Refrigerator Troubleshooting Diagram

Room Air Conditioners Evaporator Temperature

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Under average operating conditions of outdoor and indoor temperatures, all evaporator return bends should be cold and at the same approximate temperature. On most models, this check can be easily made by removing the front grille. If the first evaporator passes are iced over, or if there is a noticeable temperature increase of the return bends of the last several passes, it could be an indication of either restriction or loss of refrigerant. It must be remembered, however, that with higher outdoor temperatures, the very last evaporator pass will not have as much refrigerant to effect cooling as it would have at lower temperatures. Therefore, it will be at a slightly higher temperature if the outside temperature is high.

Frequently, servicemen check the dry-bulb temperature drop across the evaporator to determine if the unit is cooling satisfactorily. The temperature drop across the evaporator is not the same on all units. Higher outdoor dry-bulb temperatures and high inside relative humidity tend to reduce the dry-bulb temperature drop across the evaporator. On most units with an outdoor temperature between 80◦F and 90◦F and with an indoor relative humidity between 40 and 50 percent, the temperature drop across the evaporator should be between 17◦F and 20◦F. Where proper evaporator air flow is maintained, a 20◦F dry-bulb temperature drop would normally indicate satisfactory cooling. When the room air relative humidity is considerably higher than 50 percent, a smaller dry-bulb temperature drop across the evaporator will be obtained. When the relative humidity is considerably below 40 percent, a higher temperature will result. It is, therefore, important that room air relative humidity be checked and considered when checking air temperature drop across the evaporator as a check for proper cooling.

Written by sam

February 8th, 2011 at 6:56 am

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