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Block Load (BLK)

Commercial load calculation at its finest.

Carrier's Block Load program is a powerful, fully featured HVAC load calculation program suitable for commercial buildings of any size.

How Does It Work?

Block Load asks you to supply basic information about your building, and then provides you with all the sizing and load information you need to analyze and design the HVAC system and select all of the air conditioning equipment.

4 Reasons to Choose Block Load

Easy to Learn, Easy to Use

Intuitive tree view navigation lets you see your entire project, and means you won't `get lost’ in the program. All of your project data is just a single mouse click away.


Rigorous (not simplified) cooling load calculations based on the ASHRAE® Radiant Time Series (RTS) or Transfer Function Method (TFM) means you don't have to worry about over- or under- sizing your loads.


Block Load is ideal for preliminary sizing calculations or for final design submittals. You can run a single-zone rooftop job or a 100-zone VAV central air handler job with equal ease. You can run using English or S.I. Metric units. And you can generate presentation-quality output reports.


Block Load's help system and user's manual contain the answers to most of your questions. But for those especially tough questions, a staff of trained HVAC engineers provides you with free, unlimited technical support via your help desk.

Load Calculation Features

  • Uses ASHRAE procedures for Radiant Time Series (RTS) or Transfer Function (TFM) cooling load calculations, design heating load calculations, solar radiation calculations.
  • Calculates room and zone loads 24 hours a day for design days in all 12 months.
  • Identifies peak room, zone, and coil loads.
  • Suitable for sizing systems involving central station air handlers, packaged rooftop units, self-contained units, split systems, DX fan coils, hydronic fan coils and water source heat pumps.
  • Sizing data is provided for central cooling and heating coils, preheat coils, fans, terminal reheat coils, CAV and VAV air terminals, fan coils and terminal heat pumps.
  • Analysis of ventilation requirements using procedure described in ASHRAE Standard 62-2001.
  • Provides a database of design weather data for over 700 cities worldwide.
  • Block Load Screenshots

Report Features

  • Provides many well-formatted reports listing calculation results as well as input data.
  • Key system sizing report summarizes data needed for equipment selection on 1-2 pages.
  • Key ventilation report summarizes requirements for each zone in the system.
  • Additional reports provide zone and system component loads, hourly zone and system load profiles, detailed hourly psychrometric data and a graph of the psychrometric process.
  • Provides features for copy-and-paste from displayed reports into other documents.
  • Provides features for saving reports as files in RTF- or PDF-format documents.
  • Advanced output reports available to help in the diagnosis of load results and system behavior.
  • Report Samples

Other Program Features

  • Tree view in main window allows for easier program navigation and data viewing.
  • Choice of conventional input format or spreadsheet style input for building data.
  • Runs in English and SI Metric units.
  • Suitable for new construction and retrofit applications.
  • Provides a database of design weather data for over 700 cities worldwide.
  • Provides feature for archiving and retrieving project data.
  • Provides feature for converting projects created with previous Block Load v3.x and v4.x versions of the software.
  • Provides a global search and replace feature for all building data.
  • Provides a feature to automatically change the orientation of the entire building.
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