Johnson Controls RC Series Engineering Manual page 22

RC SERIES ENGINEERING GUIDE
Selection Example cont.
8. Water Temperature Rise Calculation & Assessment:
Note: 500 = parameters for water & 485 = parameters for
antifreeze solutions to 30% weight.
When we compare the Corrected Total Cooling and Corrected
Sensible Cooling figures with our load requirements stated in Step
1, we discover that our selection is within +10% of our sensible
load requirement. Further more, we see that our Corrected Total
Cooling figure is within 1,000 Btuh of the actual indicated load.
Antifreeze Corrections
Catalog performance can be corrected for antifreeze use. Please use the following table and note the example given.
Antifreeze
Antifreeze Type
% by wt
EWT - degF [DegC]
0
Water
10
20
30
Ethylene Glycol
40
50
10
20
30
Propylene Glycol
40
50
10
20
30
Ethanol
40
50
10
20
30
Methanol
40
50
Warning: Gray area represents antifreeze concentrations greater than 35% by weight and
should be avoided due to the extreme performance penalty they represent.
Antifreeze Correction Example
Antifreeze solution is Propylene Glycol 20% by weight. Determine the corrected heating and cooling performance at 30°F and 90°F
respectively as well as pressure drop at 30°F for an RC Series Console RC18.
The corrected cooling capacity at 90°F would be: 17,100 MBtuh x 0.969 = 16,569 MBtuh
The corrected heating capacity at 30°F would be: 14,300 MBtuh x 0.913 = 13,056 MBtuh
The corrected pressure drop at 30°F and 5.5 GPM would be: 18.2 feet of head x 1.270 = 23.1 feet of head
Cooling Heating
Pressure Drop
Capacity Capacity
90 [32.2] 30 [-1.1]
1.000 1.000
0.991 0.973
0.979 0.943
0.965 0.917
0.955 0.890
0.943 0.865
0.981 0.958
0.969 0.913
0.950 0.854
0.937 0.813
0.922 0.770
0.991 0.927
0.972 0.887
0.947 0.856
0.930 0.815
0.911 0.779
0.986 0.957
0.970 0.924
0.951 0.895
0.936 0.863
0.920 0.833
30 [-1.1]
1.000
1.075
1.163
1.225
1.324
1.419
1.130
1.270
1.433
1.614
1.816
1.242
1.343
1.383
1.523
1.639
1.127
1.197
1.235
1.323
1.399
22
= ∆