Unitary products group HA090, Руководство по установке, Страница: 10 / 20

035-18204-001-B-0703
10 Unitary Products Group
REFRIGERANT PIPING
GENERAL GUIDELINES
Many service problems can be avoided by taking ade-
quate precautions to provide an internally clean and
dry system and by using procedures and materials that
conform with established standards.
Use hard drawn copper tubing where no appreciable
amount of bending around pipes or other obstructions
is necessary. Use long radius ells wherever possible
with one exception—short radius ells for the traps in all
suction risers. If soft copper is used, care should be
taken to avoid sharp bends which may cause a restric-
tion.
Pack fiber glass insulation and a sealing material such
as permagum around refrigerant lines where they pen-
etrate a wall to reduce vibrations and to retain some
flexibility.
Support all refrigerant lines at minimum intervals with
suitable hangers, brackets or clamps.
Braze all copper to copper joints with Silfos-5 or equiv-
alent brazing material. Do not use soft solder.
Insulate all suction lines with a minimum of 1/2" ARMA-
FLEX or equal. Liquid lines exposed to direct sunlight
and/or high temperatures must also be insulated.
Never solder suction and liquid lines together. They
can be taped together for convenience and support
purposes, but they must be completely insulated from
each other.
A filter-drier MUST be installed in the liquid line of
every system to prevent dirt and moisture from damag-
ing the system. A properly-sized filter-drier is shipped
with each condensing unit for field installation near the
evaporator coil. The filter-drier and is taped to the top
of the compressor.
NOTE:
Installing a filter-drier does not eliminate the
need for the proper evacuation of a system
before it is charged.
A moisture indicating sight-glass may be field installed
in the liquid line(s) between the filter-drier and the
evaporator coil. The moisture indicating sight-glass can
be used to check for excess moisture in the system or
used as a visual means to verify refrigerant charge.
LINE SIZING
When sizing refrigerant lines for a split-system air con-
ditioner, check the following:
1. Suction line pressure drop due to friction
2. Liquid line pressure drop due to friction
3. Suction line velocity for oil return, and
4. Liquid line pressure drop due to static head.
NOTE:
Never base refrigerant line sizes on the O.D.
of the suction and liquid connections on the
unit.
Tables 4 and 5 list friction losses for both the suction
and liquid lines on the system. Table 6 shows the
amount of refrigerant charge required per foot of refrig-
erant line.
When the evaporator coil is below the condensing unit,
the suction line must be sized for both pressure drop
and for oil return. For certain piping arrangements, dif-
ferent suction line sizes may have to be used. The
velocity of the suction gas must always be great
enough to carry oil back to the compressor.
When the condensing unit is below the evaporator coil,
the liquid line must be designed for the pressure drop
due to both friction loss and vertical rise. If the total
pressure drop exceeds 40 psi, some refrigerant may
flash before it reaches the thermal expansion valve.
This flashing will not only cause erratic valve operation
and poor system performance, but could also damage
the expansion valve.
SERVICE VALVES
These condensing units have service valves on both
the compressor suction connection and the liquid line
leaving the condenser coil.
The liquid and suction line service valves are shipped
from the factory front-seated and closed with the valve
stem in the maximum clockwise position.
Both of the service valves have a 1/4" male flare
access port for evacuating, charging and pressure
checking the system.
NOTE:
Never remove a cap from an access port
unless the valve is fully back-seated with its
valve stem in the maximum counter-clockwise
position because the refrigerant charge will be
lost. ALWAYS USE A REFRIGERATION
VALVE WRENCH TO OPEN AND CLOSE
THESE SERVICE VALVES.