Fan System Calculator

The NCC is a performance-based code, requiring all new buildings to meet minimum performance requirements.

A deemed-to-satisfy approach is the optional pathway for achieving compliance used by this calculator – which applies to Class 2 to Class 9 buildings.

This tutorial demonstrates using the fan system calculator to assist verifying compliance of a building’s heating, cooling and/or ventilation design with the NCC.

The fan system calculator is a non-mandatory guidance tool.

It helps you apply the deemed-to-satisfy provisions of Clause J5.4 in NCC Volume One.

The calculator a Microsoft Excel based tool and can be downloaded from the ABCB website.

Using an example, this tutorial covers the basic function of the calculator to assess a typical fan system.

When you first open the calculator, you’ll notice there's a customized ribbon.

The buttons within the ribbon link to each of the sheets within the calculator.

The help guide is also available from here.

In order to achieve effective results, the calculator relies on entering accurate information.

Some information will be known by the project engineer, while some will need to be sourced from the fan supplier.

This information needs to be checked and verified against the design documentation for compliance assessment.

Let’s step through the six steps of using the calculator, using an example.

Step 1 – Enter the project information and system descriptions.

When the calculator is opened, the All Systems sheet will appear.

The gold shaded cells are input cells.

Enter the project information into the cells of the first row.

Below that is the Systems section, where each row represents a separate system within the project.

This needs to be completed for each fan.

The Calculator defaults to one row, but additional systems may be added by clicking on the plus icon.

Only one system will be active at any given time. The active system is italicised.

You can switch between systems by clicking on the rows, or using the ‘Change To’ button on the ribbon.

In this example, a single system will be covered.

Enter the System Description, fan tag and flow rate.

Step 2, system characteristics.

Navigate to the summary sheet using the ribbon.

This sheet serves as a hub for system-wide information and results.

You’ll notice that the project information and flow rate is prefilled from the previous step.

Select the system characteristics using the drop down menus.

For the purposes of this example, we’ll select a centrifugal forward-curved fan…

…with a ducted inlet…

…a ducted outlet…

…and lint representing a fouling risk.

The role of the fan is selected in the same way.

For this example, the fan is considered: ‘Any other air-conditioning or ventilation fan’.

Step 3 – the index run.

Next, navigate to the Index Run sheet.

This is where a model of the system can be analysed, by listing each component of the duct, along with its specifications.

Information is entered into the ‘Index Run Details’ section, one system component per row.

It defaults to one row, but more can be added or subtracted using the ‘plus’ and ‘minus’ buttons.

Rows can also be copied and pasted, using the ‘C’ and ‘P’ icons.

To save you time, there's also a button labelled ‘D’ for ‘Default’.

In this row, enter the most common values used for the duct system.

Then, click on the ‘D’ button to set that row as the default.

Now, as you create new rows, this default information will be pre-filled.

meaning you only need to change those properties that differ from the default system, saving you time!

Now, add each system component.

First, enter or amend…

…the description…

…shape…

…component details…

…temperature…

…flow rate…

…dimensions…

…and roughness.

The results for each row are automatically calculated.

“Red” indicates a component which doesn’t satisfy the J5.4 requirements, while "Green" indicates one that does.

However, a component showing as "Red" may still form part of a compliant system.

In this example, the next component is a fitting, so the Component Type needs to change accordingly – along with other parameters.

Continue to add rows, amending the default parameters, or copying and pasting information, as you go.

Each individual component, whether straight ducting or a fitting, needs to be entered to model the entire system.

This is how the complete duct system for this example looks.

There are high pressure drops at the connection to the dryer and in the roof riser section.

If these are difficult to change, improving the system’s performance in other areas may overcome this efficiency shortfall.

Step 4 – fan details.

Navigate to the Fan Details sheet.

On this sheet, enter the design static pressure, motor input power, and system total efficiency.

The Calculator will now determine if the fan satisfies Clause J5.4 at a component level.

In this example, it does.

Step 5 – Assess the results.

Returning to the summary sheet, the results at the system level are shown.

This system doesn't satisfy Clause J5.4 and requires better energy efficiency.

Suggested ways to achieve this are shown in the Results section.

Alternatively, a different assessment method could be considered.

Let's look at improving the energy efficiency, with a more efficient fan, or changing the specifications of the ducts, to provide a system that satisfies Clause J5.4.

Using a different fan – first, update the information on the summary sheet to specify a centrifugal backward-curved fan.

Returning to the Fan Details sheet, update the motor input power and system efficiency.

Lastly, return to the Summary sheet. It now shows the efficiency of this new fan is sufficient to offset the pressure drop of the index run, and reduces the required motor power to an appropriate level.

Therefore, the fan system now satisfies Clause J5.4 – at a system level.

Step 6 – Report the results.

The calculator can generate a report summarising the results.

On the ribbon, click ‘Go To Report’ to view it, or ‘Print Report’ to print it.

Remember, this information needs to be checked and verified against the design documentation for compliance assessment.

Further details about the Fan System Calculator – including additional examples – are provided in the Energy Efficiency Volume One Handbook, and other resources from the ABCB website.