Evaporator Coil; Thermostatic Expansion Valve (Txv); Txv Operation - Carrier WeatherMaster 50HC04 Service And Maintenance Instructions

Fig. 21 — Separating Coil Sections
Totaline Environmentally Balanced Coil Cleaner Application
Equipment
• 2 / gallon garden sprayer
1
2
• Water rinse with low velocity spray nozzle
CAUTION
UNIT DAMAGE HAZARD
Failure to follow this caution may result in reduced unit
performance or unit shutdown.
High velocity water from a pressure washer, garden hose,
or compressed air should never be used to clean a coil. The
force of the water or air jet will bend the fin edges and in-
crease airside pressure drop.
CAUTION
UNIT DAMAGE HAZARD
Failure to follow this caution may result in accelerated cor-
rosion of unit parts.
Harsh chemicals, household bleach or acid or basic clean-
ers should not be used to clean outdoor or indoor coils of
any kind. These cleaners can be very difficult to rinse out of
the coil and can accelerate corrosion at the fin/tube inter-
face where dissimilar materials are in contact. If there is
dirt below the surface of the coil, use the Totaline environ-
mentally balanced coil cleaner.
Totaline Environmentally Balanced Coil Cleaner Application
Instructions
1. Proper eye protection such as safety glasses is recom-
mended during mixing and application.
2. Remove all surface loaded fibers and dirt with a vacuum
cleaner as described above.
3. Thoroughly wet finned surfaces with clean water and a
low velocity garden hose, being careful not to bend fins.
4. Mix Totaline environmentally balanced coil cleaner in a
2 1 / gallon garden sprayer according to the instructions
2
included with the cleaner. The optimum solution tempera-
ture is 100°F.
NOTE: Do NOT USE water in excess of 130°F, as the enzymatic
activity will be destroyed.
5. Thoroughly apply Totaline environmentally balanced coil
cleaner solution to all coil surfaces including finned area,
tube sheets and coil headers.
6. Hold garden sprayer nozzle close to finned areas and apply
cleaner with a vertical, up-and-down motion. Avoid spraying
in horizontal pattern to minimize potential for fin damage.
7. Ensure cleaner thoroughly penetrates deep into finned
areas. Interior and exterior finned areas must be thor-
oughly cleaned. Finned surfaces should remain wet with
cleaning solution for 10 minutes. Ensure surfaces are not
allowed to dry before rinsing. Reapply cleaner as needed
to ensure 10 minute saturation is achieved.
8. Thoroughly rinse all surfaces with low velocity clean
water using downward rinsing motion of water spray noz-
zle. Protect fins from damage from the spray nozzle.

Evaporator Coil

CLEANING THE EVAPORATOR COIL
1. Turn unit power off. Install lockout tag. Remove evapora-
tor coil access panel.
2. If economizer or two-position damper is installed, remove
economizer by disconnecting Molex plug and removing
mounting screws.
3. Slide filters out of unit.
4. Clean coil using a commercial coil cleaner or dishwasher
detergent in a pressurized spray canister. Wash both sides
of coil and flush with clean water. For best results, back-
flush toward return-air section to remove foreign material.
Flush condensate pan after completion.
5. Reinstall economizer and filters.
6. Reconnect wiring.
7. Replace access panels.

THERMOSTATIC EXPANSION VALVE (TXV)

All 50HC units have a factory-installed nonadjustable thermo-
static expansion valve (TXV). The TXV is a bi-flow, bleed port
expansion valve with an external equalizer. The TXVs are spe-
cifically designed to operate with Puron
Use only factory-authorized TXVs. Do not interchange Puron
and R-22 TXVs.

TXV Operation

The TXV is a metering device that is used in air conditioning
and heat pump systems to adjust to the changing load condi-
tions by maintaining a preset superheat temperature at the out-
let of the evaporator coil.
The volume of refrigerant metered through the valve seat is de-
pendent upon the following:
1. Superheat temperature is sensed by cap tube sensing bulb
on suction tube at outlet of evaporator coil. This tempera-
ture is converted into pressure by refrigerant in the bulb
pushing downward on the diaphragm, which opens the
valve using the push rods.
2. The suction pressure at the outlet of the evaporator coil is
transferred through the external equalizer tube to the
underside of the diaphragm.
3. The pin is spring loaded, which exerts pressure on the
underside of the diaphragm. Therefore, the bulb pressure
works against the spring pressure and evaporator suction
pressure to open the valve. If the load increases, the tem-
perature increases at the bulb, which increases the pressure
on the top side of the diaphragm. This opens the valve and
increases the flow of refrigerant. The increased refrigerant
13
® or R-22 refrigerant.