This might be fun

[sparks1234]

I have been asked to quote today for a new sub-main, it is to feed a computer room. They want a new feed back from the incomer as there are machines off the rising main. Now, they have asked for 100 amps single phase. So far so good, I asked what are they actually going to pull, load wise and the reply was to allow for 100 amps. Now the problem, the intake is (they reckon) 250 mtrs away. Now on our calcs that would equate to a 120mm cable to get within the volt drop etc, thats not easy getting into a 8 way consumer unit.

Any comments would be appreciated. I do appreciate that the information given to me were from computer bods that have no comprehension of what they are asking for.

 

[bugsy]

Run it to a mccb minipak ( merlin Gerin ) with speader box the to c.u
They will ( if they've got any sense require clean earth , clean earth bar with disc link in comms room ,
Run Basket at high levei with commando plugs, drop down to racks with power bars, - what about UPS?

I think I might of got a bit carried away!

 

[lloyd1980]

not much experience with what your describing
but could you not step the cable down near the 8 way you need to install, via some industrial switchgear. you know the grey panel with the black handle you turn 90 degrees to open the door.
then from that wire in the cable that supports the current that is expected to flow (100amps) - if you believe the geeks and dont take into account diversity
then straight into the 8way

your cable only needs to be that enormous size due to length and volt drop, once through that switchgear it will be less than a meter away from the 8 way board so a smaller cable would be sufficient.

hope this helps u dude

this is only in my opinion by then way and i would check with nic, as I said I dont have much experience in this although this was the first thing that sprung to mind

 

[pennywise]

Why not run a 3phase supply anyway, then you could get away with a smaller cable.

 

[sparks1234]

Why not run a 3phase supply anyway, then you could get away with a smaller cable.

I had suggested it but I think they are wanting to keep it on the same phase for whatever reason,

We looked at 95 mm to start and 250 mtrs of that comes to best part of 5K so this is going to be a bundle for the completed job

 

[pennywise]

You could put a small TPN panel board as Bugsy mentioned and then come off with single phase to the smaller CU Then it's still on one phase.

 

[Guest123]

I agree, if theres 3P available then use it. Run a sub-main to a new panelboard if need be and single phase CU's run from there.

 

[sparks1234]

I agree, if theres 3P available then use it. Run a sub-main to a new panelboard if need be and single phase CU's run from there.

Really cant see the point in that?
Why bother to run additional cores you dont need? also you cant come off a normal 3-phase dis board at 100 amps.
i might as well make the SWA off into a 160 amp isolator (to get cables into) and reduce down to 25 mm into consumer unit

Sorry. just read that you had put panel board (meaning MCCB) board
I can see where you are coming from but still think its OTT for what is required

 

[pennywise]

But it may still cost less than the cost difference between 95mm 120mm. Costs were what I was thinking about just to get the job.

 

[bugsy]

The IT networking geeks have a few weird theories when it comes to 3 phase in comms rooms regarding frequency, mains harmonics etc etc . yes I know

I had suggested it but I think they are wanting to keep it on the same phase for whatever reason,

We looked at 95 mm to start and 250 mtrs of that comes to best part of 5K so this is going to be a bundle for the completed job

The IT guy's won't even blink

 

[High Tower]

I second the motion for TP&N install. How the hell would you possibly balence the phases at the incommer when you are puling 100amp extra on one phase

 

[dufjax]

I second the motion for TP&N install. How the hell would you possibly balence the phases at the incommer when you are puling 100amp extra on one phase

Exactly!

Can't see the problem with TP my self, but I think bugsy might have a point about clean earth.

Jim

 

[sparks72]

Run it to a mccb minipak ( merlin Gerin ) with speader box the to c.u
They will ( if they've got any sense require clean earth , clean earth bar with disc link in comms room ,
Run Basket at high levei with commando plugs, drop down to racks with power bars, - what about UPS?

I think I might of got a bit carried away!

Spot on bugsy.

I used to work for a firm installing comms rooms in London a while back.
Backup generator on the roof, UPS system, 185mm SWA down the riser, etc, etc.
Clean earth is a must for I.T rooms.