How to diagnose high head pressures at the air conditioning or heat pump compressor: What are the causes of high head pressure at an air conditioner or heat pump compressor motor? This article lists twelve causes of high head pressure and explains their causes, effects, and diagnosis. Some of these, such as a bad TXV or clogs in the refrigeration system are cited as the most common causes of high compressor head pressure. This air conditioning repair article series discusses the the diagnosis and correction of abnormal air conditioner refrigerant line pressures as a means for evaluating the condition of the air conditioner compressor motor, which in turn, is a step in how we evaluate and correct lost or reduced air conditioner cooling capacity. Below we list a dozen causes of high head pressure in an air conditioner or heat pump compressor motor. Of these, debris clogging or malfunctioning TXVs seem to be the most common problems. Note: air or water contamination in HVACR systems is common and can be introduced by a tech who does not purge air from gauge hoses before attaching the refrigerant gauge or by failure to evacuate the system when refrigerant has been lost and the system is to be repaired and re-charged.

Installation of a filter/drier should also always be included in such repairs. Experts note that the symptoms of air contamination and refrigerant overcharge can be similar. ACHR NEWS calls these "non-condensibles" in the refrigeration system. 6 Aug 2015 Tim nordyke said: I had a lennox system that had a very weird set of symptoms. It was an r22 3ton that was around 20 yrs old. In the course of 10 days the system kept popping the high head pressure switch (8 times total) yet the temp difference between intake and output (inside) was only 6 degrees. The AC tech from the home warranty co. blamed it all on a 20% damage area to the condenser from corrosion, and his test set was a clamp on amp meter. He never once connected gauges to check high/low pressures. 10 days after first incident, the compressor locked up and gave up the ghost. When the new system was being brought in, the installer noted the pressure in the system (both sides) was only at 100# and the ambient temp was 95 degrees (per the gauges), the installers claim that the old system did not have enough refrigerant, and that the TEV was clogged/jammed.

Does this sound right?? Too little freon, clogged TEV, 6 degree drop from intake to output, and still pop high head pressure? This question appeared originally at OVER CHARGED of REFRIGERANT, EFFECTSOne cause of high head pressure is clogging or crimping in the condensing coil. I guess the tech is seeing sometihng we don't or she was not an English major and is not a great communicator who didn't explain in more detail how the problem was traced to the coil. Perhaps the thought was that internal corrosion was causing the condensing coil, check valve, or a refrigerant metering device to clog, risking blowing a compressor? I'm suspecting a clogging TEV or a clogging valve on the compressor itself.Well that's why I'm coming here. The clueless tech only used an ammeter to check current draw, said that 6 degree drop from intake to out wasn't the best, but was not a solid indicator of a problem. I learned last night that the system had to be recharged 7 years ago and all they did was add freon.

So I'm thinking that the prior problem contaminated the system, the freon was leaking out, the TEV was clogged so it couldn't shut off flow to the evap coil, and since the return line wasn't cold enough to cool the compressor, it overheated and locked up.wholesale ac units tampa fl Had tech 1 hooked up his gauges when the system was still running he would have caught the pressure issue and saved my system.ducane ac parts listI like to assume just one snafu at a time:garrison ac unit manual Certainly if they added freon and didn't fix the leak you'd be low on freon again. Low freon can ice the coil reducing or stopping actual cooling and it might ice the TEV causing it to block all refrigerant flow. That MIGHT give a high head pressure.

The problem would continue until so much refrigerant has been lost that the TEV no longer ices (and the coil no longer cools). What does your service manager say about the repair? The tech offers nothing...... He is sticking to his claim it is all the condensers fault. When the system ran just before it gave up the ghost, there was no ice or even condensation on or around the TXV (found correct name). What has me wondering is how did I get a high head pressure (faulty switch?) when the pressures were at 100 lbs. just before they evacuated the system, and the amb. If there was debris or corrosion-produced crud in the system it may have been stirred or moved by the refrigerant evacuation and re-charge system, then causing a clog at a check valve, condensing coil, TXV or filter/drier. If the tech was convinced that the blockage was at the condensing coil it would be reasonable to replace it. If your air conditioning or heat pump system has lost its cooling capacity or won't start see REPAIR GUIDE for AIR CONDITIONERS.

