Multiple supplies in one building

[ians]

I have an interesting project...

There is a 400 amp (2 x 95mm x 4 core) supply feeding a warehouse....and another DB on the outside wall feeding some of the lights and plugs inside the building and to add to the confusion...we need to upgrade the supply to 800 amp.

The DB on the outside wall feeds "some" of the plugs and lights in the offices...and all the other adjacent separate units office plugs and lights.

The aircon is a ducted system fed from a central unit somewhere in the service passages.

The warehouse DB (400amp) is inside the factory (installed by a company as they required a more power to feed cooker units)...which also feeds some of the lights and plugs in the offices and a split unit in the office area.

Now they require more power...the best way to do it would be to upgrade the 400 amp to an 800 amp circuit in the mete room...run 2 x 185 mm x 4 core cable (maybe even the next size up) and fit a floor mounted DB...however we a re talking 100 metres from the meter room to the warehouse and because they are renting it just makes it even more difficult because they are tenants and want to remove the supply when they move to the new bigger factory.

So now we looking at running another 2 x 95 mm x 4 core cable along the side of the building which can easily be removed when they leave...installing another 400 amp floor mounted panel dedicated to the new equipment which will be installed soon...2 separate main DBs in one building...labeling becomes a critical part of the installation.

I have worked in a building where there were 12 transformers on the outside of the building...feeding into one building.

Any comments ?

[GCE]

Hi

In my opinion as long as there is one point of supply to the Erf and one point of Control there should not be a problem.
I am assuming that the sub station belongs to the factory and you would just upgrade the Main CB and then feed out an extra 400Amp. Sub Station being Main DB and the rest Sub DB's

If the sub belongs to the Municipality then I dont see the Municipality allowing 2 points of supply onto 1 Erf .

Where you talk of working with multiply transformers feeding into a building there still would have been one point of supply , MV, and one point of control for the Erf .

It is the way shopping centers are generally designed which is similar to what you describe.

[ians]

There is a transformer next to the meter room (bulk supply)...it is one building with multiple units rented out to tenants.

2500 amp main switch...feeding a panel with all the private meters.

The building i need to upgrade.

Fed from a common ground lighting a socket DB

400 amp circuit breaker in the "meter room"

we going to add another 400 amp breaker next to the existing breaker....run another 2 x 95 mm cables on a cable tray to the warehouse and install another main DB ...maybe i should label the meter room DB "main DB" then each DB feeding the warehouse ...local DB 1 ...local DB 2 ...local DB 3 Then the sub DB feed compressors ...and other parts inside the warehouse sub local DB 1 or something like that.

The part that concerns me is when you switch off the "main DB" in the warehouse some of the plugs and lights switch off ...you have to go outside to the common ground DB to switch off the other plugs and lights...now we are going to add another DB into the mix.

The only way to isolate all the power in the one unit is to go around to each DB inside and outside the building and switch off or to the "meter room" which is locked on the boundary on the other side of the property.

I have labeled most of the switches and plugs..."P1 - 1 fed from main DB 1" ....P5 - 15 fed from main common ground DB 2 outside" for example.

[GCE]

HI

I also always have concerns when buildings get split up into multiply small business type set ups

The fact that you have marked everything and made it easily recognized , I would say covers 5.3.6 and then the "main DB" being in a common area should solve 5.3.8

I cant think of anything else off hand that could cause a complication -


5.3.6 Emergency control
If, in dangerous situations, it is necessary to immediately interrupt the power
supply, the interrupting device or devices in case of mains and alternative
supplies, shall be installed such that all the devices shall
a) easily be recognized, and
b) effectively and quickly operated

5.3.8 Positioning and accessibility of electrical equipment
Electrical equipment shall be so positioned that
a) it does not impair the functioning or safety of other equipment,
b) it is readily accessible for installation, replacement, operation, testing,
inspection, maintenance and repair (see 6.6.1.9 and 6.9.4 for the main
switch). All parts of the installation shall be accessible without the need to
enter any adjoining premises (for example, in an apartment building),
NOTE Common areas (such as passages and entrance halls) are not regarded
as adjoining areas.
c) there is easy access to its location,
d) it is not likely to be physically damaged,
e) dust or moisture is not likely to accumulate on live or other parts and
cause flashover, and
f) where the distribution board is concealed by a cupboard or other
covering, the notice for live electrical apparatus referred to in annex N
shall be in a conspicuous place indicating the position of the distribution
board.