Bosch Geothermal Heat Pumps Applications Manual page 31

Applications Manual
Example 3:
In this example, we will examine the Bosch four (4) ton
geothermal heat pump unit as the possible selection for
this application. Our goal is to provide the required cooling
ability with the geothermal heat pump compressor and
associated ground heat exchanger. We will be using a
system with a two stage compressor.
We nd that when looking at the Bosch four (4) ton
geothermal heat pump system cooling capacity at full load
(Table 17), we see that at an entering uid temperature
(EFT) of 70°F EFT (the typical shallow groundwater
temperature for the location is 67°F per Bosch Geo
Solutions software) and at 75°Fdb, 63°Fwb (typical load
calculation criteria for cooling), the total capacity of
the Bosch four (4) ton geothermal heat pump is 48,370
Btu/h, with 35,920 Btu/h sensible capacity (74% of
total capacity). This leaves 12,450 Btu/h latent capacity.
The installer should meet 100% of both sensible and
latent capacity of the calculated cooling load at design
conditions (98ºF outdoor ambient). The sensible load is
34,000 Btu/h and this Bosch four (4) ton geothermal heat
pump provides 35,920 Btu/h sensible capacity. The latent
load is 8,000 Btu/h and this Bosch four (4) ton geothermal
heat pump provides 12,450 Btu/h latent capacity.
Therefore, this Bosch four (4) ton geothermal heat pump
will comply with typical minimum sizing criteria when
selecting the unit to meet the structure cooling loads, as
well as being less than the maximum allowed by ACCA
Manual S.
Capacity Data - Full Load
Entering Fluid Entering Air
Temp. (ÝF) Temp. (ÝF)
50
60
70Ýdb
70
61Ýwb
85
100
50
60
75Ýdb
70
63Ýwb
85
100
50
60
80Ýdb
70
67Ýwb
85
100
50
60
85Ýdb
70
71Ýwb
85
100
Tab. 17
(EFT Range (Standard) 50ÝF to 100ÝF)
Bosch Thermotechnology Corp.
Cooling - all performance at 1700 CFM and 12.0 GPM
Total Capacity Sensible Capacity
(MBtuH) (MBtuH)
48.95 31.89
47.04 30.90
45.13 30.01
42.27 28.85
39.40 27.84
52.46 38.15
50.41 36.97
48.37 35.92
45.31 34.54
42.24 33.33
57.59 42.14
55.35 40.84
53.11 39.68
49.75 38.15
46.39 36.82
62.72 46.16
60.29 44.74
57.85 43.47
54.20 41.80
50.54 40.35
Bosch Geothermal Heat Pumps | 31
Example 3:
f
Cooling Dominate Climate
f
Dallas, Texas [typical entering fluid temperature
(EFT) of 67°F]
f
Load Calculation Sensible Heat Loss = 35,000 Btu/h
(outdoor design temperature = 24°F; indoor design
temperature = 70°F)
f
Load Calculation Sensible Heat Gain = 34,000 Btu/h
(outdoor design temperature = 98°F; indoor
temperature = 75°F)
f
Load Calculation Latent Heat Gain = 6,000 Btu/h
f
Total Heat Gain (Sensible plus Latent) = 40,000 Btu/h
(3.3 ton unit)
f
Per Manual S, 25% larger than the total cooling load
= 1.25 x 40,000 Btu/h = 50,000 Btu/h
f
Maximum Bosch water-to-air geothermal heat pump
size = 4.16 tons (50,000 Btu/h)
Unit selected: Bosch four (4) ton
Sensible to Power Input Heat of Reject
Total Ratio (kW) (MBtuH)
0.65 2.28
0.66 2.51
0.67 2.73
0.68 3.06
0.71 3.40
0.73 2.30
0.73 2.52
0.74 2.74
0.76 3.08
0.79 3.42
0.73 2.31
0.74 2.54
0.75 2.76
0.77 3.10
0.79 3.44
0.74 2.33
0.74 2.56
0.75 2.79
0.77 3.13
0.80 3.47
EER
56.74 21.4
55.59 18.8
54.45 16.5
52.72 13.8
51.00 11.6
60.29 22.9
59.01 20.0
57.74 17.6
55.82 14.7
53.90 12.4
65.48 24.9
64.01 21.8
62.55 19.2
60.35 16.0
58.14 13.5
70.67 26.9
69.01 23.6
67.36 20.8
64.87 17.3
62.38 14.6
Data subject to change