Inspected a ranch today and thought i had a whole house fan - from the outside. Typical large mechanical louvers at the gable . Inside there was no ceiling louvers in the hallway - most common spot the whole house fan is located. Crawled up to the attic - nice and open with one side with a typical gable louver vent, other side - bag a ss fan on the gable where the whole house louvers were. Little bit confusion , are they using this large fan as an attic fan ? Usually attic fans have thermostat in attic and are powered by such when activated by temperature, and are much smaller. This fan was activated by a dial timer at the top of the basement stairs. Elderly homeowner states her HVAC tech said ’ Dont use it".
There is a Central A/C in the attic and it works fine. I’m thinking that either this 1955 yr old house had a whole house fan and when A/C was installed they moved the fan from the hallway ceiling to the gable vent and attempted to use it as a powered attic fan - way too strong obviously. No evidence that this fan was in the hallway though, less the attic access panel. I did not turn it on since her HVAC tech told her not to, even if it did work , the thing would have created a big negative pressure in the attic anyway.
Anyone see this before ? or just a bad idea on attic ventilation
I have seen it a couple of times. Definitely a job by a previous homeowner. And yes, it’s major overkill as far as attic ventilation. It was probably originally installed this way because someone was told more ventilation is better and they interpreted it as “a bigger fan is better than a smaller one”. Your assessment and the HVAC contractor’s advice is sound.
Maybe its to suck out bats if they get up there.
It then dices em uplike a bat Ninja blender 
Was there a big set of louvers in the ceiling of the hallway?
Nope. Thats how it should be set up. I honestly think they just put this huge fane in as a gable fan. At least the attic will be dust free after turning this on. There is no prior house fan framing on the ceiling joists , thinking at first maybe they removed it from hallway and put it at gable