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: 217

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

Paul Scheckel posted a blog post

Renewable Rant: Traditional Energy!

Why, when I open up a newsletter or market evaluation report about “traditional energy” markets, do…See More
11 hours ago
Rob Madden, Solar Home Broker's discussion was featured

Indoor Air Quality Monitors and Meters

I'm considering purchasing the AirAdvice for Homes indoor air quality monitor but it seems to have…See More
12 hours ago
Luis Hernandez's discussion was featured

ERV Configuration

Greetings everyone,     I did an energy audit on this new home that is too tight and needs…See More
12 hours ago
Kim Tanner's discussion was featured
12 hours ago
John Nicholas's discussion was featured

Slab Edge Insulation - A Side Thread to Melissa's Question

Melissa Baldridge inquired about installing slab edge insulation on a potential E-Star certified…See More
12 hours ago
Melissa Baldridge's discussion was featured

ENERGY STAR - Slab Insulation

Folks,Let's say I have a client who's building slab on grade and intending to certify E-STAR.  I'm…See More
12 hours ago
Sean Maxwell's discussion was featured

Blower Door Databases: ATTMA and Retrotec rCloud

Hi guys,We're pushing for blower door testing in the building code here in Australia and we think…See More
12 hours ago
Bob Blanchette's discussion was featured

Real World Ceiling Fan CFM

Has anybody done testing on delivered CFM of ceiling fans? Energy star has a test room where the…See More
12 hours ago

© 2016   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service