FORM 150.63-EG4 (1012)
9JOHNSON CONTROLS
Selection Data
The ratings shown on pages 12 through 17 are based
on unit operation in a well designed and properly piped
system.
SELECTION RULES
1. Capabilities are based on Refrigerant R-410A.
2. Ratings may be interpolated, but must not be extrapo-
lated.
3. Ratings shown are at saturated suction temperatures
corresponding to pressures at the compressor. In
actual practice, suction line pressure drop has the
effect of reducing compressor capacity, forcing the
compressor to operate at a lower suction pressure
to maintain the desired evaporator temperature.
For normal air conditioning applications, siYE the suction
line for a pressure drop of 3 PSI, corresponding to 2°F, for
R-410A refrigerant. Thus, the evaporator temperature will
be approximately 2°F higher than the compressor suction
temperature. Line loss must be taken into consideration
when selecting the evaporator.
SELECTION PROCEDURE
The air-cooled condensing unit may be selected from
the Ratings on pages 12 through 17, if the ambient air
temperature at the condenser and the saturated suction
temperature at the compressor are known. The ambient
air temperature is a known design parameter, but the
suction temperature at the compressor, in many cases,
is known only within certain allowable limits. The actual
compressor operating suction temperature and the over-
all performance of the system will depend directly upon
the choice of the evaporator. Starting with a preliminary
evaporator selection at a nominal evaporator temperature
and using data supplied by the evaporator manufacturer,
enter the ratings tables and select a unit to meet the
required cooling load at a suction temperature at least
2°F below the evaporator temperature. The 2°F allows
for normal suction line loss.
If more accurate selection is required, the evaporator
capacity should be plotted against the condensing unit
capacity to determine the balanced system performance.
Again, it is necessary to factor in the suction line loss.
After the system balance point has been determined,
the compressor KW input may be interpolated from the
ratings tables.
SAMPLE SELECTION
Select an R-410A Air-Cooled Condensing Unit with a
matched central station air handling unit having the fol-
lowing operating conditions:
Design Conditions
1. An air handling unit with four large DX coils (two per
circuit) having a total cooling load of 1320 MBH (110
tons).
2. The coil suction temperature required 7.2°C.
3. The design outdoor ambient temperature is 35°C.
4. The power supply is 400V/3∅/50 hz.
Selection
1. Enter the YLUA0408YE Rating Table (page 12).
2. The model YLUA0408YE will provide 84.1 tons with
107.9 compressor KW input at 35°C ambient air and
7.2°C suction pressure.
The YLUA0408YE is the suitable selection for the design
capacity.
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