Fan Performance Testing: ISO 5801, AMCA 210 and What Certified Ratings Mean

A fan’s published curve is only as trustworthy as the test behind it. ISO 5801 and AMCA 210 define how flow, pressure, power, and speed are measured in a standardised airway, so that ratings from different manufacturers can be compared on the same basis. Knowing what these standards cover, what installation arrangement a curve represents, and what to ask for in a test report protects you from buying a fan on numbers that will not repeat on site.

What the Standards Cover

ISO 5801, “Fans: Performance testing using standardized airways,” specifies procedures for determining the performance of fans of all types except those designed solely for air circulation, such as ceiling and table fans. Testing of jet fans is described separately, in ISO 13350. The 2017 edition provides estimates of measurement uncertainty and rules for converting test results for changes in speed, gas handled, and, for model tests, size.

AMCA 210 is the equivalent North American standard for laboratory air performance testing. AMCA’s own efficiency standard, AMCA 208, accepts physical testing to either AMCA 210 or ISO 5801, so results from either are used interchangeably for that purpose. AMCA’s Certified Ratings Program publishes rules for certified air and sound ratings, and manufacturers licensed under it may display the AMCA seal on rated models.

What a Test Measures

A fan test sets the fan to a series of flow rates and measures, at each one:

• Flow, using a calibrated measuring section such as nozzles or a pitot traverse in the airway.
• Fan pressure, as static pressure and, from that and the velocity, total pressure.
• Speed.
• Input power, at the shaft or motor terminals depending on the test.
• Air density, from barometric pressure, temperature, and humidity.

From these come the fan curve, the power curve, and efficiency. Results are corrected to a stated speed and air density, which is why a certified curve is quoted at “standard air.”

Installation Categories A to D

A fan performs differently depending on what is connected to its inlet and outlet. ISO 5801 defines four installation categories, and the same four are used in the fan sound standards.

Category	Inlet	Outlet	Typical real-world example
A	Free	Free	Wall or roof fan drawing from and discharging to open space
B	Free	Ducted	Fan drawing from a room and discharging into a duct
C	Ducted	Free	Fan connected to an inlet duct, discharging into a space
D	Ducted	Ducted	Fan fully connected in a duct system

A curve tested as category D does not automatically apply to your category A installation. The pressure basis and losses differ, so check that the tested arrangement resembles the way you will install the fan, or that the manufacturer has applied the correct conversion.

Testing on Site: ISO 5802

Laboratory standards use idealised airways. On site, inlet conditions, bends close to the fan, and uneven velocity profiles change performance. ISO 5802 covers performance testing of fans in situ. Field tests are useful for verifying commissioned performance, but they carry higher uncertainty than laboratory tests, so acceptance criteria should allow for that and be agreed before the test.

Sound Testing

Sound power is rated separately from air performance. The ISO 13347 series describes laboratory determination of fan sound power by the reverberant room, enveloping surface, and sound intensity methods, and AMCA 300 covers the reverberant room method for fans. In-duct sound power is determined under ISO 5136. Because the inlet, outlet, and casing radiate different levels, a single fan can have several sound power figures. Our guide to axial fan noise explains how to read them.

Large Fans and Scaling

Test facilities have size limits. Large fans may be tested as models or at reduced size and then scaled. ISO 5801 includes rules for conversion in the case of model tests, and AMCA publishes methods for calculating ratings for sizes and speeds that were not tested. The scaling rules assume geometric similarity and matching system conditions, and rated points must lie on the same system resistance lines as the tested points. Ask whether a rating is measured on the actual fan size or derived from a scaled test, and what tolerance applies.

Reading a Test Report

A useful report states:

1. The standard and edition used.
2. The installation category.
3. Fan model, impeller diameter, blade angle, and hub configuration.
4. Speed, air density, and test conditions.
5. Pressure basis, static or total.
6. Flow, pressure, power, and efficiency data across the range, not only the duty point.
7. Measurement uncertainty.
8. Whether the tested fan matches the fan being supplied.

Questions to Ask Any Fan Manufacturer

• Is the published curve from a test to ISO 5801 or AMCA 210, or is it calculated?
• What installation category does it represent?
• Was the actual size tested, or was it scaled from another size?
• What tolerance applies to flow, pressure, and power?
• Can you provide a witnessed test or a test report for this fan?
• What density and speed is the curve corrected to?

Performance Guarantees and Site Acceptance

Where performance is critical, agree in the contract how it will be proved: a laboratory test at the factory, a witnessed test, or a site test to ISO 5802. State the tolerance, the pressure basis, the air density, and who bears the cost. Without this, disputes about a small shortfall are difficult to settle, since real installations rarely match an idealised airway.

Ask for Test-Based Performance Data

Tell us your duty and installation arrangement, and we’ll provide performance data and explain how it applies to your installation. Contact us for a free quote.

Frequently Asked Questions