Technical Help Guide Thermal Expansion Valves Electronic Valves & Controls Solenoid Valves System Protectors Regulators Oil Controls Temperature Pressure Controls Basic Rules of Good Practice Troubleshooting Guide 2014
Introduction This Technical Guide from Emerson Climate Technologies provides a detailed explanation on the operation of common refrigeration system components such as thermal expansion valves, solenoid valves, system protectors, regulators, oil controls and temperature pressure controls. Also included in this guide is a listing of the basic rules of good practice and a detailed troubleshooting guide.
Table of Contents Thermal Expansion Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Internal Equalizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Factory Setting of TXVs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 External Equalizer . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermal Expansion Valves 1
Emerson Climate Technologies Thermal Expansion Valves Thermal Expansion Valves is charged with the same refrigerant as that in the system. The power assembly pressure (P1), which corresponds to the saturation pressure of the refrigerant gas temperature leaving the evaporator, moves the TXV pin in the opening direction.
Thermal Expansion Valves Emerson Climate Technologies External Equalizer Changes in load cause the TXV pin to move: • Increasing the superheat will cause the TXV to open • Decreasing the superheat will cause the TXV to close A TXV with an external equalizer is required when the pressure drop through the evaporator is substantial: • 3°F for residential air conditioning • 2°F for commercial air conditioning • 1°F for refrigeration low temperature range This is because the pressure drop will hold the TXV i
Emerson Climate Technologies Thermal Expansion Valves To compensate for an excessive pressure drop through an evaporator, the TXV must be externally equalized. The equalizer line should be connected to the suction line at the evaporator outlet, past the remote bulb location so that the true evaporator outlet pressure is exerted beneath the TXV diaphragm.
Thermal Expansion Valves Emerson Climate Technologies Superheat suring superheat, install a calibrated pressure gauge in a gauge connection at the evaporator outlet. In the absence of a gauge connection, a tee installed in the TXV external equalizer line can be used just as effectively. A refrigeration type pocket thermometer with appropriate bulb clamp or an electric thermometer with thermocouples may be used to measure gas temperature.
Emerson Climate Technologies Thermal Expansion Valves sible to determine that the cause of the trouble call is because of improper methods of instrumentation rather than any malfunction of the TXV. When troubleshooting in mountain areas (such as Denver, Colorado or Salt Lake City, Utah) use a Pressure-Temperature chart that has correct readings such as Emerson Climate Technologies’ 5,000 ft. pocket chart. Gauge pressures will read lower than they would at sea level.
Thermal Expansion Valves Emerson Climate Technologies Application Tips sion and faulty remote bulb contact with the line. On lines smaller than 7/8” OD the remote bulb may be installed on top of the line. With 7/8” OD and over, the remote bulb should be installed at the position of about 4 or 8 o’clock. (See fig. 8) It is good practice to insulate the bulb with a material which will not absorb moisture.
Emerson Climate Technologies Thermal Expansion Valves Large fluctuations in superheat in the suction gas are usually the result of trapped liquid at the remote bulb location. Even on properly designed suction lines, it is sometimes necessary to move the remote bulb a few inches from the original location to improve TXV performance. On multi-circuit evaporators fed by one TXV, install the remote bulb at a point where the suction gas has had an opportunity to mix in the suction header.
Thermal Expansion Valves Emerson Climate Technologies Balanced Port TXV Operation In conventional TXVs, as the pressure drop across the TXV port changes due to changes in head pressure or suction pressure, the operating superheat of the TXV will vary. Depending on the operating conditions under which the superheat was originally set, this “unbalance” can sometimes result in compressor flooding or evaporator starvation.
Emerson Climate Technologies Thermal Expansion Valves • • • • Liquid charges have the following properties: Not subject to cross-ambient control loss Little or no superheat at start-up Superheat increase at lower evaporator temperatures Slow suction pressure pulldown after start-up As in liquid charges, the remote bulb can be filled with the same refrigerant as the system refrigerant (producing a gas charge). Or, it can be filled with a different refrigerant, producing a gas cross-charge.
