2 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.
3 SUPERHEAT METHODTHE SUPERHEAT METHOD IS USED FOR SYSTEMS USING A FIXED ORIFICE TYPE METERING DEVICEOrificeMeteringDevice
4 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 TEMPERTUREGET THE OUTSIDE AMBIENT TEMPERATURE IN THE SHADE OF THE CONDENSING UNITSET ARROW TO INDOOR ENTERING AIR WET BULB TEMPERATURELOCATE CONDENSER ENTERING AIR DRY BULB TEMPERATUREREAD REQUIRED SUPERHEAT TEMPERATURE AT CONDENSER ENTERING AIR DRY BULB TEMPERATUREADD CHARGE TO LOWER SUPER HEATREMOVE CHARGE TO RAISE SUPERHEAT
5 USING SUPERHEAT TABLEGET THE OUTSIDE AMBIENT TEMPERATURE IN THE SHADE OF THE CONDENSING UNITGET THE RETURN DRY BULB TEMPERATURE AT THE RETURN AIR GRILLINTERSECT THE 2 NUMBERSTHAT WILL GIVE YOU THE AMOUNT OF SUPERHEAT YOU NEED
6 Super-heat and Sub-cooling charts The super-heat and sub-cooling charts will be posted on the back side of the control door.
7 EXAMPLEAMBIENT OUTSIDE TEMPERATURE (IN THE SHADE OF THE CONDENSOR) IS 95 DEGRESSRETURN AIR (DRY BULB) IS 75 DEGREESINTERSECT THE 2 NUMBERS AND YOUR SUPER HEAT WILL BE 5 DEGREE
8 INSTALL THERMOMETER INSTALL ON THE SUCTION LINE ( LARGER LINE ) INSULATE THE PROBE FOR AN MORE ACCURATE READING
9 READING THE SATURATED EVAPORATER TEMPERTURE ON THE LOW SIDE OF YOUR COMPOUND GAUGES ( BLUE )THE OUTSIDE READING IS YOUR PRESSURETHE INSIDE (R 22) IS YOUR SATURATED EVAPORIZING TEMPERTURE
10 EXAMPLE YOUR LOW SIDE PRESSURE IS 75 PSI DIRECTLY BELOW THAT NUMBER IS THE SATURATED EVAPORIZING TEMPERATURE, WHICH IS 44 DEGREESTAKE YOU SUCTION LINE TEMPERTURE, WHICH IS 65 DEGREE
11 EXAMPLE SUBTRACT THE 2 NUMBERS AND THAT HOW MUCH SUPEREHEAT YOU HAVE =21 SUPERHEATWE ONLY NEEDED 5 DEGREESADD CHARGE TO LOWER SUPER HEATREMOVE CHARGE TO RAISE SUPERHEAT
12 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.Check and record high stage liquid pressure at service valve.Explain that since 2 stage-procedures are different
13 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.Verifying unloader is working