Changing the main fuse

[SPECIAL LOCATION]

Thanks Apache - I guess you meant bottom right tho

well hes had too much beer hasn't he

left and bloomin right..

its that flying scottydog.. making the screen to all wide..

bet his right wrapped round to his left!!!

 

[SPECIAL LOCATION]

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

As you (or someone else ) said...

we all have to learn somewhere..

and its far better talking this though now..

rather than after you installed it..

and probably paid for unnecessary upgrade from those EDF people!

as KME just posted 20A should be more than sufficient for the garage supply.

you'll just have a few spare MCB's to keep for a later job!

 

[Apache]

well hes had too much beer hasn't he left and bloomin right..

its that flying scottydog.. making the screen to all wide..

bet his right wrapped round to his left!!!

100% sober tonight. On call

 

[SPECIAL LOCATION]

100% sober tonight. On call

I'm NOT and I'm NOT......

answering both of your points there m8!!

Do we put up a little wager that the Don will still be in single digits with his smiley count by the time Christmas comes???? ?:|

 

[avinalarf]

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

KME

Get that part.

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%)

KME

I've already run the ring for the garage - guess it doesn't matter too much apart from extra time and money spent. Rather make these errors on my own house before I'm let loose on the public.

your house "rings"- again WHY?

KME

House "rings" are original, only added new kitchen bits. Hubby does have immense fish tank which demands about 6/7 sockets to itself!!!

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!!!

Is that true:| I think my tutors have been especially "over-cautious", which is why it seems like I'm going to drain the National Grid with what I've done!

HTH

KME

Thanks & have another glass for me...

 

[Apache]

I'm NOT and I'm NOT......answering both of your points there m8!!

Do we put up a little wager that the Don will still be in single digits with his smiley count by the time Christmas comes???? ?:|

I'm a yorkshire man, I only bet if I think I can win

 

[Apache]

House "rings" are original, only added new kitchen bits. Hubby does have immense fish tank which demands about 6/7 sockets to itself!!!

ooh a lady spark!

 

[a2]

ooh a lady spark!

Thought the signing off in the OP with cheers, Natasha would have given it away, :^O

Your detective skills are slipping Apache

 

[Apache]

Thought the signing off in the OP with cheers, Natasha would have given it away, :^O Your detective skills are slipping Apache

Your right! Maybe I should go to bed earlier!

I've never met a lady spark....

 

[ABC Technical]

I know at least ten and all of them would put most to shame.

 

[Flying Scotsman]

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

UNLESS THERE IS A FAULT ]Applaud Smiley

 

[kme]

Naturally, FS.

We`re talking about standard usage though, aren`t we?????

Mrs. Larf: r.e big fishtank with lots of sockets:

Heater (maybe 2 X 500W (IF ruddy big tank!)!), lights ( ususally fluro, 58W ish?), powerhead / filter (approx 300W max(again maybe 2X? ), air pump (28W).

Or is this marine tank, with protein skimmers & reverse osmosis units? that`ll add a couple of hundred watts!

Total - if all on together:

Say 1600w. @230v =approx 6.9A

 

[avinalarf]

Apache - never met a femal spark eh? Well Yorkshire lad, come down to Cambridge and you can meet one!!!

KME - yes, it's going to be a "ruddy great Marine fish tank"! Doesn't seem to make that much difference to your calcs though.

I'm still waiting for Special to tell me how you get those calcs? Do you just go with what the average household uses and then add more to the allowance if they have any particular electrical requirements?

 

[kme]

What calcs from SL? I can`t see any in his posts on here?

KME

 

[Apache]

What calcs from SL? I can`t see any in his posts on here?KME

Think OP is refering to flying scotman's post #11 re estimated currant drawings for the various circuits.

 

[kme]

Thanks m8.

Nat - FS`s figures are average household usage figures; not calculations.

If you`d asked us all individually, we`d have probably come back with similar results.

They`re generic amounts. Unless you`ve got something special going on, they`ll work fine.

