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Guidelines for Energy-Efficient Commercial Unitary HVAC Systems



Guidelines for Energy-Efficient
Commercial Unitary HVAC Systems

Final Report

(Revised January 19, 2001)















Prepared for:

Consortium for Energy Efficiency
98 North Washington Street, Suite 101
Boston MA 02114





© 2001 Consortium for Energy Efficiency
All rights reserved.

Guidelines for Energy-Efficient Commercial Unitary HVAC Systems
Final Report i 1/19/01
TABLE OF CONTENTS
1. INTRODUCTION .. 1
1.1 Executive Summary
1.2 Applications
1.3 Benefits Due to Energy Efficient Installation Practices
1.4 How to Use This Document
1.5 References and Acknowledgements
2. UNITARY AIR CONDITIONERS AND HEAT PUMPS 4
2.1 Load Calculation New or Retrofit Construction
2.1.1 Benefits
2.1.2 Methodology
2.1.3 Design Conditions
2.1.4 Peak Load Reduction
2.1.5 Selecting Unit Capacity to Meet Calculated Loads
2.2 Equipment Selection
2.2.1 Benefits
2.2.2 Efficiency Standards for New Equipment
2.2.3 Evaluation/Replacement of Existing Units
2.2.4 Selection of Heating Equipment
2.3 Unit Configuration and Location
2.3.1 Benefits
2.3.2 Best Practices
2.4 Unit Installation
2.4.1 Benefits
2.4.2 Sealing Around Rooftop Units
2.4.3 Split-System Refrigeration Piping
2.5 Economizers
2.5.1 Benefits
2.5.2 Best Practices
2.5.3 Economizer Retrofits
2.5.4 Economizer Components New or Retrofit
2.6 Energy Efficient Ventilation
2.6.1 Benefits
2.6.2 Methodology
2.7 Additional Options & Accessories
2.7.1 Benefits
2.7.2 Options for Increasing Energy Efficiency
3. AIR DISTRIBUTION ... 13 Guidelines for Energy-Efficient Commercial Unitary HVAC Systems
Final Report ii 1/19/01
3.1 Zoning
3.1.1 Benefits
3.1.2 Best Practices
3.2 Distribution System Types
3.2.1 Best Practices for Constant Volume (CV) Systems
3.2.2 Best Practices for Variable Air Volume (VAV) Systems
3.2.3 Best Practices for Constant to Variable Volume Retrofits
3.2.4 Best Practices for Variable Volume & Temperature (VVT) Systems
3.3 Duct System Types
3.4 Duct System Parameters
3.4.1 Benefits
3.4.2 Duct Locations
3.4.3 Duct & Accessory Selection
3.4.4 Duct System Design
3.4.5 Duct Layout
3.4.6 Duct Velocity
3.4.7 Design Pressure
3.5 Ductwork Installation
3.5.1 Benefits
3.5.2 Duct Construction
3.5.3 Air Plenum Construction
3.5.4 Duct Sealing
3.5.5 Duct Insulation & Liners
3.6 Evaluation of Existing Ductwork Systems for Retrofit
3.7 Reconditioning Existing Ductwork Systems
3.7.1 Benefits
3.7.2 Best Practices
4. CONTROLS .. 22
4.1 Benefits
4.2 Best Practices
4.3 Controls Retrofits
4.3.1 Benefits
4.3.2 Evaluating Existing Controls
4.4 Systemwide Controls
4.5 Fan Controls
4.5.1 Benefits
4.5.2 Methodology
4.6 Night Ventilation
4.6.1 Benefits
4.6.2 Best Practices
5. HVAC COMMISSIONING NEW & EXISTING SYSTEMS .. 25 Guidelines for Energy-Efficient Commercial Unitary HVAC Systems
Final Report iii 1/19/01
5.1 Benefits
5.2 General
5.2.1 Existing/Retrofit Systems
5.3 Commissioning Personnel
5.4 Documentation
5.4.1 HVAC Commissioning Plan
5.4.2 HVAC Commissioning Report
5.4.3 Operation & Maintenance Manual
5.5 Commissioning Best Practices
5.6 Commissioning Unitary Equipment
5.6.1 General
5.6.2 Functional Testing of Roof Top Units
5.6.3 Air Handling Equipment
5.6.4 Cooling Equipment
5.6.5 Refrigerant Charge
5.6.6 Heating Equipment
5.6.7 Economizers
5.7 Commissioning Ductwork Systems
5.7.1 General
5.7.2 Duct & Plenum Construction
5.7.3 Duct & Air Leakage
5.7.4 Duct Insulation & Liners
5.7.5 Air Terminals
5.8 Testing & Balancing
5.9 Commissioning Controls
5.9.1 General
5.9.2 Energy Management Systems
5.10 Training
5.11 Operation & Maintenance (O&M)
5.11.1 Benefits
5.11.2 Best Practices
5.11.3 O&M Checklist
6. DEFINITIONS . 36
7. REFERENCES . 40 Guidelines for Energy-Efficient Commercial Unitary HVAC Systems
Final Report 1 1/19/01
1 INTRODUCTION
1.1 EXECUTIVE
SUMMARY
This specification is a compilation of energy-efficient best practices for the sizing, selection,
installation and commissioning of unitary air-source air conditioner and heat pump systems
up to 30 tons. Commercial new and retrofit construction projects are included. This document
is intended as a tool for improving the energy efficiency of commercial unitary HVAC
installations, which make up approximately 55 percent of the total annual tonnage of
commercial HVAC equipment sold in the United States.
15
The purpose of this document is to facilitate implementation of energy-efficient installation
practices by providing a specification guide that can easily be used by key people in the
industry, namely installing contractors, service providers, and designers. In addition, this
document may be used as a specification for equipment manufacturers and incentive
programs, and as a training tool for program managers. The program goal is a substantial
increase in commercial HVAC energy efficiency with reduced construction and energy costs
as the incentive.
The following table highlights key energy-saving practices:
Key Elements for Energy-Efficient Installations
Element
Specification for Best Practices
Potential Energy Savings*
Load Calculations
Section 2.1, calculate loads using ASHRAE
Fundamentals
2a
, ACCA Manual N
17
or software
based upon these methods
34
Up to 50 percent efficiency increase
when compared with substantially
oversized equipment
4
Unit Selection
Section 2.2, CEE HECAC Initiative
1