Thermal Expansion Valves Emerson Climate Technologies Other TXV Considerations Factory Superheat Setting Solenoid Liquid Stop Valves Unless otherwise specified, all Emerson TXVs will be preset at the factory at a bath temperature which is pre- determined by the charge symbol or the MOP rating. The bath temperature at which the TXV superheat is set is coded alphabetically in the superheat block on the TXV nameplate, as shown in Fig. 15. The TXV is produced as a tight seating device.
Emerson Climate Technologies Thermal Expansion Valves Emerson “T” Series TXVs [except “W”-(MOP), G-(MOP) or GS-(MOP) gas charged types] may be installed in any location in the system. The gas charged type must always be installed so that the power assembly will be warmer than the remote bulb. The remote bulb tubing must not be allowed to touch a surface colder than the remote bulb location.
Thermal Expansion Valves Emerson Climate Technologies TXV Charge Code Selector Applications Operating Ranges MC/FC MZ/FZ MW15/FW15 (MOP) MW35/FW35 (MOP) MW55 HCA/HAA AIR COND.
Electronic Valves & Controls 14
Emerson Climate Technologies Electronic Valves & Controls Electronic Valves – Introduction Advantages of Electronic Solution Thermostatic expansion valves and mechanical regulator valves have been used in the refrigeration and air conditioning industry to control superheat and refrigerant mass flow since the very beginning.
Emerson Climate Technologies Electronic Valves & Controls Parts Required for Electronic Valves when used as TXV and Driven by Superheat EC3-32 and EC3-33 Systems Description Type PCN Notes EX4 097719 EX5 097720 EX6 097721 Select one valve based on capacity requirements of system EX7 097722 EX8 097723 EXV-M60 097741 Cable used to connect valve to controller EXDU00 Universal Superheat Controller EC3-33 097707 Basic SH controller EC3-32 097708 Basic with option to connect to PC Termi
Emerson Climate Technologies Electronic Valves & Controls Pressure Transmitter – PT4 The heart of the transmitter is a pressure sensitive piezo resistive cell. This is surrounded by an oil cushion enclosed by a stainless steel diaphragm. The integrated electronic module conditions the output of the pressure cell to produce a temperature compensated signal of 4…20 mA. The pressure cell consists of a silicon diaphragm with strain gauges diffused into it.
Emerson Climate Technologies Electronic Valves & Controls under different operating conditions such as compressor start-up, start of further compressor, high head pressure, low head pressure, high load, low load and partial load operation. EC3-X32 is capable for diagnostics and alarm. The alarm can be received via relay output, via TCP/IP network as well as optical LED/alarm code on ECD-002.
Emerson Climate Technologies Electronic Valves & Controls Third Party Controller The direction of the rotation depends on the phase relationship of the current pulses, the amount of rotation is dependent on the number of pulses. One pulse will drive the motor one step i.e. the rotor will move by a=1.8°. Successive pulses will lead to continuous rotation. The drive shaft of the rotor is connected to a spindle which transforms the rotation into linear motion of the valve slide.
Emerson Climate Technologies Electronic Valves & Controls 3) Driving of stepper motor There are many different options to drive stepper motors like the one used in the EX4/5/6/7/8. Emerson stepper motors need a driver board with chopper drive function (constant current), an interface and a controller. 4 10 Chopper drive (constant current) The stepper motor of EX4/5/6/7/8 is a bipolar, 2phase permanent-magnet motor and operates with constant DC current in each phase.
Solenoid Valves 21
Emerson Climate Technologies Solenoid Valves Solenoid Valves In most refrigeration applications, it is necessary to start or stop the flow in a refrigerant circuit to automatically control the fluids in the system. An electrically operated solenoid valve is usually used for this purpose. Its basic function is the same as a manually operated shut off valve, but by being solenoid actuated, it can be positioned in remote locations and may be conveniently controlled by simple electrical switches.