 

[SPECIAL LOCATION]

Apache - never met a femal spark eh? Well Yorkshire lad, come down to Cambridge and you can meet one!!!KME - yes, it's going to be a "ruddy great Marine fish tank"! Doesn't seem to make that much difference to your calcs though.

I'm still waiting for Special to tell me how you get those calcs? Do you just go with what the average household uses and then add more to the allowance if they have any particular electrical requirements?

the actual Max Demand can only be accurately calculated by sticking some monitoring equipment on over a period of time to read actual power peaks & durations..

Without that specific monitoring, general assumptions have to be made based on the direct knowledge of the installation deatils...

You CANNOT just make assumptions on the size of the property & the number of circuits...

you would need to also take into account the number of persons using the property & the likely appliances / equipment they are likely to use..

e.g.

1) Two circuits that both take 10a.. BUT NOT simultaneously wound still only have a max demand of 10a.. IF simultaneous operation then max demand 20a!

2) Two identical semi-detached properties.. One has a family of six living in it...

the other has a single elderly widow, Max demand will be completely different for both IDENTICAL properties?

So Nat you would need to give us a lot more information..

but as KME said FS's rough guide figures are probably not far off the mark..

hope that helps a bit??

It is a very grey subject because a lot of variables need to be taken into account.

As another example the old electric storage heaters which charge up over night benefit from the fact that most other appliances are OFF.

If the storage heaters came on. in the middle of Christmas day when the oven is on full wack.. then maybe the main fuse may pop???

 

[avinalarf]

the actual Max Demand can only be accurately calculated by sticking some monitoring equipment on over a period of time to read actual power peaks & durations..

Thanks, we were wondering how on earth actual usage could be calculated!

e.g.

1) Two circuits that both take 10a.. BUT NOT simultaneously wound still only have a max demand of 10a.. IF simultaneous operation then max demand 20a!

Ok, this is where I'm getting confused...how is it decided what size the Main Fuse should be then? You obviously don't just add up the breakers that are in the installation, 'cos 9 times out of 10, the total would always exceed the MF size

That's why I was allowing for a 50A mcb in the main CU to cover the circuits in the garage CU:

32A - ring main

10A - rear garden lights

6A - front garden lights

6A - garage lights

Doesn't the mcb for the garage (in main CU) have to be rated higher than the highest mcb in the garage CU? <- hope that makes sense to you!!!

Obviously I was WAY off the mark, which I've now realised, but TBH, if I was to do this again (which I hope I will at some point!), I'd still be a bit stuck as to the size of fuses to use.

So Nat you would need to give us a lot more information..

but as KME said FS's rough guide figures are probably not far off the mark..

What additional info is required? Sorry to go on about this, but it's doing my head in and I really need to understand [thoroughly] what I'm doing, otherwise I don't see the point...

hope that helps a bit??

It is a very grey subject because a lot of variables need to be taken into account.

You've all been a great help so far - much appreciated.

Nat

 

[kme]

The Max Dem. will be affected by the circuit sizes; but then take diversity into account.

Diversity is relatively basic statistical probability of the amount of load which could be EXPECTED to be on any given circuit, at any given time.

e.g. If I fitted 3 no. outside wall lights on a property, each a p.i.r. security light, with a 300w halogen in it.

the MCB/RCBo would probably be 6A

The TOTAL load connected=900w - 3.92A

The max.dem on the circuit (for calculating overall demand) would be 66% of this:

ergo 1.31A.

LESS than 25% of the mcb rating.

Not all circuits use a 66% figure - a fixed load (shower, for instance) cannot have a diversity figure applied to it (AS A CIRCUIT), though you could make an allowance for the load in your overall maximum demand; because the shower is not on for MOST of the time, in a standard domestic environment.

Generally, there is a fairly high level of experience needed, to calculate a decent approximation of MD.

It does come. Just give it time.

 

[avinalarf]

Many thanks KME - I guess I just need to be a bit more patient!