Six minute solutions pdf to download hvac

November 23, Click on the link below to log in to your customer account. Customer Account. View Article 15 Nov Version 9. Design in minutes what used to take hours or even days. See our examples section for more details on some of the vast and varied possibilities of HVAC Solution software. View Examples.

Need help? We have created training videos covering topics air to water and hot to cold. Take a minute and view a topic and you will be the expert. These are the pipes through which refrigerant is circulated throughout the system.

The tubing used in household units is made of copper. Aluminum and steel are seldom used. Copper is relatively soft, flexible, and easy to bend and flare. Handle the tubing with care to prevent damage. Defrost bimetal. Also known as a termination switch or defrost thermostat. Not to be confused with the cold-control thermostat discussed earlier. A defrost thermostat is wired in series with the electric heater. It is clipped to the evaporator. No later than thirty minutes after the beginning of the defrost cycle, the timer takes the unit into the cooling cycle—at which time the operation of the compressor and the evaporator fan is restored—and the electrical circuit to the heater is opened.

Defrost bimetals play a very important role as the second component to control the defrost heater. If the heater is not de-energized, the excessive heat can cause damage to the unit. If it is not energized, the unit will no longer defrost. Often a bad defrost bimetal is mistaken for a bad defrost heater. The compressor draws in low-pressure, cool refrigerant vapor from the evaporator.

This cool vapor is compressed squeezed and changed to hot vapor within the compressor, and then forced into the condenser. In the condenser, heat from the refrigerant is radiated into the surrounding air, causing the refrigerant to return to liquid.

While a residential refrigeration unit is running, the temperature of the condenser should feel well above room temperature when touched. For optimum efficiency, the condenser should be cleaned every year. There are two types of condensers commonly employed in residential units: static and fan-forced convection.

The static type is mounted on the back of the freezers and refrigerators. It radiates heat through natural convection without the use of a fan. As air in contact with the condenser tubing or fins absorbs heat from the hot refrigerant and becomes heated, it expands and rises, and cooler air occupies its space see fig.

The fan-forced type is mounted beneath the unit. When the compressor operates, a fan moves air through the condenser tubing fins see fig. Linted condensers should be cleaned regularly to prevent any restriction of air circulation. Consequently, the evaporator will no longer cool, the unit runs continually, the temperature never drops to a point low enough to satisfy the cold control, and the high-side pressure rises higher than normal, causing the compressor to burn out.

Be sure that enough clearance is always provided for proper air circulation. When liquid refrigerant reaches the evaporator, it vaporizes or boils and absorbs heat from the freezer. Sometimes the evaporator is referred to as a cooling coil.

Due to the compressor suction power on the outlet of the evaporator and the fact that the capillary tube with its very small inside diameter is placed on the inlet side of the evaporator, the pressure in the evaporator is reduced to an average of 3. It is these low pressures that cause the refrigerant to boil and absorb the surrounding heat during its change of state essentials 1 and 3. A Simple Flat-Type These fan-forced-type evaporators are used Evaporator in frost-free refrigerators and freezers.

Four of the most common types of evaporators are illustrated above and in figures 3, 4, and 5. Figure 5 shows the cycle-defrost type of evaporator. This is basically a flat aluminum plate with a cooling coil in it. About three-fourth of this plate is in the freezer compartment while the remainder extends into the fresh-food compartment. Since fewer loops of the coil are in the fresh-food compartment, only a small portion of the cold air is produced there but adequate to maintain the proper temperature.

This type of evaporator cools the refrigerator cabinet or freezer very rapidly. Manual-defrost refrigerators have a shell-type evaporator, which is located in the top of the cabinet.

The shell type is similar to the evaporators used in the cycle-defrost type, which is a flat plate, but bent into a boxlike configuration see fig. Frozen food and ice trays are kept inside the shell while the fresh food in the rest of the cabinet is kept at the proper temperature by the cold air emitted from it.

Shell-type evaporators are almost always found in small office-type or inexpensive refrigerators. Normally, as a safety measure, an accumulator is installed at the outlet of all evaporators the small cylinder in fig. It prevents liquid refrigerant from getting into the compressor, causing serious damage.

This can be evidenced by a loud knocking when the compressor runs. The liquid refrigerant trapped there will get a chance to vaporize before entering the compressor.

