caravans can be metered on its own , then id run a cable from the house to a feeder pillar for distribution to the hook ups say a 14 way board the 16 amp MCB,s to each point , each point having its own 40a RCD and 10 amp MCB configuration into a 16 amp socket with the PEN conductor connected to an earth rod , and use an earth rod at each hook up point . IF the house supply is TNS TNCS i would run this down the site as it could be used for lighting etc , and TT the hook ups as required and i have mentioned , having not see the lay out and area coverange it may be advantagiouse to use to feeder pillars and 2 supplies from the house , sound small cdu in house supplying 2 feeder pillers supplying 7 hook ups per pillar and some outside lighting , by feeder pillars i mean an external enclosure and CDU ,

 

[Bornagainsparky]

I have been watching this with interest as I have just come across a caravan park where the cables have melted on 1 line. the scenario is this. the main cable in is 3 phase, 50mm2 to a dist board where it is split up to 3 circuits each feeding 10 caravans (30 In Total) via a 16mm swa. Like so many others, Caravan parks are new to me but if each van is rated at 16amp that gives us a potential total of 160 amps, I have seen posting which state no diversity allowed, I can't find anywhere to confirm this and have looked through section 721 and unless I need to go to specsavers, which I probably do, I can't see any reference to this so perhaps someone could assist.

However using the above 10 caravans running off 16mm over approx 100 mtrs doesn't equate with mv/a/m i.e. 2.8 x 160 x 100 /1000 = 44.8v which is miles short of the 9.2, to get this, would result in using 90mm2, which is impractical so the only option I can see is to split the vans down into smaller groups so that they could be fed of 16mm but then I guess the main incoming cable would have to be upgraded somewhat, which would be like running a power station.

So in brief:

Am I correct in my assumptions and calculations

Is there any diversity allowed and if so how much

Or do I need to go back to college and specsavers


Many Thanks

 

[Guest123]

Diversity is a bit of a minefield to say the least.

There are numerous 'rough' guides available to assist but at the end of the day it's down to you as the designer to supplement your own diversity calculations.

Caravan parks are one of the most difficult to design for as you can be almost sure that not all the pitches will be supplying their full quota of caravans all year round, and not all the vans will be pulling their full load all the time........however at peak times i.e summertimes etc there is a chance they will.

I would reccomend a consultation with the park owner to establish when his busiest times are and how many pitches are in use together with the loading of each van at full load as there is a chance they may all be used at full load.

A common method of allowing for this is to install a ring main as opposed to a radial as you could use a smaller cable to supply a larger loading and you would also be less governed by volt drop.

 

[malcolmsanford]

Diversity is something that is like a magic figure you throw calculations, usage, types of installations into the air and come down with experience, in this enviroment it is a task that would be very hard to deal with.

Let us take your post you say that the 16mm^ 3 phase supply feeds 10 caravans on each phase, so a total of 30 units. Now only one line is damaged, so was that,

a) Those 10 caravans were using a huge amount of power compared to the other 20

b) Could there have been an external influence on that one phase, ie poor termination.

If the other 2 phases are in good condition showing no signs of damage I would say that it is B, there was perhaps a poor termination which as caused a build up of heat.

You could if your worried think about wiring the park in a ring main. This would give you the added bonus of utilising a ring main and it's advantageous.

 

[Engineer54]

However using the above 10 caravans running off 16mm over approx 100 mtrs doesn't equate with mv/a/m i.e. 2.8 x 160 x 100 /1000 = 44.8v which is miles short of the 9.2, to get this, would result in using 90mm2, which is impractical so the only option I can see is to split the vans down into smaller groups so that they could be fed of 16mm but then I guess the main incoming cable would have to be upgraded somewhat, which would be like running a power station.
Many Thanks

This is the wrong calculation you are using here. The last caravan on this radial cable will only be drawing 10A, ...Not 160A!! You need to calculate VD at each pitch then add the total, to get an accurate value. Same as if you were calculating the VD/cable size for a string of street lights....

 

[pushrod]

This is the wrong calculation you are using here. The last caravan on this radial cable will only be drawing 10A, ...Not 160A!! You need to calculate VD at each pitch then add the total, to get an accurate value. Same as if you were calculating the VD/cable size for a string of street lights....

Agree and in addition even at the start of the run where you would have the max current, the 16mm² you (the OP) mentioned would be no where near big enough to cope with the 160A - probs looking at 50mm² which would then almost certainly cope with Vd if calculated properly. Unless of course i have read OP's post wrong and need to go to specsavers lol.

 

[Engineer54]

Agree and in addition even at the start of the run where you would have the max current, the 16mm² you (the OP) mentioned would be no where near big enough to cope with the 160A - probs looking at 50mm² which would then almost certainly cope with Vd if calculated properly. Unless of course i have read OP's post wrong and need to go to specsavers lol.

I didn't make any comment on any cable sizing, as i don't think the OP knows too much about the proposed requirements of the installation at this time.

He will probably need a 3 phase supply for the house and the caravan site, plus the caravan site will also probably need some area lighting too. ...Lots for him to assess before he decides on an overall design!!

 

[Bornagainsparky]

Fully understand where you are coming from and all other responses are valid and appreciated. Taking the point of 10 amps being available at the last caravan proves to me that the cable feeding is inadequate, more so if all units are being used at the same time which is entirely possible and I guess this should have been accounted for by the original designer, so the options, to my mind are: increase the size of cable, construct a ring circuit as stated by Malcolmsandford or reduce the number of vans on each circuit, all of which are costly to the operator and I think we all know what their response would be but my personal view is that this installation is not adequate enough, in it's current form, for the potential demands or is this how caravan sites are designed, based on this I wonder how other subscribers would view it

Thanks