OHAUS FC5816 Service Manual

Also see for Frontier FC5816: User guide Instruction manual Instruction manual Instruction manual

Contents

TROUBLESHOOTING3.14 Refrigeration system (FC5816R only)CAUTION: Only certified/qualify service personal should be performing therepair and service of the refrigeration system.Functional description of the refrigeration systemA capillary tube regulates how much refrigerant is being led to the evaporator. A sensor iscontinuously measuring the temperature at the evaporator output. Through this, the injectionnozzle of the expansion valve is controlled and the evaporator is supplied with the max.necessary amount of refrigerant. Therefore, maximum capability of the refrigeration systemcan be reached at any status of operation.As soon as the required pre-set temperature is reached, the compressor will switch off. Whenthe temperature rises again, the compressor will switch on again.The response time of the compressor is controlled by the microprocessor control. Theprocessor receives the chamber temperature data through a temperature sensor placed inrotor chamber. As the actual sample temperature may not be identical to the temperaturemeasured in the rotor chamber because of the air friction, the microprocessor will calculate thesample temperature for the rotor in use. This temperature value is indicated in the temperaturedisplay.The temperature adjustment of the microprocessor is based on this calculated temperaturevalue. Therefore, the user always gets the exactly requested sample temperature (±1°C). Thesamples are not being damaged through over or under temperature.Emptying and filling the refrigeration system (refrigerant R 404 a)For this performance you need a refrigerant suction plant with container, a vacuum pump, avacuum measuring device, a measuring device for refrigerants and a manometer combination.The refrigeration system has the CFC-free refrigerant type R 404 a.Emptying the refrigeration system:• Remove the housing, until the refrigeration set is exposed.• Remove the back wall plate and grounding.• Connect the suction plant to the valve.• Remove the refrigerant from the system.• You can now perform necessary repairs.Filling the refrigeration system:• Connect the vacuum pump, the manometer combination and the refrigerant bottle(R 404 a) to the valve.• Evacuate the refrigeration system for approx. 30min.• Switch off the vacuum pump.• Make sure, the reached vacuum stays constant after switching the pump off,otherwise the system is leaky.• Fill the refrigeration set with 320g refrigerant type R 404 a.• In order to reach max. cooling output, the amount of refrigerant must be adjustedPlease proceed as follows:-Insert available rotor and tighten it.-Pre-set max. admissible speed for this rotor.-Temperature pre-selection: -20°C.-Start the unit.-After approx. 30 min., lowest temperature at given amount of refrigerant isreached. This must at least correspond with the values given in Table 5 .In case it does not, you will have to remove refrigerant in small steps(approx. 1g), until the lowest possible temperature is reached.Check all tube connections with a leakage detection device for possible leakage.