Quote:
Originally posted by jtroutma
Outlet line closed off; no change, actually got a little bit louder (higher pitch)
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Just figured I'd mention that this is normal (for both fans and pumps). Load increases with flow rate. Speed decreases with load. By closing the outlet you actually drop the motor's output energy resulting in a small speed increase. You'd find exactly the same result if you covered the inlet or outlet of a fan.