Specifications

The ARI Standard 550/590-98 for Centrifugal or
Screw Water-Chilling Packages and associated
manuals define certification and testing
procedures and performance tolerances of all units
that fall within the application rating conditions.
Weighting
The percent of annual hours of operation at the
four load points are as follows:
100% Load at 1%
75% Load at 42%
Leaving chilled water temp.: 40°F to 48°F (44°F
standard)
50% Load at 45%
25% Load at 12%
Entering condenser water temp.: 60°F to 95°F
Note that the vast majority of hours are at the operating
range where dual compressor chillers excel.
Leaving chilled water temp.: 44°F
Evap. waterside field fouling allowance: 0.0001
Tolerances
Chilled water flow rate: 2.4 gpm/ton
Entering condenser water temp.: 85°F
Condenser waterside field fouling allowance:
0.00025
The ARI test tolerance, per ARI Standard 550/590-
98, for capacity (tons), power input per ton
(kW/ton), and heat balance is:
%.(.%)
%
Tolerance x FL
DTFLx FL
=− +
⎛
⎝
⎜
⎞
⎠
⎟
105 007
1500
Condenser water flow rate: 3.0 gpm/ton
Where:
IPLV/NPLV Defined
FL = Full Load
Part load performance can be presented in terms of
Integrated Part Load Value (IPLV), which is based
on ARI standard rating conditions (listed above),
or Non-Standard Part Load Values (NPLV), which
is based on specified or job site conditions. IPLV
and NPLV are based on the following weighting
equation from ARI 550/590:
DTFL = Chilled Water Delta-T at Full Load
This formula results in a ±5% tolerance on tons
and kW/ton at the 100% load point and ARI
conditions.
DCBA
DCBA 12.045.042.001.0 +++
NPLV
or
IPLV
12.045.042.001.0
1
+++
=
Where: A = kW/ton at 100%
B = kW/ton at 75%
C = kW/ton at 50%
D = kW/ton at 25%
Or
Where: A = COP at 100%
B = COP at 75%
C = COP at 50%
D = COP at 25%
18 Catalog WMC-4