Large site supplies

[kp1]

Hi all, new to this forum thing but thought I best join up as I am starting to do bigger work and need confirmation at times I am doing thing OK without being OTT.

I have some lights to wire up on a sports field, it measures 90 x 60 M and the incoming supply is some 130M from the nearest corner.

I have calculated voltage drop and was coming up with 70mm supply to the corner then going off in 25mm, but this was just for the lights.

Now the guy has said he might be building an office with electric needed. I saw the plans for this for the first time today and it's a bit bigger than I expected and has electric heating!

Re calculated and am getting 95mm supply cable (130M run) and a 70mm to office (90M run).

Calcs: 130(M) x 50(A) x 0.43(V) = 2.795 volts dropped to first dist point

90 (M) x 50 (A) x 0.57 (V) = 2.565 volts dropped to office position

Is this looking sensible as it seems mad that these are the cable sizes and he didn't like the phone call to say the cable bill alone has gone up by a lot?

Thanks for any advice.

 

[NozSpark]

Get him to ask his DNO if they will move his supply.

I'll bet he likes your price a lot more then

TBH it sounds like this should have a 3ph supply

 

[kp1]

Get him to ask his DNO if they will move his supply.I'll bet he likes your price a lot more then

TBH it sounds like this should have a 3ph supply

Thanks for the quick response.

The site has a 3 phase supply but the building I have worked out on a single phase supply as its a per fab with the circuits already done and as far as I can work out its all single phase.

 

[Andy™]

what about the lighting? run that on TP?

 

[adammid]

I am doing a similar job. I would suggest installing feeder pillar on the sports field to reduce the long cable runs. Are you feeding each light seperately are are you putting a number of them on one circuit. Id suggest feeding this on Three phase as you could unbalance the phases with your extra loading.

 

[Steve3948]

Don't make the mistake a contractor made a few years ago at our local football club.

He installed all new football flood lights, all connected and ready to go, only to find out the supply was not man enough, and DNO needed to put bigger transformer in to allow for additional load, just

 

[NozSpark]

I am doing a similar job. I would suggest installing feeder pillar on the sports field to reduce the long cable runs. Are you feeding each light seperately are are you putting a number of them on one circuit. Id suggest feeding this on Three phase as you could unbalance the phases with your extra loading.

Equidistant from each corner???? ; )

Right on the centre spot:O

 

[adammid]

Haha, sorry just re-read my post and it does sound confusing. I would suggest installing feeder pillars to prevent long cable runs. Ie. main dis board in line with corner flag, one level with half way line and another one level with the far corner flag. Although that will depend on number of lights, length of runs etc. if its one pitch then more than two dist. Boards will not be needed. I'm doing a very large car park and installing 3no. Dist boards as the cable runs would be so long if fed from one board.

I heard if similar things happening before. Bit harsh for the contractor, it's not his fault the supply wasn't big enough. The football club would still want the lights. Understandably the contractor should have assessed the existing loading and supply and provided recommendations, however if the club wanted lights, they wanted lights and thus should have paid for the transformer upgrade.

I did a job on a domestic house, it had a 50amp fuse and the customer who was a builder (know it all) wanted extra storage heaters and an electric shower. I checked the supply and found the 50amp fuse. I said it wasn't big enough and the builder got upset saying that i was wrong and he had seen lots of houses with electric showers and storage heaters.lucky for me, without warning and I emphasise without the extra loading connected the 50 amp fuse blew randomly (prob due to it being old and 'tired' and the DNO came and upgraded. It was one of those 'I told you so' moments. Haha