various commercial questions

[MTI]

hi all, been asked to do various works within an office which is part of a multi-story. Please can anyone advise on the following questions? i do have my own judgements but would like to see what you all come back with. This will also help my confidence in what i have told the client. Thanks in advance!

1) open plan office existing m/c c.u. is full and new circuits are required. The new loads are not expected to be massively high. Would you change existing board (10 way) to accomodate new circuits or will i get away with a second c.u.? Hoping to keep costs down and minimal disruption and not have to replace existing m/c c.u. as it serves computer servers etc currently.

2) If second c.u. is fitted, should i remove and extend a lighting circuit/air con unit into new board and feed new board from existing newly made spare way?

3) existing board is m/c and fed via s.w.a. sub from basement. if feeding new board off existing board spare way, what size breaker, tails and incomer on new board?
Dont want to have leave client with a very small incomer on new board really, although new loads not massive but could be added to later obviously.

4)patch panel cabinet-can anyone advise of a 'typical' load? may sound daft but premises is empty and not accessable for a few days now and would help for sizing new s.w.a. feed to it. surely it wont be massive load? cabinet is approx a 2m cube and approx 1 meter high if this helps.

5) will patch panel earthing be o.k. if fed by seperate earth from new c.u.? currently not earthed but obviously wants it if serving IT equip. what size earth too please....10mm or 16mm?

6) am i ok to use top and bottom of 3 compartment dado for cat 6? both empty and dont see why not. phones will be over IP too. also, how many data cables will fit comfortably in each compartment taking into account internal and external bends? ill have a search online but be helpfull if anyone does this often.

BIG thanks in advance guys and sorry to ramble on! may be a few more questions soon as i need this quote done today cheers!

 

[sparks1234]

hi all, been asked to do various works within an office which is part of a multi-story. Please can anyone advise on the following questions? i do have my own judgements but would like to see what you all come back with. This will also help my confidence in what i have told the client. Thanks in advance!

1) open plan office existing m/c c.u. is full and new circuits are required. The new loads are not expected to be massively high. Would you change existing board (10 way) to accomodate new circuits or will i get away with a second c.u.? Hoping to keep costs down and minimal disruption and not have to replace existing m/c c.u. as it serves computer servers etc currently.

2) If second c.u. is fitted, should i remove and extend a lighting circuit/air con unit into new board and feed new board from existing newly made spare way?

3) existing board is m/c and fed via s.w.a. sub from basement. if feeding new board off existing board spare way, what size breaker, tails and incomer on new board?
Dont want to have leave client with a very small incomer on new board really, although new loads not massive but could be added to later obviously.

4)patch panel cabinet-can anyone advise of a 'typical' load? may sound daft but premises is empty and not accessable for a few days now and would help for sizing new s.w.a. feed to it. surely it wont be massive load? cabinet is approx a 2m cube and approx 1 meter high if this helps.

5) will patch panel earthing be o.k. if fed by seperate earth from new c.u.? currently not earthed but obviously wants it if serving IT equip. what size earth too please....10mm or 16mm?

6) am i ok to use top and bottom of 3 compartment dado for cat 6? both empty and dont see why not. phones will be over IP too. also, how many data cables will fit comfortably in each compartment taking into account internal and external bends? ill have a search online but be helpfull if anyone does this often.

BIG thanks in advance guys and sorry to ramble on! may be a few more questions soon as i need this quote done today cheers!

Well what a lot of questions and I will do my best.

first thing with the consumer unit change is be sure of your final loading, if you are happy with that then I would try to move smaller loads to a sub-board off the original if you need to keep the cost down, could you install a 4-way board so they cant keep adding and say put the lighting on it, feed it with a 40 amp MCB and some 10mm.

Cant help you too much with the IT stuff but I would allow a 10mm to earth it down, that will also give it some mechanical strength

 

[Darkwood]

When you are estimating for future use i.e. them premises is empty you have to assume the worse case and in the case of the Patch panel bond it as you have to assume it could have 10mA leakage or more, so as SPARKS 1234 says bond with a 10mm earth.
Feeding fuseboards off spare way in a fuseboard upstream is bad practice as standard mcb wont give discrimination between each other under fault conditions so if you have a short circuit on lighting or socket circuit on new d.b. its may trip a 40a or 63amp you fit in the spare way. Always where possible tail up to meter or seperate isolators where discrimination can be achieved through hrc fuse, this will ensure no nuisance tripping of dist' board supply. This is the reason why some sub-main supply cables seem to be well above requirements and over the top but all it is is that its designed with dicrimination in mind.