Product Manual AGR-3
AGR 070A through 100A
9
Selection Procedure
Packaged Chiller, Model AS, R-22
Selection with Inch-Pound (I-P) units
Table 9 covers the range of leaving evaporator water temperatures and outside ambient temperatures
included under ARI 550/590. The tables are based on a 10°F temperature drop through the evaporator.
Adjustment factors for applications having other than a 10°F drop can be found in Table 3. The
minimum leaving chilled water temperature setpoint without glycol is 42°F. For glycol selections, see
Table 1 for ethylene or Table 2 for propylene glycol adjustment factors. Ratings are based on a 0.0001
fouling factor in the evaporator at sea level operation. For other fouling factors, different delta-Ts, or
altitude correction factors, see Table 3. For applications outside the catalog ratings contact your local
McQuay sales representative.
Selection example
Given: 67 tons minimum
95
°
F ambient temperature
160 gpm, 55
°
F to 44°F chilled water
0.0001 fouling factor
1.
From Performance Table 9, an AGR 070AS at the given conditions will produce 67.5 tons with a
compressor kW input of 77.1 and a unit EER of 9.6.
2.
If any elements are unknown, use the following equation (water only) to calculate them:
24
=
GPM
T
delta
tons
−
×
3
Determine the evaporator pressure drop. Using Figure 9, enter at 160 and follow up to the AGR
070AS line intersect. Read horizontally to obtain an evaporator pressure drop of 16.0 feet of water.
Selection example using ethylene glycol
Given:
64 tons minimum
95
°
F ambient temperature
54
°
F to 44
°
F chilled fluid
0.0001 fouling factor
Protect from freezing down to 0°F
1.
From Table 1, select an ethylene glycol concentration of 40% to protect against freezing at 0°F.
2.
At 40% ethylene glycol, the adjustment factors are: Capacity =0.961, kW = 0.976,
flow = 1.121, pressure drop = 1.263
3.
Select the AGR 070AS and correct with 40% ethylene glycol factors.
4.
Correct capacity = 0.961 x 67.5 tons = 64.9 tons
5.
Correct compressor kW = 0.976 x 77.1 = 75.2 kW
6.
Calculate chilled water flow:
155.8
=
10
24
9
.
64
=
capacity)
corrected
(at
flow
Water
F
tons
°
×
GPM
Glycol flow (at 40% solution) = 1.121 X 155.8 = 174.7 GPM
Determine the evaporator pressure drop. Using Figure 9, enter at 155.7 (flow rate for water) and follow
up to the AGR 070AS line intersect. Read horizontally to obtain an evaporator pressure drop of 15.5
feet. The pressure drop for 40% glycol solution = 1.263 X 15.5 feet = 19.6 feet of water.