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
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