1. . Level 3 Air Conditioning Inspections for Buildings
9. Expansion Devices & Other Components (Day2)
PRESENTED BY
Anthony Balaam

2. Expansion Device Selection
It reduces the pressure of the liquid refrigerant, post Condenser and pre-Evaporator.
Can control the flow of liquid refrigerant into the Evaporator to:-
1. Vary the system capacity to meet demand.
2. Prevents liquid refrigerant leaving the Evaporator, causing damage to the Compressor.
Types available are:-
1. Capillary tubes (small systems) and orifice plates.
2. Thermostatic, electronic or balanced port expansion valves.
3. Float valve types (High Pressure & Low Pressure).
4. Manually adjusted expansion
valve and level switch.
This area hear

3. Expansion Devices 1. Capillary Tube and Orifice Plate
Simply a length of small bore-tube.
The length and bore are selected to achieve the pressure drop.
Typically used on small systems which have constant
loads.
Cannot control flow, hence refrigerant charge is critical:-
To avoid compressor damage.
To maximise efficiency.
System cleanliness critical, to avoid blockage in capillary tube.
Larger systems may use an orifice plate in the same way.
Same disadvantages applies.

4. Capillary Orifice Plate

5. Expansion Devices 2a.Thermostatic Expansion Valves (the most common)
Refrigerant pressure is dropped through an orifice.
Refrigerant flow is regulated through a needle valve and diaphragm arrangement.
The diaphragm is moved by the pressure generated inside the controlling phial.
This controlling phial senses the temperature of the refrigerant leaving the evaporator.
This should be approximately 5K above the evaporating temperature, to ensure no liquid returns to the compressor.

6. Thermostatic Expansion Valves5K

7. Expansion Devices 2b.Electronic Expansion Valves
Works in a similar way to thermostatic expansion valves.
Temperature is sensed electronically and a signal is used to open and close the orifice by applying heat to a fluid or by driving a small electric actuator.
This device is more precise and can operate over a wider range of pressures.
Also can be integrated into an electronic or microprocessor control system (BEMS).

8. Expansion Devices 2c.Balanced Port Valves
Similar in design and operation to the TEV.
It has a special internal balanced port design.
This allows the valve to control the flow of refrigerant:-
Accurately over a
wider range of pressures.
It costs 20% more and only available in limited sizes.

9. Capillary Tubes:- Efficiency
Refrigerant charge is critical to capacity and efficiency.
If a capillary tube is damaged or partially blocked:-
Then the system will not be correctly controlled.
And the efficiency will reduce.

10. Thermostatic Expansion Valves
Efficiency
Thermostatic Expansion Valves
The superheat setting has a significant effect on the efficiency and reliability:-
1. If superheat is too low, then the liquid refrigerant can return to the compressor – causing damage or failure.
2. If the superheat is too high (above 5K), capacity and efficiency are unnecessarily reduced.
TEVs do not control well over widely varying pressure differences.
Balanced port or electronic valves are better for floating head pressure.

11. Reference Material
“Heating, Ventilation, Air Conditioning and Refrigeration”, CIBSE Guide B, Chartered Institute of Building Services Engineers, 2005 “Energy Efficiency in Buildings”, CIBSE Guide B, Chartered Institute of Building Services Engineers, 2005 “CIBSE KS13: Refrigeration”, CIBSE Knowledge Series, Chartered Institute of Building Services Engineers, 2008 BSRIA Guide AG 15/2002 –” Illustrated Guide to Mechanical Building Services” Carbon Trust Good Practice Guide GPG280 – “Energy efficient refrigeration technology – the Fundamentals” ROGERS and MAYHEW: “Engineering Thermodynamics: Work and Heat Transfer” TROTT, A. R. (2000), “Refrigeration and Air-Conditioning (3rd ed.)” WANG, S. K.: “Handbook Of Air Conditioning And Refrigeration” JONES, W. P.: “Air Conditioning Applications and Design” “BS EN 378: Specification for Refrigeration Systems and Heat Pumps; Part 1: 2000: Basic Requirements, Definitions, Classification and Selection Criteria; Part 2: 2000: Design, Construction, Testing, Marking, and Documentation; Part 3: 2000: Installation Site and Personal Protection; Part 4: 2000: Operation, Maintenance, Repair and Recovery”, London: British Standard Institution, 2000

12. LEVEL 3 Air Conditioning ENERGY ASSESSORS TRAINING
ANY QUESTIONS OR FEEDBACK ON ANY SLIDE
Any questions or clarity needed over this topic and slides 12

13. Contacts:- STROMA Certification Ltd – Contacts Web Links
Contacts:-
STROMA Certification Ltd.
4 Pioneer Way, Castleford, WF10 5QU

14. End of Day 2 Course