建筑环境与能源应用工程专业英语15

Why use VAV?
– Provides multiple zones of comfort – Life cycle cost will be less than other HVAC
Systems trying to accomplish similar comfort levels – Load diversity
Prepare Checklists
and Testing Plans
Verify Components,
Witness Start-Up
and Component
Testing
Perform Functional Testing, Resolve Deficiencies,
Review O&M
Prepare CX Report,
– Operates as an owner’s representative to insure the installed systems meet the owners requirements and the plans and specifications
– Usually hired by the owner, sometimes by the architect, or general contractor.
• First year of occupancy was frustrating for the owner
• Contractors spent more money during the warranty periods
• Contractors can be rushed without enough time to double-check their work
Why Not ??
– Higher first cost than comparable single zone
• Controls, equipment, commissioning
– Increased maintenance cost
• More pieces to look after
Constant volume - variable temperature system have been dominating the HVAC applications in the past for obvious reasons. The implementation of variable volume control has been done with dampers or other mechanical control methods.
建筑环境与能源应用工程专业英 语15
• Definition: What is Commissioning (Cx) ?
• “A quality-focused process for enhancing the delivery of a project. The process focuses on verifying and documenting that the facility and all of its systems and assemblies are planned, designed, installed, tested, operated, and maintained to meet the Owner’s Project Requirements.〞
• Electrical Systems – Switchgear, major disconnects, backup generators and UPS (Uninterrupted Power Supply)
• Fire Safety Systems • Security Systems • Kitchen equipment • Irrigation system • Laboratory Fume hoods, gas control
Staff Training, Define Seasonal Testing
Other Types of Commissioning
• Retro-commissioning – Performed to existing buildings that have not previously been commissioned, after they have been occupied – Usually instigated as a result of high energy bills or poor occupant comfort
• Hold contractors accountable for the specifications
Commissioning Scope
• Mechanical Systems – All HVAC equipment – Building automation system and hardwired controls
occupants • Provide improved documentation of system characteristics
Commissioning - What did we use to do and why do we need it?
• CX of mechanical and electrical systems was done by the
Benefits of Commissioning
• Reduced change orders • Less warranty and callbacks for contractor • Smoother turnover to maintenance • Improved equipment reliability • Reduced IEQ problems
All participants in the construction project have a commissioning responsibility. Participants include the commissioning authority, owner, design professionals, construction manager, general contractor, subcontractors, operation and maintenance manager, suppliers, and equipment manufacturers.
• ASHRAE Guideline 0-2005, The Commissioning Process
Commissioning Person
– Commissioning is often performed by an independent third-party engineering company.
• Recommissioning – Performed 5 to 10 years after a building was previously commissioned – Sometime used as a form of deferred maintenance
Variable Air Volume (VAV)
• Design Engineers do not have enough budget to oversee the
construction in detail
• Owners have had bad experiences with prolonged project closeout, and see CX as a solution
– Reduced occupant complaints – Improved productivity • Correct system operation and installation • Facility meets Owner’s expectation and operational needs • Reduced utility consumption and operational costs
use of varying airflow to control the condition of air, in contrast to the use of constant flow (often) with varying temperature.
VAV system controls temperature in a space by varying the quantity of supply air rather than varying the supply air temperature. A VAV terminal unit at the zone varies the quantity of supply air to the space. The supply air temperature is held relatively constant: while supply air temperature can be moderately reset depending on the season, it must always be low enough to meet the cooling load in the most demanding zone, and to maintain appropriate humidity.
Commissioning and Construction Phases
Planning
Design
Construction Acceptance Occupancy
Prepare, Design Intent,
CX Plan, and
Specifications
Review Submittals,
• Smaller equipment ( lower AC unit first cost compared to Constant Volume)
• Less supply air ( less energy consumption)
– Able to adapt to changes in building useinstallingcontractors
• No standardization, or clear approach
• Most of the real CX occurred during the warranty period as warranty calls
• Buildings operated less efficiently
The advantages of variable air volume system implemented with variable speed control are:
Fast control to keep the comfort zone limits
Commissioning Objectives
• Ensure the facility meets the owner’s performance requirements • Provide a safe and healthy environment • Provide optimum energy performance • Provide a facility that can be efficiently operated and maintained • Provide complete orientation and training to facility staff and