Overview
Chvac quickly and accurately calculates the maximum heating and cooling loads for commercial buildings. The cooling loads can be calculated with either the CLTD method or the new RTS (Radiant Time Series) method. The program allows an unlimited number of rooms which can be grouped into as many as 100 air handling systems. Chvac automatically looks up all cooling load and correction factors necessary for computing loads. In addition, it can look up outdoor design weather data for over 2000 cities located around the world. There is also provision for editing the weather data as well as adding data for other cities. Comprehensive reports list the general project data, detailed room loads, air handler summary loads, outside air loads, total building loads, building envelope analysis, tonnage requirements, CFM air quantities, chilled water flow rates (if applicable), and complete psychrometric data with entering and leaving coil conditions. Other outstanding features include ASHRAE Standard 62 analysis, automatic building rotation, 360 degree wall orientations, tilted glass, exterior shading, internal operating load profiles, variable indoor design temperatures, people diversity, pretreated outside air, seasonal infiltration and ventilation rates, reheat loads, duct gains and losses, and return air plenums.
Calculation method
Chvac performs cooling calculations using either the CLTD method or the new RTS (Radiant Time Series) method. The RTS method is described in the latest edition of the ASHRAE Handbook of Fundamentals, while the CLTD method is from earlier editions of the Handbook. The RTS method is especially accurate because it calculates the delayed effect of radiant heat gains during each of the past 24 hours in determining the current cooling load. That means, for example, that the program gives proper consideration to the effect of an external shading device that shades a window in the morning in a room that peaks in the afternoon. The CLTD method, on the other hand, uses exact table values from the Handbook where possible, which means that you can verify the results by hand. You can actually switch back and forth between RTS and CLTD for any project. All you have to do to switch between the two methods is to enter equivalent Master Data definitions for roofs, walls and glass and then change the Cooling Calculation Method input to the other method.
Features
- Calculates Peak Heating and Cooling Loads
- Calculates Both Heating & Cooling CFM Requirements
- Calculates Runout and Main Trunk Duct Sizes
- Automates Compliance with ASHRAE Standard 62
- Provides Overall Building Envelope Report
- Creates Spreadsheet File with Calculated Results
- Performs Complete Psychrometric Analysis
- Prints Bar Graphs and Exploded Pie Charts
- Exterior Shading Handles Overhangs, Fins, & Glass Tilt
- Uses Exact ASHRAE RTS or CLTD Procedures
- Built-in Design Weather Data for Hundreds of Cities
- Analyzes Up to 12 Months Per Calculation
- Calculates 24 Hours per Design Day
- Allows Unlimited Number of Rooms per Project
- Rooms May Be Grouped Under 100 Air Handlers
- Rooms May Be Optionally Grouped Under VAV Boxes
- Allows 100 Walls, 100 Windows, and 100 Roofs per Room
- Allows Simultaneous Infiltration and Ventilation
- Allows Different Summer and Winter Air Rates
- Allows Different Indoor Conditions for each Room
- Allows 20 Master Roof Types, 20 Master Wall Types, 20 Master Partition Types, and 50 Master Glass Types
- Provides a User-Defined Library of Custom Materials
- Provides a List of your Favorite Materials
- Allows Up to 10 Internal Operating Load Profiles
- Allows Full 360 Degree Wall and Glass Orientations
- Allows Glass to be titled from 0 to 180 degrees
- Allows for Roof and Wall Color Effects
- Provision for Both VAV and Constant Volume Systems
- Proper Handling of Return Air Plenum Loads
- Accounts for People Diversity in Total Building Load
- Computes Supply Fan Horsepower and Heat Gains
- Accounts for Both Draw-thru and Blow-thru Fans
- Calculates Reheat Requirements if Necessary
- Computes Supply and Return Duct Gains and Losses
- Allows Direct Specification of Supply CFM Quantities
- Allows Specification of Minimum Supply Air Quantities
- Allows Heating Only, Cooling Only, or Both
- Excess Supply Air Can be Handled as Reheat, Reserve Capacity, or by Adjusting the Leaving Coil Conditions
- Leaving Coil Conditions Can be Specified with a Desired Dry Bulb Temperature or a Relative Humidity
- Calculates Chilled and Hot Water Coil Flow Rates
- Allows for Pretreated Outside Air
- Calculates benefits of Heat Recovery Ventilators (HRV) for heating and cooling
- Allows Heating and Cooling Safety Factors
- Lighting & Equipment Watts along with No. of People can be Entered Directly or on a Per Square Foot Basis
- Selects Equipment from the ARI/GAMA Databases
- Creates Custom Sales Proposals
- Creates Spreadsheet Output File