Heating, Air Conditioning, Fridge, HVAC/Swamp cooler pulley ratios


I have a swamp cooler that was running on a 1/3 hp motor with a 2.25" motor pulley and 7" squirrel cage pulley.  This motor was old and finally died.
I tried to replace the motor with a used 1/2 hp motor and bumped up the motor pulley to 2.5" as recommended by the hardware store, leaving on the 7" pulley for the cage.
That kept cutting out.
So, I bought a new 1/3 hp motor and new 2.25" motor pulley, thinking if I restored it to the configuration it was before, it would at least run as well as before.
Now the swamp with that configuration is making noises.
I keep hearing about a ratio between pulleys.  If I bump up to a 1/2 hp motor and a 2.5" motor pulley as recommended by the motor manufacturer, what size squirrel cage pulley do I need?

Leave the  7" squirrel cage pulley as is,
get a 3" adjustable motor pully, you can adjust the motor pully to the size you want but don't exceed the amps on the motor plate.
the faster the   squirrel cage runs the more amps are produced on the motor, the motor can shut off on thermal overload or blow a breaker if it runs to fast,
adjust the motor so that fan belt is not tight at the motor pully.

Heating, Air Conditioning, Fridge, HVAC

All Answers

Answers by Expert:

Ask Experts


Jim Barnhart


Fifty + years conditioning the air.


Answer questions about , residential and commercial. Answer questions about sheet metal fabrication. Fifty years plus experience. No answers for oil equipment, No answers for kitchen appliances, No answers for laundry appliances, I don't specialize in one particular area of the HVAC area, I'm more of a General Practitioner, Limited in refrigeration/

Hands on since 1950

©2016 About.com. All rights reserved.