Evaporator Coils Part 2: Multi-Circuit Coil Staging

Whos on first



  1. You have a two stage coil; what coil section is first stage?
  2. What coil section is second stage?
  3. Does it even matter?


  1. It depends.
  2. It depends.
  3. Most of the time.

Face-split, row-split or tube-split; they need to be staged correctly.


The leaving side should be first stage.


Humidity control. You never want condensate to flow onto warm coil fins; the moisture will re-evaporate into the air stream.

Row Split 1 2







The bottom must be 1st stage. The 2nd row is 2nd stage, the 3rd row is 3rd stage, and so on and so forth….


Humidity control. Condensate running over a warm coil will re-evaporate into the air-stream; always keep condensate flowing over a cold coil section.

Face Split 1 2








First stage should be nearest the outdoor air entry


Humidity control. This allows cooling and de-humidification of warm / humid ventilation air when only 1st stage is energized.

Tube Split 1 2






(Note: Tube split is very uncommon, you’ll probably never see one of these)


That’s it. Hey, they cant all be zingers…

Patrick is Zen HVAC’s diagnostic and training guy. Patrick started in the trade the day he left technical school and never looked back. He's served in various technical and training roles in the HVAC industry but specializes in system troubleshooting and diagnostics, retro commissioning, and technical training. His moto: If I can understand it, anybody can. Patrick uses the Zen common sense approach to teach Patrick’s Likes- His Wife, kids and dog. Old pickup trucks. Hiking. The industrial Revolution. Patrick’s Dislikes- Taking work too seriously. Anything unintuitive. Emoticons :( Patrick’s Favorite famous person- Theodore Roosevelt “I am only an average man, But I work harder at it than the average man" Famous Patrick Quote- “Well, that was stupid of me”

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