4598770
Description
| Question | Answer |
| what are the basics of a metering device? | Provides small opening, or orifice, through which only a small amount of refrigerant can flow at one time. |
| Name 6 types of metering devices? | 1. Capillary tube 2. TXV 3. Automatic expansion valve (AXV) 4. Electronic expansion valve 5. low side float (LSF) 6. High Side Float (HSF) |
| Name the main two types of fixed metering devices. | 1. Capillary tube 2. Fixed orifice |
| What appliance is commonly used with cap tubes? | Refrigerators and window AC units |
| What application uses fixed orifice? | Residential splits and heat pumps |
| Describe a cap tube? | a length of tubing with a small and precisely form inside diameter. |
| What defines the performance of a cap tube? | - tube length - Inside diameter - number of turns |
| Where is the cap tube usually attached? | Between the evap and the liquid line. |
| How is the cap tube usually positioned? | A portion of it is positioned so a portion of it is in contact with the suction line. |
| Why is the cap tube positioned that way? | This causes the cap tube to transfer some of it's heat to the suction line (super heat and subcooling created with transfer) |
| With a cap tube system, what happens to the high and low side once the compressor shuts off? | both pressures equalize |
| What is a static condenser? | Condensers that do not have a fan, rely on convection to cool it off. |
| common cause of cap tube failure? | - Bent - crimped - plugged |
| When replacing a cap tube it is good practice to replace what? | Filter Drier |
| What is a fixed orifice? | Small fitting with a small hole that fits between the inlet and outlet. |
| How does the Thermostatic expansion valves work? | Adjust refrigerant flow rate to compensate for varying loads. |
| How does a sensing bulb function? | It is filled with a volatile fluid, and pressure inside the bulb change with the temp of the evap outlet. |
| What is refrigerant vapor that forms in the evap due to a sudden drop in pressure between high and low side of the system called? | Flash Gas |
| Difference in temperature between the evap inlet and the sensing bulb is called? | Super Heat |
| Turning the TXV adjustor clockwise will do what? | increase spring tension. |
| Turning the TXV adjustor counter clockwise will do what? | decrease spring tension. |
| When a TXV is going too far in one direction and then over correcting and returning too far in the other direction is called what? | Hunting |
| The bottom of the TXV diaphgram is exposed to what? | The pressures at the evap inlet. |
| The top of the TXV diaphgram is exposed to what? | to the sensing bulb pressures |
| Which sensing bulb is uses the same refrigerant as the system? | Liquid Charged - Gas charged Sensing bulb |
| Which sensing bulb is uses the different refrigerant as the system? | Liquid cross charged sensing bulb and gas cross charged. |
| Which sensing bulb contains two substances? | Adsoprtion Gas cross charged sensing bulb. |
| What does the adsoption bulb contain? | - Non condensing gas (carbon dioxide) - Carbon, silica gel or charcoal. |
| What splits the flow of refrigerant into several paths to reduce pressure drops in the evap? | Distributors |
| Which metering device is controlled by low side pressure? | Automatic expansion valve |
| if an AXV is not equipped with ______ it will not equalize the high and low side during off cycle. | Bypass or Valve Bleeder. |
| Which metering device uses an electric operator instead of a diaphragm power assembly. | Electronic Expansion Valves. |
| What metering device uses a flooded system? | Low side float |
| Do Pressures balance on a LSF during off cycle? | No. |
| What metering device regulates refrigerant flow into the evap based on volume of a certain liquid receiver? | High Side Float. |
| Which Valve type is used to deliver discharge vapor into an externally equalized TXV during off cycle and suction vapor during on cycle? | Bypass valve. |
| How many inputs and output do bypasses have? | Bypass valve has one input valve and two output valves. |
| Which valve is frequently used in heat pumps? | Reversing valves |
| Which valve is commonly installed between the suction line and the compressor inlet to prevent compressor overloading? | Pressure Regulating valve |
| what prevents high pressure vapor and refrigerant oil from backing up into the evap during off cycles? | Check Valves |
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