Capillary tube. A length of thin tubing connected to the high-pressure side liquid line from its inlet side and to the low-pressure side of the system the evaporator from its outlet side. Liquid refrigerant is forced to flow through the capillary tube by these two forces. Because of the small inside diameter of the capillary tube, a constriction in the flow of refrigerant is created in the sealed system. This constriction maintains the pressure difference between the high and low side.

Without continually maintaining this pressure difference, the vaporization and liquification of the refrigerant would not be possible. When refrigerant reaches the larger space of the evaporator by the suction power of the compressor , the low pressures in this environment immediately cause the refrigerant to vaporize and absorb the heat from the evaporator.

If a capillary tube must be replaced for any reason such as a restriction that cannot be cleared with a tube cleaner , it is most important to replace it with one of exactly the same length and inside diameter. The diameter is measured by a capillary tube sizing kit. Capillary tubes are used in different sizes and lengths according to the capacity of the unit see fig.

Defrost heater. It is an electric resistant heating element clipped to the evaporator in frost-free refrigerators and freezers. The purpose of the defrost heater is to melt the frost accumulated on the evaporator surface during the run cycle. At this point, a termination bimetal senses the rise in temperature and disrupts the flow of current to the defrost heater, even before the defrost cycle ends.

In many models, a length of electrical resistance heating element is also installed on the inlet of the drainpipe. It is energized during the defrost cycle to prevent condensation from the evaporator from freezing and blocking the flow down the drain tube. In cycle-defrost refrigerators, an electric resistant heating element wired in series with the compressor is clipped to the inlet and outlet tubing of the fresh-food evaporator to defrost the frozen food evaporator during the off cycles see fig.

The heater is energized when the temperature control is satisfied. Evaporator fan. In frost-free refrigerators and freezers, a fan is installed over the evaporator to move air through the evaporator and circulate it in the freezer and the fresh-food compartments. The pattern of air Various parts courtesy of Marvel Industries, Division of Northland Corporation on the evaporator coil.

Consequently, frost will B. A condenser fan motor build up on the coil. A commercial double freezer compartment s h a f t fa n m o to r. As a obtained separately. The same thing happens in air conditioners. If the evaporator blower fails, air will no longer be circulated through the cold evaporator fins, causing an accumulation of ice on the evaporator plate, and a sudden temperature rise in the air-conditioned area. Condenser fan.

In automatic-defrost freezers and refrigerators and in larger-capacity units that require a more rapid cooling of the condenser, additional air movement through the condenser is provided by a fan called forced draft cooling.

Air is drawn into the compressor compartment from one side of the front grille, circulated through the condenser, and expelled through the other side of the front grille. In some side-by-side models, air is expelled at the rear of the compressor compartment. In addition to the rapid cooling of the condenser, the condenser fan also causes rapid evaporation of water in the condensation tray. The hot refrigerant causes the accumulation of frost on the evaporator coil to melt.

What are the primary parts of a refrigeration unit? Where is the evaporator located? What is a sealed system? What is the function of an evaporator?

What is the primary function of a defrost timer? What are the most common troubles with defrost timers? What happens when loose connections on a defrost timer fuse together? What is the primary function of a thermostat? What is a thermostat sensing bulb, and where is it attached? What purpose does an overload protector serve? Where is an overload protector located? What is the role of a starting relay?

Which compressor winding s is are are energized at the instant a compressor starts? How many windings are there in a compressor? What is the suction port of a compressor connected to? How are the pressures in a sealed system checked? What is the primary purpose of a filter-drier? What are other names for a defrost bimetal? What is the primary purpose of a termination switch?

What is the defrost bimetal clipped to? How many types of condensers are used in residential refrigeration? How many types of evaporators are there? Where is an accumulator installed? What is the primary function of a capillary tube? What is the most important thing to consider before replacing a capillary tube?

How many types of defrost systems are there? What are the most common types of condensers used in residential refrigerators and freezers? What is the purpose of insulating materials in refrigerator walls? How is airflow regulated in a side-by-side refrigerator?

What is the principal difference between a refrigerator and a freezer? What components are activated in opening the flow of hot gas in a hot gas defrost system?

Why is fan-forced circulation used in frost-free refrigeration? What is the capillary tube connected to? What is the function of an accumulator? It includes flaring, brazing, swaging, bending, and cutting tubing. Silver brazing: Brazed joints are very strong and considered to be the best method of making Figure 17 leakproof connections.

