JRE-Series
R e v. : A u g u s t 1 9 , 2 0 2 0
T H E S M A R T S O L U T I O N F O R E N E R G Y E F F I C I E N C Y
I n s t a l l a t i o n , O p e r a t i o n , M a i n t e n a n c e
29
Condenser Hot Water Reheat – Benefits and Applications, Cont’d.
20
30.0
3.8
8.7
Operation not recommended
87.7
9.23
56.2
88.3
2.8
30
15.0
0.7
1.7
145.1
92.6
6.59
167.6
22.0
94.9
9.37
62.9
89.9
3.0
22.5
1.6
3.7
144.7
90.3
6.33
166.3
22.9
98.4
9.44
66.2
90.7
3.1
30.0
3.4
7.8
143.9
88.5
6.23
165.2
23.1
100.4
9.48
68.1
91.2
3.1
40
15.0
0.6
1.4
143.3
93.5
7.05
167.3
20.3
107.2
9.62
74.4
92.8
3.3
22.5
1.2
2.8
144.9
93.0
6.69
167.7
21.7
111.8
9.72
78.6
93.8
3.4
30.0
2.7
6.2
145.1
92.2
6.53
167.4
22.2
114.3
9.77
81.0
94.4
3.4
50
15.0
0.5
1.2
139.5
92.7
7.61
165.4
18.3
120.4
9.90
86.6
95.8
3.6
22.5
0.8
1.8
142.5
93.4
7.16
167.0
19.9
126.0
10.02
91.8
97.1
3.7
30.0
2.0
4.7
143.7
93.5
6.97
167.5
20.6
129.1
10.09
94.7
97.8
3.7
60
15.0
0.3
0.7
134.3
90.6
8.28
162.5
16.2
134.1
10.20
99.3
99.0
3.9
22.5
0.5
1.2
138.3
92.3
7.76
164.8
17.8
140.8
10.35
105.5
100.5
4.0
30.0
1.7
4.0
140.1
92.9
7.52
165.8
18.6
144.5
10.44
108.9
101.4
4.1
70
15.0
0.3
0.6
128.0
87.8
9.05
158.9
14.1
148.3
10.52
112.4
102.3
4.1
22.5
0.5
1.1
132.7
90.0
8.47
161.6
15.7
156.1
10.70
119.5
104.0
4.3
30.0
1.6
3.8
135.0
90.9
8.19
162.9
16.5
160.3
10.81
123.4
105.0
4.3
Water/Brine
Cooling - EAT 80/67°F
Heating - EAT 70°F
EWT
°
F
Flow
GPM
PD
PSI
PD
FT
TC
SC
kW
HR
EER
HC
kW
HE
LAT
COP
80
15.0
0.2
0.5
121.2
84.8
9.93
155.1
12.2
162.8
10.86
125.7
105.6
4.4
22.5
0.4
1.0
126.2
87.0
9.28
157.9
13.6
171.5
11.08
133.7
107.6
4.5
30.0
1.5
3.6
128.7
88.1
8.97
159.3
14.3
176.2
11.20
138.0
108.7
4.6
85
15.0
0.2
0.5
117.6
83.2
10.43
153.2
11.3
170.0
11.04
132.3
107.3
4.5
22.5
0.4
0.9
122.6
85.4
9.75
155.9
12.6
179.2
11.27
140.7
109.4
4.7
30.0
1.5
3.5
125.2
86.6
9.41
157.3
13.3
184.1
11.40
145.2
110.5
4.7
90
15.0
0.1
0.3
114.0
81.7
10.92
151.3
10.4
177.3
11.22
139.0
108.9
4.6
22.5
0.4
0.9
119.1
83.9
10.21
153.9
11.7
186.8
11.47
147.7
111.1
4.8
30.0
1.5
3.4
121.7
85.0
9.87
155.3
12.3
192.0
11.60
152.5
112.4
4.9
100
15.0
0.1
0.2
107.0
79.1
12.02
148.0
8.9
Operation not recommended
22.5
0.3
0.8
111.8
80.9
11.25
150.2
9.9
30.0
1.4
3.3
114.4
81.9
10.87
151.5
10.5
110
15.0
0.1
0.2
100.5
77.2
13.24
145.6
7.6
22.5
0.3
0.7
104.8
78.4
12.40
147.1
8.5
30.0
1.4
3.2
107.2
79.1
12.00
148.1
8.9
120
15.0
0.1
0.1
94.8
76.6
14.59
144.6
6.5
22.5
0.3
0.7
98.5
76.9
13.67
145.1
7.2
30.0
1.3
3.0
100.5
77.2
13.23
145.6
7.6
With the condenser water reheat option, return air from
the space is cooled by the air-to-refrigerant (evaporator)
coil, and then reheated by the water-to-air (reheat)
coil to dehumidify the air, but maintain the same space
temperature (thus operating as a dehumidifier).
The moisture removal capability of the heat pump is
determined by the unit’s latent capacity rating. Latent
capacity equals Total capacity minus Sensible capacity.
Using unit performance data from submittals, select
the correct model, use your maximum entering water
temperature (EWT) and flow rate to select TC and
SC. For example, at 80°F [26.7°C] EWT and 15 GPM,
the moisture removal capability (latent capacity) of a
Johnson Controls JRE120 is 36.4 Mbtuh as shown in
figure 10.
Dividing the latent capacity by 1,069 BTU/LB of water
vapor at 80°F DB and 67°F WB [26.7°C DB and 19.4°C
WB] moist air enthalpy, converts the amount of moisture
removal to pounds per hour (multiply pounds per hour by
0.4536 to obtain kg/hr). Calculations are shown in figure 10.
Most Johnson Controls water source heat pumps have
a sensible-to-total (S/T) ratio of 0.72 to 0.82. Therefore,
approximately, 25% of the cooling capacity is dedicated
to latent cooling capacity (moisture removal). When
selecting a unit with condenser water reheat, the space
sensible and latent loads should be calculated. If the unit
will be used for space cooling, a unit with at least enough
capacity to satisfy the building sensible load should be
selected. If the latent cooling load is not satisfied by the
selection, a larger unit with enough latent capacity will
be required. If the unit will be used for dehumidification
purposes only, the latent capacity is the only consideration
necessary. In this case, sensible load is immaterial.
Figure 10: Example JRE120 Performance
Dividing the latent
capacity by 1,069 BTU/
LB of water vapor at
80°F DB and 67°F WB
[26.7°C DB and 19.4°C
WB] moist air enthalpy,
converts the amount
of moisture removal to
pounds per hour (multiply
pounds per hour by
0.4536 to obtain kg/hr).
Calculations are shown in
figure 10.
4000 CFM Nominal (Rated) Airflow
LC = TC - SC = 121.2 - 84.8 = 36.4 Mbtuh
36,400 Btuh ÷ 1,069 = 34.1 lbs/hr (15.4 kg/hr)
