Operating instructions

9
the PumpPAK with a call for heating or cooling. The
use of impedance protected pumps eliminates the need for
additional fusing on the PumpPAK.
VIII. 24 VOLT CONTROL
CIRCUIT
The wiring diagrams in Figures 5 and 6 shows the low
voltage controls of the heat pump. This section will break
down the three basic components of the low voltage
circuit; transformer, thermostat, and controller.
A. Transformer
Electrical diagrams are provided in Figures 5 and 6 and
on the electrical box cover panel of the GeoSource 2000
heat pump. An internal 24-volt, 55 VA transformer is
provided to operate all control features of the heat pump.
Table 4 shows the transformer usage for GeoSource 2000
heat pumps.
Table 4 – Transformer Usage (VA)
Component 18-67 98-120
Contactor 7 7 x 2
4-Way Valve 4 4
Controller 2 2
Thermostat 1 1
Blower Relay 6 6 x 2
Electric Heat Relay (optional) 6 NA
Total 26 33
Available 29 22
If any system’s external controls require more than the
VA available for external use from the transformer, a
separate transformer must be used. The heat pump's
transformer can generally power simple external control
systems consisting of a few relays or a zone valve
(depending, of course, on the VA draw of the
components). On more complicated control systems the
transformers capacity is used up very quickly.
FF Note: For units operating on 208V electrical service,
the transformer must be switched to the correct lead (see
electrical diagram – Figures 5 and 6). Units are factory
shipped with the transformer set for 240V service.
Operating a unit on 208V with the transformer set to
240V will cause the unit to operate with lower than
normal control voltages.
B. Thermostat
A 2-heat/1-cool thermostat is recommended for proper
operation of GeoSource 2000 heat pumps. Eight wire
thermostat cable is required for proper operation of the
thermostat. Consult the instructions in the thermostat box
for proper mounting and thermostat operation.
II CAUTION- miswiring of control voltage on system
controls can result in fuse or transformer burnout.
FF Note: If a single thermostat controls multiple heat
pumps, the control wiring of the heat pumps must be
isolated from each other. This will prevent the heat
pumps from receiving high voltage through the common
wiring if it is turned off at the circuit breaker for service.
Power is supplied to the thermostat by connecting the R
and X terminals to the heat pump terminal strip. The fan
is controlled through the G terminal and will operate
continuously in the FAN ON position or when the
compressor is running in the FAN AUTO position. The
Y terminal energizes the compressor. The unit is put into
the air conditioning mode when the thermostat energizes
the O terminal, which operates the 4-way reversing valve.
A lockout condition is indicated by the L terminal, which
lights a red light on the thermostat (depending on the
thermostat). This lockout condition means that the unit
has shut itself down on a low or high-pressure switch to
protect itself, and will not come back on until power has
been reset to the heat pump. If a lockout condition exists,
the heat pump should not be reset more than once. A
service technician should be called immediately.
Repeated reset can cause damage to the system.
If second stage heating (e.g. electronic resistance strip
heat) is used, its control wiring is connected to X and W2
on the heat pump terminal strip. Fan interlock relays are
not required since the thermostat energizes the blower
whenever the second stage is calling. W2 on the terminal
strip is wired directly to second stage heating on the
thermostat. In the event of a heat pump shutdown,
switching the thermostat to emergency heat energizes the
E terminal, which runs the blower and second stage heater
but does not energize the compressor. The thermostat
will indicate whenever second stage heating is energized.
These wiring connections are listed in Table 5.
Table 5 – Wiring Connections
Function Terminal Strip Thermostat
24 Volt Power R R
Common X C(X)
Blower G G
Reversing Valve O O
1
st
Stage Heat/Cool Y1 Y1
Lockout Signal L L
2
nd
Stage Heat W2 W2
Emergency Heat E E
Use of a programmable setback thermostat in conjunction
with a geothermal heat pump and a second stage backup
electric resistance heater has the potential to cause
inefficiency. The energy savings supplied by night
setback could be less than the energy used by the electric
elements if they operate in the morning to warm the space
to the daytime temperature setting. Second stage usage
should be monitored and setbacks adjusted to maximize
energy savings of the entire system.
FF Note: If the thermostat is provided by others and is
equipped with an anticipator, it should be set to its highest
setting to avoid interfering with heat pump operation.