Clean and burnish the joints with fine sandpaper. The parts to be brazed must be fitted snugly and Figure 18 accurately, clean, and securely supported so that no part can move during brazing. Apply the recommended flux fig. Be sure the joint is firmly supported to avoid movement during brazing or cooling.

Heat the joint evenly with a torch figs. More heat will be hacksaw to cut tubing. Start heating Figure 19 about one-half inch to one inch away from the joint.

Never hold the torch in one spot. Keep it moving until the joint turns cherry red. Apply the brazing alloy at the top and allow it to seep into the heated joint. Since alloy always flows toward heat, hold the torch at 1. Teflon Tape the back of the joint to let the alloy flow into 2. Flux the joint and fill it up. Brazing Rods 4. Inspection Mirror 5. Cool the joint with a piece of wet rag, then use hot water and a brush to clean it.

If the brazing alloy contains any amount of cadmium, do not inhale the fumes or allow them to come in contact with your eyes or skin. Swaging copper tubing. Swaging is a process Figure 20 by which the end of one tube is enlarged to allow the end of another tube of the same diameter to fit inside for brazing.

This method of joining two lines of the same diameter eliminates the use of fittings. As a general rule, the length of the swaging, or overlap, should equal the outside diameter of the tubing being joined. For instance, when joining one-half-inch tubing, the swaged overlap should be one-half inch; for three-fourth-inch tubing, the length of the swage should be three-fourth-inch, etc.

Figure 22 illustrates two pieces of tubing where one has been swaged to create a connection with the other. There are two types of swaging tools available: the lever type and the more popular punch type fig. Different sized collars and punches Heat tubing with Figure 21 the yellow flame.

To use the punch type, insert Correct Brazing Technique for the tubing in the correct size hole in the Joining Copper Tubing anvil block. Select the proper size punch 1. Use fine sandpaper to clean the joint and insert it in the tubing. Hammer it before applying flux. Heat tubing starting one-half inch to one inch from the joint.

Move torch toward joint and heat that area briefly. Concentrate heat a little above the joint until joint turns cherry red and apply flux around joint. It is easy to take brazed joints apart using the same method by which they were joined. Heat the joint with a torch until it becomes cherry red in color, and then grab the tubing near the joint with a pair of pliers and pull it apart.

Before removing the old part, you can use this method to disconnect the tubing. To do this, use an access valve. Refer to figs. Insert the punch in the end of the tubing and hammer it down until the desired expansion Figure 22a is obtained. A typical brazing outfit: acetylene and oxygen tanks, pressure gauge, acetylene-regulating valve and torch.

Above, a service valve wrench. Instead of connecting tubing by swaging before brazing, special couplings can be used to join tubing of similar or different sizes by silver brazing.

Figure 24 illustrates some of these couplings. They are available in most tubing sizes. Reduction 3 and Straight with stop 5. Straight without stop 6, 7, and 9. Tee 10, 11, and This is a metal-to-metal connection without the use of a solder. To create a flared connection, the ends of the tubing to be joined should be cut straight and square with a tubing cutter fig.

To do this, the tubing must be held securely while cutting. Use a small vice, C-clamps or Vice-Grip pliers. Then ream the inside of the cut to make it smooth. Most tubing cutters have a reamer attached.

When using either method, make sure that no chips or shavings remain inside the tubing. Flaring couplings. The flared fitting relies on the airtight connections of the fittings rather than brazing. The fittings are a flared half union coupling and two female flare nuts. They are retained on the tubing by a small flaring on each of the ends to be joined.

For this type of connection, a different set of tools is needed from those used in making a brazed connection. They are inexpensive and available almost everywhere in hardware and refrigeration supply stores. Cut and clean the ends of the tubes as described earlier. Use a fine- toothed file to smooth the ends or to make a slight correction if the tubing is not cut perfectly square.

Place a female flare nut on each of the tubes with the larger end facing the cuts. Do this prior to making the flare because the nut will not slide over the end after the flare is made. Slide the nuts back on the tubes to provide enough working room. Then put the end of the first tube into the flaring block hole with the same diameter as the tube. The end of the tube should extend slightly above the chamfered end of the hole to allow enough metal to form a satisfactory flare.

The tools have directions with them for guidance in this step. As a rule of thumb, the extension above the block should be about one-third of the height of the flaring. Put a drop of refrigerant oil on the bottom of the flaring cone where it comes in contact with the tubing.

Tighten the spinner until the flare is formed. Avoid overtightening as this will thin out the wall of the tube and weaken the flare.

