Mini-Space Series Installation, Operation & Maintenance Manual

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Mini-Space Series Installation, Operation & Maintenance Manual6. Block off the intake air to the condenser withcardboard (or reduce the water glycol flow) untila constant discharge pressure (225-280 psig)can be obtained. This will lower the possibility ofovercharging and avoid the occasional bubblesthat may appear in the sight glass during fancycling (for units with fan cycling only).7. If the unit has a hot gas reheat option, the previoussteps are still followed except the hot gasreheat valve must be opened to allow refrigerantto flow into the reheat coil to obtain the properamount of unit charge. This process may need tobe repeated several times, which can be done byenabling a call for dehumidification. After cyclingthe system through the hot gas reheat cycle, recheckthe system charge in the COOLING-ONLYmode.8. Ensure the crankcase heater is operational bychecking the amperage.CAUTIONRemove the blockage to the air intake of the condenser(or restore the water/glycol flow).9. Fill out applicable blocks of Warranty Registrationand Start-Up Checklist.2.9.1.2.2 -30ºF Flooded Head Pressure ControlThe following instructions are for charging systems withfl ooded head pressure control using R22 refrigerant.1. Bleed air from hoses and “break” the system vacuumby supplying R22 liquid to the service valve ofthe receiver until the receiver is full. Then supplyR22 vapor to the suction port until the pressureis raised to about 50 psig (low pressure switchmakes).2. Start the system and use the microprocessorcontroller to lower the temperature set point3-5°F below room temperature. This will ensurecooling remains on during the charging procedure.CAUTIONAn adequate heat load must be supplied to the unitto ensure a proper charge.2-153. After starting the system, immediately supplyR22 vapor to the suction port until the liquid linesight glass has cleared of all bubbles.4. Raise the discharge pressure to 300-325 psigand hold it constant by blocking the air intake ofthe condenser.5. Once the discharge pressure has stabilized for 5to 10 minutes, additional refrigerant R22 vapormust be added to the suction port until the “fl oatball” in the level indicator of the receiver begins tofl o at.CAUTIONRemove the blockage to the air intake of the condenser.6. Take a superheat temperature reading on thesuction line near the feeler bulb from the thermalexpansion valve. The ideal superheat temperatureis 12-15°F. The maximum allowable superheattemperature is 20°F.7. Ensure that the crankcase heater is operationalby checking the amperage.8. Fill out applicable sections of the Warranty Registrationand Start-Up Checklist.2.9.2 R407C Refrigerant Charging ProceduresR407C is a blended refrigerant recognized for beingsafer for the environment. R407C refrigerant containsno chlorine, the component in HCFC’s that destroythe earth’s ozone layer. The same care should betaken to prevent leakage however, because R407Ccan contribute to the greenhouse effect if released.Refrigerants that are multi-component blends havecomponent parts with different volatilities that result ina change in composition and saturation temperatureas evaporation and condensation occur. Typically, thecomposition of R407C vapor is different than that ofR407C liquid within a contained system. The compositionof liquid R407C refrigerant remains relativelyconstant however, the refrigerant vapor tends toseparate into its component parts even when circulating.When charging a system using a blended refrigerant,it is essential that the composition of the refrigerantis maintained. To ensure correct composition, introduceR407C into the system in liquid form rather than(©April, 2008)Air Technology Systems, Inc.
Mini-Space Series Installation, Operation & Maintenance Manualvapor form. Cylinders which are not provided with diptubes should be inverted to allow only liquid refrigerantto charge the system. Keeping the temperature ofthe cylinder below 85°F will help maintain the correctrefrigerant composition while the cylinder is emptied.CAUTIONPOE oil is used in systems with R407C refrigerant.POE oil quickly absorbs moisture whenexposed to air. High POE oil moisture levelsreact with refrigerant to form acid, which resultsin system contamination. Keep the entire systemsealed as much as possible and minimizeexposure of POE oil to outside air.Familiarize yourself with the charging proceduresdiscussed in Section 2.9.1 of this manual. Instead ofadding R22 vapor to the suction port as describedunder “Preparing System for Charging”, the initialcharge will be performed by introducing R407C liquidto the discharge side of the compressor. (See thefollowing steps.)PREPARING SYSTEM FOR CHARGING1. With all the system piping connections made,perform a dry nitrogen leak detection test on thesystem. Using dry nitrogen only, pressurize thesystem to 150 psig. Since there is no refrigerantin the system to detect, leaks may be detected byobserving the standing pressure.2. After ensuring there are no leaks, evacuate thesystem to 50 microns and hold the vacuum for 2hours minimum.3. Break the vacuum by supplying R407C liquid tothe discharge port near the compressor until thepressure is raised to about 50 psig. This smallholding charge allows the low pressure switchto “make” through the process of fine tuning thesystem charge.FINE TUNING THE SYSTEM CHARGE4. Disconnect the refrigerant cylinder from the dischargeside of the compressor and connect it tothe suction side.5. Referring to Section 3.0, start the system anduse the microprocessor controller to lower thetemperature setpoint 3-5°F below room temperature,ensuring cooling remains on as the unit ischarged.6. Allow the discharge pressure to rise to 225-280psig and hold it constant. On cool days it may benecessary to restrict the airfl ow across the condenser(or reduce the water glycol fl ow), to raisethe pressure.7. Slowly meter R407C liquid refrigerant through thesuction side while watching the sight glass to clearof bubbles.CAUTIONAdd liquid refrigerant slowly to prevent the refrigerantoil from “washing out” of the compressor.8. Take a superheat temperature reading on thesuction line near the feeler bulb from the thermalexpansion valve. The ideal superheat temperatureis 12-15°F. The maximum allowable superheattemperature is 20°F.9. While monitoring the sight glass, take a subcoolingtemperature reading on the output side of thecondenser. The subcooling temperature shouldbe 10-20°F.10. If necessary, add liquid refrigerant to maintainadequate subcooling temperature.2.9.2.1 Flooded Head Pressure Control SystemsIn units with R407C refrigerant using fl ooded headpressure control, a receiver is provided to store therefrigerant during the time the condenser is not usingthe extra refrigerant charge. Once a clear sight glasshas been achieved, additional refrigerant must beadded to the receiver.A level indicator is located on the side of the receiverto assist the service technician in chargingthe air conditioning system. The proper charge canbe determined by viewing the position of the “fl oatball” while the unit is running. If the “fl oat ball” ispositioned at the bottom of the sight indicator, additionalrefrigerant charge is needed. When the “fl oatball” reaches the top of the indicator, the unit is fullycharged.(©April, 2008)2-16Air Technology Systems, Inc.
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