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EXPANSION VALVE SYSTEM

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EXPANSION VALVE SYSTEM. 1. Purge gauge lines. Connect service gauge manifold to base-valve service ports. Run system at least 10 minutes to allow pressure to stabilize.

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expansion valve system
EXPANSION VALVE SYSTEM
  • 1. Purge gauge lines. Connect service gauge manifold to base-valve service ports. Run system at least 10 minutes to allow pressure to stabilize.
  • 2. Temporarily install thermometer on liquid (small) line near liquid line service valve with adequate contact and insulate for best possible reading.
  • 3. Check subcooling and superheat. Systems with TXV application should have a subcooling and superheat of 9 ±3 ºF.
    • a. If subcooling and superheat are low, adjust TXV to 9 ± 3ºF then check subcooling.
    • b. If subcooling is low and superheat is high, add charge to raise subcooling to 9 ± 3ºF then check superheat.
    • c. If subcooling and superheat are high, adjust TXV valve to 9 ± 3ºF then check subcooling.
    • d. If subcooling is high and superheat is low, adjust TXV valve to 9 ± 3ºF superheat and remove chargeto lower the subcooling to 9 ± 3ºF.
  • NOTE: Do NOT adjust the charge based on suction pressure unless there is a gross undercharge.
  • 4. Disconnect manifold set, installation is complete.
  • Subcooling Formula = Sat. Liquid Temp. - Liquid Line Temp.
slide3

SUPERHEAT METHOD

THE SUPERHEAT METHOD IS USED FOR SYSTEMS USING A FIXED ORIFICE TYPE METERING DEVICE

Orifice

Metering

Device

using superheat calculator
USING SUPERHEAT CALCULATOR
  • GET THE RETURN WET BULB TEMPERATURE AT THE RETURN AIR GRILL USING A SLING PSYCHROMETER OR METER CAPABLE OF READING WET BULB TEMPERTURE
  • GET THE OUTSIDE AMBIENT TEMPERATURE IN THE SHADE OF THE CONDENSING UNIT
  • SET ARROW TO INDOOR ENTERING AIR WET BULB TEMPERATURE
  • LOCATE CONDENSER ENTERING AIR DRY BULB TEMPERATURE
  • READ REQUIRED SUPERHEAT TEMPERATURE AT CONDENSER ENTERING AIR DRY BULB TEMPERATURE
  • ADD CHARGE TO LOWER SUPER HEAT
  • REMOVE CHARGE TO RAISE SUPERHEAT
using superheat table
USING SUPERHEAT TABLE
  • GET THE OUTSIDE AMBIENT TEMPERATURE IN THE SHADE OF THE CONDENSING UNIT
  • GET THE RETURN DRY BULB TEMPERATURE AT THE RETURN AIR GRILL
  • INTERSECT THE 2 NUMBERS
  • THAT WILL GIVE YOU THE AMOUNT OF SUPERHEAT YOU NEED
super heat and sub cooling charts
Super-heat and Sub-cooling charts
  • The super-heat and sub-cooling charts will be posted on the back side of the control door.
example
EXAMPLE
  • AMBIENT OUTSIDE TEMPERATURE (IN THE SHADE OF THE CONDENSOR) IS 95 DEGRESS
  • RETURN AIR (DRY BULB) IS 75 DEGREES
  • INTERSECT THE 2 NUMBERS AND YOUR SUPER HEAT WILL BE 5 DEGREE
install thermometer
INSTALL THERMOMETER
  • INSTALL ON THE SUCTION LINE ( LARGER LINE )
  • INSULATE THE PROBE FOR AN MORE ACCURATE READING
reading the saturated evaporater temperture
READING THE SATURATED EVAPORATER TEMPERTURE
  • ON THE LOW SIDE OF YOUR COMPOUND GAUGES ( BLUE )
  • THE OUTSIDE READING IS YOUR PRESSURE
  • THE INSIDE (R 22) IS YOUR SATURATED EVAPORIZING TEMPERTURE
example1
EXAMPLE
  • YOUR LOW SIDE PRESSURE IS 75 PSI
  • DIRECTLY BELOW THAT NUMBER IS THE SATURATED EVAPORIZING TEMPERATURE, WHICH IS 44 DEGREES
  • TAKE YOU SUCTION LINE TEMPERTURE, WHICH IS 65 DEGREE
example2
EXAMPLE
  • SUBTRACT THE 2 NUMBERS AND THAT HOW MUCH SUPEREHEAT YOU HAVE
  • 65 - 44 =21 SUPERHEAT
  • WE ONLY NEEDED 5 DEGREES
  • ADD CHARGE TO LOWER SUPER HEAT
  • REMOVE CHARGE TO RAISE SUPERHEAT
charging two stage units
Charging Two Stage Units
  • Set unit to operate at low stage cooling.
  • Operate for 10 minutes.
  • Check and record low stage liquid pressure at the service valve.
  • Set thermostat to operate at high stage.
  • Operate for 10 minutes.
  • Check and record high stage liquid pressure at service valve.
charging two stage units1
Charging Two Stage Units
  • The high stage pressure should be noticeably higher than the low stage liquid pressure.
  • If the pressures are identical, the compressor did not switch from low to high stage.
  • Verify wiring and t-stat settings.
  • Run the unit on low stage and make the final charge adjustments on low stage.
  • Do not adjust charge to change sub-cooling on high stage. Charge adjustments must only be made under low stage cooling.
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