Bosch Geothermal Heat Pumps, Руководство по применению

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5 8 | Bosch Geothermal Heat Pumps
Bosch Thermotechnology Corp. Data subject to change
Applications Manual
HDPE pipe is heat fused and joined using both socket and
butt fusion procedures. Material, grade, density and other
variables help determine if the particular grade of pipe can
be fused with either method. Some HDPE materials cannot
be socket fused. HDPE pipe for typical residential ground
heat exchangers is socket fused.
Both socket and butt fusion yield highly reliable joints
when properly performed. These joints are typically
stronger than the pipe itself. Typical fusion times are
shown in Table 27.
Typical Fusion Times
Pipe Size
Socket
Fusion
Time
(Sec.)
Butt Fusion
Holding
Time
Curing
Time
Time
(Sec.)
Bead in.
[mm]
¾
" IPS
8 - 10 8
¹/
[1.6]
60 sec. 20 min.
1" IPS 10 - 14 12
¹/
[1.6]
60 sec. 20 min.
1
¼
" IPS 12 - 15 15
¹/
-
[1.6 - 3.2
60 sec. 20 min.
1
½
" IPS
15 - 18 15
¹/
-
[1.6 - 3.2]
60 sec 20 min.
2" IPS 18 - 22 18
[3.2]
60 sec 20 min.
Tab. 27
Aways use a timing device.
9.8 Heat Transfer Fluids (Antifreeze)
In areas where minimum entering loop temperatures can
drop below 40°F, or where piping may be routed through
areas subject to freezing, antifreeze is required (Fig. 49).
Alcohols and glycols are commonly used as antifreeze.
This heat transfer uid is needed to transfer heat between
the ground heat exchanger and the Bosch geothermal
heat pump system when a closed-loop system is used.
The antifreeze should exhibit acceptable heat transfer and
pumping characteristics, be safe to install, reasonable in
cost, provide corrosion protection to system materials,
and not produce an unacceptable risk to the environment
in the event of a system leak.
Fig. 49 Heat transfer uids
The antifreeze is normally placed in the system from
inside the structure after the entire ground heat
exchanger (or “loop eld”) is completed, pressure tested,
ushed, and purged. The concentration of the antifreeze
solution should be checked to assure proper freeze
protection. Freeze protection should be maintained to
approximately 15°F below the lowest expected entering
loop temperature. The volume of the ground heat
exchanger and the volume of the structure piping will
determine the amount of antifreeze needed for the desired
protection. If concentrate is added, time for proper mixing
will need to be considered. At the antifreeze add point
there should be identi cation posted of the antifreeze
material, manufacturer, and other identifying information.
Additionally, antifreeze must always be transported in
identi ed containers.
Several different types of antifreeze are available for use
with Bosch closed-loop geothermal heat pump systems.
These include but are not limited to methanol, propylene
glycol, ethanol, and urea. The geothermal industry has
historically used methanol, propylene glycol and ethanol
for most applications.
Methanol has been the rst choice for many installers
of geothermal heat pump systems and has delivered
outstanding performance in closed-loop ground heat
exchangers for over 20 years. This toxic antifreeze works
very well because it is typically less expensive to buy and
ows better (has low viscosity) down to approximately
15°F than other types of antifreeze available. Methanol