Shoreline_
Well-known member
Like on your car. Does the txv close completely and the pressure switch turn off the compressor on the subcool side?
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What happens with no load on an evaporator
- Thread starter Shoreline_
- Start date
Off the internet for the main functions of a TXV valve with equalization.
Temperature and Pressure are in balance: A refrigerant-filled bulb clamped to the suction line accurately reads the temperature of the refrigerant inside the line. As the temperature of the refrigerant changes, the pressure inside this bulb changes, which forces open the needle valve inside the TXV against the opposite force of an adjustable spring. On the other side of the TXV, there’s an equalizer that adjusts for pressure changes at the outlet of the evaporator.
The TXV adjusts refrigerant flow based on these two inputs to maintain a balance. If the refrigerant leaving the evaporator is too warm and the pressure is low, the valve will open to allow more refrigerant in. If it’s too cold, the valve will close to reduce the flow of refrigerant. This constant adjustment ensures optimal efficiency and performance.
Protection: By preventing the evaporator coil from getting flooded or starved, the TXV plays a key role in protecting your compressor from damage. Too much flow could send liquid refrigerant to the compressor causing severe mechanical damage. Too little flow will cause the compressor to overheat as it depends on cool refrigerant vapor for internal cooling.
The compressor will remain running unless the call for cooling has been met while the TXV's mechanics and design adapt to keeping the designed temperature and pressure in balance (10-20 degrees of superheat).
High pressure sensor shutting down the compressor shouldn't be in play and means perhaps the condenser coil is dirty or the dryer filter needs replacing.
Temperature and Pressure are in balance: A refrigerant-filled bulb clamped to the suction line accurately reads the temperature of the refrigerant inside the line. As the temperature of the refrigerant changes, the pressure inside this bulb changes, which forces open the needle valve inside the TXV against the opposite force of an adjustable spring. On the other side of the TXV, there’s an equalizer that adjusts for pressure changes at the outlet of the evaporator.
The TXV adjusts refrigerant flow based on these two inputs to maintain a balance. If the refrigerant leaving the evaporator is too warm and the pressure is low, the valve will open to allow more refrigerant in. If it’s too cold, the valve will close to reduce the flow of refrigerant. This constant adjustment ensures optimal efficiency and performance.
Protection: By preventing the evaporator coil from getting flooded or starved, the TXV plays a key role in protecting your compressor from damage. Too much flow could send liquid refrigerant to the compressor causing severe mechanical damage. Too little flow will cause the compressor to overheat as it depends on cool refrigerant vapor for internal cooling.
The compressor will remain running unless the call for cooling has been met while the TXV's mechanics and design adapt to keeping the designed temperature and pressure in balance (10-20 degrees of superheat).
High pressure sensor shutting down the compressor shouldn't be in play and means perhaps the condenser coil is dirty or the dryer filter needs replacing.
OP
Shoreline_
Well-known member
This doesn't tell me anything I asked for. But thanks for your google search
whateg01
Well-known member
Yes, the expansion valve closes when there's not enough heat transfer to keep the refrigerant evaporating. The high side pressure will go up since there's no place for the refrigerant to go. The expansion valve doesn't control the compressor though. The high pressure cutout switch opens when the threshold is exceeded and this cuts power to the compressor. On some vehicles with a variable displacement compressor, the flow is just reduced instead of the clutch disengaging.
Are you trying to solve a problem?
Are you trying to solve a problem?
danski0224
Well-known member
How new of a vehicle?Like on your car. Does the txv close completely and the pressure switch turn off the compressor on the subcool side?
Some don't have AC clutches anymore. The compressor runs all the time, there's a sort of bypass valve. My Sprinter is like this.
My hybrid doesn't even have a belt, the AC is driven by an electric motor, comparable to a hermetic compressor (sealed shut except for power and refrigerant connections). It also varies capacity- I can see the EV battery watts change on the Scan Gauge.
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Wrench97
Well-known member
The expansion valve never closes completely, there is a low side switch, a thermistor/temp probe or both depending on design to control the compressor clutch or flow valve. The evaporator should never be below 33 degrees. Antique systems did have a desert setting which let them go lower but with any humidity they will turn into a ice cube air can't blow through a ice cube so no cooling.
The high side switch is there to save the system if there is no air flow through the condenser or a blockage in the system to prevent damage to the system.
The high side switch is there to save the system if there is no air flow through the condenser or a blockage in the system to prevent damage to the system.
fitter30
Well-known member
Post 6 ex valve doesn't close completely. With no load ex valve closes to a minimum setting from the bulb getting cold, suction pressure falls below freezing starts to form ice on the fins. Ice builds and will ice all the way back to the compressor super heat and subcooling would fall. Low pressure control on a R410A air conditioning is set at 50lbs = 1° making control for low refrigerant. You tube would have some videos of how much ice can form on equipment
Wrench97
Well-known member
Are we talking about a car or a house A/C unit?
Blueshound_GJ
Well-known member
- Joined
- Feb 21, 2022
- Messages
- 421
What you really need is a droid that speaks Bahchi, the binary language of moisture evaporators.