Operating temperature spec
Specifications for the Purple and Gold Firewallas say: "Operating Temperature (with airflow) 32°F to 113°F" (or °C to 45°C).
What "airflow" would that be? A zephyr? Cyclonic? It is a guide but hardly a specification.
It seems reasonable to suppose that 45°C is actually a case temperature limit, so you would adjust airflow (if needed) to stay below that.
I have a FWG in a large open room which is not normally conditioned. Case temperature according to an IR thermometer sits 16°-17° above ambient, could be higher given more work. Adding a little 40 mm AC Infinity fan a few cm away on a pedestal blowing over the top of the strakes halved the rise in measured case temperature. It is not hard to cool them, but you should consider some active cooling if ambient still air temperature gets up towards 30°C (above 80°F).
However, it begs the question about a practical, useful, specification. If there is a case temperature limit (probably 45°C) then call it that and leave users to measure and cool as needed (make decisions around fans) depending on ambient temperature and measured external temperature on the FW. The statement "with airflow" by itself is far too vague to be usefully included in a specification.
I have not discussed CPU temperature because the thermal resistance in °C/W from CPU to heatsink/air junction is fixed. It is what happens around the case and heatsink that matter.
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So the specification "with airflow" is really "a room sufficiently sized that there are convection flows with adequate heat sinking through the walls such that the room temperature does not noticeably rise". Or, in any sized space, forced airflow with requisite sinking or exhausting of the heat from the air.
The implication of 45°C air temperature in an open room is that case temperature could be in the low to mid sixties (C). Some people do in fact have relatively small enclosed spaces where the external connection and patch panel sit in their house, so must use forced ventilation to maintain reasonable air temperatures in the semi-enclosed box, or some form of non-air heat piping to extract heat reliably. Again, a specification of limiting case temperature would be more useful, although a same-enclosure nearby air temperature measurement (< 45°C) should suffice as a proxy.
In general terms, I now know where I should set (assume to be) that limiting temperature.
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The FWG I purchased sits in a 12U wall mounted cabinet with solid sides and a glass door under the stairs. I've left the door open but the FWG case surface can approach a temperature that is significantly hot to touch (although never too hot that I cannot keep my hand on it) so purchased one of these AC Infinity 120mm multifans:
https://acinfinity.com/component-cooling/component-usb-fans/multifan-s3-quiet-usb-cooling-fan-120mm/With only a 10mm gap between the top of the fan and the Ubiquiti switch in the rack unit above, and the fan speed set to LOW and the door now closed, the top surface temperature of the FWG case has dropped significantly to being only slightly warm. It is a match made in heaven.
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It's okay I'm adding the fan because the rack produces no airflow that will allow the passive heatsink on the Firewalla Gold to do it's thing. I could add fans to the rack but it is easier and cheaper to just sit it directly on top of the singular device that needs adequate airflow.
Passive heatsinks require conditions that do not trap heat around the heatsink. The conditions in my rack trap heat around the heatsink and the fan on low is enough to allow the heatsink to do it's job exceptionally well 👍
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see the bottom of this https://help.firewalla.com/hc/en-us/articles/360010465893
All units should work at 32F
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