Solenoid Valves Emerson Climate Technologies 2. Pilot Operated Valve The pilot operated solenoid valve uses a combination of the solenoid coil and the line pressure to operate. In this type valve the plunger is attached to a needle valve covering a pilot orifice rather than the main port. The line pressure holds an independent piston or diaphragm closed against the main port. See figures 2a and 2b. When the coil is energized, the plunger is pulled into the center of the coil, opening the pilot orifice.
Emerson Climate Technologies Solenoid Valves Solenoid Valve Selection Minimum Operating Pressure Differential The selection of a Solenoid Valve for a control application requires the following information: 1. Fluid to be controlled 2. Capacity required 3. Maximum operating pressure differential (MOPD) 4. Electrical characteristics 5.
Solenoid Valves Emerson Climate Technologies Installation Emerson Solenoid Valves Solenoid Valves having a spring loaded piston or diaphragm may be installed and operated in any position, but installing more than 90° from vertical is not recommended since dirt or debris may collect in the solenoid area and prevent it from operating. An adequate strainer or filter drier should be installed ahead of each solenoid valve to keep scale, pipe dope, solder, and other foreign matter out of the valve.
System Protectors 26
Emerson Climate Technologies System Protectors Liquid line and suction line filter driers are often referred to as System Protectors because they remove harmful elements from the circulating refrigerant before serious damage results. Keeping the system clean and free of foreign contaminants that can restrict the operation of valves, block capillary tubes or damage compressors is the best way to assure trouble-free operation. These contaminants can be solids, such as metal filings, flux, dust and dirt.
System Protectors Emerson Climate Technologies Absorption vs. Adsorption One factor to consider in selection is ab- vs. adsorption. Absorption means a material’s ability to take another substance into its inner molecular structure. An adsorbed substance doesn’t penetrate the molecular structure. It simply starts building up on the surface of the adsorbent. Walls, cracks, crevices are part of the surface area and are able to hold other substances, greatly increasing capacity.
Emerson Climate Technologies System Protectors HFC Refrigerants and POE Lubricants 2500 2000 Water Content (ppm) 1500 1000 500 0 Mineral POE Oil Oil R-12 R-134a R-22 R-502 R-404A R-410A 0.2 Total Acid Number The use of HFC refrigerants and Polyolester (POE) lubricants for air-conditioning and refrigeration has generated new system chemistry related problems.
System Protectors Emerson Climate Technologies Flow Restriction Suction Filter Driers EK Typical drier Solid Contamination Captured Figure 4 Filtration Capability of Filter driers The filter driers for use in HFC and POE oil systems must keep the system dry and free of any acids generated. However, since water capacity is of primary importance the filter drier should contain a higher percentage of molecular sieve than was required for CFC and HCFC systems.
Emerson Climate Technologies System Protectors Internal Design Internally, suction line filter driers employ the same types of elements as liquid line units. One is the core type, in which the filter drier consists of a rigid, cylindrical, porous core that may perform both the filter and drier functions, or be used in combination with a separate accordion-type filter element.
System Protectors Emerson Climate Technologies Compressor Burnout A compressor burnout can be expected to release a variety of pollutants into the system, including acids. The clean-up procedure below describes the use of system protectors in cleaning up a system. Clean-Up Procedure for Compressor Motor Burnout 1. Determine the extent of the burnout.
Emerson Climate Technologies System Protectors Filter Driers for Heat Pumps A heat pump is essentially a refrigeration system that can flow in either direction. The key to its operation is a four-way reversing valve that routes the discharge gas from the compressor. Depending on whether the system is cooling or heating, the indoor and outdoor coils swap roles, taking turns serving as the condenser and evaporator.
