Bigger Maximal Static Pressure Tested, Axial Fan


We bought two axial fans Sanyo Denki 9GA0712P1H001. For our needs, what is important is the static pressure reached. This axial fan shall generate a 4,55 mbar overpressure according to the datasheet We are testing the fans in a closed box, in which we have some pressure sensors.

My question comes as I’m experiencing much higher pressures than expected. More concretely, powering one fan with a power source and 12 V DC and limiting it to 1,1 A, It reaches about 13 mbar of overpressure. The power source opperates in Constant Current mode, and voltage supplied decreases to around 6 V with 1,1 A.

We write you because we are wondering the reason of this. We have an objective pressure of 3-4 mbar and we bought this fans in order to use them for this application. I see that limiting current to 0,4 - 0,5 A, we reach this objective pressure. But we don’t understand why is this happening.

Thank you very much for your support.
Best regards,


Hello Jesús,

Let me start my saying that I’m an electrical not a mechanical engineer. I’ll do my best to answer your question in the hopes that someone with more knowledge can assist.

My textbook understanding of fans is limited to this ideal pressure-flow (PQ) curve.

As I understand your situation, you are stating that the fan has a static pressure (sealed box) higher than the specified 1.830 in H2O (455.8 Pa).

There are several possibilities that I would like to explore with you:

  1. Did DigiKey send you the correct fan? For example, did you somehow obtain a fan with higher performance than expected.

  2. Did DigiKey or the manufacturer incorrectly specify the static pressure?

  3. Did the manufacturer change the design?

  4. Is your instrumentation correct. I’ve made many mistakes over the years. My last mistake was a late dinner when the oven thermometer was set to C instead of F.

  5. Is there something else we are missing? I do hope a community member with more experience can elaborate.

Please reply to help us eliminate some of these possibilities.

Best Wishes,



Hi jesus.ezquerra,

Reading through the Sanyo Denki catalog documentation regarding measurement of airflow and static pressure, it sounds like it is a very complex procedure, and perhaps methodology differences are affecting your readings. Page 613 of their catalog shows a bit about their testing method.

Here’s a diagram showing their testing method:

However, as far off as your apparent results are, it is worth considering some of the things @APDahlen mentions. In particular, the 9GA0712P1G001 has a very similar part number, but it draws significantly more current at 12Vdc and has a higher fan speed, resulting in higher static pressure and airflow for a given input voltage.

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