max demand and diversity

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naz786

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Hi Guys,

I have been to a delicatessen, Where they would like to have 3 1.5KW patio heater installed, They have 18way double stack cu, Single phase supply, All the beakers adds up to 280+ amps. Even taking diversity into account still over 100amps,

What would you guys suggest here,

Many thanks

Naz

 
Your diversity calculation is probably incorrect. We need more details about the circuit composition to give any realist answers. Adding up the rating of the breakers carries no relevance, it is the circuit loading that is needed for correct evaluation. If you can provide more detail we may be able to help.

Doc H.

 
Thanks Doc,

They have

40Amp air con

32amp ring

32amp ring

16amp radial x 4 supply different fixed loads

6 amp lights x 4

32amp x 2 rings

20amp radail

20amp spare

16amp x 2

thanks

Naz

 
Hummmmm..... I think Doc meant a little more detail than that Naz..... :C :coat

He needs to know at the very least what sort of loads, and ideally the ratings of those loads that your calling ''Fixed''....

 
Thank for replying,

I am not sure rating of the equipment,

They have verious Coffee machiines, Meat slicers, hand dryers, Air con system,

Many thanks for your help,

naz

 
Thank for replying,I am not sure rating of the equipment,

They have various Coffee machiines, Meat slicers, hand dryers, Air con system,

Many thanks for your help,

naz
Well this IS what you need to know to work out max demand with ref to diversity where applicable!!!

It is rather like asking how many miles can I travel in my car on a full tank of fuel

And only using the manufactures handbook recommended 'X' miles per gallon....

(empty @ 55mph!!)

The "real" miles per gallon is only relevant when you take into account other factors such as....

The speed you are traveling at

How much weight is in the car

Has it got a roof-box & a bicycle on the roof

Is it towing a caravan....

etc...

etc..

etc..

A circuit with a 32A breaker may only be taking 8Amps for 3 hours per day!!!!

When you are seriously getting concerned about the Max demand of an installation..

you have to go into more in depth analysis of ALL related circuits...

ALSO consider there may be two circuits that each take 10Amps...

but if they are never on simultaneously the real max demand of these circuits will NEVER exceed 10 amps!!!

Had a job a few years ago where both the cooker and shower shared the same 30Amp fuse....

Single 6.0mm leaving fuse box.. J-box under bathroom floor splits to cooker & shower!!

Fortunately this property was occupied by a single person.. So the probability of both cooker & shower been on simultaneous was negligible!

(p.s. while changing the CU I did split the cooker & shower onto more appropriate circuits! :Salute )

I always find that Diversity is one of those areas that trips up the less experienced electrician..

they think they can just read some tables out of a book, do a bit of addition and/or multiplication and there's your figure!!!

Re-read paragraph 2 of page 95 of On Site Guide..

where it says, with ref to the guidance and tables given...

It is impossible to specify appropriate allowances for diversity for every installation !
 
Had a job a few years ago where both the cooker and shower shared the same 30Amp fuse....

Single 6.0mm leaving fuse box.. J-box under bathroom floor splits to cooker & shower!!

Fortunately this property was occupied by a single person.. So the probability of both cooker & shower been on simultaneous was negligible!
But, but but ....

I always put the Dinner in the oven before I go for a shower, then it's ready to eat then I get out. :innocent

 
But, but but ....I always put the Dinner in the oven before I go for a shower, then it's ready to eat then I get out. :innocent
I always eat my dinner IN THE SHOWER..

Cuz Mrs SL says I make too much mess at the table!!!!!

:p

:slap :slap:slap

 
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