In most cases, after the spinner touches the tubing, about six and a half turns should form the flare. Do the same with the other piece of tubing that is to be joined. Use Pipetite a pipe-fitting compound or a short length of Teflon tape around the male threads to establish an airtight seal. Teflon is the better of the two. If the compound is used, be sure to apply it sparingly to prevent it from getting into the lines when the flare nuts are connected.

NOTE: Connections made in plastic tubing [such as a water supply to an ice maker] use compression-type fittings since plastic cannot be flared. Put nut on tubing and insert tubing into correct size collar in anvil block. Turn spinner about six and a half turns. Figure 26 3. Remove spinner and tubing from anvil block. Tubing can now be connected to a male counterpart. Use Teflon tape to ensure an airtight seal.

A variety of compression fittings used in refrigeration and air-conditioning. To prevent possible leaks, do Figure 26a not overtighten nuts and couplings. Unless the tubing is supported around its circumference, it will flatten at the bend and possibly crack, causing it to leak.

Use a tool called a bending spring shown here in figure 27 on the right. The bending springs are inexpensive and do the job properly.

Place the spring over the tubing at the area to be bent, then bend it slowly and carefully, making a curve as large as practical. Do it in short stages until the appropriate curve is made. Remove the spring by twisting while sliding it off. For tubing larger than one-half inch in diameter, a bending lever with a flange attached to the end is used. See illustration below. Figure 27a Spring-type benders upper right make it easy to form bends by hand without collapsing the tubing.

They can also be used to protect tubing during installation and repair procedures. The special coil spring wire easily slips over the outside of the tubing, and the belled end simplifies insertion and removal.

The lever-type tubing benders illustrated on the left are used for the larger sizes of tubing as they require considerably more effort to bend. The curved radius on the stationary bar has a scale in degrees. When the movable lever bends the tubing, its index mark indicates the degree of the curve. What method is used to bend larger diameter tubing? Generally, how many half turns of the spinner should be sufficient to form a flare? Name 4 different types of flare unions.

What are the most commonly practiced ways of joining tubing? How should the torch be positioned while silver brazing? When applying heat to a joint, how is it determined when to apply the silver solder? What steps should be taken after a joint is silver-brazed? When should flux be applied to the joint? At what temperature does silver alloy melt? How is refrigeration tubing normally cut?

What kind of coupling is used to braze tubes of the same diameter? How and why should a silver-brazed joint be cleaned? What is the general rule to determine the overlap length when swaging copper tubing?

What is the purpose of punches with different sized diameters? How is tubing bent with a spring-type bender? What should be done before applying heat to the tubing? What is used when more heat is required for brazing larger-diameter tubing? How is a brazed joint disassembled? In what direction does alloy flow while it is being heated? This knowledge, coupled with the information on the troubleshooting charts, provides a quick diagnosis of the most common problems encountered in this career field.

Some of these compressors, used commercially, could be belt-driven or hermetic. The hermetic type has its motor and compressor coupled directly together in a sealed airtight metal housing, whereas the others are powered with a separately mounted motor and driven with a V belt s and pulleys. All residential and many light commercial refrigeration units are operated with hermetically sealed motors and compressors because they are compact and require little space.

In heavy commercial and industrial use, where large capacity units are required and space is not a problem, the separately mounted motors with v-belts and pulleys to drive the compressors work well. A reciprocating compressor is similar to an automotive engine with a piston moving up and down in a cylinder. Instead of relying on exploding and expanding gas to drive the piston, the piston is powered by an electric motor.

As the piston moves downward or backward , the inlet valve opens and vapor is drawn in from the evaporator. When the piston starts up toward the top or forward , the inlet valve closes and the gas is compressed thereby raising its temperature. Before the piston reaches the top or its most forward position , the discharge valve opens and allows the gas to be propelled into the condenser see fig. They are used in commercial and residential units, light and heavy applications.

These compressors can be hermetic or externally driven. As the piston moves upward, the vapor is compressed and converted to a hot gas, which is then forced into the condenser fig. In a reciprocating hermetic compressor, the circular motion of the rotor causes a back-and-forth movement of the piston. Right: A motor stator, B motor rotor, C compressor cylinder, D compressor piston, E connecting rod, F compressor winding, G compressor terminals under a plastic cover, H compressor housing weld, I compressor suction tube, J compressor discharge tube, K compressor housing.

