Carrier PERFORMANCE 50VT-A Installation Instructions Manual

Also see for COMFORT 50VT-A: Owner's information manual Owner's information manual Installation instructions

Contents

Carrier PERFORMANCE 50VT-A Installation Instructions Manual Manual pdf 18 page image

18turning backwards, the difference between compressor suction anddischarge pressures may be near zero.Checking and Adjusting Refrigerant ChargeThe refrigerant system is fully charged with Puron (R--410A)refrigerant and is tested and factory sealed.NOTE: Adjustment of the refrigerant charge is not requiredunless the unit is suspected of not having the proper Puron(R--410A) charge.A subcooling charging chart is attached to the inside of thecompressor access panel (see Fig. 21). The chart includes therequired liquid line temperature at given discharge line pressuresand outdoor ambient temperatures.An accurate thermocouple-- or thermistor--type thermometer, and agauge manifold are required when using the subcooling chargingmethod for evaluating the unit charge. Do not use mercury or smalldial--type thermometers because they are not adequate for this typeof measurement.NOTE: Allow system to operate for a minimum of 15 minutesbefore checking or adjusting refrigerant charge.IMPORTANT: When evaluating the refrigerant charge, anindicated adjustment to the specified factory charge must always bevery minimal. If a substantial adjustment is indicated, an abnormalcondition exists somewhere in the cooling system, such asinsufficient airflow across either coil or both coils.Proceed as follows:1. Remove caps from low-- and high--pressure service fittings.2. Using hoses with valve core depressors, attach low-- andhigh--pressure gauge hoses to low-- and high--pressureservice fittings, respectively.3. Start unit and let run until system pressures stabilize.4. Measure and record the following:a. Outdoor ambient--air temperature (°F [°C] db).b. Liquid line temperature (°F [°C]) at TXV.c. Discharge (high--side) pressure (psig).d. Suction (low--side) pressure (psig) (for reference only).5. Using Cooling Charging Charts compare outdoor--airtemperature (°F [°C] db) with the discharge line pressure(psig) to determine desired system operating liquid linetemperature (See Fig. 18).6. Compare actual liquid line temperature with desired liquidline temperature. Using a tolerance of ±2°F (±1.1°C), addrefrigerant if actual temperature is more than 2°F (1.1°C)higher than proper liquid line temperature, or removerefrigerant if actual temperature is more than 2°F (1.1°C)lower than required liquid line temperature.NOTE: If the problem causing the inaccurate readings is arefrigerant leak, refer to Check for Refrigerant Leaks section.Indoor Airflow and Airflow AdjustmentsUNIT OPERATION HAZARDFailure to follow this caution may result in unit damage.For cooling operation, the recommended airflow is 350 to450 cfm for each 12,000 Btuh of rated cooling capacity. Forheating operation, the airflow must produce a temperaturerise that falls within the range stamped on the unit ratingplate.CAUTION!NOTE: Be sure that all supply--and return--air grilles are open,free from obstructions, and adjusted properly.ELECTRICAL SHOCK HAZARDFailure to follow this warning could result in personalinjury or death.Disconnect electrical power to the unit and install lockouttag before changing blower speed.! WARNINGThis unit is factory-set up for use with a single cooling fan speed.In addition, this unit has the field-selectable capability to run twodifferent cooling fan speeds: The rated cooling fan speed (350~400CFM/Ton) and an enhanced dehumidification fan speed (As low as320 CFM/Ton) for use with either a dehumidistat or a thermostatthat supports dehumidification.The cooling speed is marked “LOW” on the interface fan board(IFB) (See Fig. 16) . The factory-shipped settings are noted inTable 4. There are 4 additional speed tap wires available for use ineither electric heating or cooling (For color coding on the indoorfan motor leads, see Table 3). The additional 4 speed tap wires areshipped loose with vinyl caps and are located in the control box,near the interface fan board (IFB) (See Fig. 16).Single Cooling Fan Speed Set-up (Dehumidificationfeature not used)To change cooling speed:1. Remove the vinyl cap off of the desired speed tap wire(Refer to Table 3 for color coding). Add the wet coilpressure drop in Table 7 to the system static to determine thecorrect cooling airflow speed in Table 4 that will deliver thenominal cooling airflow as listed in Table 1 for each size.2. Remove the current speed tap wire from the “LOW”terminal on the interface fan board (IFB) (See Fig. 16) andplace vinyl cap over the connector on the wire.3. Connect the desired speed tap wire to the “LOW” terminalon the interface fan board (IFB).NOTE: If accessory electric heat is installed, and the electric heatfan speed is chosen to be the same as the normal cooling fan speed,the dry airflow must meet or exceed the minimum airflow speedspecified in Table 2 for the specific size unit.Two Cooling Fan Speeds Set-up (Dehumidificationfeature used)IMPORTANT: Dehumidification control must open controlcircuit on humidity rise above set point.Use of the dehumidification cooling fan speed requires use ofeither a 24 VAC dehumidistat or a thermostat which includescontrol of a 24 VAC dehumidistat connection. In either case, thedehumidification control must open the control circuit on humidityrise above the dehumidification set point.1. Using Fig. 16, move the two pin DEHUM jumper from the“STD” position to the “DEHUM” position.2. Remove fan speed tap wire from the “LOW” terminal onthe interface fan board (IFB) (See Fig. 16).3. Determine correct normal cooling fan speed for unit andapplication. Add the wet coil pressure drop in Table 7 tothe system static to determine the correct cooling airflowspeed in Table 4 that will deliver the nominal coolingairflow as listed in Table 1 for each size.NOTE: If accessory electric heat is installed, the dryairflow must meet or exceed the minimum airflow speedspecified in Table 2 for the specific size unit. The electricheat fan speed will be the same as the normal cooling fanspeed.50VT-- A