Carrier 48VT(N) Gas Heating Fan Speed Set-up, Continuous Fan Operation, 48VT--A

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Gas Heating Fan Speed Set-up

!WARNING

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could result in personal injury or death.

Before making any indoor wiring adjustments, shut off gas supply. Then disconnect electrical power to the unit and install lockout tag before changing blower speed.

This unit has independent fan speeds for gas heating and cooling. In addition, this unit has the field-selectable capability to run two different cooling fan speeds: A normal cooling fan speed (350~400 CFM/Ton) and an enhanced dehumidification fan speed (As low as 320 CFM/Ton) for use with either a dehumidistat or a thermostat that supports dehumidification.

This unit is factory-set up for use with a single cooling fan speed. The cooling speed is marked “LOW” on the interface fan board (IFB) (Fig. 14) . The factory-shipped settings are noted in Table

10.There are 3 additional speed tap wires available for use in either gas heating or cooling (For color coding on the indoor fan motor leads, see Table 6). The additional 3 speed tap wires are shipped loose with vinyl caps and are located in the control box, near the interface fan board (IFB) (Fig. 14).

Gas Heating Fan Speed Set-up

To change the gas heating speed:

1.Remove the vinyl cap off of the desired speed tap wire (Refer to Table 6 for color coding). Table 10 shows the temperature rise associated with each fan speed for a given static pressure. Make sure that the speed chosen delivers a temperature rise within the rise range listed on the unit rating plate.

2.Remove the current speed tap wire from the “GAS HEAT” terminal on the interface fan board (IFB) (Fig.14) and place vinyl cap over the connector on the wire.

3.Connect the desired speed tap wire to the “GAS HEAT” terminal on the interface fan board (IFB).

Single Cooling Fan Speed Set-up (Dehumidification feature not used)

To change cooling speed:

1.Remove the vinyl cap off of the desired speed tap wire (Refer to Table 6 for color coding). Add the wet coil pressure drop in Table 8 to the system static to determine the correct cooling airflow speed in Table 10 that will deliver the nominal 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) (Fig. 14) and place vinyl cap over the connector on the wire.

3.Connect the desired speed tap wire to the “LOW” terminal on the interface fan board (IFB).

Two Cooling Fan Speeds Set-up (Dehumidification feature used)

IMPORTANT: Dehumidification control must open control circuit on humidity rise above set point.

Use of the dehumidification cooling fan speed requires use of either a 24 VAC dehumidistat or a thermostat which includes control of a 24 VAC dehumidistat connection. In either case, the dehumidification control must open the control circuit on humidity rise above the dehumidification set point. Dehumidification controls are available with the reverse logic; these must not be used.

1.Remove fan speed tap wire from the “LOW” terminal on the interface fan board (IFB) (Fig. 14).

2.Determine correct normal cooling fan speed for unit and application. Add the wet coil pressure drop in Table 8 to the system static to determine the correct cooling airflow speed in Table 10 that will deliver the nominal cooling airflow as listed in Table 1 for each size.

3.Remove the vinyl cap off of the desired speed tap wire (Refer to Table 6 for color coding) for the normal cooling fan speed and place desired speed tap wire on “HIGH” on the interface board.

4.Refer to airflow tables (Table 10) to determine allowable speeds for the dehumidification cooling fan speed. In Table 10, speeds that are not allowed for dehumidification cooling are shaded.

5.Remove the vinyl cap off of the desired speed tap wire (Refer to Table 6 for color coding) for the dehumidification cooling fan speed and place desired speed tap wire on the “LOW” connection on the interface board (IFB). Verify that static pressure is in the acceptable range for the speed tap to be used for dehumidification cooling.

6.Use any spare vinyl plugs to cap any unused speed tap wires.

NOTE: For heat pump operation, the recommended airflow is 350 to 450 CFM for each 12,000 Btuh of rated cooling capacity.

Continuous Fan Operation

When the DEHUM feature is not used, the continuous fan speed will be the same as cooling fan speed. When the DEHUM feature is used, the continuous fan will operate on IFB “LOW” speed when the DH control lead is not energized, or IFB “HIGH” speed when the DH lead is energized (see Fig. 14).

