Operating instructions

9
Pressure relief valves are required on hydronic applications.
A 30 psig relief is adequate if the system is operated at 12
to 15 psig pressure. If a water heater is used for a storage
tank, the 150 psig pressure relief may be acceptable (check
local codes).
E. Application Diagrams
Figures 1 through 4 show the components of a hydronic
heat pump system discussed above used in some common
applications. These figures by no means represent all the
possible hydronic heat pump applications, but they do show
some important principals that can be applied to any
system.
VIII. ELECTRICAL SERVICE
 Note – Always refer to the inside of the electrical box
cover for the correct wiring diagram, and always refer to
the nameplate on the exterior of the cabinet for the correct
electrical specifications.
WARNING – ELECTRICAL SHOCK CAN CAUSE
PERSONAL INJURY OR DEATH. Disconnect
all
power
supplies before installing or servicing electrical devices.
Only trained and qualified personnel should install, repair
or service this equipment.
WARNING – THE UNIT MUST BE PROPERLY
GROUNDED!
The main electrical service must be protected by a fuse or
circuit breaker and be capable of providing the amperes
required by the unit at nameplate voltage.
All wiring must
comply with the national electrical code and/or any local
codes that may apply. Access to the line voltage contactor
is through the knockouts provided on the side of the heat
pump next to the front corner. Route EMT or flexible
conduit with appropriate size and type of wire.
Ensure adequate supply wiring to minimize the level of
dimming lights during compressor startup on single-phase
installations. Some dimming is normal, and a variety of
start-assist accessories are available if dimming is
objectionable.
Important – some models already have a
factory-installed start assist. Do not add additional start
assists to those units.
CAUTION – route field electrical wiring to avoid
contact with electrically live bare metal parts inside the
electrical box and to avoid contact with the surface of the
factory-installed start assist (if provided).
CAUTION – Three-phase units must be wired properly
to ensure proper compressor rotation. Improper rotation
may result in compressor damage. An electronic phase
sequence indicator must be used to check supply-wiring
phases. Also, the “Wild” leg of the three-phase power
must
be connected to the middle leg on the contactor.
Note – GW240 and 360 do not have an internal pump
relay. A pump for the GW240 and 360, or a pump larger
than 1/3 horsepower on any other unit, must be powered
from a separate fused power supply and controlled through
an isolation relay that has its 24Vac coil wired to the Y and
X terminals.
IX. 24 VOLT CONTROL CIRCUIT
Note – Always refer to the inside of the electrical box cover
for the correct wiring diagram.
There are three basic sections of the low voltage circuit;
transformer, remote hydronic controls, and controller.
A. Transformer
An internal transformer provides 24Vac for all control
features of the heat pump. Even though the transformer is
larger than the industry standard, it is in a warm electrical
box and can be overloaded quickly. Table 5 shows the
transformer usage.
Table 5 – Transformer Usage (VA)
Component 240 360
Contactor
16 (2)
27 (2)
Pump Relay
N/A
N/A
Reversing Valve
18
18
Controller 20-1038
2
2
Compressor Overload
N/A
6 (2)
Contactor Pilot Relays
4 (2)
4 (2)
Remote Hydronic Control
2
2
Plug Accessory (PA)
10
10
Total
72VA
106VA
Transformer VA size
150
150
Important – If the system’s external controls require
more than shown in Table 5, an external transformer and
isolation relays should be used. In contrast, Figure 4 shows
a fan coil system with its own power supply, which must
interface to the heat pump to put the heat pump into the
cooling mode. This can be accomplished by using the fan
coil’s independent power supply to energize the coil of an
isolation relay with contacts located in heat pump's control
circuit.
WARNING – GW240 and 360 use a large-capacity
24Vac Control Transformer, and field wiring to remote
hydronic controls must be suitable for NEC Class 1.
Important – Miswiring of 24Vac control voltage on
system controls can result in transformer burnout.
Important – Units with a dual voltage rating (example,
208/230) are factory-wired for the higher voltage (example,
230). If connected to a power supply having the lower
voltage, change the wiring to the transformer primary to the
correct lead; otherwise premature failure, or inability to