Cable Size

[Spazz]

Hi all - can someone confirm my thoughts please

Here is the situation:

• 6 floor hotel
• 45 bedrooms over 4 floors
• bottom 2 floors are reception and kitchen - not worried about these at present
• 3 phase supply coming into building - 1 phase per 2 floors - current setup
• Each floor has 2 DBs
• The manager now wants to put separate DBs in each room (I am pushing for RCBOs in main floor DB and no DB in each room)
• 12 rooms per floor (on average) (6 rooms per DB)
• The supply cables from main supply DB to floor DBs are traveling up an old shaft over 100mm from surface - no need for RCD protection
• Between floor DB and Room is less than 50mm from surface - would need 30mA RCD protection via RCBOs

The manager wants separate DBs in each room so if a room develops a fault it wont effect anything else - RCBOs in main floor DB would do this anyway - separate circuit per room - (1 for lighting and 1 for sockets) - also thinking about discrimination here! - with 30mA RCD in each room.

I need to work out:

• cable size to the main floor DB (from the basement 3-phase supply)
• cable size to the individual room DBs

Each room has:

• 1 kettle
• 2 bedside lamps
• main lamp on ceiling
• 4 sockets in total
• shower is NOT electric

If im not mistaken each room would draw 25A max first thing when someone boils the kettle and using their hair dryer/straightener
Was thinking about a 4mm radial to the 4 sockets and 1.5mm to lighting

Was thinking a 10mm cable from main floor DB to individual room DB (could get away with 6mm as max current would be less than 36A - RCBO in main floor DB would be a 40A)


Not sure about the cable from floor DB to main supply DB - it currently has 16mm T&E installed - not sure if this is enough or would have to be 25mm?????? - thought please

 

[bigbaddave]

That's a big job to be taken on. If its the case good luck to you but if your asking a forum about the design stage then I think you have got your work cut out.

 

[Guest55]

Nic have you ventured into doing this work? If so have you come up with?

Sent from my GT-I9300 using Tapatalk 2

when the client sees the price of putting 2 DB's on ever floor and 1 CU per room and 4mm radials i think the project ( or contractor ) will be binned ;-)

 

[Knobhead]

Note to Nic Re you're PM. Nothing to do with me this time!

 

[Knobhead]

when the client sees the price of putting 2 DB's on ever floor and 1 CU per room and 4mm radials i think the project ( or contractor ) will be binned ;-)

You forgot the 1000KVA 11/.44KV transformer!

 

[DPG]

Am I missing something here? The OP wasn't Nic. Not where I'm looking anyway.

Daz

 

[Quinnysparks]

Most the hotels i've tested usually have 1 DB supplying 2 rooms, located in the riser between the 2 rooms. Usually fed by a 10 or 16mm T+E, protected by a 32 or 40A MCB back at the sub board on the same floor. Never seen a sub board supplied by a 16mm T+E. They're usually a 25mm SWA at least. Good luck!

 

[Knobhead]

Am I missing something here? The OP wasn't Nic. Not where I'm looking anyway.

Daz

Mr. Owen AKA Spazz is like Walter Mitty. A figment of his own imagination.

Not that I’m suspicious but I think someone is trying (unsuccessfully) to distance himself from his more bizarre posts.

 

[DPG]

Ah, yep - with you there Tony!