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: 242

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.

Featured Forum Discussions

Too many BTU's. Too much horsepower?

Started by Steve in General Forum. Last reply by Eric Kjelshus on Saturday. 4 Replies

Stack/wind pressure and flow networks.

Started by Daniel James Grundy in Training. Last reply by Daniel James Grundy on Thursday. 5 Replies

BDT with vermiculite in hollow CMU walls?

Started by Brad Cook in General Forum. Last reply by John Nicholas on Thursday. 2 Replies

Videos

  • Add Videos
  • View All

Latest Activity

Profile IconMatt Ward and Lucifer Prescott joined Home Energy Pros
7 hours ago
Kent Mitchell replied to Rob Madden's discussion Energy auditing as a stand-alone business model...
"Swiftsure Energy has run as consultants, verifiers and raters for 8 years- we audit very few (about…"
9 hours ago
Horace Douglas Hunt, Jr. commented on Home Energy Magazine's blog post The Elephant in the Room
"poignant and timely story!"
12 hours ago
Horace Douglas Hunt, Jr. liked Home Energy Magazine's blog post The Elephant in the Room
12 hours ago
Home Energy Magazine's blog post was featured

The Elephant in the Room

Last week I attended the annual Home Performance Coalition (HPC) Conference & Trade Show in…See More
19 hours ago
Home Energy Magazine posted a blog post

The Elephant in the Room

Last week I attended the annual Home Performance Coalition (HPC) Conference & Trade Show in…See More
yesterday
Diane Chojnowski replied to Quinn Korzeniecki's discussion Don MacOdrum Receives BPI's 2017 Tony Woods Award and Four Others Inducted in to Hall of Fame in the group Building Performance Institute (BPI)
"Congratulations Mike! Thanks for all you do for the home performance industry!"
yesterday
Sarah OConnell's blog post was featured
yesterday

Home Energy Pros

Welcome to Home Energy Pros – the unique digital community by and for those who work in the home energy performance arena.

Home Energy Pros was founded by the developers of Home Energy Saver Pro (supported by the U.S. Department of Energy) and brought to you in partnership with Home Energy magazine.  Home Energy Pros is sponsored by the Better Buildings Residential Network. Please honor our Guidelines

© 2017   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service