Top 5 Changes to ACCA Manual S

     As I had brought up years ago, right here on Excess Air, ACCA's Manual S was in dyer 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!

UPDATED: Big Changes for Duct Testing in MA

      If you have not been asked to complete a duct test by your local Massachusetts Inspector, it is just a matter of time before you are surprised by this stringent/updated code requirement.  Despite some push-back from Contractors  and Inspectors, all of MA is required to test new or altered duct systems.  All of MA adopted the 2012 International Energy Conservation Code (IECC), enforced as of August 16, 2014.  Unlike the previous code, this makes what was considered the "Stretch Code" now the base residential code.  Also, it pays to know their permit structure, to avoid losing what could amount to be a significant part of your profit on these jobs.

Procedure with TEC Duct Blaster

     If you are working in any of the cities and towns across MA, you are required to complete a "Total Leakage Duct Test".  Unfortunately for most, the new required qualification of being a HERS Rater or BPI Certified Professional can be a stumbling block.  True, we have many certified individuals throughout the state - myself being one.  This may be an added cost to your job, one you may not have been prepared to pay for.  For New Construction, this test is typically completed by the HERS Rater as part of the building permit process.  Just imagine you are asked for the duct leakage report on a retrofit, a new duct system in an existing home.  Surprise, lost profit!
      The code is now three times more stringent than it was last week.  Gone are the days of passing a total leakage duct test by chance.  We are now required to make a whopping 4CFM / 100 SqFt., or 4% leakage rate.  One must take careful attention to seal all seams with UL Listed mastic in order to reach this goal.  The fortunate alternative is that if all ducts are in conditioned spaces, they do not have to be tested!
     Anyhow, take a look at the attached document I created, I think it will help those that are just becoming involved with Duct Testing in MA.  Also, please share your experiences with the local city and town requirements by commenting below - nobody likes to be surprised.

No Bubbles, No Troubles!

  Or is there?  This saying is an old adage in our industry to let the technician know that the refirgerant charge is "all set".  You see, there must be a steady stream of liquid to the metering device for it to function properly.  For sake of conversation, let's use the TXV.  In order for most TXV's to throttle and correctly maintain the desired Superheat, there must be a minimum of 2F of subcooled liquid at the valve (not where it is measured, near the condenser).  If the liquid were to flash off ahead of the valve, destruction to the TXV may occur.  So, some old timer along the way figured he would look into the sight glass (what we install in residential air-conditioners this day and age are moisture indicators), and determine if there was a steady stream of liquid, or in other words: "No Bubble, No Troubles!".  For years, this method combined with "beer can cold", or "sweating back to the compressor" were used to determine the refrigerant charge was 'close enough'.  Those that know me know that I speak from experience here, I have tried them all!
  What we were missing was the fact we were overcharging systems, significantly.  Sometimes to the point of slugging compressors, particularly with fixed orifice systems.  Having a steady stream of liquid does not mean the refrigerant charge is correct!  I know, I am preaching to the choir here.  You see, if you are reading my blog than you care enough to learn how to do things right.  I am sure you have picked up an installation manual recently and actually flipped through it, instead of kneeling on it and tossing it into the trash!  If you have, you will notice that no where in these books does it read, "No Bubbles, No troubles!"  If it were that simple, than they would have put it into the start-up procedure.  Do me a favor: stop wasting energy and killing compressors, okay?  Take the extra ten minutes to measure the Superheat and Subcooling on the system, and verify they are within manufacturer specs.  Believe me, you will have less warrantied labor work where you make zero profit replacing compressors!