Charging Heat Pumps and Airs

8/7/2019 Charging Heat Pumps and Airs

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EXPANSION VALVE SYSTEM1. Purge gauge lines. Connect service gauge manifold to base-valve service ports. Run systemat least 10 minutes to allow pressure to stabilize.

2. Temporarily install thermometer on liquid (small) line near liquid line service valve withadequate contact and insulate for best possible reading.

3. Check subcooling and superheat. Systems with TXV application should have a subcooling andsuperheat of 9 3 F.

a. If subcooling and superheat are low, adjust TXV to 9 3F then check subcooling.

b. If subcooling is low and superheat is high, add charge to raise subcooling to 9 3F thencheck superheat.

c. If subcooling and superheat are high, adjust TXV valve to 9 3F then check subcooling.

d. If subcooling is high and superheat is low, adjust TXV valve to 9 3F superheat andremove chargeto lower the subcooling to 9 3F.

NOTE: Do NOT adjust the charge based on suction pressure unless there is a grossundercharge.

4. Disconnect manifold set, installation is complete.

Subcooling Formula = Sat. Liquid Temp. - Liquid Line Temp.


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SUPERHEAT METHOD

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

OrificeMetering

Device


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USING SUPERHEAT

CALCULATORGET THE RETURN WET BULB TEMPERATURE AT THE RETURN

AIR GRILL USING A SLING PSYCHROMETER OR METER CAPABLEOF READING WET BULB TEMPERTURE

GET THE OUTSIDE AMBIENT TEMPERATURE IN THE SHADE OFTHE CONDENSING UNIT

SET ARROW TO INDOOR ENTERING AIR WET BULBTEMPERATURE

LOCATE CONDENSER ENTERING AIR DRY BULB TEMPERATURE

READ REQUIRED SUPERHEAT TEMPERATURE AT CONDENSERENTERING AIR DRY BULB TEMPERATURE

ADD CHARGE TO LOWER SUPER HEAT

REMOVE CHARGE TO RAISE SUPERHEAT


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USING SUPERHEAT TABLEGET THE OUTSIDE AMBIENTTEMPERATURE IN THE SHADE OF THECONDENSING UNIT

GET THE RETURN DRY BULBTEMPERATURE AT THE RETURN AIR GRILL

INTERSECT THE 2 NUMBERS

THAT WILL GIVE YOU THE AMOUNT OFSUPERHEAT YOU NEED


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Super-heat and Sub-coolingcharts

The super-heat andsub-cooling charts

will be posted on theback side of thecontrol door.


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EXAMPLE AMBIENT OUTSIDE TEMPERATURE(IN THE SHADE OF THECONDENSOR) IS 95 DEGRESSRETURN AIR (DRY BULB) IS 75DEGREES

INTERSECT THE 2 NUMBERS ANDYOUR SUPER HEAT WILL BE 5DEGREE


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INSTALL THERMOMETERINSTALL ON THE SUCTION LINE( LARGER LINE )

INSULATE THE PROBE FOR ANMORE ACCURATE READING


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READING THE SATURATEDEVAPORATER TEMPERTUREON THE LOW SIDE OF YOURCOMPOUND GAUGES ( BLUE )

THE OUTSIDE READING IS YOURPRESSURE

THE INSIDE (R 22) IS YOURSATURATED EVAPORIZINGTEMPERTURE


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EXAMPLEYOUR LOW SIDE PRESSURE IS 75PSI

DIRECTLY BELOW THAT NUMBER ISTHE SATURATED EVAPORIZINGTEMPERATURE, WHICH IS 44DEGREES

TAKE YOU SUCTION LINETEMPERTURE, WHICH IS 65DEGREE


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EXAMPLESUBTRACT THE 2 NUMBERS AND THATHOW MUCH SUPEREHEAT YOU HAVE

65 - 44 =21 SUPERHEAT

WE ONLY NEEDED 5 DEGREES

ADD CHARGE TO LOWER SUPER HEAT

REMOVE CHARGE TO RAISE SUPERHEAT


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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 atservice valve.

Charging Two Stage Units


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Documents

Charging Heat Pumps and Airs