HOME OF "OFF-THE-CHARTS"
EQUIPMENT SELECTION AND OPTIMIZATION SOFTWARE
The concept of using Expanded Data Charts for equipment selection is a joke.
ICC CODE REQUIRES USE OF AN ACCA
THIS "APPROVAL" IS FROM THE BUILDING CODE OFFICIAL, NOT ACCA. OTC does not need data charts.
NOTE TO CODE OFFICIALS:
(please feel free to email firstname.lastname@example.org with any technical questions.)
But unlike ACCA Manual
The accuracy of results with
OTC is more predictable than when using manufacturer expanded data,
With OTC you can then proceed with
duct sizing, permit filing, etc., without having to wait on your suppliers'
exact equipment inventory report.
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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