Ian -
Another consideration, since you have more than one fan, is that you can
disable *all* fans simultaneously to demonstrate that no cooling is
necessary for safety reasons. This is a multiple fault scenario, but it's
at your discretion to do so to prove your case and eliminates the need for
cfm ratings.
Stalled rotor testing should not be needed in the end product unless:
1) the test was not done on the fan when it was safety certified
(very common, even among UL Recognized fans)
2) the fan if it is not safety certified at all (you state the
fans you're using are UL Listed, but I think you mean UL Recognized)
3) the fan is a type whose motor current under stalled conditions
can overload another component of the power supply (the impulse start dc
motors I've tested can go an interminably long time without getting more
than a smidgeon above the local ambient temperature)
Disabling (removing power) serves most of the thermal concerns.
There are flammability issues that may need to be met, as mentioned by
another poster, and providing the manufacturer and model can provide a
level of traceability to the relevant materials.
If you can successfully eliminate the need for cfm ratings and stalled
rotor testing, your only concerns are reduced to flammability and loading
of the power supply. In some cases, you can use the fan ratings alone to
meet the standard's and certifier's requirements.
As a final word, alternate or substitution of components is an ongoing
issue for everyone involved in product safety certifications. You can try
to have a handful of alternates ready when the certification evaluation is
performed and still have this concern because there's always a less
expensive alternative available.
Peter Tarver
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