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Phoenix

Clever solutions needed for caravan park loading issue

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Phoenix

Just thought I'd put this here incase someone can see a solution that I cannot.

Basically we look after electrical maintanece for a caravan park which suffers with loading issues in the colder months. There are 60 pitches although rarely are they all used together.

The supply was originaly single phase 100A (earthing is TT as you would expect) into a 3ph board linked across. They were taking out the board fuse so sometime in the distant past (before we looked after it). They had a second SP 100A service added. One service now feeds into the red busbar on the board , the other into yellow and blue. There is no neutral from the new service, so three tails into the board a live from each service and a neutral from the old service all neutrals are combined in the board as you would expect as it is a 3ph board.

Board has a 415v warning on it, but investigation reveals both services to be on the same phase.

The RCD setup is a 4pole 100A rated 100ma time delayed RCD, with a live through a pole each and the neutral through two poles in parralel using a bit of busbar. Not ideal, certainly the neutral tail is overloaded, but at least the poles in the RCD are doubled up.

We keep getting called out there on a saturday nights when the RCD has burnt out. Was up there last night and the RCD at burnt out on one of the poles carring a live (not the neutral), not the terminals, from the location of the burn mark on the side its clear that the burn out was within the RCD.

So it seems that the 100A service fuse (which was still warm when I rocked up there) did not protect the 100A contacts on the RCD! I suppose I do need to check when I go back that there is actually a fuse and not a conduit coupler in there!

When I got it back on, clamp meter on the tails showed 40A in one live and 60A in the other.... but everyone was out in adjacent field watching bonfire and fireworks. Half an hour later and it was pushing on for 90 odd in each and the neutral was carrying 175A and feeling quite warm!

Now we can have a custom DB built to suit the supply arrangements (if they'll go for it!), but that doesn't help with the fact that the supply is on its limit and the board fuses have gone a few times. Supply board want about 30grand to put in a proper 3 phase supply as there is only 2 lines from the 11kv to the local tx and they'd have to upgrade the lines as well as the tx. They tell us that split phase is not available.

So I'm looking for clever ideas to manage the load becuase signs saying "Electric heaters not permitted" are ignored. Basically something that maybe can be set to beep a warning to a particular hookup if load goes over a certain figure and if not reduced than to drop out a contactor, requiring a wait and a trip outside to push a button before it'll go back in

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apprentice87

Hi there,

I am only a newbie, but the whole lot sounds a complete bodge to me... Never mind the neutral tail being overloaded ,what about the neutral in the service cable..

Anyway, i would think that the caravan park people will just have to pay for a proper supply... Why should you be worrying about half baked schemes to get around what is obviously an undersized supply.

I read this quotation in a book once;

"Before you do any electrical work, remember that one day you may be called upon to give evidence in a coroners court"

I am not for one second saying that you are doing anything, or have done anything not quite right, but, to be honest, do you yourself really want to get involved with this "half baked" installation, or put your name to anything involved with it, merely because the site owners are happy enough to take money in, but not so keen to spend any on a proper installation..

So it might be 30k, so what, that is

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Apache

Got to be that current in the neutral frying the RCDs. No bloody good, and the neutral isn't fused so no over-current protection.

I can't see there's anything you can do other than rip it out and start again on a decent 3 phase supply, unless you put another supply in elsewhere and have only a proportion of vans on this supply.

Sounds like it wants reporting and a danger notice issuing!

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ProDave

so 200 amps (total) supply and 60 pitches = 3.33A per pitch.

Now they are not all going to be on at once, but I would say a 6A MCB at each outlet should "solve" the problem. I'm betting it's 10A or 16A at the moment?

I'm assuming (because of the time of year) these are static van's, not tourers? If so that supply is wholey inadequate, and the site should stump up for the 3 phase feed. Even that 300A (effectively) over 60 pitches is only 5A per van which IMO is still not enough.

But to solve the immediate problem, I think the only reason for the 100mA RCD is the TT supply. Can you ask if the DNO will provide a PME earth? If they can, you can dispense with the 100mA troublesome RCD as you will have an RCD at each pitch outlet.

You should still TT each outlet, but having the (presumably burried SWA) protected by a PME earth (in fact anything other than TT) means you don't need RCD protection on them.

