Code of Practice to eliminate halocarbon emissions from refrigeration and air conditioning systems: chapter 2

Part 1 - Stationary Refrigeration and Air Conditioning Systems (Stationary Cooling Systems)

2.0 Design

The term “cooling” is used throughout the document and refers to both refrigeration and air conditioning.

Good design includes a load calculation, the consideration of environmental impacts and energy efficiency, a life-cycle analysis, and the selection of the most efficient cooling system required for the task. Incorporating the input of all the major disciplines involved in a project into the design concepts will improve the overall project.

Load Calculation

A load calculation is an estimate of the amount of cooling that will be needed. The information input into the calculation dictates how precise the calculation will be. The appropriate refrigerant and associated cooling system should be selected to meet the calculated design cooling load.

• Standards for air conditioning systems usually take into account the size of the building, the cooling requirements, the amount of insulation installed, the contributors to heating and cooling in the building, air changes, siting of the system in the plant and a host of other factors.
• Standards for refrigeration systems take into account the type and quantity of products to be cooled, the desired temperature, the contributors of heat gain to the system, and the frequency and length of time the doors are expected to be open, as well as other factors.

Environmental Impacts

Additional factors to consider in the selection of the appropriate cooling system include the system's environmental impacts. The selection of a refrigerant with low ozone-depleting potential and/or low global-warming potential can be considered at the design phase.

Energy Efficiency

The integration of energy efficiency and conservation into decision making, as well as knowledge about the different energy efficiency ratings and programs such as ENERGY STAR®, will positively affect the whole life cycle of a cooling system. The Leadership in Energy and Environmental Design (LEED)® program requires high levels of energy efficiency that should allow a reduction in the environmental footprint of a building. Many of these efficiencies will have an effect on reducing the cooling requirements of the building.

Life-Cycle Costing/Analysis

Life-cycle costing is a financial analysis tool that looks at the total costs of constructing, operating and servicing a system. The analysis is usually carried out very early in the conceptual stages of a design while there is the greatest opportunity for cost savings, and can reduce under- or over-designing.

General Considerations in the Selection of a Cooling System

The designer should consult the equipment manufacturers' and refrigerant manufacturers' specifications to select the appropriate system for the client's needs. A cooling system should be designed with safety in mind and operate within applicable jurisdictional requirements. It should be reliable, easy to inspect and service, and have readily available replacement parts. The material should also be compatible with the installed environment (for example, the material will not rust). To maximize the benefit of monitoring systems, the designer should inform the client that resources will be needed over the life of the system to collect, compile and analyze the data necessary for monitoring the system's performance and environmental impacts.

Manufacturers should ensure that the design of a cooling system includes a series of proven features that will minimize refrigerant leaks and premature failure; plant designers should select systems with such features. Consider incorporating the following components into a cooling system:

• Condensers and evaporators with refrigerant charge that is as small as possible.
• Separate oil pump on compressor to lubricate the seal prior to starting.
• Chiller to cool the compressor lubricating oil to prolong the life of shaft seals on large open compressors.
• Vibration eliminators in sufficient quantity to ensure that vibration stresses do not exceed material endurance limit, especially at piping connections.
• Tubes and pipes adequately supported to protect against abrasion due to movement and to allow for thermal expansion.
• Filtration device in condenser tubing to reduce erosion caused by foreign particles.
• Receivers to enable pump-down of refrigerant during servicing. It can be an in-system (for example, separate container attached or shell and tube condenser) or auxiliary receivers that can hold the complete refrigerant charge and are isolatable and protected by a pressure-relief device.
• Access valves to allow connection of a recovery unit on any section of the system.
• Isolation valves to facilitate servicing of the compressor, condenser and evaporator.
• Clamps, fittings and components made of rust-free materials.
• Hoses with near-zero permeability and high temperature-resistance attached with heavy-duty clamps.
• Heavy-duty rotary shaft seals designed to withstand extreme temperatures, maintain seal lubrication while the system is idle for extended periods, and provide external protection against rusting shafts, dust and grit.
• Hermetic compressors.
• Self-reseating pressure-relief valves.
• Control panels with “alerts” built in so that corrective action can be taken before system failure; these panels should be able to be easily monitored by the operator.
• Safety controls to prevent freeze-up of water-chilling machines during operation
• Compressor crankcases with the capability to pump-down to below atmospheric pressure before removing the oil.
• Oil separator on discharge line of compressor for high-pressure systems.
• Physical barrier for the system and its components to provide a high degree of protection.
• Accessibility for inspection, cleaning and replacing the system or its components.

System Owner Manual

A manual should be prepared for the system and all its associated components including the alarms and the control instruments. The manual should be a compilation of all the manufacturers' manuals with explanations of how the pieces fit together.

Basic Requirements in System Design by Manufacturers of Cooling Systems

Manufacturers of cooling systems should perform the following activities:

• Evacuate and dry the system by deep vacuum evacuation (75 mm or less) during the manufacturing process to reduce the risk of contamination.
• Verify that stand-alone systems (for example, refrigerator) are leak-free before charging with refrigerant.
• Document the refrigerant name and charging quantity.
• Provide instructions on installation, operation, servicing and disposal of system.
• Clean, dry, evacuate, leak-test and seal the system before shipment.
• Use dry nitrogen or dry air (-40°C dew point) meeting accepted standards in the industry as a holding charge when shipping equipment.