Step 2 : calculation of the diversity factor and the diversity flow
- Kristof Smits
Introduction
In this step we will calculate the diviersified flow and the diversity factor.
The diversity flow is the maximum sum of all domestic hot water flows within the building, taking into account that not all tapping points are used at the same time.
The diversity factor is defined by the division of the diviersified flow through the theoretical total domestic hot water flow, and results in a number between 0% and 100%, indicating the maximum “probability“ or “statistic chance“ of having simultaneous tappings.
The theoretical total domestic hot water flow is the sum of all individual tap design hot water flows.
Calculation method & order of calculations
The first thing a user must select is the “calculation method“ to calculate the diversity flow and diversity factor. This selection is important because it will influence the order in which we calculate both, as explained below.
static
If static is selected, the user must enter the diversity flow directly.
Depending on the diversity standard, the diversity standard will be calculated, as explained below.
diversity standard
If diversity standard is selected, the user can (or must in some cases) enter the tapping points.
Depending on the diversity standard, the diversity flow will be calculated, as explained below.
Case 1 : “number of dwelling” based diversity standards
Some diversity standards are only dependent on the number of dwellings, like :
In this step we calculate for one single dwelling, so the diversity factor can be defined by the formula with the number of dwellings (N) equal to one.
1a) diversity standard calculation for “number of dwelling” based diversity standards
Diversity flow : we will calculate the diversity flow as follows :
for the Based on the French Costic MTA 2016 and the Based on the French DTU 11-60, we will use a default of 0.6 m3/h
for the Based on the Cibse CP1 2015 / Danish Code of Practice DS 439 and Based on the Swedish regulation DHA F:101 , we will recalculate the diversity flow based on the default power of one dwelling as defined in the standard, and the domestic temperature regime as chosen by the user.
Diversity factor : for all currenty known standards based on number of dwellings, the diversity factor within one dwelling is 100%
1b) static calculation for “number of dwelling” based diversity standards
Diversity flow : as entered by the user
Diversity factor : calculaed by the diversity formula with N = 1, for all currenty known standards based on number of dwellings, the diversity factor within one dwelling is 100%
Case 2 : “flow based“ diversity standards
Some diversity standards are only dependent on the tapping flows, like :
2a) diversity standard calculation for “flow based” diversity standards
Diversity flow : calculated by the formula, e.g. Based on DIN 1988-300
Diversity factor : diversity flow / theoretical total domestic hot water flow
When calculating the diversity flow, we sum up the individual flows without recalculating them (as explained in Step 1 : recalculation of the tapflows). In other words : we calculate the diversity factor for a “standardised“ situation.
Why? because diversity formula’s are inted to express a “probability“, a “statistic chance“ of having parallel tappings. These probabilities are independent of temperature regimes. We call this probability the diversity factor as explained further on.
Some flow based diversity standards have no standard flows defined for individual tapping points. I n that case, this option is not supported. Example : Based on the CIBSE CP1 2020 / Danish Code of Practice DS 439
2b) static calculation for “number of dwelling” based diversity standards
Diversity flow : as entered by the user
Diversity factor : first we “reverse engineer“ the total domestic hot weater flow using
the inverse formula of the diversity standard
the recalculation formula used in Step 1 : recalculation of the tapflows
Based on the total flow, we can calculate the diversity factor as diversity flow / theoretical total domestic hot water flow