Applying Diversity for a Boat Yard (Help)

[paul nelson]

Been asked to replace 4 Db's in a boat yard. Each to be fitted with 4 x 16A RCBO, 1 x 6A MCB and 100A Isolator. The sub main feed also has 4 x 16A RCBO and 1 x 6A MCB.

I see this as a Maximum current of 70A per DB, applying diversity could get this to 43A...

Now my problem is the main feed is via a C50 type B 30A RCCB, feeding the whole compound via a 10mm SWA!!! Table 4E4A shows maximum current of 71A.

Each DB daisy chained via 10mm SWA apart fromt the furthest which is 4mm SWA.

I guess that the whole compound has the ability to draw 215A after applying diversity for the DB's. This would mean replacing the main sub main feed with either a 70 or 95mm SWA. Also upgrading the swa trhoughout the chain of DB's. Also the main breaker to be upgraded to the maximum available to meet the cable spec.

Are my assumptions correct or is there another way of tackling this?

Your input is appreciated.........

 

[malcolmsanford]

Paul you have been asked to replace 4 DBs, so what is there existing at the moment?

Have you been able to take any sort of load readings during peak hours?

Though it is a boat yard I assume you would have welding equipment, perhaps some metal working machines, what do you have there.

The bottom line really is , it's worked for XXXX years with what it's got now, why do you feel the need to upgrade the loading capacity 9 times it is now? Have the client complained about overload tripping?

First thing is look at what the demand is now mate, have a chat with the customer and see if they are thinking about expansion , adding new equipment etc, and see what you may need in terms of future proofing

 

[ackbarthestar]

Only single phase? I would have thought this would be a 3-phase set-up. Also are you running out onto pontoons?

 

[telectrix]

Only single phase? I would have thought this would be a 3-phase set-up. Also are you running out onto pontoons?

if so, be careful not to fall off. water is wet and bad for the health of your mobile phone. i know, been there, done it, got the wet t shirt and the knackered phone full of seawater. lucky the pontoon was adjacent to the pub, so was able to get wet inside to deaden the pain.

 

[ackbarthestar]

My advice would be not to run along the pontoons with a bucket of tools and a roll of swa.......

 

[telectrix]

haha, send the apprentice.

 

[HandySparks]

Is this a boat yard, ie a working area for making/fitting out/repairing boats or is is a marina? A boat yard may have a few high power tools which get used in various parts of the yard, so total load may be quite low. You haven't said what these 16A and 6A MCBs are supplying. Is it socket outlets, fixed equipment, lighting, ???

 

[Farmelectrics]

im well aware of what diversity is but can some one give me an example of how to apply it awiting to start design course later this year

 

[paul nelson]

Is this a boat yard, ie a working area for making/fitting out/repairing boats or is is a marina? A boat yard may have a few high power tools which get used in various parts of the yard, so total load may be quite low. You haven't said what these 16A and 6A MCBs are supplying. Is it socket outlets, fixed equipment, lighting, ???

This is is a dry area where as you say boats are repaired etc, it is not near the water. Frequent use of power tools, heaters, dehumidifiers etc. Currently overloaded and tripping.


The 16A RCBO's will be socket outlets and 6A being street lighting.

 

[paul nelson]

The customer has ordered the new DB's, containing the 4 x 16A RCBO's to replace current setup. The current installation is 4 DB's, each containing one 10A MCB feeding 2 socket outlets and a 6A MCB feedind a street light.

The current installation is always tripping at source. Also qoute " the user is always daisy chaining extention leads to supply portable equipments" unqoute

So the new requirement is 4 x DB's each containing 4 x 16A socket outlets and a 6A feeding a street light.

Paul you have been asked to replace 4 DBs, so what is there existing at the moment?

Have you been able to take any sort of load readings during peak hours?

Though it is a boat yard I assume you would have welding equipment, perhaps some metal working machines, what do you have there.

The bottom line really is , it's worked for XXXX years with what it's got now, why do you feel the need to upgrade the loading capacity 9 times it is now? Have the client complained about overload tripping?

First thing is look at what the demand is now mate, have a chat with the customer and see if they are thinking about expansion , adding new equipment etc, and see what you may need in terms of future proofing

 

[Adam W]

It sounds like the main problem is with sockets being overloaded due to 'daisy chaining' which I would guess is because it's the easiest way for the end users to get power to where they need it.
I think 16A sockets are a good start, or you could install a 32A socket for each boat, then use a distribution unit on each boat which splits the circuits down to 16A sockets, then the tradesmen use long 16A to 13A extension leads and short 13A extension leads. That way the main lead onto the boat will be man enough for the job, a single cable will ensure single phase on each boat, and the tradesmen will be less tempted to 'daisy chain' extension leads together because that would be more hassle for them.

 

[malcolmsanford]

To me your first priority is the supply. We have to assume that the 30amp RCCB (MCB More likely) is not a dedicated DNO supply but is being fed of off another installation. This will have to be changed and like everything today the client will want it to be done to cost. So you will need to

1. See if you can actually upgrade that BS 3871 which though possible may take some finding 50/63 amp
2. If you can get one, can this existing installation carry the load expected of this upgrade
3. If you can't find one then is there a chance you can cut into a supply with blocks and fit a stand alone enclosure.

Onto the installation as you say it is not in a wet area, so we can assume that there is no hook up to boats. So can I ask why your wanting to supply RCBOs to installation?

Your design is of 4 x DBS each with 4 x 16amp RCBOs ( MCBs) and 1 x 6amp RCBO (MCB). I assume that the 4 16amps circuits will be doing 4 16amp BS EN.60309-2 Cee sockets. I may be depending on your set up be looking at a slightly different design. I would consider wiring these sockets in a Ring main say 40amp using 4mm SWA, and tap off sockets where you need them. How many rings would depend on area, equipment and access but lets say you do 2 of these. The advantages it would give is

1. Saving on DBs instead of 4 you may get away with just 2
2. Cable instead of 16 x radials in say 2.5mm SWA you have a ring of 4mm
3. On protection devices instead of 16 you will have just 2
4. Accessibility you can put the sockets off the ring where you eant, providing you do not tap off more than 3 metres
5. Cost cutting on materials and on labour

Disadvantages

1. Your limited to a distance of 3 metres per tap, but that should be no problem
2 Each tap off point would need an adaptable box again not a huge problem when looking at savings on other items

Finally diversity. There is no way your are going to need the 200+ amps you were looking at. Though impossible to tell without seeing the site, but what you wrote I would wager 60amps would be more than adequate in the set up I proposed