Service cable, service head, meter tails

[Sharpend]

Pleased you said that  this is with/through the UKPN. 

Can I ask do they insist on an isolator prior to a ryefield or the like, only I have been reading up on their document which says that they strongly recommend the use of one, although the field manager we are dealing with says its up to us, the original document that Tony linked to suggests it's not necessary? So a little confused. We have also be spec'd to use a ryefield which is designed to fit straight on top of service head so would look pretty rubbish with isolator in between? 

Any suggestions? 

 

[leesparkykent]

We fitted the fused switch and do so on every block that we do to give a single point of isolation for the whole building. Off the top of my head you would need a single point of isolation to meet some of the requirements of chapter 53 from bs7671 point of view . I did think the DNO insisted on it as well and give you the option of either fitting a fused switch or isolator but could be wrong. Imo though I think it would be prudent to do so. I'll take some pics of the room I done when I'm there next. To give you some idea the service head come in on the left hand side of the wall, trunking on top of service head which ran to the right hand side of wall. Fused switch on top of trunking to the right of service head, T in trunking to right of fused switch which then comes down the wall then sweeps to right which the ryfield is sat on top off and butted up to trunking running along the top and the bit that comes down the wall from the T piece. Meters and switch fuses on top of trunking above ryefield. Tri rated from service head to fused switch and from fused switch to ryefield. Obviously paxolin used between slots in trunking and service head, ryefield, fused switch, etc.

 

[Sharpend]

Thanks lee most helpful, is it necessary to have so many fuses? Are they discriminated? Wouldn't a standard isolator be acceptable after the meter given that the ryefield would all be fused, don't see how a fuse after the meter is going  to do much unless it's a lower rated one than the ryefield? We are pushed for space on the cupboard that's been built. 

 

[SLIPSHOD & SLAPDASH]

We haven't done any flats  mains for at least 18 months now, but UKPN never wanted any switchfuse, I was told to stop tampering. Also Bs7671 does not come into the equation as this will all  be beforevthe meter.

 

[Sharpend]

Ah not quite slips. 

Have a read of the document and you will find that the dno responsibility stops at the service head unless agreed otherwise, then the rest is to be compliant with bs7671, the meter is still metering responsibility. 

Page 6 https://library.ukpowernetworks.co.uk/library/en/g81/Design_and_Planning/Planning_and_Design/Documents/EDS+08+-+0118+Supplies+to+Multi-occupied+buildings.pdf

 

[leesparkykent]

Thanks lee most helpful, is it necessary to have so many fuses? Are they discriminated? Wouldn't a standard isolator be acceptable after the meter given that the ryefield would all be fused, don't see how a fuse after the meter is going  to do much unless it's a lower rated one than the ryefield? We are pushed for space on the cupboard that's been built. TBH it would pretty hard to achieve full discrimination in this situation. The ryefield gets sealed up by the meter operator as its before the meters. For this reason we have been installing switch fuses for the distribution circuits to each flat. But I do get your point and due to the lack of full discrimination I couldn't be sure what fuse would go first lol. The ryefield has 100A fuses and the switch fuses are 60A fuses so there is at least partial discrimination.

 

[Sharpend]

Therein lies our problem. The electrical engineer that's designed all this tosh has asked for a 100A tpn service to supply four modern all electric flats (inc Ashp's) and landlords supply- go figure, stop laughing, thus giving a cheeky max 60a per flat so ryefield is 60a fuses. 

The best bit is that UKPN have told us they can't upgrade it to 200a incomer- but it's alright as the electrical engineer told us with diversity it'll be alright. 

Thoughts! 

 

[leesparkykent]

hmmm....are there electric showers or they off the cylinder/heat pump? What KW are the hest pumps out of interest?

 

[Sharpend]

Showers off heat pump/cylinder which has solar thermal supply too. 

Ashp are 8kw, the induction hob is 11kw, then there's the 3kw oven, 3kw microwave, electric underfloor heating, electric towel rails, dishwasher, wash mach, 

now I appreciate there is diversity which will drop it quite a bit, but I was thinking more winter when the Ashp will be at full operation, family Christmas cooking, even the Sunday roast. 

I suspect it will all work just busy periods may be heavy pull. 

 

[leesparkykent]

yeah the designer may well be pushing his luck. Just hope they don't have all the family over for Xmas, cooking dinner, ASHP running with the under floor heating on