The CEC has just sent out an update of their filter grill requirements which are a critical part of the return duct system. Here is there update.
"Filter Grille Area Requirements
When complying with the Alternative to Section 150.0(m)13B,
the nominal size of the air filter media should be used to calculate the minimum
total return filter grille gross area. If the air filter is not located at the
filter grille, use the nominal size of the filter grille to determine the area.
The calculated area must be equal to or greater than the values in TABLES
150.0-C or D.
Additionally, TABLES
150.0-C and D also require that:
1. Each return duct
must be no longer than 30 feet.
2. Each return duct must not have more than 180 degrees of
total bend.
3. If the total bending of a return duct is more than 90
degrees, one bend must be a metal elbow.
4. Return grille
devices, which include the air filter and return grille locations, must be
labeled in accordance with the requirements of Section 150.0(m)12A.
5. The label must
state the grille’s design airflow rate and a maximum allowable clean-filter
pressure drop of 12.5 Pa (0.05 inches water) for the air filter, as rated in
accordance with AHRI Standard 680 for the design airflow rate for the return
grille. Please note that additional air filtration requirements of Section
150.0(m)12 may apply."
I've seen some contractors who were shocked at how much filter area the code was calling for. Of course, the best way to make sure that the filter grill requirements are met is to use a proper duct design system such as Right Soft. The vast majority of installations that I see are not designed at all.
I hope that bringing this to light could alleviate some of the pain I've seen in the eyes of someone who has to redo their hard work often in a sweltering attic.
No comments:
Post a Comment