24VNA6 / 25VNA4: Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
35
REFRIGERATION SYSTEM
Refrigerant
In an air conditioning and heat pump system, refrigerant transfers heat
from one place to another. The condenser is the outdoor coil in the
cooling mode and the evaporator is the indoor coil.
In a heat pump, the condenser is the indoor coil in the heating mode and
the evaporator is the outdoor coil.
In the typical air conditioning mode, compressed hot gas leaves the
compressor and enters the condensing coil. As gas passes through the
condenser coil, it rejects heat and condenses into liquid. The liquid
leaves condensing unit through liquid line and enters metering device at
evaporator coil. As it passes through metering device, it becomes a
gas-liquid mixture. As it passes through indoor coil, it absorbs heat and
the refrigerant moves to the compressor and is again compressed to hot
gas, and cycle repeats.
Compressor Oil
Servicing Systems on Roofs With Synthetic
Materials
Polyvinyl ether (PVE) compressor lubricants are known to cause long
term damage to some synthetic roofing materials. Exposure, even if
immediately cleaned up, may cause embrittlement (leading to cracking)
to occur in one year or more. When performing any service which may
risk exposure of compressor oil to the roof, take appropriate precautions
to protect roofing. Procedures which risk oil leakage include but are not
limited to compressor replacement, repairing refrigerants leaks,
replacing refrigerant components such as filter drier, pressure switch,
metering device, coil, accumulator, or reversing valve.
Synthetic Roof Precautionary Procedure
1. Cover extended roof working area with an impermeable
polyethylene (plastic) drop cloth or tarp. Cover an approximate 10
x 10 ft area.
2. Cover area in front of the unit service panel with a terry cloth shop
towel to absorb lubricant spills and prevent run-offs, and protect
drop cloth from tears caused by tools or components.
3. Place terry cloth shop towel inside unit immediately under
component(s) to be serviced and prevent lubricant run-offs through
the louvered openings in the base pan.
4. Perform required service.
5. Remove and dispose of any oil contaminated material per local
codes.
Brazing
This section on brazing is not intended to teach a technician how to
braze. There are books and classes which teach and refine brazing
techniques. The basic points below are listed only as a reminder.
Definition: The joining and sealing of metals using a nonferrous metal
having a melting point over 800°F/426.6°C.
Flux: A cleaning solution applied to tubing or wire before it is brazed.
Flux improves the strength of the brazed connection.
When brazing is required in the refrigeration system, certain basics
should be remembered. The following are a few of the basic rules.
1. Clean joints make the best joints. To clean:
– Remove all oxidation from surfaces to a shiny finish before
brazing.
– Remove all flux residue with brush and water while material is still
hot.
2. Silver brazing alloy is used on copper-to-brass, copper-to-steel, or
copper-to-copper. Flux is required when using silver brazing alloy.
Do not use low temperature solder.
3. Fluxes should be used carefully. Avoid excessive application and do
not allow fluxes to enter into the system.
4. Brazing temperature of copper is proper when it is heated to a
minimum temperature of 800°F and it is a dull red color in
appearance.
Service Valves and Pumpdown
Service valves provide a means for holding original factory charge in
outdoor unit prior to hookup to indoor coil. They also contain gauge
ports for measuring system pressures and provide shutoff convenience
for certain types of repairs.
The service valve is a front-seating valve, which has a service port that
contains a Schrader fitting. The service port is always pressurized after
the valve is moved off the front-seat position.
The service valves in the outdoor unit come from the factory
front-seated. This means that the refrigerant charge is isolated from the
line-set connection ports. The interconnecting tubing (line set) can be
brazed to the service valves using industry accepted methods and
materials. Consult local codes.
Before brazing the line set to the valve, the belled ends of the sweat
connections on the service valves must be cleaned so that no brass
plating remains on either the inside or outside of the bell joint. To
prevent damage to the valve and/or cap “O” ring, use a wet cloth or
other acceptable heat-sinking material on the valve before brazing. To
prevent damage to the unit, use a metal barrier between brazing area and
unit.
After the brazing operation and the refrigerant tubing and evaporator coil
have been evacuated, the valve stem can be turned counterclockwise
until back-seats, which releases refrigerant into tubing and evaporator
coil. The system can now be operated.
The service valve-stem cap is tightened to 20 ± 2 ft/lb torque and the
service-port caps to 9 ± 2 ft/lb torque. The seating surface of the valve
stem has a knife-set edge against which the caps are tightened to attain a
metal-to-metal seal.
WARNING
!
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this warning could result in personal injury or
equipment damage.
Puronr refrigerant which has higher pressures than R-22 and other
refrigerants. No other refrigerant may be used in this system. Gauge set,
hoses, and recovery system must be designed to handle Puronr. If you
are unsure consult the equipment manufacturer.
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage or
improper operation.
The compressor in a Puron system uses a polyvinyl ether (PVE) oil.
This oil is extremely hygroscopic, meaning it absorbs water readily.
PVE oils can absorb 15 times as much water as other oils designed for
HCFC and CFC refrigerants. Take all necessary precautions to avoid
exposure of the oil to the atmosphere.
WARNING
!
PERSONAL INJURY AND UNIT DAMAGE HAZARD
Failure to follow this warning could result in personal injury or
equipment damage.
Never attempt to make repairs to existing service valves. Unit operates
under high pressure. Damaged seats and o-rings should not be replaced.
Replacement of entire service valve is required. Service valve must be
replaced by properly trained service technician.
