Expansion valve system
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EXPANSION VALVE SYSTEM PowerPoint PPT Presentation


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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

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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.


Expansion valve system

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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