System Protectors Emerson Climate Technologies Simplifying While Servicing Cross section showing BFK internal components INTERNAL CONSTRUCTION Inlet Flapper Valve Molded Desiccant Block When servicing or repairing heat pump systems, especially older units, it’s a good idea to simplify them by replacing unidirectional driers and check valves with bi-directional driers. When a bi-directional filter drier is installed, check valves, and filter driers can all be replaced at once with copper tubing.
Regulators 35
Emerson Climate Technologies Regulators Types of Regulators: Suction Line Regulators EVAPORATOR PRESSURE REGULATOR Suction line regulators provide a wide variety of refrigerant control functions, but are mainly used for regulating suction gas pressures. These regulators provide a method of balancing the output of the refrigeration system with the load requirements. Two basic types are covered here: 1) Upstream pressure regulators, which control from an inlet pressure signal.
Emerson Climate Technologies Regulators Upstream Regulators Series EPRB & IPR The sole function of the Evaporator Pressure Regulator is to prevent the evaporator pressure from falling below a predetermined pressure setting. This enables the system to meet certain load requirements over a wide range of conditions and offers improvement over the simple “on-off” compressor control usually provided by thermostats or pressure switches.
Emerson Climate Technologies Regulators Crankcase Regulators Normally open, the CPR (Fig. 4) closes when compressor pressure rises above the pre-set maximum, forcing the valve back onto its seat. As suction pressure drops, the valve starts to reopen, maintaining a balance. Fig 5. Cutaway of evaporator pressure regulator (Emerson EPRB). Where to Apply Regulators Fig 4.
Emerson Climate Technologies Regulators HeadMaster Head Pressure Controls The application of air-cooled condensers for yearround operation, or during periods of low ambient temperature, requires some means of control to maintain adequate condensing pressures that ensure proper system performance. It is essential that proper liquid refrigerant pressure be controlled to: 1) Maintain liquid subcooling and prevent liquid line flash gas.
Emerson Climate Technologies Regulators NOTE: Should the outdoor temperature fall below design conditions, more refrigerant will be required. The total above is the total charge needed for satisfactory system performance during the lowest expected ambient air temperature conditions. During summer operation the receiver must be sized to safely hold the total system charge. Good refrigeration practice states that the total system charge should not exceed 80% of the receiver capacity. CAUTION: 1.
Emerson Climate Technologies Regulators Hot Gas Bypass HP Parallel Piping Demand continues to mount for improved comfort conditioning combined with lower operating costs. New architectural designs have created real problems for contractors and engineers to maintain humidity control at reduced loads, and to control load variations. Refrigeration and air conditioning systems are usually designed to provide a given capacity at maximum conditions.
Emerson Climate Technologies Regulators Applications: Hot Gas Bypass to Compressor Suction Line Figure 6 shows the most common hot gas bypass system. In this system, the bypass line is taken directly from the compressor discharge line, through a bypass regulator, and into the suction line at the compressor. Although the hot gas bypass regulator is considered a downstream control, there is a big difference in function between a Crankcase Regulator and a hot gas regulator.
Emerson Climate Technologies Regulators Thermal Valves for Liquid Injection Application and Installation When hot gas is bypassed directly into the suction line, it is necessary to make some provision for desuperheating the gas returning to the compressor. Without a small Thermal valve to lower suction gas temperature to tolerable limits, compressor damage may occur. Standard Thermal Valves cannot be adjusted for control over 20°F superheat and, therefore, are not recommended.
Emerson Climate Technologies Regulators Adjusting the Set Point Application Tips The suction pressure at which the valve opens is selectable by increasing or decreasing the load on the spring by turning an adjusting screw. To set it, the evaporator must be cooled down by shutting off the fans, blocking off the airflow, or some other means, until the suction pressure drops to at least five pounds below the desired set point.
Oil Controls 45
Oil Controls Emerson Climate Technologies Oil Controls Any time that compressors are operated in a parallel operation (Suction and Discharge lines manifolded together), an oil control system in needed to ensure that each compressor has enough oil to operate properly. Oil control systems are sometimes as basic as a common line connected between compressors to allow oil and gas equalization. This is usually referred to as a “passive” oil system.
