Q: What is the failure mode of the R-3W below -20°C down to -40°C, will it work once it returns to normal operating temps or is it damaged.

The R-3W was tested at lower temperatures and will work at -40°C. The R-3W will operate normally there is no failure mode, however materials may become weaker due to cold so avoid hitting it. Anything below the recommended operating temperature -20°C is not covered under UL.