A follow-up on my fan install.. The AC fan pictured in my previous post turned out to be the wrong one. Amazon switched fans, but kept the same
product link, and I didn't look closely at the specs. It's only rated for +14F (-10C). I need a fan that can handle lower temps. (Thanks @ValentineWeather for pointing this out!)
Also, while I had it installed, I noticed my temps where running high. Using an infrared gun, I checked the fan motor temperature while it was running - it read 110-115F. I realized I should not have the fan placed so far down the fan housing as it put the motor within an inch of the temp sensor. I moved it to the top of the opening and temps were more normal.
But, since I needed a new fan anyway, I wanted to try out a DC fan instead, as I had read here they run cooler.
I decided on the
Noctua NF-A8 ULN fan. This is a high-quality whisper-quiet fan that can run at two speeds, 20 CFM (1400 RPM) or 15 CFM (1100 RPM), (which is close to the standard Davis DC fan speed). The motor temp after one hour of operation was 68F, basically ambient temp - much lower than AC fans. Operating tolerance is rated at -4F (-20C), (which is better, but still may not be able to handle winter temps here - we'll see).
Only the lower corners of the fan frame were filed-down this time. The upper corners were left intact so that the fan rests on top of the fan opening. I used metal tape instead of rope caulk to seal around the fan. The Lunar Module:
Because DC fans require a
power adapter, it was necessary to install a weather-proof enclosure near the DFARS. (A 24in 3-pin
fan extension cable was also needed.):
If it turns out this fan can't handle winter temps here, after much searching, I found a 80mm 12v DC fan,
NMB 08015JE-12M-BA-F0, 22 CFM, that is meant for installation in freezers and is rated for -40F (-40C) on the low end (but only 104F (40C) on the high end - so possibly not suited for hot areas). (Also, if desired, fan speed for 12v fans such as this one can be reduced using a
resistor cable (Noctua includes one of these with the fan shown above).)