Temperature Pressure Controls 47
Emerson Climate Technologies Temperature-Pressure Controls Temperature Pressure Controls Temperature pressure controls serve a number of purposes in refrigeration systems, including the control of compressor cycling, pump-down, defrost control, pressure limiting, loss of charge freeze protection and fan speed control. TS1 Introduction tion are capillary type of sensors, which do not have a bulb, instead, their capillary serves as the bulb directly.
Emerson Climate Technologies Temperature-Pressure Controls Adsorption Charge – Sensor Type F Adsorption charged sensor types operate on a temperature dependent adsorption material, which is inside the bulb only. These sensor types always respond to temperature changes at the bulb only. This makes them suitable to applications where it is not always defined which part of the thermal system the coldest point is (cross ambient applications). An example for such applications is defrost control.
Emerson Climate Technologies Temperature-Pressure Controls For operational safety, all TS1 with manual reset are designed as trip-free controls, i.e. pressing the manual reset button while the temperature has not reached its reset threshold will not operate the electrical contacts. Bellows Heater TS1 with vapor charges, i.e. sensor types A, E, P (not frost monitors function C or D) have a bellows heater wired across the contacts in the following way.
Emerson Climate Technologies Temperature-Pressure Controls Setpoints PS1/PS2 are adjustable controls with external adjustment spindles for range and differential. Note that manual reset controls have a fixed differential and no differential spindle. By turning the range spindle, the upper setpoint is defined and by adjusting the differential spindle, the differential and the lower setpoint is defined.
Emerson Climate Technologies Temperature-Pressure Controls PSC Pressure Switch The Emerson PSC is a Pressure Switch with fixed switch-point settings.
Emerson Climate Technologies Temperature-Pressure Controls FSX Introduction Description of control behavior FSX electronic speed controllers are designed to control the speed of fan motors in commercial refrigeration system depending on condensing pressure changes. It is suitable for single phase. FSX can be used in air-cooled condensers, air-cooled condensing units and air-conditioning units.
Basic Rules of Good Practice 54
Emerson Climate Technologies Basic Rules of Good Practice Basic Rules of Good Practice Doing a good job in any line of work almost always involves following some basic “good practice” rules, and servicing refrigeration systems is no exception. Knowing and observing such basic rules, to the point that it becomes automatic, can prevent a lot of problems by cutting them off at the pass before they have a chance to happen.
Basic Rules of Good Practice Emerson Climate Technologies DON’T be a “parts-changer.” DON’Ts Analyze problems based on the symptoms, and determine the specific cause before making any changes or repairs. Emerson’s Troubleshooting Guide describes a wide variety of problems that may be encountered, and their probable causes. DON’T think of a TXV as a temperature or pressure control. Thinking of it as a superheat control is basic to achieving optimum system performance.