Edited by ProDave

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Phoenix

In answer to the question:

1) yes it is a total bodge I agree, the client will not pay for the supply upgrade so we are stuck constantly telling them theres no easy answer in that case and trying to make improvements where we can and emergency repeairs

2) They are touring caravans!, Please is open all round the year. While I was there last night they were telling me that same campers rocked up with a canvas tent and delared that it wasn't that cold!!!... perhaps they were scottish :P

3) Pitch outlets do have 30mA RCD, the older ones have 16A MCB. We installed a new one at one location after one got squashed! and went down to 10A mcbs in that... 6A would be an idea but bit worried about the short term load of boiling kettles knocking them out (I dont see kettles as a problem because the load is for a short duration and you'd unlikely to get many brewing up at same time)

4) I'm not 100% sure what the back story on the earthing is (though there is a PME terminal on the cutouts), its all TT now (and Ra is poor), Going on what I've managed to pick up, it used to be either TNCS all over (a complete no no with caravans) with the odd pitch supply having a tye down rod. Or that it was TT with no main RCD, leaving the DB, circuits in the laundry/WC/Shower areas, and buried SWA without RCD protection. Either situation is clearly unacceptable. I think we will end up going down the road of converting the distrubution and facilities all to TNCS, and dropping this at the pitch supplies and using a local TT for the outlets as you suggets Dave, which will eliminate the problem of the burnt out main RCDs.

5) At the end of the day the loading issue is not going away, so wanted to be able to suggest some solution which might be able to 'manage' it at the cost of inconvienceing the users of the site.. they might even then make a business decision to pay for increase in capacity! The figure caravan parks are designed on I'm told is 2kw per pitch... so even assuming the place is not going to be more than 90% full.... 54pitches thats still 108kva needed... and they have 46kva to play with headbang .... infact if you calculate what is needed it comes to 200A TPN needed (though that is with allowing the heater ban to be revoked, if heater ban is in place then this allows a bit less... but certainly on a new site its what you'd spec!)

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sellers

Upgrade to 3phase best option all round.

Or limit each van, like said before, and prepare them for complaints when everyones van trips out.

Or as it will probably be, leave it as is, keep going out to repair it untill it burns down.

I hate customers.

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ProDave

As you have a TNCS earth available, use that for the distribution and remove the troublesome RCD.

At each bollard, obviously don't connect the TNCS earth, but connect to a local TT earth. You might need to go and buy a lot of earth rods.

Upgrade the neutral tail to something larger (or 2 in parallel) as it's clearly overloaded and getting hot.

Change all MCB's down to 10A. If individual van's keep tripping, they won't use the heater as much.

That should solve most of your emergency calls. But won't stop the DNO's fuse popping from time to time.

Edited by ProDave

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SLIPSHOD & SLAPDASH

As i am simple i cant work out if the rcd will operate correctly as it is presently wired. Even so i would fit 2 separate 100A S RCD's, one to each of the lives. Obviously bring seperate neutrals through each and connect to a Henley block as close to the supply head as you can. This gives the added benefit of only 50% ish dropping out on a RCD fault. You need to make a sign fixed to the main board explaing the 2 X single phase supplies at 240v.

Edit, As soon as i posted that i realised you cant double up on the neutrals. You would have to fit one new fed via one RCD & the other RCD feeding the existing board. Are there two meters at the property ? It is a very strange set up & i thought against the supply rules to have more than one supply ?

Edited by SLIPSHOD AND SLAPDASH

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Doc Hudson

Did this site originally have less electric hook-up points and more pitches with no electrical service? I always thought that pitches were typically 6A or 10A. I think they have either got to upgrade the supply or remove some of the electrical pitches.

Doc H.

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PC Electrics

I've got a nifty little 1kW travel kettle. So I'd say sod letting them use a 'proper' kettle and put each pitch on a 6A. It's enough for some lights and small kettle, but will prevent the use of fan heaters on anything more than 1kW setting.

Not a proper solution, but at least it will limit peak load.

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batty

Not sure i would want to remove RCD's you really may have a fire on your hands then. Probably best to sort problem rather than trying to get over it by bodging it by putting in a main swich. I think somebody needs to spend a bit of money or cut down the amount of pitches.

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Riggy

Been here so often! Most caravan parks are in this situation.

Until you can convince the park owner to upgrade the supply (get a DNO rep there, they usually have some good ideas when you get them on site in my experience), fit 6A MCBs at each pitch and make sure the owner has a stock of 1kW kettles to sell to punters when they come whinging!

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NozSpark

This year I went camping near Pontypool and we had an electric hookup... On the outlet box it stated that electric kettles, toasters, heaters etc were not allowed to be connected to the points and that any transgression of this rule would result in a blown fuse and callut of an electrician,, the person who did it would get the bill for the callout.

So IMHO you definately need to look at the supply arrangements and as a stop gap you could change all the breakers to 6A

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kerching

As said before, limit the loads to 6A. Put MCB in a locked box to which the only key is held by the landlord. Charge them

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