Changing the main fuse

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avinalarf

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Evenin' all

I'm a newby so forgive my ignorance.

I've just had 2 quite large extensions put on my home and I've done all the cabling work myself.

I knew I would have to have my main fuse raised as it's only 60/80A, so I've been doing my calculations to work out possible total load with all additional circuits.

After diversity, I'm coming up with a total of 159A. What's the maximum size fuse that a supplier will provide for a domestic dwelling? This isn't enough to warrant a three-phase supply is it?

Cheers

Natasha

 

avinalarf

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forgot to add...

I'm about to put in a 17th Hi Int board, plus a separate CU to supply the garage and outside lights. Unsure what size cable to use between main CU and garage CU. I was thinking of having a 50A mcb for the garage supply.

Ta

 
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195A love?

Could you post cct info? methinks that a tad high.

Standard domestic max - 100A

Why 50A for the garage, FCOL?? What the heck are you intending to have on the line?????

Cable to garage - under standard conditions - max 2.5, or MAYBE 4.0, on a 16/20A. Depends how much load you realistically expect to be stuffing on there!

But, to repeat. Can you provide details of circuits, please?

 
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Evenin' allI'm a newby so forgive my ignorance.
FORGIVEN! at least you are not called KME, Moonpig, Apache, Theory, Admin.. etc.. so that has got to go in your favour!!! :D :D:D

I've just had 2 quite large extensions put on my home and I've done all the cabling work myself.
not sure if you are spark - non-spark - DIY - competent or just keen to try' date='

so at this point we wont even consider the 'Inspection Testing & certifictation or Part P'... BUT this fuse rating bit & diversity????

I knew I would have to have my main fuse raised as it's only 60/80A, so I've been doing my calculations to work out possible total load with all additional circuits.

After diversity, I'm coming up with a total of 159A. What's the maximum size fuse that a supplier will provide for a domestic dwelling? This isn't enough to warrant a three-phase supply is it?

Cheers Natasha
So you are saying that currently 80A has been sufficient for the property..

But now you have had the extensions built..

you are expecting DOUBLE the amount of appliances to be simultaneously switched on?

possibly double the number of persons using the property that actually warrant the additional appliances in use?

IMHO 80A to 160A seems very unlikely to me??

What are your actual circuit figures??

Just because a property is physically bigger.. doesn't mean it will necessarily take up the same proportion of extra electricity!

 
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I think you will find the 60A fuse is probably sufficient. I seem to recall the supply companies estimate about 14A per average house when calculating their ring main. For what you have calculated a 3 phase supply is needed.
or maybe 80A??? ?:|

Back in July we had both out Gas & Electric meters replaced with these

"smart meter" jobbies that talk to each other & send the readings over the mobile phone network for automated billing. :)

Anyway.. the electric man wot did the lectric meter also did a routine replacement of the main fuse.. (which was 100A).. but down rated it to 80A..

He said it was the standard procedure now. {this was an e-on engineer} :|

 

ABC Technical

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As I mentioned in another post, I am installing a massive length of cable at work for 2 new pumps on one of the printing machines, this is coming from an existing 3 phase supply. That cable is only rated for 30A, so methinks that somewhere you have got your calculations wrong.

Furnish us with all the necessary info & between us all I am sure we will sort this out for you. :)

 

avinalarf

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Thank you all for your input thus far. Following circuits as follows:

smoke alarms - 6A rcbo

32A downstairs RM & immersion

10A Extension & bed 5 lights

40A hob (induction so no diversity allowed I have been informed)

50A garage CU (for exterior front lights, exterior front lights, garage lights & RM)

6A downstairs lighting

32A upstairs RM

16A oven radial

16A Microwave radial

6A upstairs lighting

32A kitchen RM

Have recently qualified Special Location, hence severe lack of experience!

Followed my Amicus regards calculating demand so really not sure where I'm going wrong?????? :eek: :O:O:O

 

Flying Scotsman

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Thank you all for your input thus far. Following circuits as follows:smoke alarms - 6A rcbo likely to only be about 1-2 mps max if that for smokes

32A downstairs RM & immersion i would be surprised unless the house only has one socket circuit that 32amps will be used off this circuit in on hit i would say if only downsatirs sockets like tv dvd etc then 10-15 amps max.

10A Extension & bed 5 lights depending on lights use d i would ssay between 2-3 amps max as not all the lights will be on at the same all the time

40A hob (induction so no diversity allowed I have been informed) but how long will it running at full load for as it has a thermostat

50A garage CU (for exterior front lights, exterior front lights, garage lights & RM) i would hazard a guess that the most the current draw on this load would be no more than 20A max

6A downstairs lighting 2-3 amps max

32A upstairs RM very little if only table lamps, pc, and other low power items used like latop and printer etc 10 amps max i would think if that

16A oven radial posibly would be correct depending on wattage of oven

16A Microwave radial i would say that no more than 10-15 amps max on this circuit

6A upstairs lighting again 2-3 amps max not all lights would be on for the same amount of time at the same time

32A kitchen RM this would possibly have a loading of approx 20-25 amps as there may be appliances washing machine etc and dishwasher but i wouldnt have thought they would all be on at the same time generally,

Have recently qualified Special Location, hence severe lack of experience!

