Photograph of client using tissue to look for air conditioning air flow Air Conditioner
Dehumidification Basics
Fix an A/C or Heat Pump that is not adequately dehumidifying indoor air

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Diagnose & fix indoor humidity or dehumidification problems with air conditioners: Here we explain the cause & cure of an air conditioning system that is not adequately dehumidifying or removing moisture from building air.

This article forms part of our series on how to diagnose an air conditioner or heat pump that is not cooling: this article explains how to diagnose and correct air conditioning problems like lost or reduced air conditioner cooling capacity, reduced or no cool air flow, reduced or no actual lowering of the air temperaturer, or an air conditioner that won't start.

Green links show where you are. © Copyright 2017, All Rights Reserved.

Air Conditioning System Dehumidification Problem Diagnosis & Cures

Sketch explaining that oversized air conditioners are a mistake (C) Carson Dunlop Associates

A summary of indoor A/C or heat pump dehumidification problerm diagnosis is just below.

Air Conditioning Dehumidification Problems: air conditioning system cools but does not dehumidify the room.

The most common cause of inadequate dehumidification by an air conditioning system is the installation of a cooling unit which has too much capacity, or is "over-sized" for the space it is being used to cool. What happens is simple:

If an air conditioning compressor unit is oversized (too many BTUH of cooling capacity) what happens is it cools the room so quickly that the system does not move enough total volume of air across the cooling coil to remove much moisture before the room temperature has dropped to the A/C cut-off point.

In other words, an air conditioner needs to run longer, and move more total volume of air through itself to drop room humidity than it does to just cool the air.

"Bigger" cooling capacity or higher BTU capacity for an air conditioning system is not necessarily better, and it can actually prevent the air conditioner from adequately dehumidifying indoor air.

Sketch courtesy of Carson Dunlop Associates.


Continue reading at DEHUMIDIFICATION PROBLEMS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see


AIR CONDITIONER BTU CHART - where we discuss the air conditioning system sizing problem at

COOLING RULES OF THUMB to guesstimate how many tons or BTUs of cooling a building needs

RATED COOLING CAPACITY to determine the cooling capacity of existing air conditioning equipment.

Suggested citation for this web page

DEHUMIDIFICATION BASICS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Questions & answers or comments about air conditioner system diagnosis & repair

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Comment Box is loading comments...

Technical Reviewers & References

Click to Show or Hide Citations & References

Publisher's Google+ Page by Daniel Friedman