maximum demand kva 3 phase

[iamelectric]

try rapidtables.com kva calculator , but in my opinion 200amp 3 phase supply is plenty and if you ask for a 400amp 3 phase supply when the builder gets the price in he will stick with the 200

 

[Flanders]

Try This Amps (A) to kVA conversion calculator

 

[Flanders]

Sorry Iameletric just noticed you posted the same web site I guess the prob you've got is having no gas I did some calcs for a 2 bed flat with no gas max demand was about 80amps just hope they don't cook a sunday roast with all the trimmings and then decide to have a shower with all the heater on and make a cup of tea :laugh3:

 

[i=p/u]

Isit not 1.73

 

[Darkwood]

Isit not 1.73

Try it on a calculator then confirm on the link a few posts back...

73Kva / 0.73 = 100amps (ballpark) actual long calc method approx 105amps

100amps x 0.73 = 73Kva

It doesn't work with 1.73 don't mix my quick method up with other methods where 1.73 is used as a cube routing factor of 3ph.
As i said it was a easy onsite method to use with one equation answer.

 

[i=p/u]

So if I have 125A on each phase , 125 x .73= 91Kva each phase ? Yes ? Ok

if I got a machine and it said 324kva over 3ph , would = 324 x .73 / 3 = 78.8kva per phase, ah fuk it lol

- - - Updated - - -

Il use my converter if I ever have too

 

[Darkwood]

So if I have 125A on each phase , 125 x .73= 91Kva each phase ? Yes ? Ok

if I got a machine and it said 324kva over 3ph , would = 324 x .73 / 3 = 78.8kva per phase, ah fuk it lol



- - - Updated - - -

Il use my converter if I ever have too

Machines which are 3ph will give a Kva rating per phase not across 3 phases so you above machine would be stamped 108Kva

Come on IPU i clearly give kva to amps as division and i know you must be on the wind now as i know from your time on here your not stupid :smilielol5:

If you convert KVA to amps you divide not multiply 0.73

So your sum if you ever did find a machine with a total rating across the phases -
324 / 0.73 / 3 = 147.95amps.

well its a quick method for most God help the generation when the internet breaks down and they have to go back to maths

 

[i=p/u]

By writing a load of jumble, I found out you would never get amachine with kva for 3ph.

 

[Megavolt]

Went to large flat last week. When I traced feed to CU it was fed from a 40mcb tenant been there 5 years never had any probs.

 

[Darkwood]

By writing a load of jumble, I found out you would never get amachine with kva for 3ph.

You do but not often usually found on imported Japanese machines sometimes or the likes it can at first be a pain to figure out the actual demand without load assessing the different parts of the machines... most machines will give max demand in amps but large machines with big heating banks tend to be Kva.

You stick to the original then
S[SUB](kVA)[/SUB] = √3 × I[SUB](A)[/SUB] × V[SUB]L-L(V)[/SUB] / 1000

I'll stick to my onsite quick calc' KVA / 0.73 = roughly same as above

 

[Engineer54]

X 0.4 of the proposed final circuit ratings and you'll have your ballpark figure, forget the the 100% of the highest rated protective device, all at X 0.4!! Oh and even then the figure will be airing on the high side. But that is about as accurate as your going to get, unless you're a design engineer with a good few years experience under your belt!!

Forget using those methods in BS7671 or it's guides they don't work and never have worked. They are only there to use as exam questions, then to be forgotten about!! ...lol|!!

 

[Risteard]

After using the OSG for diversity have come up with the following

The OSG is completely inappropriate for judging maximum demand for that. Diversity does not have to be calculated this way - a competent person should consider the load and work out what is/is not likely to be used together and for how long.

Looking at what is connected to the flats I can't see them ever using more than 40A and that is when severely loaded!

 

[telectrix]

what's the electric boiler? that could be anything up to 10kW.

 

[GLENNSPARK]

yes the size of the main fuse

no...not the size of the main fuse...

this is a common and incorrect statement that i often come across on forms..

you can use your intuition to guestimate what the max demand will/should be...for a average 3 bed house i put down 60A...for a smaller 2 bed house i use 50A-60A...for a flat or say a back to back on 2 lifts with shower i go for 40A-50A

you can also take a direct measurement using a current clamp with all the appliances/loads that could be expected to be on at the same time...so for instance the shower, cooker and stuff like TV and some lighting...you clamp the tails...take a direct reading.

or as has been said above already you can go for a calc such as the highest load (typically a shower where theres no diversity allowed for an instantanious water heater)...then 40% of the rest.....

either way you wont get 100A

 

[Silly Sausage]

Dave, a bit of a dark art, diversity!

My house, 100A Supply, 25mil tails, 3 bed, 5 people; no electric heating, showers or cookers; big fridge/freezer, TV/HiFi etc...
We average < 3 or 4 Amps over about 12 or 14 hours, the occasional spike when the kettle goes on.

This maybe of interest...

Estimation of actual maximum kVA demand - Electrical Installation Guide

 

[iamelectric]

no...not the size of the main fuse...

this is a common and incorrect statement that i often come across on forms..

you can use your intuition to guestimate what the max demand will/should be...for a average 3 bed house i put down 60A...for a smaller 2 bed house i use 50A-60A...for a flat or say a back to back on 2 lifts with shower i go for 40A-50A

you can also take a direct measurement using a current clamp with all the appliances/loads that could be expected to be on at the same time...so for instance the shower, cooker and stuff like TV and some lighting...you clamp the tails...take a direct reading.

or as has been said above already you can go for a calc such as the highest load (typically a shower where theres no diversity allowed for an instantanious water heater)...then 40% of the rest.....

either way you wont get 100A

are you serious?

 

[Clive P]

Hi,

Read this the other day for a ballpark figure, but can't say how accurate it is?

Loading--
Domestic 15W/Sq ft
Commercial 30W/ Sq ft
Industrial 100W/Sq ft

Diversity--
Domestic 0.4
Commercial 0.5
Industrial 0.8

Regards.

 

[daveb1]

Just out of interest after giving these figures to the supply companies do they use there own diversity to the values you give them???????

Also what would your average 80amp BS1361 actually operate at from over current built up gradually???

Thanks Dave

 

[GLENNSPARK]

are you serious?

are you with 100A/whatever the bullit is?

 

[Darkwood]

When the DNO do their own calcs for a block of flats i believe they only attribute 8-15Kva per flat.. obviously diversity between different flats is used but really give you a idea just how little demand multiple properties can have.