It can be hermetically sealed or rely on an external conventional electric motor. They are used in commercial and residential units. As the rotor revolves inside the cylinder on an eccentric cam, the spring-loaded vanes pass the intake and discharge ports.

As one vane passes the intake port, suction begins and cold vapor is drawn into the cylinder. As the rotor continues its turn, the gas is compressed. When the other vane clears the discharge port, the gas is propelled through the high-pressure line into the condenser.

It is then forced into the condenser. Rotary compressors are very susceptible to liquid refrigerant. As a safety measure, they are equipped with an accumulator on the suction inlet to prevent any unvaporized refrigerant from getting into the compressor motor. Courtesy of Tecumseh Products Company In a rotary hermetic compressor, the circular motion of the motor rotor in the top causes the rotary compressor in the bottom to turn.

A motor rotor, B motor stator C rotary compressor, D compressor terminals, E accumulator, F motor winding, G compressor discharge connection, H compressor suction connection. As the impeller turns, a vacuum is created at its center, causing cold vapor to be drawn in.

It is then compressed and expelled into the discharge port through the sides caused by high rpm. These compressors can be hermetic or externally driven and are used commercially. A screw-type compressor is similar in operation to a turbocharger. It has two cylindrical vanes with deep, spiraling flutes that mesh together like gear teeth. The extremely high rpm of the vanes meshing into each other creates vacuum on one side and high pressures on the other, causing refrigerant vapor to be drawn in from the intake port , compressed, and forced out through the compressor discharge port.

Screw-type compressors are used in heavy commercial applications. Figure 31 Courtesy of Gates Rubber Company The high-pressure-side service valve is usually located on the receiver, and the low-pressure-side service valve is installed on the compressor suction inlet. A quick way to determine the condition of a compressor is to check the wattage consumption of the unit.

A worn-out compressor may be indicated by a wattage reading below its wattage rating. Connect the wattmeter to the compressor circuit to be measured as shown in the diagram.

Depress button E. At first the meter needle will fluctuate to the right; then, immediately, it deflects to the combined reading the compressor start and run windings both engaged. In a second or two, the needle will deflect to the wattage consumption of the run winding.

The wattage readings are then compared with figures published by the manufacturer. A shorted winding is indicated by a high wattage drain. An open circuit is indicated by a low wattage drain. If the compressor has to be replaced, it can be isolated and removed from the rest of the sealed system without having to discharge the refrigerant from the system see figs.

The service valves are bolted to the compressor housing with two bolts from one side and connected to the tubing by flared connections from the other side. Refrain from running the motor to prevent pressure from climbing to a dangerous level too fast. When the unit does not cool as well as it is expected to, and the compressor is suspected to be inefficient an inability to pump , conduct this test as indicated in figure 45h for residential units.

Testing the efficiency of commercial units is an easy task because they come with service valves. This eliminates the necessity of installing piercing valves and pinching off tubing.

The compound gauge reading should drop to 29" inches of vacuum within 60 seconds or so. At this point turn off the compressor. If within this period, the reading on the compound guage begins to move toward zero, the compressor has an internal lear Bad Gasket, O' Ring, Bearing, etc. An efficient compressor must reach about 29" or vacuum, an maintain the level of vacuum after it is turned off. Residential refrigerators and freezers that do not come with access valves can be tested for efficiency by pinching off the liquid line see Figure 45g by using a pinch off tool, and by installing a tap value see Fig.

Before beginning a compressor test, check the power supply to see if low voltage is the problem. If after start-up this initial speed is never reached, the run winding will never engage, causing the start winding to overheat in a few seconds. When the compressor start winding cools down, the overload protector closes the circuit to the compressor again, and the short-cycling continues.

Should this occur, advise the customer to call the power company to remedy the problem as there may be nothing wrong with the unit. There are transformers on the market today that can remedy the low-voltage problem by increasing the supply voltage. Sometimes there are too many pieces of equipment connected to the same receptacle causing a voltage drop below the acceptable range. Just disconnect some of the load and reconnect it to another wall outlet. Set the voltmeter on the proper scale, i.

Put the voltmeter probes into receptacle A fig. Plug the unit into socket B while keeping an eye on the voltmeter needle. If at the first instant the unit is plugged in and starts running, the voltage drop registered exceeds or falls under the minimum compressor requirement, chances are that there is too much load on that particular circuit. Advise the customer to have an electrician provide the unit with an independent line to meet the requirement of the compressor manufacturer.

