Charging; Expansion Valve System - Daikin ComfortNet DX16TC Series Service Instructions Manual

SERVICING
S-103 CHARGING
WARNING
REFRIGERANT UNDER PRESSURE!
* Do not overcharge system with refrigerant.
* Do not operate unit in a vacuum or at negative
pressure.
Failure to follow proper procedures may cause
property damage, personal injury or death.
CAUTION
Use refrigerant certified to AHRI standards. Used
refrigerant may cause compressor damage and is
not covered under the warranty. Most portable
machines cannot clean used refrigerant to meet
AHRI standards.
Damage to the unit caused by operating the
compressor with the suction valve closed is
not covered under the warranty and may
cause serious compressor damage.
Charge the system with the exact amount of refrigerant. Refer
to the specification section or check the unit nameplates for
the correct refrigerant charge. An inaccurately charged system
will cause future problems.
NOTE: R410A should be drawn out of the storage container
or drum in liquid form due to its fractionation properties, but
should be "Flashed" to its gas state before entering the sys-
tem. There is commercially available restriction devices that fit
into the system charging hose set to accomplish this. DO NOT
charge liquid R410A into the compressor.
NOTE: Power must be supplied to the 18 SEER outdoor units
containing ECM motors before the power is applied to the
indoor unit. Sending a low voltage signal without high voltage
power present at the outdoor unit can cause malfunction of
the control module on the ECM motor.
Adequate refrigerant charge for the matching evaporator
coil or air handler and 15 feet of line set is supplied with the
condensing unit. If using evaporator coils or air handlers other
than HSVTC coil it may be necessary to add or remove refrig-
erant to attain proper charge. If line set exceeds 15 feet in
length, refrigerant should be added at .6 ounces per foot of
liquid line.
NOTE: The outdoor temperature should be 60°F or higher
when charging the unit.Charge should always be checked using
subcooling when using TXV equipped indoor coil to verify
proper charge. Open the suction service valve first! If the liq-
uid service valve is opened first, oil from the compressor may
be drawn into the indoor coil TXV, restricting refrigerant flow
and affecting operation of the system.
When opening valves with retainers, open each valve only until
the top of the stem is 1/8" from the retainer. To avoid loss
of refrigerant, DO NOT apply pressure to the retainer. When
opening valves without a retainer remove service valve cap
and insert a hex wrench into the valve stem and back out the
stem by turning the hex wrench counterclockwise. Open the
valve until it contacts the rolled lip of the valve body.
NOTE: These are not back-seating valves. It is not necessary to
force the stem tightly against the rolled lip.
After the refrigerant charge has bled into the system, open the
liquid service valve. The service valve cap is the secondary seal
for the valve and must be properly tightened to prevent leaks.
Make sure cap is clean and apply refrigerant oil to threads and
sealing surface on inside of cap. Tighten cap finger-tight and
then tighten additional 1/6 of a turn (1 wrench flat) to properly
seat the sealing surfaces.

EXPANSION VALVE SYSTEM

NOTE: Units matched with indoor coils equipped with non-ad-
justable TXV should be charged by subcooling only.
NOTE: The TXV should NOT be adjusted at light load conditions
55º to 60ºF. Use the following guidelines and methods to
check unit operation and ensure that the refrigerant charge is
within limits. Charge the unit on low stage.
Units Equipped with Adjustable Expansion Valves
should be charged by Subcooling and Superheat
adjusted only if necessary.
1. Purge gauge lines. Connect service gauge manifold to base-
valve service ports. Run the system in low stage at least 10
minutes to allow pressure to stabilize.
2. Temporarily install a thermometer on the liquid line at the
liquid line service valve and 4-6" from the compressor on
the suction line. Ensure the thermometer makes adequate
contact and is insulated for best possible readings. Use
liquid line temperature to determine subcooling and vapor
temperature to determine superheat.
3. Check subcooling and superheat. Systems with TXV appli-
cation should have a subcooling of 5 to 7°F and superheat
of 7 to 9 °F.
a. If subcooling and superheat are low, adjust TXV to 7 to 9
ºF superheat, and then check subcooling.
NOTE: To adjust superheat, turn the valve stem clockwise to
increase and counter clockwise to decrease.
b. If subcooling is low and superheat is high, add charge to
raise subcooling to 5 to 7 °F then check superheat.
c. If subcooling and superheat are high, adjust TXV valve to
7 to 9 ºF superheat, then check subcooling.
d. If subcooling is high and superheat is low, adjust TXV
valve to 7 to 9 ºF superheat and remove charge to lower
the subcooling to 5 to 7 ºF.
NOTE: Do NOT adjust the charge based on suction pressure
unless there is a gross undercharge.
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