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ACCA manual S            
                                                                                                                                                                              

The concept of using Expanded Data Charts for equipment selection is a joke.

ICC CODE REQUIRES USE OF AN ACCA MANUAL S
"OR OTHER APPROVED HEATING AND COOLING CALCULATION METHODOLOGIES" FOR THIS TASK. 

THIS "APPROVAL" IS FROM THE BUILDING CODE OFFICIAL, NOT ACCA. OTC does not need data charts.

NOTE TO CODE OFFICIALS:
THIS PRODUCT IS INTERPOLATING FOR: 
OUTDOOR TEMPERATURE, INDOOR TEMPERATURE, INDOOR R/H, INDOOR CFM, COIL BYPASS FACTOR, ALTITUDE, and LOAD CALCULATION SENSIBLE / LATENT RESULTS; in the same way manufacturers create their expanded data charts from AHRI data. 

(please feel free to email krservices@cox.net with any technical questions.)

But unlike ACCA Manual S, 
with OTC you only have to enter your design conditions, 
and the AHRI RATING of what you want to use,
and you will see whether you've made
the right choice. 

You can then adjust your airflow,
to possibly match it closer to the latent / sensible needs from your heat load,
and you're done.

If you have manufacturer data,
you can also fine tune the OTC output to it if desired,
or verify whether IT is corrupt.

The accuracy of results with OTC is more predictable than when using manufacturer expanded data, 
which ACCA claims can also be corrupted. ACCA's Manual S prescribed method is more likely to cause errors, if an average imperfect human has to 
examine and precisely copy MULTIPLE BTU/hr figures from charts, over to into interpolation tools. 

With OTC you can then proceed with duct sizing, permit filing, etc., without having to wait on your suppliers' exact equipment inventory report.

You can also find and easily change your Brand selection and model numbers, at any later time with 
this same program, without having to locate more expanded data, which is what you have to do 
with the ACCA manual S prescribed method.

Why is manufacturer expanded data use difficult?

A. If you are not a product dealer, you will likely need an access password to get the data. So that restricts third party consultants from serving their clients in a timely way. Many small contractors sub their design work out.

B. Some manufacturers no longer provide the data charts in a convenient hardcopy or Adobe pdf format. You have to know the EXACT model match-up you intend to use, input that and the design conditions, in order to have a single chart generated for one single model. If that one's capacity doesn't match, then "lather, rinse, and repeat".

Here is the actual text of a MAJOR manufacturer's web page:

This tool provides capacity details to meet equipment selection procedures required by building code requirements (2009 & 2012 IRC), Energy-Star new home construction requirements and utility company

rebate program requirements.

In three easy steps, you'll have the information you need for the ACCA Manual S Residential Equipment Selection Speed Sheet.

Step 1: Select your system components.

Step 2: Enter your Design Conditions.

Step 3: Get the results!

So they actually WANT you to use the complex freebie spreadsheet from ACCA. And you do it over and over, until you get a match-up that works!!

C. While doing our error verification trials, we found 2015 data charts which appeared to be corrupt, until we realized that the wet-bulb numbers on the chart had been simply printed in reverse order by the manufacturer. When we reversed their temperature number order, and used all the chart values as is, our OTC results matched perfectly!!! Now how would any contractor have caught those messed up data charts! And this came from one of the worlds largest manufacturers of HVAC on a very popular model!

D. Some expanded charts only show values at 80 degree indoor air conditions. So you have to adjust every value by a factor for systems with return air of 75 degrees. That's a lot of time spent with a calculator, for a system which may not even be a match. Newer charts have begun to include 75 degree columns, but you must be aware that the wet bulb changes too!

OTC GETS YOU CLOSE TO WHAT YOU NEED FIRST, THAN YOU CAN GO HUNT DOWN THE SPECIFIC CHART IF YOU WANT TO.

 

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