Do not touch any wires until the power source is disconnected. Unit dead. No hum. Insert the a. Check circuit breaker. Flip breaker to two check light probes into the power ON position if open. Remove every wire from the compressor 1. Set cold control at its lowest setting. Remove compressor compartment 2. Connect the three test cord clips see fig.

Connect power to the unit. Connect the two test light alligator 4. Depress the button on the test cord clips to the two relay terminals that momentarily and release it. If compressor starts and continues a. The light glows. If compressor does not start, replace compressor. If compressor starts, but stops 1.

Connect the two test-light probes to the when test cord button is released, two terminals behind the compressor replace compressor. Plug the power cord into the power 45a instead of a test cord. It can receptacle. If light glows, proceed. This is a good tool to use on compressors that no longer run due to wear and tear to make them operational again.

Find the cold-control thermostat adjusting knob in the unit cabinet. Fasten the two jumper wire clips when the door is opened, check for a to the two terminals. Using a screwdriver, 3. Turn on the power. If the unit starts running, hear a click. If the unit starts running, replace the thermostat.

If unit remains dead, proceed. Connect the two test wire clips to the two electrical circuits while power is connected terminals on the overload protector. Always disconnect the power 2. Plug the unit into the power supply. If the unit starts running, replace component. If you are checking a compressor with a capacitor s , follow the same procedure after checking the capacitor s as outlined below.

If the capacitor is bad, it must be replaced with one of the same microfarad mfd or mf rating. If there is no exact capacitor replacement or a capacitor tester available, you can make a compressor test cord that can test capacitors too. See figure 34a and follow these instructions: 1. Disconnect the unit from the power supply. Discharge the capacitor and remove it from the unit. Put a watt light bulb in socket A fig.

Insulate the alligator clip marked S and connect the alligator clips marked C and R to the two capacitor poles. Connect plug B to power. The lamp will, a. If the capacitor checks good, replace the watt bulb with a watt bulb and leave the capacitor as it is for no longer than five seconds. Disconnect the cord from the power. Using a heavy insulated wire short across the two capacitor terminals.

A spark is the indication of a good capacitor meaning that the capacitor can load and discharge. Bigger compressor motors that require more starting or running torque due to heavier loads use capacitors to increase their torque. This is especially true in commercial refrigeration and air-conditioning. They are referred to as start or run capacitors. Some compressors use only run capacitors, and some use both.

Capacitor testers can be purchased at refrigeration supply houses for very affordable prices. Disconnect the power supply. Remove the compartment cover, compressor terminal cover, start relay, and the wire connecting the overload protector to the common terminal.

Connect the appropriate test cord wires to the proper compressor terminals. The three test wires are marked C, S, and R. Plug the test cord into a proper power supply and depress the switch for no longer than three seconds. If the compressor never starts, or if it stops when the switch is released, it must be replaced. A good compressor will continue to run because the power is still connected to its run and common windings through the test cord.

Poor connections also cause compressor failure. Be sure to check these too, prior to replacing a compressor. Tight and clean connections are essential for good current flow. If a compressor must be replaced, all the data for a duplicate replacement can be copied from the compressor nameplate to ensure getting the right one. Do not remove the nameplate! The compressor may still be under warranty; if it is, removing the nameplate will void it. For compressors that require capacitor s to operate, figure 36 illustrates a testing cord that can be easily made.

You must use fourteen gauge or heavier wire. It shows wiring to the compressor terminals a run capacitor, a start capacitor, and a momentary-contact push-button switch. Consequently, the test cord should be made with quick-disconnect fittings and adapters. Otherwise, the compressor is defective and it must be replaced. When the ohmmeter probes touch a single terminal and the housing ground , the meter should register a no-continuity reading an open circuit, an infinity reading, a figure 8 on the meter lying on its side ; otherwise, the compressor is shorted and it must be replaced.

Scratch or sand the paint off a small spot on the compressor housing to get a good contact. Disconnect the unit from the power source. Remove the compressor terminal cover. Remove the overload protector and starting relay from the three compressor terminals. Set the ohmmeter on its RX1 scale and zero it. Touch the probes to the compressor C and S terminals. The meter should register a continuity reading. Otherwise, replace the compressor.

Touch the probes to the compressor C and R terminals to get a continuity reading. Touch the probes to the compressor S and R terminals to get a continuity reading. If not, the compressor is defective. Touch one probe to the compressor housing and the other one to each terminal in turn. In each case, the meter should register no-continuity reading.

