Refrigerator Troubleshooting Diagram

Archive for the ‘Evaporator Section’ Category

Refrigerator Water Float Switch

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In certain installations where the evaporator section was installed in the attic, an auxiliary condensate drain is used. If the main condensate drain pan should become restricted, the condensate wa­ter will overflow into the auxiliary drain pan. A float switch that has the control circuit wired through it is mounted inside this auxiliary pan. When the float rises, the switch opens and stops the unit. This auxiliary pan should be separately piped out of the attic to a place outside the structure that would be obvious when water dripped from the drain. Perhaps near the front entrance would be a good location. There if the owner of the structure sees water dripping from that pipe, he knows that his main drain line for the air conditioning is clogged. This procedure helps avoid costly ceiling repairs and per­haps damage to the furniture located beneath the evaporator section. It helps if the service technician installing a water float switch leaves a note in the condensing unit stating that a float switch is in use. The same note can leave instructions as to circuit breaker numbers or any other data would be helpful.

Run capacitors are usually located for the evaporator fan motor inside the cabinet of the evaporator section. A fan relay is also located in the same section.

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December 23rd, 2010 at 2:26 pm

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Refrigerator Heat Strips Sequencers

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These are shown in Fig. 10-6 and are commonly used in electric furnaces to stage heat. In most residential units, resistive heat strips  are placed in the evaporator section in five kW increments. For instance, there can be two 5-kW heaters giving the total capacity of heat of 10 kW. The proper way to energize the units and not cause a severe power drain, is to start each with a delay. Imagine this operation with three strips, you can see there would be a tremendous power demand if all three units were energized at the same time. The sequencer, or time delay switch, helps to eliminate this condition. These can also be used with an appropriate thermostat and sub-base to stage the heating system. All strips do not have to be energized if the thermal demand isn’t present. This too provides an energy savings. On larger units that are found in the commercial and industrial line, the heat strips have much higher kilowatt ratings. Usually in a residential application the strips can be acquired in sizes of 5, 7.5, and 10 kW. A kWh (kilowatt-hour) of electricity will yield approximately 3,400 Btu (British thermal unit). You can see that it will require much more energy to heat the same size area, that is being cooled, with an electric furnace.

The sequential switch operates with bimetal switches. The first switch to close is actuated by the thermostat within the conditioned space. The first bimetal switch will flex causing a current flow in the second switch which will heat the bimetal and cause it to flex causing the third switch to start heating the bimetal, and so on. When the control voltage is removed, the bimetal switches begin cooling and drop out the resistive heating coils in the reverse order.

sequencer

Written by sam

December 23rd, 2010 at 2:24 pm

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Evaporator Heat Strips Sail Switches

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This switch is seen primarily in commercial units, and in my opinion it is a valuable safety switch for both heating and cooling. It is generally located downstream of the evaporator fan. The common of the low-voltage control circuit is wired through the sail switch. The Y terminal (cooling and generally wired to the compressor) or the W terminal (heating and used with electric furnaces) is wired in series through the sail switch. In Fig. 10-5 a sail switch is shown. There has to be a certain volume of air blowing across the sail switch for it to close its circuit. Diaphragm type of pressure switches can be used also. These are found in some light commercial applications. With this control, if filters are dirty, or a fan belt is broken, or the fan motor isn’t operating, the system will not operate preventing possible damage to any of its components. In units not equipped with limit switches, this type of switch is invaluable.

sail-switch

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December 23rd, 2010 at 2:19 pm

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Evaporator Heat Strips Fuses

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In the event a limit switch should fail, there is a back-up protection called fusible links. Unlike the regular fuse you have worked with, the links are constructed somewhat differently. In Fig. 10-4 two of the typical fusible links are shown. When these fuses open, they must be replaced as an assembly. They only open if the heat or amperage exceeds the unit limits.

fuse-link

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December 23rd, 2010 at 2:17 pm

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Refrigerator Heat Strips Limit Switch

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In Fig. 10-1 an electric strip heater assembly is shown. The limit switch is found in the electric furnace as it is in the fossil fuel furnaces. Its main purpose is to protect the unit from reaching excessively high temperatures. The electric furnace can overheat if there is a fan failure or if not enough air is being blown across the resistive elements. Figure 10-2 shows a typical limit switch. Some of these are dual-purpose switches. The first stage of heat rise is wired to control the fan. In this way a blast of cold air is not felt when the electric furnace begins to operate. When the air in the plenum reaches a comfortable, heating temperature, the fan will start operating. If the heat continues to climb, a second set of contacts contained in the limit switch opens. Figure 10-2 shows a surface mount limit switch. On some applications an insertion type, as shown in Fig. 10-3, is used.

heat-strips

heat-strips-limit-switch

limit-switch-insetion

Written by sam

December 23rd, 2010 at 1:46 pm

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