3ph Mot bay - advise much needed!!

[spark-ticus]

Hi all, I would like some advise on a job i am about to undertake, A large industrial unit being used as an mot garage with an incoming 3ph supply of 63A. The client has ramps and testing equipment which totals 97A (this is adding together the various A ratings printed on the motor plates of each piece of equipment) along with a ring final circuit and a good chunk of flourecent tubes this puts it at well over 100A. Im not sure of the diversity allowance on this kind of install but i know all machinery will not be used at the same time. I think Its going to be a case of having a bigger supply fitted but would like to know how to put the wheels in motion and how big i should/can go

Thanks in advance guys an gals

 

[spark-ticus]

......sorry that was supposed to say "Do all of he conductors need to be SWA or can i use the appropriate sized flex.? I will be Using cable tray swell

 

[Lucien Nunes]

the 97A is across all 3ph not per Phase,

I have ascertained all these A values from the motor plates

As i have 63A on EACH phase can i to some degree divide my 97A by 3 as it is shared across the 3 phases ?

These don't hang together. The fact that you are looking at figures with all three phases added makes me think Davesparks is right and you should work through this project with someone experienced in machinery and motor installation, who can fill in some of the blanks and help consolidate your knowledge base regarding 3-phase theory etc. There may be other aspects to consider, such as permissible voltage drop when starting motors, which are difficult to advise on without being on the spot and having all the data.

Personally I bet the whole place would run off a 32A supply so long as the voltage doesn't sag too much when two people hit their up buttons while the third is taking a spin on the rolling road.

e2a:

Do all of he conductors need to be SWA or can i use the appropriate sized flex

Surely you would use whatever type of wiring system the circumstances require? CY, SY, MIMS, SWA, any or all might suit depending on a bazillion factors we can't tell from here...

 

[Simlec]

......sorry that was supposed to say "Do all of he conductors need to be SWA or can i use the appropriate sized flex.? I will be Using cable tray swell

This is going to be one well spec job this.. Flex supply's in a workshop.. Love it.
Save your self some pain and get a local electrical contractor in.

 

[ian.settle1]

With comments like you have made above you won't be here much longer.

From your previous questions it sounds as if you don't know what your doing as you are clearly out of your depth here.

 

[Knobhead]

I didn’t realise you could get banned for incompetence, what else has our OP done?

 

[GMES]

I didn’t realise you could get banned for incompetence, what else has our OP done?

I was just thinking the same tony, he must have got a bit naughty judging by Ian's comment in post 19

 

[Engineer54]

I didn’t realise you could get banned for incompetence, what else has our OP done?

You must have only just missed it Tony... Came back at Simlec with a barrage of abuse, ''strangely'' that post now looks as if it has disappeared. ..lol!!

 

[Knobhead]

Oh well, I’ll just have to find someone else to have a go at.

 

[davesparks]

......sorry that was supposed to say "Do all of he conductors need to be SWA or can i use the appropriate sized flex.? I will be Using cable tray swell

Is be looking at steel conduit/trunking for a start from scratch job like this.

But then I was taught to do a job properly to a high standard!

 

[Engineer54]

Is be looking at steel conduit/trunking for a start from scratch job like this.

But then I was taught to do a job properly to a high standard!

Agree, a metal containment system would in my opinion be a must in such an environment. Ideally underfloor to supply the ramps and brake testing rig.... Trouble is, most electricians these day's only consider SWA cable...

 

[davesparks]

Or Flex as it appears here!

Underfloor probably won't be economically possible in a rented industrial unit, but it is possible to feed most ramps from above (if you use a bit of common sense about where you make the drop)

 

[telectrix]

SWA with the drops on strut (and maybe tray) would be my preferred way

 

[camerabloke]

Wet string would be the ops

 

[snowhead]

Wet string would be the ops

Bit over the top that.
Could be wet Cotton thread.

 

[davesparks]

SWA with the drops on strut (and maybe tray) would be my preferred way

Why do you day SWA?

Steel pipe/trunking gives better mechanical protection, and is much easier to add to when the inevitable changes are needed down the line.