The compressor runs without being able to create the necessary pressure difference in the system simply because the parts are worn. This can be checked by using the pressure gauges. With the compound gauge connected to the low side and the pressure gauge connected to the high side, if the high-side pressure reads lower than normal and the low-side pressure reads higher than normal, the compressor will have to be replaced as it has lost its compression efficiency.

Since it is unable to maintain the required pressure difference in the sealed system, the evaporator temperature never reaches low enough to satisfy the thermostat, causing the unit to run constantly. Note that the evaporator may be covered with a heavy layer of soft frost. An efficient compressor produces a layer of hard frost on the evaporator coil. As more experience is gained, the evaporator frost pattern will become very evident. When a compressor is turned off, the evaporator frost pattern disappears very quickly.

The frost on the accumulator disappears in few seconds when placing a hand around it. An accumulator in a properly operating system is covered with hard frost. There is an easy way to determine the compressor C, S, and R terminals. Here is how: Set the ohmmeter on its lowest scale. In figure 38, imagine the unmarked terminals as 1, 2, and 3. The highest reading between any two terminals means that the remaining one is the common terminal. Since number 2 and number 3 terminals have the highest reading, it can be deduced that number 1 has to be the common terminal.

Some terminal configurations appear as in figure Use the same method to identify these too. Figure 37a Different styles of compressor terminals. The chart above shows the color coding for those wires connected to the compressor terminals. This color coding can be used to identify the compressor terminals when the letter marking is not visible. For example, when checking the compressor in an Admiral freezer, a glance at the chart will show you that the run terminal has a white wire connected to it, the start terminal has a black wire, and a red wire is connected to the common terminal.

Reversing the rotation of the compressor by the following method may break it loose: A. Prepare a single-pole, double-throw SPDT switch, two capacitors rated mfd, a line plug, and three alligator clips. Disconnect the unit from the power supply and remove all wires from the compressor terminals.

Hook up the reversing circuit as shown and plug the cord into a VAC wall receptacle. Operate the reversing switch by rocking it back and forth to alternately reverse the rotation, causing the compressor to break loose. These are called hermetic because they are mounted inside an airtight container with the compressor.

Basically, there are four types of hermetic motors in commercial use today: 1. Split-phase hermetic motor as it has separate run and 1.

Split-phase compressor generally used start windings used mainly in in residential and commercial units 2. A capacitor-start compressor used in residential units with limited commercial equipment use in small commercial units. A rotary compressor 2. Capacitor-start, induction-run Courtesy of Tecumseh Products Company motor. Capacitor-start, capacitor-run motor. Split-phase hermetic is the simplest kind, used mostly for household refrigerators since the compressor motors do not require a lot Typical wiring for a hermetic, of starting torque.

In these split-phase compressor motor operating on a units, when the thermostat current-type relay. In heavy commercial Typical wiring of a hermetic, units, the pressures do not split-phase compressor motor equalize because they use operating on a potential type TEV thermostatic electric relay.

These valves isolate the high and low sides, and the pressures in the system do not equalize very easily in the off cycle. In these motors, a relay controls the engagement of the start windings. The starting relay used may be of the thermal type, the current type or the potential type, which will be covered later. Capacitor-start compressor motor is a popular type of hermetic motor in refrigeration units. A capacitor is installed in series with the motor start winding to produce more starting torque by providing more initial voltage.

This capacitor is isolated from the circuit during the run cycle see fig. This type of compressor is normally used in walk-in coolers, salad bars, beverage coolers, ice machines, and similar commercial refrigeration units. Capacitor-start, capacitor-run compressor motor is a very efficient type of motor. A start capacitor increases its starting torque, and a run capacitor increases its efficiency during the run cycle. It is used in commercial refrigeration for heavier applications such as larger walk-in coolers, heavier air conditioners, etc.

Figure 44 illustrates how they are wired. Permanent-split, capacitor-run compressor motor. This type of hermetic compressor motor is widely used in wall- or window-type air conditioners. It is not equipped with a start capacitor. Its starting torque is almost low. Consequently, it is sensitive to the fluctuation of the line voltage. A run capacitor is installed between its start and run windings to provide more efficiency during the run cycle. Figure 45 shows a typical wiring diagram of these motor compressors.