Troubleshooting Guide 57
SYSTEM TROUBLESHOOTING GUIDE System Problem Discharge Pressure Suction Pressure Superheat Overcharge Undercharge Liquid Restriction (Drier) Low Evaporator Airflow Dirty Condenser Low Outside Ambient Temperature Inefficient Compressor TXV Bulb Loose Mounted TXV Bulb Lost Charge Poorly Insulated Bulb 58 Subcooling Amps
Troubleshooting Expansion Valves Superheat Is Too Low -- TXV Feeds Too Much Problem Symptoms 1) Liquid Slugging Valve Feeds 2) Low Superheat Too Much 3) Suction Pressure Normal or High Causes Corrective Action Oversized Valve Replace with correct size valve Incorrect Superheat Setting Adjust the superheat to correct setting Moisture Replace the filter-driers; evacuate the system and replace the refrigerant Dirt or Foreign Material Clean out the material or replace the valve Incorrect Charge Sel
Superheat Appears Normal -- System Performs Poorly Problem Symptoms Valve Doesn't Feed Properly Causes 1) Poor System Performance 2) Low or Normal Superheat 3) Low Suction Pressure Corrective Action Unequal Circuit Loading Make modification to balance load Flow From One Coil Affecting Another Coil Correct piping Low Load Correct conditions causing low load Mismatched Coil/Compressor Correct match Incorrect Distributor Install correct distributor Evaporator Oil-Logged Increase gas velocity t
Troubleshooting Electronic Valves & Controls EC3-X33 TROUBLESHOOTING – (Controller with Keypad) Symptom Cause Action Superheat is several degrees Incorrect signal from pressure or higher or lower than set-point temperature sensors 1. Check the sensors 2. Make sure ECN-Nxx temperature sensor is used 3. For optimum accuracy, please use: PT4-07S for R22/R134a/R507/R404A/R407C/R124 PT4-18S for R410A or for economizer applications PT4-30S for R744 4.
Troubleshooting Electronic Valves & Controls EC3-X33 TROUBLESHOOTING – (Controller with Computer) Symptom Cause Action Superheat is several degrees Incorrect signal from pressure or higher or lower than set-point temperature sensors 1. Check the sensors 2. Make sure ECN-Nxx temperature sensor is used 3. For optimum accuracy, please use: PT4-07S for R22/R134a/R507/R404A/R407C/R124 PT4-18S for R410A or for economizer applications PT4-30S for R744 4.
Troubleshooting Solenoid Valves Problem Normally Closed Valve Will Not Open -orNormally Open Valve Will Not Close Causes Corrective Action Movement of plunger or diaphragm restricted a) Corroded parts b) Foreign material lodged in valve c) Dented or bent enclosing tube d) Warped or distorted body due to improper brazing or crushing in vice Clean affected parts and replace parts as required. Correct the cause of corrosion or source of foreign materials in the system.
Special Considerations For Industrial Solenoid Valves Symptoms Causes High Internal Seat Leakage (high temperature steam up to 400°) Corrective Action Wrong Seat Elastomer Used (Buna N) Use Valve with Teflon Seat Elastomer External Leakage (high temperature steam up to Wrong Gasket Material Used (Neoprene) 400°) Use Ethylene Propylene Gasket High Internal Seat Leakage (high temperature steam up to 250° or water up to 210°) Wrong Seat Elastomer Used (Buna N) Use Valve with Ethylene Propylene Seat E
Troubleshooting Regulators Problem Causes Erratic Pressure Control Pilot inlet filter screen obstructed Piston bleed hole restriction Excessive dirt in pilot/solenoid Regulator Will Not Open (EPRBS Version) Coil is damaged or not energized Verify coil is energized. Replace if necessary. Piston bleed partially obstructed Disassemble and clean regulator. Piston bleed port obstructed Pilot inlet filter screen obstructed Regulator Will Not Close (EPRBS Version) Replace pilot assembly.
Problem Causes Compressor tripping on Internal Thermal Protector - Fails to Start-Up and Run Long Enough to Pull Down Temperature Corrective Action CPR setting too high Re-adjust the CPR to a lower setting - see adjustment procedure CPR setting is too low Valve Fails to Open Valve defective - bellows leak, pressurizing the upper adjustment assembly Replace valve Troubleshooting Head Pressure Controls Problem Causes Low Head Pressure During Operation System Runs High Head Pressure -orCycles on Hi
Troubleshooting Oil Controls - OMB Problem Causes Oil Level Too High In Sight Glass Corrective Action OMB out of calibration Replace OMB Too much oil in system Remove oil from oil separator or reservoir until proper level is maintained Too much oil coming back from evaporator Check system piping design for: - Proper velocities - P-traps at the bottom of all suction risers - Piping pitched to compressor - Overlapping or defrosts that are not staggered Debris under solenoid valve seat Unscrew solen
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