As I had brought up years ago, ACCA's Manual S was in dire need of an update.  Written in 1995, Manual S Residential Equipment Selection was passed by with huge technical and efficiency strides within the HVAC industry.  Think about it: ECM Motors were in their infancy, condensing furnaces were still prone to failures, and variable refrigerant flow was far from mainstream in the U.S.  All addressed in the updated Manual S! I have to say, their committee did a thorough job addressing updates to a process that is essential to system design and a code requirement in most of our country!  I highly recommend HVAC Sales Staff, System Designers, and Building Analysts purchase a copy of the new text, but in the meantime here is a teaser:

1.  Multi-Stage Central A/C: can be sized between .90 and 1.20 of the total building load.  This additional 5% of capacity vs. 1995 becomes increasingly important as homes get tighter and Sensible Heat Ratios rise.  Higher airflow to handle the increase in sensible loads lends to higher capacities.

2.  Variable Capacity Central A/C: can be sized between .90 and 1.30 of the total load.  See #1 for sensible capacity reasons, but variable capacity equipment is great for handling high latent capacities when operating on part load days as well.

3.  Cold Climate Heat-Pumps: can be sized to the total cooling building load + 15,000 btu/hr maximum.  This goes for single-stage, two-stage, and variable capacity equipment.  For mini-split heat-pumps, this 15K is above the total block load.

4.  Heat Pump Supplemental Electric Heaters: can be no larger than 5KW if the heat load is < 15,000 btu/hr.

5.  Fossil Fuel Burning Furnaces and Boilers: can be sized between 1.0 and 1.40 of the total heat load.  Ok, this isn't a change, just thought it was important to know!  If installing a furnace that needs a larger blower for cooling, maximum is now 2.0.

     Loaded with up to date examples, the new Manual S is far from a dust collector.  A great reference manual, but lets just hope it is not for another two decades like it's predecessor...but don't take my word for it!

Excess Air

Views: 233

Comment

You need to be a member of Home Energy Pros to add comments!

Join Home Energy Pros

Comment by Eric Kjelshus on August 28, 2014 at 8:33am

I run loads each day.  BUT my completion does not,    I see so much over sizing  last job was needing 34,000 and he put in 120,000 BTU's ( the box fit)  I took out 1/2 the burners so the BTU fit the duct work and closer to the building.    My grand Pa would size 3 times needed or down to -40  so you could open the windows in bedrooms 8" to get "air" at night.   in the 1880 the gas was made from coal and was very high CO  when would burn,  some  Lights would be gas and CO in the building go high so would open window's to vent the home.    Gas was so cheap that was not metered  just so much a yr.

Videos

  • Add Videos
  • View All

Twitter

Latest Activity

Profile IconAlfonso Scott, Susan Benford, HomeWiz and 2 more joined Home Energy Pros
9 hours ago
Hannah Wood added a discussion to the group Building Performance Institute (BPI)
Thumbnail

Healthy Home Evaluator (HHE) certification + recorded webinar

Thanks to those of you who joined BPI's webinar on the Healthy Home Evaluator certification…See More
9 hours ago
Michelle Usher posted a blog post

Addison Homes Wins Pinnacle Award for Best Achievement in Energy Efficiency

Addison Homes was amongst the home building industry’s best and brightest honored with a 2016…See More
9 hours ago
Eric Kjelshus replied to Beverly Lerch's discussion Fireplace drafts
"A brick chimney will take some 70,000 BTU's to heat up to draft on a fireplace.   A…"
21 hours ago
Ed Voytovich replied to Beverly Lerch's discussion Fireplace drafts
"Our solution was to install a Lopi Answer wood burning insert that vents directly through a metal…"
yesterday
Jim Gunshinan's blog post was featured

A Healthy Home and a Healthy Bottom Line

There has been a lot of interest of late in the weatherization and broader home performance…See More
Monday
Jonathan Beers commented on Home Energy Magazine's blog post Natural Gas is Becoming Less Attractive
"The carbon intensity of electricity use (lbs. of CO2/MWh) varies a lot from region to region. For…"
Monday
Diane Chojnowski posted events
Monday

© 2016   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service