Discuss Max Demand in the Electrical Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

H

hutch6447

Hi all just got quick question 60 A Main service fuse total house rewire worked out tat Max demand using x 0.4 will be 64.8 A just wondering if it might be worth giving DNO a ring to see if its possible to upgrade to 80 A main fuse is it worth ringing?
 
I've never used the x4...use the diversity checks though (even as a Mate to a Spark) I guess it would be sensible for future proofing? Would like to hear how you get on...
 
not until it blows. don't hold your breath. a 60A fuse will happily take 100A for a short while, and i doubt if you'll ever get near that. diversity calculations for max. demand are about as accurate as the luftwaffe bombing. they missed the spitfire factory and hit our chippy, 20 miles away.
 
yeah well that's what I thought but then out the blue he said in future he might be installing a hot tub in the garage now I don't know if he will go through with it but with this in mind might be worth just seeing if I can get and upgrade.
 
Didn't think anyone used the diversity tables in BS7671 these days!! The only one that has any credibility is for cookers... The rest well..... lol!!!
 
Customers say a lot, like 'I'll pay you tomorrow'... :)
I'd worry about it when he installs the hot tub, if it ever happens. At the moment he'll have little interest in paying for the work, but when he's bought the tub and wants the work doing he will be interested then?
 
Didn't think anyone used the diversity tables in BS7671 these days!! The only one that has any credibility is for cookers... The rest well..... lol!!!

Without sounding too wet behind the ears, it's what has been drummed into me by 3 years of C&G...therefore in the 'Real' World of ignoring said instruction would you share what perhaps they should have taught me & I'm kinda waiting for the 'experience' part...All seems a contradiction though, to comply with BS7671 seems I need to rip a couple of pages out as it's worthless referring to?...
 
depends on the hot tub. last one i worked on was to replace a low IR SWA feed to the tub. it was "professionally installed" --- 13A BS1363 plug "fitted" ( and i use the term loosely) on the SWA, no earthing of the armour. plugged into a RCD socket adaptor, even though the circuit was RCD protected anyway. once up and running, it only drew 8A. mind you, it did take 3 days to get warm.
 
Yeah no this is the business this hot tub apparently according to what he say's will have to put it on its own circuit will know for sure when I see manual but I am thinking of getting the main fuse upgraded or enquiring about upgrading it in case he goes for a steam room and sauna lol.
 
and this is probably a customer that fits those goddamawful cfl bulbs to save the planet.
 
I used the diversity calcs for my own house and got 130A including a 9kW pool heater on for days at a time, I could afford it at one time:-( It has run on a 60A fuse for the last 30 years! It has got a bit warm though.
 
Didn't think anyone used the diversity tables in BS7671 these days!! The only one that has any credibility is for cookers... The rest well..... lol!!!

Agreed - I've currently got a new build that according to the official sums comes out at something like 250A after diversity, sitting happily on an 80A DNO fuse being fed from a 16kW pole transformer!
 
Without sounding too wet behind the ears, it's what has been drummed into me by 3 years of C&G...therefore in the 'Real' World of ignoring said instruction would you share what perhaps they should have taught me & I'm kinda waiting for the 'experience' part...All seems a contradiction though, to comply with BS7671 seems I need to rip a couple of pages out as it's worthless referring to?...

No quite right Claret if that was how your were taught then you are right in questioning why ................ personally I would think diversity is something that is impossible to teach.

I assume your talking about Appendix A in the OSG when dealing with diversity, and if you read the the cover page to this appendix you will see the IET take pains to tell you that

'The information and values given in this appendix are intended for guidance because it is impossible to specify the appropriate allowances for diversity for every type of installation and such allowances call for special knowledge and experience'

I've highlighted the crucial part to any diversity calculations. The 0.4 rule of thumb for domestic is perhaps still the best and most accurate way of doing any rule of thumb calculation, I still believe that the DNO use this when sizing up their network requirements


View attachment Guidelines_network_design.pdf
 
I still believe that the DNO use this when sizing up their network requirements


essential information when determining the size of nail required in the head.
 

Reply to Max Demand in the Electrical Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

YOUR Unread Posts

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock