Trane 2GN Series, Installer'S Manual

Page: 13 / 32

18-GL07D1-4 13
2GN SPLIT INSTALLER’S GUIDE
CLOSED LOOP GROUND SOURCE
SYSTEMS
Note: For closed loop systems with antifreeze protection, set
SW2-2 to the “loop” position (see DIP Switch Settings table).
Once piping is completed between the unit, pumps and the
ground loop (see fi gure below), fi nal purging and charging of
the loop is required. A fl ush cart (or a 1.5 HP pump minimum) is
needed to achieve adequate fl ow velocity in the loop to purge
air and dirt particles from the loop itself. Antifreeze solution
is used in most areas to prevent freezing. Flush the system
adequately to remove as much air as possible then pressurize
the loop to a static pressure of 40-50 PSI (summer) or 50-
75 PSI (winter). This is normally adequate for good system
operation. Loop static pressure will fl uctuate with the seasons.
Pressures will be higher
in the winter months than
during the cooling season.
This fl
uctuation is normal
and should be considered
when initially charging the
system.
After pressurization, be sure
to remove the plug in the end
of the loop pump motor(s) (if
applicable) to allow trapped
air to be discharged and
to ensure that the motor
housing has been fl ooded.
Ensure that the loop
pumps provide adequate
fl
ow through the unit(s)
by checking the pressure
drop across the heat
exchanger and comparing
it to the unit capacity data
in the specifi cation catalog.
Usually 2.5 to 3 GPM of fl ow
per ton of cooling capacity is
recommended in earth loop
applications.
Multiple Units on One Flow Center
When two units are connected to one loop pumping system,
pump control is automatically achieved by connecting the SL
terminals on connector P2 in both units with 2-wire thermostat
wire. These terminals are polarity dependant (see Figure 8).
The loop pump(s) may be powered from either unit, whichever
is more convenient. If either unit calls, the loop pump(s) will
automatically start. The use of two units on one fl ow center is
generally limited to a total of 20 GPM capacity.
Figure 7: Typical Split System Application Closed Loop - Earth Coupled
Disconnect
Thermostat Wire
From Air Handler
Vibration Absorbing Pad or Air Pad
P/T Plugs
Lineset
To Air
Handler
Insulated
Flow Center
Electrical Supply
GeoLink
Flow Center
To Loop
DHW Out
Rubber Hose Connector
Kit CK4L or CK4S
DHW In
GN-Series to
Electromechanical Units
Shut
Down
C C
SL1
In
SL1
Out
GN-Series Unit #1
To Electromechanical Unit
C S
Shut
Down
C C
Shut
Down
C C
SL1
In
SL1
Out
SL1
In
SL1
Out
Single Speed
GN-Series Unit #1
With pump
wired to Unit 1
With pump
wired to
Unit 2
GN-Series to GN-Series
Microprocessor Units
GN-Series Unit #2
Single Speed
With pump
wired to Unit 1
With pump
wired to
Unit 2
Shut
Down
C C
Shut
Down
C C
SL1
In
SL1
Out
SL1
In
SL1
Out
Dual Capacity
GN-Series Unit #1
GN-Series Unit #2
Dual Capacity
GN-Series to GN-Series
Microprocessor Units
Figure 8: Primary/Secondary Hook-up