Table 6 – Color Coding for Indoor Fan Motor Leads

Black = High Speed

Orange = Med---High Speed

Red = Med Speed

Pink = Med---Low Speed

Blue = Low Speed

48VT-- A

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Contents SAFETY CONSIDERATIONS TABLE OF CONTENTSFig. 1 - Unit 48VT-A Installation InstructionsINTRODUCTION RECEIVING AND INSTALLATIONStep 1 - Check Equipment Step 2 - Provide Unit SupportA09146 Fig. 2 - 48VT-A24-30Unit Dimensions48VT--A A09147 Fig. 3 - 48VT-A36-60Unit Dimensions48VT--A 48VT Fig. 4 - Roof Curb DimensionsSMALL CURB ROOF CURB DETAILStep 5 - Rig and Place Unit ACCESS PANELS MUST BE IN PLACE WHEN RIGGINGInspection Rigging/Lifting of Unit See FigStep 8 - Install Gas Piping Step 7 - Install Flue HoodStep 6 - Connect Condensate Drain Fig. 6 - Condensate TrapConfiguring Units for Downflow Vertical Discharge Step 9 - Install Duct ConnectionsFig. 7 - Sediment Trap FIRE OR EXPLOSION HAZARDFig. 8 - Supply and Return Duct Opening Table 1 - Physical Data - Unit 48VT-A48VT--A Horizontal Duct CoversTable 2 - Maximum Gas Flow Capacity Table 1 - Physical Data - Unit 48VT-ACont’dTable 3 - Heating Inputs 48VT--ASpecial Procedures for 208-VOperation Step 10 - Install Electrical ConnectionsHigh-VoltageConnections Control Voltage ConnectionsPRE-START-UP Balance Point Setting-Thermidistator HybridTransformer Protection ThermostatSTART-UP Step 3 - Start-upHeating and Make Adjust- mentsStep 1 - Check for Refrigerant Leaks Step 2 - Unit Sequence of OperationFig. 11 - Burner Assembly Adjust Gas InputCheck Heating Control Check Gas InputCheck Burner Flame Limit SwitchesNormal Operation Airflow and Temperature RiseRollout Switch Step 4 - Start-upCooling and Make Adjust- mentsChecking and Adjusting Refrigerant Charge Indoor Airflow and Airflow AdjustmentsContinuous Fan Operation Gas Heating Fan Speed Set-upTable 6 - Color Coding for Indoor Fan Motor Leads 48VT--ATable 8 - 48VT-AWet Coil Pressure Drop Fig. 14 - Interface Fan Board IFB48VT--A Table 7 - Filter Pressure Drop Table IN. W.CUNIT 48VT--AHeating 48VT--A1295 48VT--A1445 48VT--A1448 48VT--A48VT A Fig. 15 - 208/230-1-60Wiring Diagram, Unit 48VT-AA09209 Fig. 16 - 208/230-3-60Wiring Diagram, Unit 48VT-A48VT--A 48VT--A Fig. 17 - Cooling Charging Table-Subcooling50VT500173 REV A09099Cleaning the Blower Motor and Wheel MAINTENANCEAir Filter Indoor Blower and MotorInduced Draft combustion air Blower Assembly Limit SwitchFig. 18 - Blower Housing and Flue Collector Box Fig. 19 - Unit Access PanelsOutdoor Fan Electrical Controls and WiringRefrigerant Circuit Fig. 20 - Removal of Motor and Blower WheelLoss of Charge Switch Pressure SwitchesHigh-PressureSwitch Gas InputPage LCS - Loss of Charge Switch HPS - High Pressure SwitchFig. 24 - Refrigerant Circuit AccuraterMetering De viceSTART-UPCHECKLIST TROUBLESHOOTINGUNIT OPERATION AND SAFETY HAZARD Synthetic Roof Precautionary Procedure48VT--A PURONR R-410AQUICK REFERENCE GUIDE48VT--A SYMPTOM48VT--A Table 12 - Troubleshooting Guide-HeatingTable 13 - Troubleshooting Guide-LEDStatus Codes I. PRELIMINARY INFORMATION MODEL NO Remove and Store in Job FilesTEMPERATURES PRESSURESCatalog No 48VT---05SI 48VT--AEdition Date 04/09 Replaces 48VT---04SI
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