Thinking Ahead to a Humid Summer
A version of this article appears in the March/April 2005 issue of Home Energy Magazine.
March 01, 2005
Q. I recently read that a variable speed, two stage air conditioner can maintain 50% relative humidity (RH) even when the latent load is 60% of the total load.Would this really work? A. What you heard exaggerates the true capability of a two-speed compressor, variable-speed fan machine. I know of no residential air conditioner made that can accomplish 60% latent cooling (moisture removal) and 40% sensible cooling with a 50% indoor RH. Using a Carrier 38TDB060-31 with an FV4BNB006 indoor section for example, the absolute best you will get at low speed (300 CFM per ton) is 23% latent cooling (77% sensible heat ratio). That occurs only in the following unlikely scenario: 75ºF and 50% RH inside, 75ºF outside, running continuously, with no heat gains in the return duct system. The way latent cooling increases with conventional A/C (including a two-speed machine) is that the indoor RH rises above 50%.The indoor RH rises until there is a balance between the latent capacity and the latent load. For example, at the same conditions as above except that the indoor RH has risen to 66%, the unit produces ...
To read complete online articles, you need to sign up for an Online Subscription.
Once an order has been placed there is an automatic $10 processing fee that will be deducted with any cancellation.
The Home Energy Online articles are for personal use only and may not be printed for distribution. For permission to reprint, please send an e-mail to firstname.lastname@example.org.