Product Manual ALR2-3 ALR 110F – 150F 9
Selection Procedure
Selection Procedure
Table 4 (R-22) covers the range of leaving evaporator water temperatures and ambient air temperatures
encompassed under ARI 550/590-98. Table 5 covers SI units. The tables are based on a 10 degree F
temperature drop through the evaporator (2.4 gpm/ton). Adjustment factors for applications having
other than a 10 degree F drop can be found in Table 3. The minimum leaving chilled water temperature
setpoint without glycol is 40°F. For brine selections, see Table 1 for ethylene glycol or Table 2 for
propylene glycol adjustment factors. Ratings are based on a 0.0001 fouling factor in the evaporator at
sea level operation. See Table 3 for other fouling factors, derates for different delta-Ts, or altitude
correction factors. For applications outside the catalog ratings contact your local McQuay sales
representative.
Selection example
Given:
R-22, 110 tons minimum.
95°F ambient temperature
264 gpm, 54°F - 44°F chilled water
0.0001 evaporator fouling factor
1. From Performance Table 4, an ALR 110F at the given conditions will produce 110.9 tons with a
compressor kW input of 120.6 and a unit EER of 9.8
2. Use the following formula (for water) to calculate missing elements:
24
= gpm
FT
tons
°∆
×
3. Determine the evaporator pressure drop. Using Figure 5, enter at 264 gpm and follow up to the
ALR 110 line intersect. Read horizontally to obtain an evaporator pressure drop of 14.3 feet of
water.
Selection example using ethylene glycol
Given:
R-22, 105 tons minimum
95°F ambient air temperature
54°F - 44°F chilled water temperature
0.0001 evaporator 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% glycol: Capacity = 0.961, kW = 0.976,
flow = 1.121, pressure drop = 1.263
3. Consider the ALR 110F and correct with 40% ethylene glycol factors.
4. Correct capacity = 0.961 x 110.9 tons = 106.6 tons
5. Correct compressor kW = 0.976 x 120.6 kW = 119.5 kW
6. Correct chilled water flow for flow required for the glycol solution:
gpm 256 =
10
246.106
= capacity) corrected(at flowWater
FT
tons
°∆
×
Glycol flow (at 40% solution) = 1.121 x 256 gpm = 286.8 gpm
Determine the evaporator pressure drop. Using Figure 5, enter at 256 gpm (water flow rate) and follow
up to the ALR 110F line intersect. Read horizontally to obtain an evaporator pressure drop of 13.6
feet. The pressure drop for 40% solution = 1.263 x 13.6 feet = 17.2 feet of water
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