Carrier 30HXC Series Installation, Operation And Maintenance Instructions

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Carrier 30HXC Series Installation, Operation And Maintenance Instructions Manual pdf 29 page image

2915 - MAINTENANCE15.1 - Refrigerant charging - adding chargeIMPORTANTThese units are designed for use with R-134a only. DO NOTUSE ANY OTHER refrigerant in these units.CAUTIONWhen adding or removing charge, circulate water throughthe condenser (HX) and cooler at all times to preventfreezing. Freezing damage is considered abuse and may voidthe Carrier warranty.CAUTIONDO NOT OVERCHARGE system. Overcharging results inhigher discharge pressure with higher cooling fluidconsumption, possible compressor damage and higher powerconsumption.15.2 - Indication of low charge on a 30HXC systemNOTETo check for low refrigerant charge on a 30HXC, severalfactors must be considered. A flashing liquid-line sightglass isnot necessarily an indication of inadequate charge. There aremany system conditions where a flashing sightglass occursunder normal operation. The 30HXC metering device isdesigned to work properly under these conditions.1. Make sure that the circuit is running at a full-load condi-tion. To check whether circuit A is fully loaded, follow theprocedure described in the Controls manual.2. It may be necessary to use the Manual Control feature toforce the circuit into a full-load condition. If this is the case,see the instructions for using the Manual Control feature inthe Controls manual.3. With the circuit running at full-load, verify that the coolerleaving fluid temperature is in the range of 6°C ± 1.5.4. At this condition, observe the refrigerant in the liquid linesightglass. If there is a clear sightglass, and no signs offlashing, then the circuit is adequately charged. Skip theremaining steps.5. If the refrigerant appears to be flashing, the circuit isprobably low on charge. Verify this by checking the EXVposition (see Controls IOM).6. If the opening position of the EXD is greater than 60%, andif the liquid-line sightglass is flashing, then the circuit islow on charge. Follow the procedure for adding charge.15.2.1 - To add charge to the 30HXC systems1. Make sure that the unit is running at full-load, and that thecooler leaving fluid temperature is in the range of 5.6 -7.8 °C.2. At these operating conditions, check the liquid-linesightglass. If there is a clear sightglass, then the unit hassufficient charge. If the sightglass is flashing, then checkthe EXD Percent Open. If this is greater than 60%, thenbegin adding charge.NOTEA flashing liquid-line sightglass at operating conditions otherthan those mentioned above is not necessarily an indicationof low refrigerant charge.3. Add 2.5 kg of liquid charge into the evaporator using thecharging valve located on the top of the evaporator.4. Observe the EXD Percent Open value. The EXD shouldbegin closing as charge is being added. Allow the unit tostabilize. If the EXD Percent Open remains above 60%, andthere are still bubbles in the sightglass, add an additional2.5 kg of liquid charge.5. Allow the unit to stabilize, and again check the EXDPercent Open. Continue adding 2.5 kg of liquid refrigerantcharge at a time, and allow the unit to stabilize beforechecking the EXD position.6. When the EXD Percent Open is in the range of 40 - 60%,check the liquid line sightglass. Slowly add enoughadditional liquid charge to ensure a clear sightglass. Thisshould be done slowly to avoid overcharging the unit.7. Verify adequate charge by continuing to run at full-loadwith 6°C ± 1.5 evaporator leaving fluid temperature. Checkthat the refrigerant is not flashing in the liquid-linesightglass. The EXD Percent Open should be between 40and 60%. The cooler level indicator should be in the rangeof 1.5 - 2.5.15.2.2 - Indication of low charge on 30GX systems1. Make sure that the circuit is running at a full-load conditionand that the condensing temperature is 50°C ± 1.5. Tocheck whether circuit A is fully-loaded, follow theprocedure in the Controls IOM.2. It may be necessary to use the Manual Control feature toforce the circuit into a full-load condition. If this is the case,see the instructions for using the Manual Control function(procedure in the Controls IOM).3. With the circuit running at full-load, verify that the coolerleaving fluid temperature is in the range of 6°C ± 1.5.4. Measure the air temperature entering the condenser coils.Measure the liquid temperature after the tee where the twocoil liquid lines join. The liquid temperature should be8.3°C above the air temperature entering the coils. If thedifference is more than this and the sightglass is flashing,the circuit is uncharged. Proceed to step 5.5. Add 2.5 kg of liquid charge into the cooler using chargingvalve located in the top of the cooler.6. Allow the system to stabilize and then recheck the liquidtemperature. Repeat step 5 as needed allowing the systemto stabilize between each charge addition. Slowly addcharge as the sightglass begins to clear to avoid over-charging.15.2.3 - Space temperature, outdoor air temperature(optional)These temperatures are used to measure the temperature of thespace or the outside air temperature respectively for resetcontrol based on Outside Air or Space Temperature resetoptions.