Carrier Infinity 25VNA0 Service Manual

Also see for Infinity 24VNA0: Owner's manual

46CAUTION!UNIT DAMAGE HAZARDFailure to follow this caution may result in equipment damageor improper operation.To avoid filter drier damage while brazing, filter drier must bewrapped in a heat--sinking material such as a wet cloth.Install Liquid--line Filter Drier IndoorRefer to Fig. 33 or Fig. 34 and install filter drier as follows:1. Braze 5 in. liquid tube to the indoor coil.2. Wrap filter drier with damp cloth.3. Braze filter drier to 5 in. long liquid tube from step 1.4. Connect and braze liquid refrigerant tube to the filter drier.A05178Fig. 33 – Liquid Line Filter Drier -- ACA05227Fig. 34 – Liquid Line Filter Drier -- HPSuction Line Filter DrierThe suction line drier is specifically designed to operate withPuronr, use only factory authorized components. Suction line filterdrier is used in cases where acid might occur, such as burnout. Heatpump units must have the drier installed between the compressorand accumulator only. Remove after 10 hours of operation. Neverleave suction line filter drier in a system longer than 72 hours(actual time).Thermostatic Expansion Valve (TXV)All fan coils and furnace coils will have a factory installedthermostatic expansion valve (TXV). The TXV will be a bi--flow,hard--shutoff with an external equalizer and a balance port pin. Ahard shut--off TXV does not have a bleed port. Therefore,minimal equalization takes place after shutdown. TXVs arespecifically designed to operate with Puronr or R--22 refrigerant,use only factory authorized TXV’s. Do not interchange Puronand R--22 TXVs.TXV OperationThe TXV is a metering device that is used in air conditioning andheat pump systems to adjust to changing load conditions bymaintaining a preset superheat temperature at the outlet of theevaporator coil. The volume of refrigerant metered through thevalve seat is dependent upon the following:1. Superheat temperature is sensed by cap tube sensing bulbon suction tube at outlet of evaporator coil. Thistemperature is converted into pressure by refrigerant in thebulb pushing downward on the diaphragm which opens thevalve via the push rods.2. The suction pressure at the outlet of the evaporator coil istransferred via the external equalizer tube to the undersideof the diaphragm. This is needed to account for the indoorcoil pressure drop. Residential coils typically have a highpressure drop, which requires this valve feature.3. The pin is spring loaded, which exerts pressure on theunderside of the diaphragm. Therefore, the bulb pressureworks against the spring pressure and evaporator suctionpressure to open the valve.If the load increases, the temperature increases at the bulb,which increases the pressure on the top side of thediaphragm. This opens the valve and increases the flow ofrefrigerant. The increased refrigerant flow causes theleaving evaporator temperature to decrease. This lowers thepressure on the diaphragm and closes the pin. Therefrigerant flow is effectively stabilized to the load demandwith negligible change in superheat.AccumulatorThe accumulator is specifically designed to operate with Puronror R--22 respectfully; use only factory--authorized components.Under some light load conditions on indoor coils, liquid refrigerantis present in suction gas returning to compressor. The accumulatorstores liquid and allows it to boil off into a vapor so it can be safelyreturned to compressor. Since a compressor is designed to pumprefrigerant in its gaseous state, introduction of liquid into it couldcause severe damage or total failure of compressor.The accumulator is a passive device which seldom needs replacing.Occasionally its internal oil return orifice or bleed hole maybecome plugged. Some oil is contained in refrigerant returning tocompressor. It cannot boil off in accumulator with liquidrefrigerant. The bleed hole allows a small amount of oil andrefrigerant to enter the return line where velocity of refrigerantreturns it to compressor. If bleed hole plugs, oil is trapped inaccumulator, and compressor will eventually fail from lack oflubrication. If bleed hole is plugged, accumulator must be changed.The accumulator has a fusible element located in the bottom endbell. (See Fig. 35.) This fusible element will melt at 430_F//221_Cand vent the refrigerant if this temperature is reached either internalor external to the system. If fuse melts, the accumulator must bereplaced.To change accumulator:1. Shut off all power to unit.2. Recover all refrigerant from system.3. Break vacuum with dry nitrogen. Do not exceed 5 psig.NOTE: Coil may be removed for access to accumulator. Refer toappropriate sections of Service Manual for instructions.

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