for new
10-20 percent compared with U.S. Fed.
equipment - Minimum Efficiency: Tier 1,
minimum efficiency units4, or up to
Premium Efficiency: Tier 2
40 percent compared with older units.
15b
Ductwork Design
Section 3, installation should comply with
ASHRAE Fundamentals
2a
, ACCA Manual N
1
,
Varies
or SMACNA HVAC Systems Duct Design
12d
System Installation
Sections 2-4, manufacturers instructions,
SMACNA HVAC Duct Construction Stds
12a
,
and ASHRAE 90.1-1999
2a
Up to 20 percent supply air leakage can
result in a 60-70 percent increase in fan
power
19
Controls
Section 4, design & installation per
Economizers may save 15 - 80 percent of
ASHRAE 90.1-1999
2a
cooling energy
4
Commissioning
Section 5 & mgrs instructions
Up to 20 percent energy savings
18
Operation &
Section 5 & manufacturers instructions
11-42 percent energy savings
16
Maintenance
*savings are not additive Guidelines for Energy-Efficient Commercial Unitary HVAC Systems
Final Report 2 1/19/01
1.2 APPLICATIONS
This document provides specifications for energy-efficient installation practices relating to
the following commercial systems: Unitary Air Conditioners and Air-to-Air Heat Pumps up to 30 tons capacity,
including packaged rooftop units and matched split systems. Built-up systems,
packaged terminal air conditioners (through-the-wall), chilled water systems and
water-cooled equipment are not included. Heating systems integral with the above unitary air conditioners and heat pumps,
including gas furnaces, electric resistance, electric heat pumps and water/steam coils. Air Distribution Systems applicable to the above unitary equipment, including
ductwork, accessories, controls, commissioning and maintenance. New Construction and Retrofits of existing unitary HVAC systems of the above
types.
This document covers installation practices relating to energy efficiency and is not meant as a
complete guide for installation, nor does it directly address elements of installation that can
impact occupant and installer health and safety. This document is a supplement to applicable
codes and manufacturers instructions. Whenever uniform or local codes or standards require
stricter measures or differing practices, the codes and sta