# HVAC Guys' Q: Heat Pump Design Secret

**URL:** <https://boards.straightdope.com/t/hvac-guys-q-heat-pump-design-secret/243873>\
**Category:** Factual Questions\
**Created:** [May 6, 2004, 5:25pm UTC](https://boards.straightdope.com/t/hvac-guys-q-heat-pump-design-secret/243873 "2004-05-06T17:25:34Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\
**Post date:** [May 6, 2004, 5:25pm UTC](https://boards.straightdope.com/t/hvac-guys-q-heat-pump-design-secret/243873/1 "2004-05-06T17:25:34Z")

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I’m trying to recall something from an HVAC training course I once took. It had to do with the fan coil inside the air handler for a heat pump. I believe we learned the coil is sized properly for A/C only. As such, it will always be undersized for heating hence yet another reason why supplemental heating coils are needed. Am I remembering correctly? - Jinx