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Technical Tips from Mark W. Persons
Building Cooling System

Here are a pair of small squirrel-cage fans used to cool a small transmitter building that houses a McMartin BA-1K AM Transmitter.  These fans are near the ceiling and are identical.  It is important to note that each is on its own 120 VAC circuit breaker and its own thermostat.  You an set one thermostat at 75 degrees and the other at 80 degrees F.  The fans are sized so that one is plenty to cool the building.  The redundancy means that a single fan failure, thermostat failure, or circuit breaker trip will not allow the building to overheat.

Hardware cloth with 1/4 x 1/4-inch openings is just about right to keep mice out.  The screens act as finger-guards too.  Note there is a screen where the air is pushed out of the building.


From the outside of the building there is a metal rain hood.  Inside, you can see that there are two rubber flaps to allow air to leave, but not return to the building.  They help keep warm air in during cold winter months in Minnesota as well.  They keep mosquitoes out in the summer too.    


The stories go on and on.  Stop in again sometime.  I'll leave the soldering iron on for you. 
Mark W. Persons   ham W0MH      

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