Followed my Amicus regards calculating demand so really not sure where I'm going wrong?????? :eek: :O:O:O
i reckon a 100 amp fuse would be fine tbh,

 

avinalarf

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Thanks FS

So how does one estimate the total load for consumer usage then??? I understand the theory of no-one ever having ALL lights on simultaneously and appliances etc, but I thought that was taken care of using the diversity formula?

Are your estimations for my circuits based on experience?

I've got to give these totals to EDF for them to upgrade my main fuse. should I just give them what you have estimated?

Cheers

 
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Thanks FSSo how does one estimate the total load for consumer usage then??? I understand the theory of no-one ever having ALL lights on simultaneously and appliances etc, but I thought that was taken care of using the diversity formula?

Are your estimations for my circuits based on experience?

I've got to give these totals to EDF for them to upgrade my main fuse. should I just give them what you have estimated?

Cheers
adding to what FS said.. and looking at you garage circuit..

50a what are you running that will be taking 11.5kWatts?

FS assumptions approx 4.5kWatts..

still more that ample for the "Average garage sockets & lights"?

 

avinalarf

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Special

Garden designer has allowed for 20 exterior lights to rear and 7 exterior lights to front. I cabled for 3 lights in the garage. Have also run ring for sockets (1 providing power for garage door).

I thought that 100w per lamp had to be allowed for when doing calcs?

 

avinalarf

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ALSO - is it a bit overkill to use "hi-tuf" cable on an outside wall for a light that will be 2m high? My guess is just to use T&E.

 
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SpecialGarden designer has allowed for 20 exterior lights to rear and 7 exterior lights to front. I cabled for 3 lights in the garage. Have also run ring for sockets (1 providing power for garage door).

I thought that 100w per lamp had to be allowed for when doing calcs?
that is a rule of thumb for your average internal pendant batten lamp holder.

BUT you also only assume max 66% simultaneously switched one

I think you would have some SERIOUS light pollution issues if you are banging 100watt bulbs in all around the garden.

I would think with that quantity of lights they are several low wattage bulbs..

(unless its an airfield and you are marking out the runway?)

what physical fittings are you putting in the garden..

i.e. some lamp fittings cannot have a 100watt lamp put into them because they don't exist.

e.g. are they deck lights.. garden border/path lights..

230v, 12v, LED ???

There are hundreds of houses in the country with only 60amp for the whole property.. so 50amp for your garage & garden is quite large to say the least!

You also would be wise to take into consideration guidance toward installing more low wattage energy saving lamps... ;)

 

avinalarf

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You're right - she has allowed for a variety inc. LV - need to count them up properly.

So, for example, how do I calculate correctly if I have the following:

8 x 60w

12 x LV

I guess I was rather overzealous purchasing such a high rated mcb. :| What should I replace it with IYO?

BTW, how do you respond to threads and include what the other person has said???

 
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You're right - she has allowed for a variety inc. LV - need to count them up properly.So, for example, how do I calculate correctly if I have the following:

8 x 60w

12 x LV

I guess I was rather overzealous purchasing such a high rated mcb. :| What should I replace it with IYO?

BTW, how do you respond to threads and include what the other person has said???
If you click "quote" in bottom left of the post you quote origional the ""+ button lets you quote multiple posts

 

avinalarf

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If you click "quote" in bottom left of the post you quote origional the ""+ button lets you quote multiple posts
Thanks Apache - I guess you meant bottom right tho:)

 
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Okay `tash.

Sorry for any mistakes - it`s late & i`ve been at the wine bottle.

8 60w blubs=480w

12 lv? what lv are they? led? lv halogen?

The voltage doesn`t matter AT ALL! the total wattage is the figure you need.

The LED`s would probably be max 3W

LV halogen dichroic 20 or 35

lets say 35W halogen.

35 X 12 =420W

+ 480 from earlier

=900W

@230v

=3.9A

Even if you could draw 32A from you "garage ring" (WHY!!!) that`s still 36A

make the garage a 20A radial. external lighting (and internal, for that matter) can go on 6A generally (unless specifics dictate otherwise)

Don`t forget, that outside lighting figure doesn`t include diveristy, at 2/3 (66%)

your house "rings"- again WHY?

Other than kitchen/util, you could put the whole of the house on a 16A radial (normal sized house; not 50 bed mansion), and you won`t EVER trip it!!!

HTH

KME

 
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