Goodman Mfg VC8 instruction manual Start-Up Procedure And Adjustment

START-UP PROCEDURE AND ADJUSTMENT

4.Calculate the furnace input in BTUs per hour (BTU/hr). Input equals the sum of the installation’s gas heating value and a conversion factor (hours to seconds) divided by the number of seconds per cubic foot. The measured input must not be greater than the input indicated on the unit rating plate.

EXAMPLE:

Installation’s gas heating (HTG) value: 1,000 BTU/ft3 (Obtained from gas supplier)

Installation’s seconds per cubic foot: 34 sec/ ft3

Conversion Factor (hours to seconds): 3600 sec/hr Input = (Htg. value x 3600) ÷ seconds per cubic foot Input = (1,000 BTU/ft3 x 3600 sec/hr) ÷ 34 sec/ ft3 Input = 106,000 BTU/hr

Minor changes to the input rate may be accomplished through manifold pressure adjustments at the gas valve. Refer to Sec- tion XIV, Startup Procedure and Adjustment - Gas Manifold Pressure Measurement and Adjustment for details. NOTE: The final manifold pressure cannot vary by more than ± 0.3” w.c. from the specified setting. Consult your local gas supplier if additional input rate adjustment is required.

5.Repeat steps 2 through 4 on high stage.

6.Turn ON gas to and relight all other appliances turned off in step 1. Be certain that all appliances are functioning properly and that all pilot burners are operating.

TEMPERATURE RISE

Temperature rise must be within the range specified on the unit rating plate. An incorrect temperature rise may result in con- densing in or overheating of the heat exchanger. An airflow and temperature rise table is provided in the Specification Sheet applicable to your model. Determine and adjust temperature rise as follows:

1.Operate furnace with burners firing for approximately ten minutes. Ensure all registers are open and all duct dampers are in their final (fully or partially open) position.

2.Place thermometers in the return and supply ducts as close to the furnace as possible. Thermometers must not be influenced by radiant heat by being able to “see” the heat exchanger.

3.Subtract the return air temperature from the supply air temperature to determine the air temperature rise. Allow adequate time for thermometer readings to stabilize.

4.Adjust temperature rise by adjusting the circulator blower speed. Increase blower speed to reduce temperature rise. Decrease blower speed to increase temperature rise. Refer to Startup Procedure and Adjustment -Circulator Blower Speeds for speed changing details.

HEAT EXCHANGER

RADIATION "LINE OF SIGHT"

SUPPLY

AIR

TSUPPLY

RISE = TSUPPLY - TRETURN

TRETURN

RETURN

AIR

Temperature Rise Measurement

CIRCULATOR BLOWER SPEEDS

WARNING

TO AVOID PERSONAL INJURY OR DEATH DUE TO ELECTRICAL SHOCK, TURN OFF POWER TO THE FURNACE BEFORE CHANGING SPEED TAPS.

This furnace is equipped with a multi-speed circulator blower. This blower provides ease in adjusting blower speeds. The Specification Sheet applicable to your model provides an air- flow table, showing the relationship between airflow (CFM) and external static pressure (E.S.P.), for the proper selection of heating and cooling speeds. The heating blower speed is shipped set at “B”, and the cooling blower speed is set at “D”. These blower speeds should be adjusted by the installer to match the installation requirements so as to provide the cor- rect heating temperature rise and correct cooling CFM.

Use the dual 7-segment LED display adjacent to the dipswitches to obtain the approximate airflow quantity. The airflow quantity is displayed as a number on the display, rounded to the near- est 100 CFM. The display alternates airflow delivery indication and the operating mode indication.

Example: The airflow being delivered is 1225 CFM. The dis- play indicates 12. If the airflow being delivered is 1275, the display indicates 13.

1.Determine the tonnage of the cooling system installed with the furnace. If the cooling capacity is in BTU/hr divide it by 12,000 to convert capacity to TONs.

Example: Cooling Capacity of 30,000 BTU/hr. 30,000/12,000 = 2.5 Tons

2.Determine the proper air flow for the cooling system. Most cooling systems are designed to work with air flows between 350 and 450 CFM per ton. Most manufacturers recommend an air flow of about 400 CFM per ton.

Example: 2.5 tons X 400 CFM per ton = 1000 CFM

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