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.

 

[Engineer54]

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.

Are you implying here that the installation of a generator and it's overall running costs is going to be a cost effective solution over the DNO's charges for uprating the supply fuses??

If you are, then you obviously have no experience of running prime power generators....

 

[dominicbatty]

Hi guys, thanks for all your responses. Here is a little bit more detail for those of you who have asked some questions of my original posting. I also note a number of criticisms about that I should find an electrician (which we will) and that when I turn we turn the lights on my electricity usage might go up (yep, understand that). A number of years ago, the club upgraded it's supply into the premises when it installed a new hockey pitch with a plan to provide enough power availability for floodlighting at a point in the future. For a variety of reasons the floodlight project was never done and here we are a number of years later looking at it again. I had an initial enquiry with the DNO some months back before I really knew what I was doing and I sent some photographs of our installation which terminates into a "Lucy Oxford 4MC200 Insulated Cutout" and it was them who told me I had a 95mm cable supplying the building and I also know from historic notes that the supply is fused at 150 amps (DNO fuses) in our premises inside this cutout. The problem is hockey pitch lighting has moved on and the previous power installation may no longer be enough so all I am really trying to establish is whether it might be possible to pull more capacity from the existing supply cable with just a fuse upgrade (I appreciate this assumes substation capacity availability) and I think from the responses I have got they indicate this might be possible without a cable change. Thanks to everyone for the help and apologies for the slightly vague approach.

 

[telectrix]

if we wanted an easy life, we'd all be plumbers.

 

[Richard Burns]

If your original design was a few years ago it was presumably planned with metal halide lamps, the use of high quality LED lighting could reduce your energy consumption by about 10-30% and so may negate the need for an upgrade. The additional initial cost of which could be offset against the need not to upgrade fuses, and the reduced running costs would be significant from an ongoing point of view.

 

[Engineer54]

You really need to know what the loading is going to be for this proposed hockey pitch lighting. So a design needs to be put forward and accepted, that meets whatever association governs hockey these days. (if this hockey pitch is to meet official minimum standards) Only then will you have loading figures that are going to mean anything as regards assessing if your present supply is adequate for it's intended purpose!!

So do you have a suitable club pitch lighting design in place as yet or not??

 

[dominicbatty]

Hi RichardBurns, the supply over to our pavilion was put in to handle up to 63 amps per phase as the requirement, 15 years ago for hockey pitch lighting was much lower than it is today so we definitely don't have enough capacity in the existing cable but thanks for the suggestion.

 

[dominicbatty]

Hi Engineer54, I have a full lighting design from Philips, and I know the power requirements for both designs, 350/500 lux and for the lamps that are required so I'm well on my way with regards to that side of things, this power side is a steep learning curve but I'm getting there slowly. The problem with this sort of thing is the power side of things might make it or break it depending on availability of power and the cost of any change on the DNO side.

 

[dominicbatty]

Could someone answer me this. I'd just like to point out I'm enquiring so I can understand this whole thing better, I am fully aware this will all have to be re-done by suitable electricians and such like but getting good advice in the very early stages of grant funded applications is quite difficult hence why I'm leaning on a potentially helpful sole on these forums at the current time. The total power requirements of our project would be 28 x 2119w lamps, where each lamp is connected to 2x power phases. This results in a total load of 59.33 KW to achieve 500 lux lighting levels. We also have an option for 350 lux lighting levels using 20 lamps of the same type giving a total load of 42.38 KW. What I would like to know is what current per phase is required to support this project and what would this also be in KVA. If I have not supplied enough information then please let me know.

 

[Engineer54]

As R, Burns has stated above LED light fitting may be an option, but in any case a reappraisal of the overall lighting design for your pitch should be conducted. Things change over a 15 year period, especially as the trend these days is more and more towards lamp efficiencies etc...

 

[dominicbatty]

Hi, sorry I should have been more clear, the lighting design is brand new and based on modern standards. I've investigated LED lighting but it's not a viable option which would have been great in power terms. We're talking about lighting a 100m x 50m space to 500 lux and from the people I have spoken to who do this for a living, LED is not quite there yet.