Primarily, this kit see fig. Very often, a compressor that is thought to be defective can be restored to service by using a hard start kit. A hard start kit is a great tool for the service technician. It eliminates a lot of work and time spent in testing several components and looking for the defective part when a compressor fails to run or cycles on overload.

Some hard start kits are designed for use on compressors operating on VAC and on air conditioners up to several tons. The wires on the kit are either color coded or individually labeled Start, Run, and Common.

Disconnect the power from the unit. Remove the overload protector and starter relay. Connect the start terminal of the compressor to the wire on the kit marked Start. Connect the run terminal of the compressor to the wire on the kit marked Run. Connect the common terminal of the compressor to the wire on the kit marked Common. Find the lines that supply power to the compressor.

Normally, one goes into the overload protector and one to the start relay. Connect these lines to the remaining two wires on the hard start kit. Plug the unit back in to the power source, and if the compressor starts and continues to run, then the problem is solved. If it does not, the compressor is defective. In which case, remove the new hard start device and replace the compressor. Due to its length, the capillary tube may run through places difficult to reach. In such cases, it is easier to unclog it rather than replacing it.

A capillary tube cleaner can be purchased from most major refrigeration supply houses. The way the device works is that it forces wax and dirt out of the capillary tube under high pressure. Some of these devices are capable of producing pressures as high as 3, psi. An obvious sign of a clogged capillary tube is that the back pressure reads lower than normal or even vacuum , the head pressure reads higher than normal, the unit no longer cools while running constantly, and the condenser feels cooler than normal.

To use a capillary tube cleaner, disconnect the capillary tube at both ends. Flux and apply heat to the brazed joint to remove it. Connect the tube cleaner to one open end of the capillary tube by using an adapter fitting; then turn the handle to create the pressure necessary to clear the tube. In these devices, either oil or R is used as a pressure fluid.

After removing the obstruction from the tube, install a new filter-drier and silver-braze the tube back into the system before evacuating and charging the unit.

Figure 45b Capillary tubes are not expensive, but sometimes they are hard to reach particularly in residential units. The capillary tube begins in the compressor compartment in residential refrigerators and freezers, runs through the body of the unit and it is silver-brazed to the evaporator inlet.

A lot of work and replacement time can be saved if a blockage can be cleared with a capillary tube cleaner. Some of them are available with different sized strainers while some are fitted with a calibrated wire inside to control the flow of refrigerant see fig. If a new capillary tube is needed, it must always be replaced with one having the same inside diameter and the same length; Patented tubes can be used for capillary tube replacement.

This is a tool similar in appearance to a spark plug gapping tool used by auto mechanics. It consists of a number of different sized wires to measure the inside diameter of capillary tubes see fig. See the chart on the next page for the required length of tubing based on its inside diameter, the horsepower, and temperature rating of the compressor.

When handling capillary tubes, it is important to remember that 1. It is then bent carefully until it breaks. Using a pair of pliers, crimp the opposite wall of the larger tubing until it fits snugly around the capillary tube.

Then clean and silver-braze the joint as instructed earlier. Because small tubing absorbs heat very rapidly, be careful no solder gets far enough inside to block the opening of the small tube and cause a restriction.

Fit the correct size valve body number 1 on the tube and crimp the saddle tabs around the tube with pliers. Then braze in place. Apply heat from below being careful not to overheat the body. Always sand the surfaces to be brazed and use flux.

When cooled, insert the piercing shaft number 2 into the body being careful not to damage the O-ring. Do not overtighten.

Screw on access valve cap number 5. Tighten securely with one wrench while holding the body nut with another. Figure 45f Courtesy of Wagner Products Corp. Figure 45g shows a typical pinch-off tool. To use it, put the tubing through the opening to the point where it is to be sealed. As the shaft is turned by the T-handle, the tubing is compressed between a ball bearing at the end of the shaft and the die at the base of the tool.

A permanently pinched line is made by turning the handle slowly and not overtightening. This too becomes necessary when there is a need to test the compressor efficiency or in an emergency, such as a severe leak, when a section of the sealed system must be isolated for repair. For example, in commercial units where there are multiple evaporators, the one with a leak can be isolated while allowing the rest of the system to operate during the repair work.

Thus, the contents of the unit can stay cold and be saved. When a leak occurs, oil escapes with the refrigerant and must be replaced for proper lubrication. Loud compressor noises can sometimes be remedied by adding a small amount of oil usually no more than one-half cup to the hermetic system.