Continue reading at REFRIGERANT PRESSURE DIAGNOSIS or select a topic from the More Reading links or topic ARTICLE INDEX shown below.What is air conditioner expansion valve? The expansion device is the fourth major component in air conditioner units. It’s also known as meter devices.Air conditioner expansion valve is the divided point between the low side and the high side of the air conditioner units. Another dividing point is air conditioner compressors. The meter device is located indoor (air handler) units with the evaporator coils. It’s small and hard to see, unless you open the evaporator compartment. The meter devices process is showed between points 5 and 6 in PH charts.Types of air conditioner expansion valveHave a few types of ac expansion valve in air conditioner units: I’ll discuss the operating principles of two types of air conditioner expansion devices, the thermal expansion valve and the capillary tube. Thermal Expansion ValveThe thermostatic expansion valve (TEV or TXV) is used for refrigerant flow control and operates at varying pressures resulting from varying temperatures.

This valve maintains constant superheat in the evaporator. Thermal expansion valve has a sensing bulb, which is connected to TXV by a length of capillary tubing. The capillary tube transmits sensing bulb pressures to the top of the TXV valve’s diaphragm. A capillary tube is a refrigerant control; its common types of air conditioner expansion valve. The capillary is simply a length of tubing with a small inside diameter which acts as a constant throttle on the refrigerant entering the evaporator.A fine filter or filter drier installed at the inlet of the capillary prevents dirt from blocking the tube.A recent development in the design of capillary tubes for air conditioning system uses capillary tubes with a larger insider diameter and a longer tube length. A larger diameter tubes are less likely to become plugged with dirt and other impurities than a smaller diameter tube. The long length provides the necessary resistance to create the desired pressure difference across the metering device.

The capillary tube equalizes the pressure in the system when the unit stops. This pressure equalizing characteristic of the capillary allows a low starting torque motor to be used with the compressor. Typically, a capillary does not operate as efficiently over a wide range of conditions as does the thermostatic expansion valve. However, because of its counterbalance factors in most applications, its performance is generally very good. Refrigeration systems using a capillary tube doesn’t require the use of a liquid receiver since all the liquid is stored in the evaporator during the off cycle. However, a suction accumulator is often found in the suction line to prevent any non vaporized refrigerant from reaching the compressor. This will prevents damage to the compressor when excessive liquid refrigerant enters the evaporator on a low evaporator load condition. How does capillary tube works?The capillary tube can be described as a fixed length of small bore tubing connecting the high pressure side (condenser) of a refrigeration system to the low pressure side (evaporator).

Capillary tube works by restricting and metering the liquid flow, the capillary tube can maintain the required pressure differential between the condenser and the evaporator. Because of friction and acceleration, the pressure drops as the liquid flows through the tube.In order to reduce the temperature of the liquid to the saturation temperature of the evaporator, some of the liquid must turn into a vapor in the capillary tube, “flash”, just as it does with all refrigerant controls. *Notes: All air conditioner expansion valve works in similar fashion. It shapes, size, capacity, and manufacture are different, but it operation principle are alike. The capillary tube diameter and length must be such that the flow capacity at the design pressures (condensing and evaporating) equals the compressor pumping capacity at these same conditions.For example, if the tube diameter is too small (resistance to high) the liquid refrigerant flow will be less than the pumping capacity of the compressor with the evaporator being “starved” and the suction pressure being low.

Less liquid will enters the evaporator and the excess will build up in the condenser reducing the effective condensing surface and increasing the condensing temperature and pressure. This pressure change tends to increase the flow in the tube and at the same time reduces compression capacity. The system will now balance at different from design capacity with a reduction in compressor and system capacity. If the capillary tube resistance to the refrigerant flow is too low, (diameter of tube too large) the flow rate will be greater than pumping capacity. This results in the flooding or overfeeding of the evaporator and flood back of liquid to the compressor.The refrigerant system uses a capillary tube selected for capacity balanced conditions. A liquid seal is present at the capillary inlet but not excess liquid in the condenser. The compressor discharge and suction pressures are normal and the evaporator is properly charged. How does air conditioner expansion valve works?AC expansion valves work by controlling the amount of refrigerant flows to the evaporator coils.

It acts as restriction to provide a specific amount of refrigerant flows into the evaporator coils. This is the basic principle behind any metering valves.There are different types of expansion valves used in air conditioner units, but the function of the metering device used in any central air conditioner units are two fold: First: It controls the amount of liquid refrigerant entering the evaporator coils. The amount of liquid refrigerant entering the evaporator must equal the amount of refrigerant boils in the evaporator coils. Second: It maintains a pressure difference between the high and low pressure sides of the system to permit the refrigeration to vaporize. The pressure difference allows the ac Freon to vaporize at low pressure and temperature in the evaporator; while at the same moment, the refrigerant in the air conditioner condenser condenses at a high pressure, high temperature in the condenser units. Read other central air conditioner parts Return to Central Air Conditioner and Refrigeration Cycle from Air Conditioner Expansion Valve