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What is the difference between a cold wall and an automatic defrost merchandiser?
The auto defrost unit uses a blower coil to circulate air for the cooling and it is self-defrosting. The cold wall merchandiser requires it to be manually defrosted.
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How often should a cold wall merchandiser be defrosted?
The frequency of defrosts are determined by the amount of frost built up on the inside of the cabinet. Anytime the frost gets near 1" in depth the cabinet is in need of defrosting.
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What is the difference between a low back pressure compressor and a high back pressure compressor?
The low back pressure compressor is designed to operate with lower evaporator temperatures than a high back pressure compressor. Typically these are used in freezer applications. The high back pressure is better suited for use in a cooler application. The "high back" unit is generally rated at a +20 degree evaporator temperature while a "low back" unit is generally rated to operate with an evaporator temperature well below zero.
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How do you check a compressor relay?
There are 3 tests on a relay. One is the rattle test; the plunger inside the relay should be free to move. The second is the coil test. This is accomplished by using an ohmmeter and testing for continuity. The final test is for the contacts. Typically you would insert an ohm meter probe into the start winding sleeve and touching the other probe to the capacitor connection. The relay is then turned upside down. There should be continuity when this happens and not before.
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How do you check out a defrost timer?
Make sure the timer is in the refrigeration mode. Using an ohmmeter, check for continuity between terminals 4 and 3 only. Advance the timer into defrost. There should now be continuity between terminals 3 and 2 only. The final test is between terminals 1 and 3. This is the timer motor and you should get an ohm reading.
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Is it all right to transport merchandisers while lying on their backs?
It is highly advisable not to transport any refrigeration equipment lying on its side. If there is no way around it then you should stand the merchandiser upright as soon as possible and not attempt to operate the system for several hours.
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Is there anything special that should be done on initial start up of a merchandiser?
Generally there is nothing special to do. The exception would be during the summer months when the inside temperature of the closed and crated merchandiser can reach extremes. In this case you should open the door and allow the cabinet temperature to drop before starting the merchandiser.
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Can glass doors and solid doors be interchanged?
They can be but it will require some work. There is 1" difference between the glass door and solid door in width. There will be some screw holes that will require some bodywork to repair. If changing from a solid door to a glass door there will also be a j-bolt hole that will also require filling.
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When corresponding with the factory, what information should be provided in order for my merchandiser to be identified?
The model and serial number are the two most important pieces of information that can be provided to aid the factory in providing parts and service. This information is located on a serial tag either on the left end or on the inside left end (on newer glass door merchandisers).
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What problems could be caused from using an extension cord?
The merchandiser could be getting low voltage that will cause damage to the compressor in the form of excess heat and high amperage. Ice may melt due to the compressor being unable to start properly.
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How often should the condenser coil be cleaned?
The frequency of cleaning will be determined by the surroundings of the merchandiser. The dirtier and dustier the area, the faster that the condenser will become clogged. Even in good locations the condenser should be cleaned at least twice a year.
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Is the condenser fan shroud important? Why?
The condenser fan shroud is extremely important. Without the shroud in place the air will tend to go around the condenser rather than through it. This will cause high head pressure and will cause damage to the compressor.
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How do you check a start capacitor?
You will require an ohmmeter for this test. Many digital type ohmmeters have a built in capacitance checker. If your meter has this ability then you can use it directly to measure the capacitance, Do this by connecting the meter probes to the wires coming from the capacitor. You then should get a microfarad reading. If you do not have the capacitance measuring ability then you will need to check using the ohmmeter only. If you have an analog meter then you should get a needle deflection going up and returning. If you have a digital meter then you should get a rapid reading and then returning to nothing. Reverse the probes and repeat the process.
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When going out to check a merchandiser and you find that the condenser fan motor is running but the compressor in not, where would you look first for the source of the problem?
You would look at the starting components and or the compressor.
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When you check the three main points of the system using the "touch and feel" method, where should you feel and what should each are feel like in a properly operating refrigeration system?
The three points are the compressor discharge line, which should be hot, the drier that should be lukewarm, and the suction line that should be cool or cold.
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In an automatic defrost merchandiser, if you check and find that neither the condensing unit or the evaporator fan motor is running, what would you suspect as the source of the problem?
The defrost timer. The only time that all these components should be off is during defrost.
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What function do the plastic ice pallets in the bottom of a merchandiser serve?
The plastic pallets are there to keep the ice off of the unrefrigerated floor. In the auto defrost merchandisers they also allow air to flow between the ice and the floor which is critical to the proper operation of the auto defrost merchandisers.
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When you go up to a merchandiser and hear a clicking sound, what is the most likely source of that sound? The overload.
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Name some possible causes that make an overload trip out.
The compressor being too hot, too many amps being drawn, clogged condenser,
a missing fan shroud and low voltage.
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What effect would a broken heat exchange have on a refrigeration system?
There would be a frost buildup on the suction line as well as a very likely reduction in capacity of the refrigeration system.
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