SERVICE PROCEDURE

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SERVICE PROCEDURE

• Airflow measurement
• System charging
• Performance measurement

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Airflow measurement

• An accurate airflow measurement must be
  performed before the system can be properly
  charged with refrigerant or before any attempt is
  made to measure performance.

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Airflow measurement

• BTUH (OUTPUT)
• CFM TEMP DIFFERENCE X 1.08

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Measurement Methods

• power measurement - watt-hour meter
• electric resistance heat and heat pumps
• power measurement - volt-ampere
• electric resistance heat
• clocking a gas meter
• natural gas furnaces
• calculating input by orifice capicity
• propane gas furnaces
• total static pressure

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WATT-HOUR METER

• Power input measurements, by the watt-hour meter
  require power interruption to all appliances in
  the structure except the indoor fan motor and
  electric heaters.
• Do not turn off power to
• Life support devises
• Appliances subject to damage from power
  interruption

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WATT-HOUR METER

• Set the thermostat to heat or emergency heat and
  adjust the setpoint to 90 degrees.
• Locate the watt-hour meter serving the structure.
• Clock the black mark on the meter disc for 20
  revolutions using a stop watch or the second hand
  on your wrist watch.

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Power Input Formula

• Revolutions x KH factor x 3.6
• KW (KILOWATT) INPUT
• Seconds
• 20 revolutions
• kh 7.2
• 65 seconds

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Power Input Formula

• 20 rev x 7.2 kh x 3.6 518.4
• KW 7.97 kw
• 65 65

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1 KW 3413 BTU PER HOUR

• 7.97 kw x 3413 27,202 btuh (input)
• electric resistance heat is 100 effecient
• input output

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Take Return Air Temperature Measurement as Close
to Equipment as Possible
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Do NOT Take Temperature Measurement in the Line
of Sight of Heat Source.
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Take an Average of ALL Supply Duct Temperatures
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Use a Calibrated Thermometer to Measure
Temperature.
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Use the Same Thermometer for ALL Temperature
Measurements
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Airflow measurement

• BTUH (OUTPUT)
• CFM TEMP DIFFERENCE X 1.08
• EXAMPLE
• 27,202 BTUH (output)
• 27 degrees delta T

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Airflow measurement

• 27,202 BTUH 27,202 BTUH
• CFM 933 CFM 27 X 1.08
  29.16

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Measurement Methods

• power measurement - volt-ampere
• electric resistance heat

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POWER MEASUREMENT VOLT-AMPERE

• set the thermostat to the heat or emergency heat
  mode, in the case of a heat pump, so that only
  the resistance heaters and the fan motor are
  activiated.
• measure the applied voltage to the resistance
  heaters while they are operating.
• measure the current draw for each circuit if more
  than one and add them together.
• measure the temperature difference entering and
  leaving the air handler.

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POWER MEASUREMENT VOLT-AMPERE

• multiply the applied volts times the total
  current draw (amperes)
• VOLTS X AMPERES WATTS
• BTUH (OUTPUT) WATTS X 3.413

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Measurement Methods

• Clocking a gas meter
• Natural gas furnaces

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2 cubic feet per revolution
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GAS FURNACE INPUT

• make sure no other appliances are on during the
  test.
• set the thermostat to heat mode and 90 degrees.
• record the seconds required for one revolution of
  the 2 cubic foot dial on the gas meter.
• determine the gas flow rate in cubic feet per
  hour from the following equation or use a gas
  flow table.

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GAS FURNACE INPUT

• 2 cu. feet per
  revolution x 3600
• cu. ft per hour

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GAS FURNACE INPUT

• 2 cu. feet per
  revolution x 3600
• cu. ft per hour
• time (in seconds)
  per revolution

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GAS FURNACE INPUT

• 2 cu. feet per
  revolution x 3600
• cu. ft per hour
• time (in seconds)
  per revolution
• example 1 rev. (2cu.ft. dial) 60 seconds

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GAS FURNACE INPUT

• 2 cu. ft. per
  revolution x 3600
• cu. feet per hour
• 
  60
• 2 x 3600
  7200
• cu. feet per hour
  120 CFH
• 60
  60

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60 SECONDS
120 CFH
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GAS FURNACE INPUT

• BTUH HEAT CONTENT X CUBIC FOOT/HOUR
• BTUH 1000 BTU X 120 CFH 120,000 BTUH (INPUT)
• BTUH (OUTPUT) BTUH (INPUT) X EFFECIENCY
• USE A MIN. OF 80 EFFICIENCY FOR NAT. GAS
• USE FURNACE AFUE EFFECIENCY IF HIGHER THAN 80

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GAS FURNACE INPUT

• 120,000 BTUH X 92
• CFM
• 55 X 1.08
• 110,400 BTUH (OUTPUT)
• CFM
  1858 CFM
• 59.4

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Measurement Methods

• calculating input by orifice capacity
• propane gas furnaces

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CALCULATING CFM AND INPUT BY ORIFICE CAPACITY

• determine the burners orifice size.
• count the number of orifices in the furnace.
• set the gas valves outlet manifold pressure to 11
  inches of water column.
• set the thermostat to heat mode and 90 degrees.
• measure the temperature difference entering and
  leaving the furnace.

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CALCULATING CFM AND INPUT BY ORIFICE CAPACITY

• determine the btu per hour input for the selected
  orifice size using table f-2 in apendix f of the
  national fuel gas code.
• multiply the btu per hour input times the number
  of orifices counted in the furnace.
• multiply the btu per hour input times the furnace
  effeciency (minimum 80).

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table F-2
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Measurement Methods

• total external static pressure

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STATIC PRESSURE

• Definition
• The pressure measured above or below
  atmospheric pressure created by the blower
  independant of air velocity. It is exerted in all
  direction to the inside walls of the ductwork and
  is measured at a 90 degree angle to the airflow.

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Measure return static pressure close to air
handler or furnace cabinet.
messure return static pressure as close to air
handler or furnace cabinet as possible
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Measure supply static pressure downstream of all
pressure drops. Average readings where turbulant
airrflow is present
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PRODUCT DATATWEO48C140B - BAY96X1415PUB
22-1298-03 PAGE 8

• EXAMPLE
• Measured external static pressure .5 In. W.C.
• Blower set on high speed tap

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Product DataTWE048C140B - BAY96X1415

• EXAMPLE
• Measured external static pressure .5 In. W.C.
• Pressure drop accross heater .13 In. W.C.
• Final static pressure .63
• Airflow approx. 1550 CFM

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TUD100C948H - TXC049C4HPB

• EXAMPLE
• Measured external static pressure .30 In. W.C.
• Blower set on black - high speed tap

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Product Data TUD100C948H - TXC049C4HPB

• EXAMPLE
• Measured external static pressure .30 In. W.C.
• Pressure drop accross coil .30 In. W.C.
• Final total external static pressure .60 In.
  W.C.
• Blower set on black - high speed tap
• Airflow 1595 CFM

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Product Data TUD100C948H

• EXAMPLE
• Temperature rise 47 degrees
• Airflow 1550 CFM