Applications Manual Bosch Geothermal Heat Pumps
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Bosch Thermotechnology Corp.
Data subject to change
Supplemental heating (electric coils) will be necessary
to provide heating assistance to the compressor at this
structure balance point outdoor temperature and below,
energizing for longer time periods as outdoor ambient
drops. When outdoor temperatures are warmer than 10°F
and heat loss is excessive (i.e., doors open, windows open,
etc.), these supplemental heaters will energize, but will
occur only for a short period of time. The supplemental
heaters will also operate in the emergency heat mode
if the compressor fails. These heaters must be sized to
meet the total structure heat loss at design conditions
to adequately provide emergency heating if necessary.
The size of heater should typically meet 90% of the heat
loss of the structure minimum (58,500 Btu/h) at design
conditions. This will be a 17 kW heater minimum. The
installer should therefore install a 20 kW electric heater for
this application.
If the EWT falls at the installation location due to outdoor
climate conditions, the installer can determine the
approximate heating ability of the Bosch four (4) ton
geothermal heat pump unit at low temperature situations
as well from published speci cations.
Examining the “Low Temp Heating” data for the Bosch four
(4) ton geothermal heat pump unit at full load (Table 14),
we nd that at 30°F EFT and 70°F Entering air temperature
(return air temperature), the full load heating capacity
(compressor operating at 100% ability) of the unit will
be 36,840 Btu/h. This provides approximately 57% of the
structure heat loss at design conditions. The auxiliary
or supplemental electric heater installed in the unit will
provide the necessary heating capacity to maintain 70°F
in the structure but will be energized longer than when
outdoor ambient temperatures are warmer during heating
months.
Capacity Data - Full Load Low Temp Heating
Entering
Fluid Temp.
(F)
Entering
Air Temp.
(F)
Total
Capacity
(MBtuH)
Power
Input
(kW)
Heat of
Abs.
(MBtuH)
COP
25
60
36.81
2.74
27.45
3.9
30
38.95
2.79
29.44
4.1
40
43.22
2.87
33.41
4.4
25
70
34.83
2.79
25.31
3.7
30
36.84
2.83
27.17
3.8
40
40.88
2.93
30.89
4.1
25
80
32.49
2.85
22.77
3.3
30
34.37
2.89
24.49
3.5
40
38.13
2.99
27.93
3.7
Tab. 14
(Antifreeze required)
(EFT Range (Standard) 25F to 80F)
If the installation location in Minneapolis, Minnesota is
experiencing milder (warmer) winter days, the Bosch four
(4) ton geothermal heat pump unit will be able to operate
at part load conditions. The installer can
determine the capacity of the unit at these conditions as
well.
Examining the corresponding part load heating data
(Table 15) for the Bosch four (4) ton geothermal heat
pump unit (compressor operating at 67% ability), we
nd that at 50°F EFT and 70°F entering air temperature
(return air temperature), we determine the total capacity
for heating of 34,330 Btu/h. Our calculated heat loss
at design conditions is 65,000 Btu/h at -11°F outdoor
temperature. We will be able to meet approximately 53%
of the structure total heat loss with the Bosch four (4) ton
geothermal heat pump unit capacity if it was operating
at design conditions. Since we will not be at heating
design conditions, the actual structure heat loss will be
lower and the compressor will likely be able to meet the
structure heating needs adequately. The supplemental
heating (electric coils) will be used to meet the portion
of structure heat loss not met by the compressor at that
condition. The heater will still provide the necessary
heating if operating in emergency heat mode (compressor
failure).
Capacity Data - Full Load Heating
Entering
Fluid Temp.
(F)
Entering
Air Temp.
(F)
Total
Capacity
(MBtuH)
Power
Input
(kW)
Heat of
Abs.
(MBtuH)
COP
50
60
36.30
1.93
29.72
5.5
60
39.48
1.97
32.75
5.9
70
42.66
2.02
35.78
6.2
80
45.84
2.06
38.82
6.5
50
70
34.33
1.96
27.64
5.1
60
37.34
2.01
30.49
5.5
70
40.34
2.05
33.35
5.8
80
43.35
2.10
36.20
6.1
50
80
32.02
2.00
25.19
4.7
60
34.82
2.05
27.83
5.0
70
37.62
2.09
30.47
5.3
80
40.42
2.14
33.11
5.5
Tab. 15
(EFT Range (Standard) 25F to 80F)
If the EWT falls at the installation location due to outdoor
climate conditions but the structure is experiencing
milder (warmer) winter days, the Bosch four (4) ton
geothermal heat pump unit will be able to operate at
part load conditions in the heating mode. The installer
can determine the capacity of the Bosch four (4) ton
geothermal heat pump unit at these conditions as well.
