My ASI294 cools slowly when connected to my ASIAIR Pro, but I still ran into dew issues. The bigger issue is camera case temperature management.
The hot side of the TEC dissipates heat into the case of the camera, which is aluminum and a good heatsink for the 24W the TEC can dissipate. The heatsink is attached to the outside of the sealed camera chamber. Since the fan kicks on at full speed when cooling is enabled, there's more cooling than heating which leads to dew and frost issues.
To test my theory, I added a 3 position toggle switch to the fan on my ASI294, either turning the fan off, giving it 6V, or the full 12V. Since a TEC only creates a temperature difference between the hot and cold sides, hot side temperature can be monitored by monitoring TEC load. By keeping the fan off until TEC load exceeds 50%, I've yet to have a dew issue. Even with 80°F ambient temperature, full fan speed isn't needed to keep TEC load under 75%, which I arbitrarily established as an upper limit. I anticipate that in winter the fan won't be needed at all.
Yes I understand that I could have added the stick on heater, but another 4W of heating can't compete with >24W of cooling plus whatever the wind carries away. I tried this last winter, and it didn't buy me much margin.
