What is the cubic feet per minute (CFM) rating of the fan system?
The individual fans are rated 40 CFM in open air with no restriction and at full operating voltage of 12 volts DC. When mounted in their metal support frame the three fan system (QFF-2803-V) has a rating of 85 CFM, and the four fan system (QFF-3804-V) a rating of 120 CFM. They can be adjusted up to full power by the owner if desired.
Depending on the individual fireplace, the operational flow rate will probably range from 20 to 50 CFM for the two fan system and 50 to 80 CFM for the three fan system and 80 to 120 CFM for the four fan system. The variable speed fans have a voltage adjustment feature to allow tuning the fan for minimum noise and sufficient flow to ensure the warm air exiting the top of the fireplace gently launches out into the room. This prevents the normally convective flow from sliding up the front of the fireplace and overheating the mantle and any objects above it (like an expensive flat panel TV).
High CFM fans mean high noise levels, which is why we designed our fans to produce the most air flow at the lowest possible noise level.