 

[dominicbatty]

Aha, so Scottish Power got back to me today we are on a 95mm waveform cable and this can be moved to 200 amp fuses by just changing the fuses. 246.77 + VAT, great result. The one thing it does state is our requirements, one of them being "Provide interconnecting cable of an approved type between the termination equipment and your main switch gear. The cable size shall not be less than 25sq mm copper and must not exceed two metres in length". Does 25mm square sound enough for 200 amps per phase?

 

[Darkwood]

Your getting confused here the 25mm is the minimum by regulation not the size they are suggesting, you are at a stage now where you really need to get a competent Electrician on board with experience in commercial and industrial circuit design, ensure that this is there field and you don't get a souped up domestic electrician out of his comfort zone, there are too many questions to ask and info you need to provide us, a simple missed bit of info can be vital to a correct install.

Comments regarding discrimination earlier between consumer and DNO are usually not an issue as long as your fuses are less than or equal to theirs... normally we fit type II fuses where the DNO will fit type III or IV.

As the incoming N on the DNO will be possibly combined with Earth you will need an Electrician to establish that any consumer cabling upgrade is correctly done regarding the Earthing system

The original question seems to have been answered by yourself through enquiry but TBH this was the only way it could have been done with liaising with DNO as you will have been allotted a set KVA for which you will have a standing charge, if your supply was upgraded yrs ago without the alloted KVA set it could be the case they could turn around and say the supply upgrade isn't available and a very high cost of a new sub-station may have been on the cards, if you were marked up for your alloted KVA when supply was upgraded then you have been paying over the odds for your standing charge but safe guarding your KVA reserve within the local network.. this seems to be the case or you have been lucky that your requirements were still available in the local network.

We could ask you question after question and still miss crucial info as we would need to see the physical set up. I can appreciate you questioning for groundwork but this will all be normally done by your contracted electrician so don't get too involved or misunderstood info or incorrect spec's you provide may be costly and we aint talking a few quid here... we could be talking the whole cost of the install down the drain... ive seen this happen before.

 

[driverman]

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.

To be honest, I left them in. Never had any problems.

 

[Engineer54]

Modern daylight robbery being practiced.... £250+ VAT to change out 3 cartridge service fuses. Now that's what you call a profit margin!! lol!!

 

[Knobhead]

Sounds reasonable to me

 

[Guest55]

Sounds reasonable to me

agreed.
to be honest , the replacing of fuses is neither here nor there.
what you are really paying for is authorisation / approval from the dno to increase your max available supply.

so to get 200A for under £300 is actually pretty miraculous lol.

 

[mechelec]

Sounds reasonable to me

Totally agree. It is not just a site visit to change fuses. A study on the network capacity will need to be undertaken before any increase in supply capacity can be agreed. A connection agreement will be required (depending on DNO) which takes time to generate. It may seem a lot of money to change 3 fuses but there is a considerable amount of time required before that is carried out.

 

[Engineer54]

I understand what you're saying, but the processing work within the company is being carried out on a day to day basis as a matter of course anyway. It's not going to cost the company a penny in any additional costs.


I don't think i've ever seen a reasonable costing to any work the DNO's quote for. It's just that we've all been brainwashed to expect extortionate figures!!

 

[Knobhead]

Sorry E54, we’re both “old school”

It has to be done therefore it will be done to my book.

To be honest costing a job hasn’t figured much in my life..
I want, I get!.
The joys of multinationals!

 

[Engineer54]

Sorry E54, we’re both “old school”

It has to be done therefore it will be done to my book.

To be honest costing a job hasn’t figured much in my life..
I want, I get!.
The joys of multinationals!

It's all down to what i have always called ''Creative Accounting'' with these large utility companies...
They make the fee's up as they go, and according to what they think they can get away with, depending on client/customer status they are quoting. ...lol!!