skip spacers, the fan should be flush with the opening, not inside where it creates less 'vacuum' in front of itself and more turbulence behind it .... makes a lot of difference .... and the shroud opening shouldn't be much bigger than the fan diameter

Bill


Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics