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Anonymous Poster

Calculation of Diversity Factor and Demand Factor

08/13/2010 2:50 AM

How to calculate diversity factor and demand factor for a commercial building consisting of the following electrical appliances

(1) 40Watt Tube Light with conventional choke.

(2) Power Plug Three Pin.

(3) AC Split unit 1.5 ton

(4) Ceiling Fan,

(5) Computers

(6) TV

(7) Laptop

(8) Fridge

(9) Fax Machine

(10) Printer

What is the assumed diversity and demand factor for above appliances that is 1, 0.75, 0.5. Is it correct that diversity factor for above appliances should be above unity if so what is the reason.

Can any one please forward me the writeup regarding diversity factor and demand factor.

In case my question seems to be of basic nature please do not mind because I am not cleared about diversity and demand factor.

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Power-User

Join Date: Feb 2010
Posts: 189
Good Answers: 11
#1

Re: Calculation of Diversity Factor and Demand Factor

08/13/2010 5:38 AM

it is a very important question let me give some information.

Two terms constantly used in electrical design are
1- demand factor
2- diversity factor

Demand Factor: is the ratio of the maximum demand of a system, or part of system to the total connected load on the system or part of the system under consideration. This factor is always less than unity.

If you are using NEC-Code you can find all demand factors for equipments. Table220.42, table 220.44, Table 220.54, Table 220.55, Table 220.56 and etc

Ex-1: To find the demand load for the 82 kW cooking equipment load.

Step-1- Calculating percentage Table 220.56 17 pieces allows 65%
Step-2 Applying demand factors Table 220.56: 220.56 82kW x 65% = 53.3kW

Now the Demand Load is 53.3 kW.

In this way, you can find demand load for each equipment.

Diversity Factor: is the ratio of the sum of the individual maximum demands of the various subdivisoins of a system or part of a system to the maximum demand of the whole system or part of the systsem under consideration. This factor generally varies between 1 and 2.

Diversity factor is mostly used for distribution feeder size and transformer as well as to determine the maximum peak load and diversity factor is always based on knowing the process. You have to understand what will be on or off at a given time for different buildings and this will size the feeder. Note for typical buildings diversity factor is always one. You have to estimate or have a data records to create 24 hours load graph and you can determine the maximum demand load for node then you can easily determine the feeder and transformer size.

Demand factors and diversity factors are used in design. For example, the sum of the connected loads supplied by a feeder is multiplied by the demand factor to determine the load for which the feeder must be sized. this load is termed the maximum demand of the feeder. The sum of the maximum demand loads for a number of subfeeders divided by the diversity factor for the sub feeders will give the maximum demand load to be supplied by the feeder from which the subfeeders are derived.

Hope this will help you.

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Guru
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#2
In reply to #1

Re: Calculation of Diversity Factor and Demand Factor

08/13/2010 6:04 AM

Interesting. i always thought that diversity factor (used as a multiplier of the total connected load) was always less than 1. Thus meaning that the total connected load is never all on at one time.

And demand is related to the inrush current drawn, for example motor loads, like the fridge.

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Power-User
Engineering Fields - Power Engineering - New Member

Join Date: Aug 2010
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#3
In reply to #2

Re: Calculation of Diversity Factor and Demand Factor

08/14/2010 2:07 AM

it is because diversity factor is the reciprocal of load factor...

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Guru
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#4
In reply to #3

Re: Calculation of Diversity Factor and Demand Factor

08/14/2010 4:16 AM

That was exactly my point. Diversity is less than 1. So i got confused when Haeedullah mentioned it as between 1 & 2. Maybe there is a teminlogy difference between IEC countries and the Americas.

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Power-User

Join Date: Feb 2010
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#5
In reply to #4

Re: Calculation of Diversity Factor and Demand Factor

08/14/2010 5:45 AM

kvsridhar,

Please note that diversity factor is always equal or greater than one regardless of any code. It has clear formula

Here per IEEE std. Please read this article there is something you might think that.

http://en.wikipedia.org/wiki/Diversity_factor

Load Factor: is defined as the ratio of average load to maximum demand. Load factor play an important part on the cost of generation per unit. The higher the load factor the lesser will be the cost of generation per unit for the same maximum demand.

Demand Factor: is defined as the ratio of maximum demand to connected load.

Note: load factors and demand factors are always less than unity.

I have used both IEC code and NEC in different projects but the concept is same.

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Guru
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#6
In reply to #5

Re: Calculation of Diversity Factor and Demand Factor

08/14/2010 6:36 AM

Ah, thank you for the clarification.

However, wiki talks also about 'diversity' being different from 'diversity factor' and explains. What i took to be Kd is not what is the actual as per code it appears.

Curious that IEC 60439 gives this :

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Commentator

Join Date: Sep 2009
Location: Singapore
Posts: 75
Good Answers: 1
#10
In reply to #3

Re: Calculation of Diversity Factor and Demand Factor

08/16/2010 6:10 AM

The reciprocal of diversity factor is coincidence factor. load factor is different

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Power-User

Join Date: Feb 2010
Posts: 164
#7
In reply to #1

Re: Calculation of Diversity Factor and Demand Factor

08/14/2010 9:39 AM

dear hameeddullah.thanks for the answer for my question which i thought readers will laugh but i am great full to you for the detail reply.will it be possible for you to pass on the link to down load NEC CODEs thanks

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Power-User

Join Date: Feb 2010
Posts: 189
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#8
In reply to #7

Re: Calculation of Diversity Factor and Demand Factor

08/14/2010 10:53 AM

He who understands will not do that. Anyway, here it is.

http://www.4shared.com/file/PKqi86iS/National_Electrical_Code__NEC_.htm

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Guru
Engineering Fields - Mechanical Engineering - New Member

Join Date: May 2008
Location: CHENNAI, TAMIL NADU, INDIA.
Posts: 1285
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#11
In reply to #8

Re: Calculation of Diversity Factor and Demand Factor

01/27/2013 9:21 AM

Dear Mr. HameedullahEklas,

The link referred by you is NOT OPENING and I get a pop-up screen showing "FILE NOT FOUND" and I feel some problem in reaching the Link.

Requesting you pl. post me the code - through Personal Messaging System in CR4 SYSTEM, as Personal Mail Ids.are not allowed.

By the way, your Photo is missing in this post. Earlier i used to see your Photo.

Thanks,

DHAYANANDHAN.S

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Associate

Join Date: Oct 2007
Posts: 44
#9

Re: Calculation of Diversity Factor and Demand Factor

08/15/2010 9:41 AM

Please read the article which you will find on the following link:

demand and diversity

You will find some worked out examples in addition to what some eminent engineers have replied to you.

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