Some Advice Needed Please

[switch10]

hi all, im looking for some advice,  I have been asked to do a rewire on a 1st floor unit consisting of 7 offices and a communal area which has a small kitchen and toilets.

the job is over 150miles away from me so only in discussions with the customer at present and pictures they have sent me and details from there records.

right there was 3 fuse boards feeding this area and now they would like the following.

1 x new consumer unit in communal area (others are old wylex and would be in offices so all coming out)

there is only 2 x sockets and 2 x lights in each office (they do not want any more, which is strange)

couple of sockets to be installed in communal area with small kitchen area.

now my problem is this.

1.  1 of the old fuse boards were fed from a 3 phase db from a 63 amp mcb

2.  1 fuse board was then fed from the above fuse board

3. the last fuse board was fed from meter to a switch fuse with fuse rating of 60amp, then from there 20 meters to the consumer unit in 16mm twin and earth.

now what would you guys recommend I do for this?

get the switch fuse upgraded and then run armour to new consumer unit location? as its approx. 30meters away from the meter? this would be run up a box section to then above suspended ceiling to consumer unit? what size armour 16mm?

the owner has asked for fuse board configuration to be  a socket & lighting circuit for each office and then same for communal area.

so there would be 8 socket circuits & 8 lighting circuits

I look forward to some advice on this,  I am hopefully going to be able to drive to look at the job in next week or so , but at present my partner is pregnant and baby due any day so been trying to discuss as much with out driving there so i'm local if my partner goes into labour.

 

[ProDave]

Small 3 phase DB at the origin feeding submains to remote DB's as appropriate.  Sounds like there is a 3 phase DB there already so you might be able to just use that.

If there are no 3 phase loads anywhere then just single pole mcb's in in the 3 phase DB.  Use appropriate cable and installation method so you don't need rcd protection of the submains e.g SWA, surface in trunking etc etc.

 

[switch10]

thanks for your reply pro dave.  unfortunately the 3 phase board that was feeding one of the existing boards is now in a completely different location.

there is only going to be 1 consumer unit to feed the 7 offices,  and the supply is required to be brought from the meter ..  this is where I need advice.   hard with out seeing it to be honest, the offices aren't even that big from there meausrements given, and with only 2 sockets and lights not very much power will be used per office.

 

[Andy™]

 and with only 2 sockets and lights not very much power will be used per office.

except in winter when it gets cold and all the staff bring in their own 2kw heaters in each office..

 

[switch10]

Possibly but there is gas central heating in all offices

 

[Evans Electric]

Not the easyist thing to help with Switchy without seeing the job or drwgs.   Suggest you talk to client and work out the estimated load requirement .  Economics these days often dictate that you would take the Gas heating as a given and design accordingly .

If they plug in 300 x 2kw fan heaters the fuse blows ....shytte happens .  

We are not far away from energy saving  government  power cuts apparently ....so as all businesses & commerce enter the digital age , we find we don't have the energy to power it all  :C  

Back to the power cuts as we had before ....no petrol 'cos theres no pumps working ...........queue at the filling stations near the hospitals as they never went off. 

Building site suddenly plunged into darkness .....usually in the afternoons ........ bodies piling up at the morgues as the crematoria were off power.

Can't remember now if it was the Miners striking , the power workers or an energy crisis .  

Early 70s they issued petrol coupons ( which I still have somewhere)  and announced that there would be no petrol left in 10 yrs .

There we go again ..................OFF TOPIC !!

 

[switch10]

What would you suggest then? Only single phase supply present? Open to suggestions

 

[Evans Electric]

Well the expected load is'nt much really at 2 plugs per office and a light .  Not sure why he wants a seperate circuit in each office ...you could probably put the lot on one circuit if you had to .

 A guess at  8 PCs  & printers  , a fridge and a kettle .  

8 fluorescent fittings  . 

So two power circuits and two light circuits .   WHy would you want 16 circuits in a place like that .?

A 60A  SP supply is avaliable you say , so stick a 10way  board on the end of it  and down the road like a couple of big dogs.  

All without seeing the job and discussions with client of course ,

Any jobs not local ( you say 150 miles )  can be problematical if theres call backs of course , but I'm sure you know all that .

 

[switch10]

The suppliers fuse I have been informed is 100amp , but I'm unsure as there's a 60amp switch fuse after this. I appreciate your advice and understand it's hard with out seeing the job, same as what I am having trouble with. Also meter being 30 metres away from where customer wants consumer unit.

Unsure why customer wants each office on own circuits is a odd one to me but what he has suggested. And doesn't seem to want to budge when I suggest even putting 4 offices on one and other 4 on another

 

[Evans Electric]

I'd suggest he doesn't really understand what a "circuit" means .   Unless he wants to meter each office seperatly for whatever reason .

Tell him  it will cost 8 times as much .....utterly stupid to have all those circuits .....unless theres some reason we don't know that they are not all in an open plan office anyway. 

 

[switch10]

I believe it may be to meter each office eventually as I know one of there local branches do similar. Not certain though . Will hopefully be speaking to them tomorrow and will find out more.

 

[switch10]

Ok bit of a update on this after a conversation with the customer for the last 40 minutes.

The offices are not open plan.

Right you enter through a communal corridor then off this is all 7 independent offices each to be rented to different customers. Then a communal area with few chairs and small kitchen area.

The customer plans to in the future sub meter all offices, however will not do this now as a customer may wish to take on more than one office .

So we have a single phase supply .

60amp switch fuse after supply

Then. Customers wants 7 socket circuits

7 lights for offices then a further lighting and socket for communal.

What would you guys suggest?

I have informed customer this will be a dear way of doing these works but he's not bothered about that. Just wants it installed like this.

Could the 60amp switch fuse be upgraded and then mains run from there to large consumer unit? Or would you advise against it?

This is a quick drawing maintenance man has just sent me via txt so not the best

 

[switch10]

Drawing keeps failing to upload sorry

 

[NozSpark]

How are you going to meter each unit if they each have 2 circuits fed directly from the main DB?

They'd be better off running submains to local dbs and then you could meter the submains... Or just run 20A radial ccts to 2 x fused spurs (local) and run the lighting and sockets from there....... You could then use din rail meters in a double stack enclosure with the OCPDs above/below..... I'm sure SBSdave could knock something up

 

[switch10]

Forget this, area manager has called me and said he is happy to have 2 circuits for lights and 2 socket circuits , will certainly make my life easier

 

[Adrian]

how about emergency lighting and fire alarm are these not required

data, telephone ?

 

[switch10]

Fire alarm and emergency lighting already in off a communal fire alarm panel and fuseboard