Yep, you got it- if you the cut trap in half, you would see the "dam like" resevoir. And yes, although 99.9% of home owners would never think of cleaning a condensate trap, it is good to do so! Once it cannot drain anymore, the water will back up into the collector box to the point that it will enter the inducer assembly and kill the air flow. This causes the air pressure switch to shut down the unit. At this point, most customers think that the air switch or inducer are bad, when in fact, it's only a clogged trap, or a crimped drain hose
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Hope those parts sit around for awhile before you use them! Then again, as proactive as you are, you may be secretly desiring a failure at this point
NorthAmericaHVAC.com
Joe