DNO Supply Question

[dominicbatty]

Hi there, I was wondering if I might be able to call on the knowledge of someone with experience of three phase mains supplies from our energy provider. We are a sports club looking into the possibility of installing some new floodlighting around our pitch and are currently in the very early process of understanding what supply we have and what we might be able to achieve if we needed to. I am led to believe that we have a 95mm DNO, 3 phase supply cable terminated into 150 amp DNO fuses supplying our clubhouse. What I am trying to understand is (assuming for a moment our local sub-station could supply as much power as we needed), what the maximum load that the DNO would fuse a 95mm cable into our building with. The reason I'm asking is that once we have established what we need in terms of additional power and what we have in terms of current supply then if it means this would result in having to change the supply cable into the main club, this might be an immediate nail in the coffin of our project as the cost of changing this main supply cable would be prohibitive. I'd be really grateful with someone with knowledge of distribution helping me out with this. Regards, Dominic.

 

[snowhead]

I think you'll find that once the DNO start quoting prices for upgraded supplies you'll find you can install a generator cheaper, just for the floodlights .

 

[dominicbatty]

Hi snowhead, thanks for that, I'm also looking into that possibility. The issue is this, I need around 100 amps per phase for the lighting project. At the moment the 150 amp DNO supply splits to a 100 amp fuse for the club and a 63 amp fuse for a pavilion. The club barely pulls 60 amps at its highest load and I accept someone will have to do a diversity test and all that stuff and the pavilion pulls 20 amps with everything on. So lets assume in simple terms the load is currently 80 amps, I therefore have about 70 amps of capacity in the supply. The cable terminates in a 200 amp cut out but is fused at 150 amps so if the cable could support 200 amps, there is capacity at the sub station then I might just be in for a fuse upgrade as I might only be looking for another 30 amps of headroom. However, if the 95mm DNO cable won't support 200 amps I'm stuff before I start as a new sub-main is a defo non starter.

 

[nick611]

just finished a job with 95 mm supply cable . they gave me 185A PER PHASE. HOPE THIS HELPS

 

[dominicbatty]

Nick, that is really interesting, many thanks. Could I ask, was it fused at 185 because that is what they asked for or do you think that is probably just a standard they tend to adopt for this size of cable?

 

[mechelec]

You would not get 185A fuses as these are non standard. 95 wavecon buried direct is good for approx 200A and will give you a 138kva supply. Get in touch with the DNO the network may be good for only 100A or it may be good for 200A. It may just be a case of changing fuses and signing a connection agreement for the required capacity.

 

[dominicbatty]

Hi mechelec, I'll give that a go, thanks for your help on the cable. I started with the DNO enquiry line which was like wading through treacle, but now I've got a bit more info I'll go back to them and see how I get on. Thanks to everyone for their assistance, really appreciate the advice.

 

[Engineer54]

Be prepared for your clubs lecky bill to go through the ceiling if you are presently only pulling 20A...lol!!

Where are you getting this information you're posting here from?? The club really needs to get a professional on board, someone that can conduct an on-site assessment of your present installation along with planned future needs and supply requirements. They can then also communicate with the local DNO on the club's behalf. Trying to self assess and deal with the DNO (even if you do manage to find the right person at the DNO to talk too) on your own, is putting it not too bluntly, Very Foolish of you!!

 

[Paultrim123321]

You are talking about the DNO supply here and not a 95mm from your local sub DB? If the 95mm is to the DNO cut-out then I would imagine if THEY needed to, they would put 300Amp fuses in if it saved them money. They're interpretation of current carrying capacities and BS7671 guide for current carrying capacities are two wildly different things!
Here's the conversation;
You: I need a 200A supply
DNOk, well we need to do some calcs, more calcs, alter supply characteristics etc etc that will cost you £kkkkkk and our engineer will be along to replace 150A fuses with 200A fuses.

As has been previously posted, this will come down to generator costs outweighing DNO fuse replacement costs.

 

[Guest55]

theres no way the dno service cable is 95mm to a sports club that uses less than 150A.
they could do that with a 35mm cable.
check again with your network operator for the max available demand from the existing service.

and as for an extra 100A per phase needed for pitch lighting , well thats an awful lot.
has an electrician produced a design current for the proposed installation ?
if not then you could be asking for alot more power than you actually need , and paying un -neccesarily for the privilage.

 

[driverman]

theres no way the dno service cable is 95mm to a sports club that uses less than 150A.
they could do that with a 35mm cable.
check again with your network operator for the max available demand from the existing service.

The DNO could of installed 95cne cable. If when sports club was built the expected loading was not known, they might of decided to put in cable large enough to cope. It's done in many industrial units whereby 3 Phase installed but only 1 Phase used.

If DNO's cut out fused at 200amp, discrimination will be required.

 

[Guest55]

discrimination with what ?
theres no requirement in bs7671 for protection devices on the consumers side to discriminate with the dno service fuses.

 

[driverman]

discrimination with what ?
theres no requirement in bs7671 for protection devices on the consumers side to discriminate with the dno services fuses.

i did a job fair bit back like above my fuses were 200amp same as DNO (lecky Board then). Was told to down size mine.

 

[Guest55]

and what did you downsize it to ?
because to achieve fault discrimination with 200A bs88 fuses , youre going to be limited to around 130-140A as the maximum sized protective devices on the consumer side.
which makes it pointless getting a 200A supply in the first place.

 

[mechelec]

and what did you downsize it to ?
because to achieve fault discrimination with 200A bs88 fuses , youre going to be limited to around 130-140A as the maximum sized protective devices on the consumer side.
which makes it pointless getting a 200A supply in the first place.

Agreed, you will rarely achieve discrimination with DNO fuses.