Table 1. Outdoor/Indoor Relative Humidity Conversion Chart; Table 2. Load Calculation Summary Sheet - Nortec NHPC Engineer's Manual

Table 1. Outdoor/Indoor Relative Humidity Conversion Chart

100% 2 4
95% 2 3
90% 2 3
85% 2 3
80% 2 3
75% 2 3
70% 1 2
65% 1 2
60% 1 2
55% 1 1
50% 1 1
45% 1 1
40% 1 1
35% 1 1
30% 0 1
25% 0 1
20% 0 1
15% 0 0
10% 0 0
5% 0 0
0% 0 0
-20° -10°
Chart shows what the residual indoor RH would be at 70°F under varying outdoor conditions if a proper humidification
system were not installed in the building. Studies indicate that the recommended RH should be between 40% and 60%
for optimum benefits to the occupants.
Determine the moisture required in the space (Table 3)
Grains from Table 3 at space temp. ______ x Indoor RH
Determine the moisture level of incoming air (Table 4)
Grains from Table 4 at space temp. ______ x Outdoor RH
Therefore: moisture to be added: (moisture) M - A - B ______ gr/ft
Determine the volume of air to be humidified. Choose the largest
value.
1. Natural ventilation: Volume x number of air changes.
2. Exhaust air: CFM x 60 min/hr
3. Make-up air: CFM x 60 min/hr
Therefore: Gross humidification load = L (load) = MxC = ______ lbs/hr
NOTES: 1. 7,000 grains = 1 pound
2. If HVAC system uses economizer cycle, check load using formula 6.
10-10
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2008-10-01
5 6 7 9
4 6 7 9
4 5 6 8
4 5 6 8
4 5 6 7
4 4 5 7
3 4 5 6
3 4 4 5
3 3 4 5
3 3 4 4
2 3 3 4
2 3 3 4
2 2 3 4
2 2 2 4
2 2 2 3
1 1 2 3
1 1 2 2
1 1 1 1
0 1 1 1
0 0 0 0
0 0 0 0
-5° 0° +5° +10°
Outdoor temperature

Table 2. Load Calculation Summary Sheet

7,000
12 17 19 23
12 16 17 22
11 15 16 21
11 14 15 20
10 13 15 19
10 12 14 18
9 11 13 17
8 10 12 15
7 9 11 14
7 8 10 13
6 8 9 12
6 7 8 11
5 7 7 10
5 6 6 9
4 5 6 7
3 4 5 5
3 3 4 5
2 3 3 4
2 2 2 3
1 1 1 2
0 0 0 0
+15° +20° +25° +30°
3
= A ______ gr/ft
3
= B ______ gr/ft
3
3
______ ft /hr
3
______ ft /hr
3
______ ft /hr
29 36 43 52
28 34 41 50
26 31 39 48
24 29 37 45
23 27 35 42
22 26 33 39
20 24 31 36
19 23 29 34
17 21 26 31
16 19 24 29
14 18 22 26
13 16 20 24
12 14 18 21
10 12 15 18
9 11 13 15
7 9 11 13
5 7 9 10
4 5 6 8
3 3 4 6
2 2 3 3
0 0 0 0
+35° +40° +45° +50°
→
3
M ______ gr/ft
→
3
C ______ ft /hr
→
L ______ lbs/hr