Hot Water Generator - Carrier GT-PX Split Series Installation, Operation & Maintenance Instructions Manual

The HWG (Hot Water Generator) or desuperheater
option provides considerable operating cost savings by
utilizing excess heat energy from the heat pump to help
satisfy domestic hot water requirements. The HWG
is active throughout the year, providing virtually free
hot water when the heat pump operates in the cooling
mode or hot water at the COP of the heat pump during
operation in the heating mode. Actual HWG water
heating capacities are provided in the appropriate heat
pump performance data.
Heat pumps equipped with the HWG option include
a built-in water to refrigerant heat exchanger that
eliminates the need to tie into the heat pump
refrigerant circuit in the fi eld. The control circuit and
pump are also built in for residential equipment. Figure
15 shows a typical example of HWG water piping
connections on a unit with built-in pump. This piping
layout minimizes scaling potential.
Electric water heaters are recommended. If a gas,
propane, or oil water heater is used, a second preheat
tank must be installed (Figure 16). If the electric water
heater has only a single center element, the dual tank
system is recommended to insure a usable entering
water temperature for the HWG.
Typically a single tank of at least 52 gallons (235 liters)
is used to limit installation costs and space. However,
a dual tank, as shown in Figure 16, is the most effi cient
Figure 15: Typical HWG Installation
(Indoor Compressor Section)
Shut-off Valve #2
Shut-off Valve #3
[16mm OD, 15 meters
maximum]
Cold Inlet
Domestic
Hot Outlet
Cold Supply
to home
Shut-off Valve
Upper
element to
120 - 130°F
[49 - 54°C]
Lower
Powered element to
Water
100 - 110°F
Heater [38 - 43°C]
Shut-off
Valve #4 Tee and drain
Insulated water lines -
5/8" OD, 50 ft maximum
C a r r i e r : Tu r n t o t h e E x p e r t s
R e s i d e n t i a l S p l i t - 6 0 H z R 2 2 & R 4 1 0 A

Hot Water Generator

system, providing the maximum storage and temperate
source water to the HWG. Using a concentric or coaxial
hot water tank connection fi tting eliminates the need to
tie into the hot water tank cold water piping, but is more
susceptible to scaling. The optional concentric fi tting
(part # S69619804) is available from your equipment
supplier and should be installed as shown in Figure
17 for applications with low scaling potential or where
a water softener is used. Consult Table 3 for scaling
potential tests.
It is always advisable to use water softening
equipment on domestic water systems to reduce
the scaling potential and lengthen equipment life.
In extreme water conditions, it may be necessary to
avoid the use of the HWG option since the potential
cost of frequent maintenance may offset or exceed
any savings.
R-410 systems inherently have a lower hot gas
temperature than R-22 systems because the
equipment is more effi cient (i.e. less waste heat
is available). It is possible that energy could be
transferred from the water heater to the hot gas line
instead of from the hot gas line to the water heater
during certain times of the year. To prevent this from
occuring, a temperature switch will deactivate the
pump at those conditions that typically occur in the
cooling mode with entering water temperatures of less
than 50°F [10°C].
Figure 16: HWG Double Tank In stal la tion
(Indoor Compressor Section)
Hot Outlet
Shut Off Valve #2
Shut-off
Valve #3
Insulated water lines - 5/8" OD, 50 ft maximum
R e v. : 5 J u n e , 2 0 0 8
Hot Outlet to
house
Cold Inlet
Cold Inlet from
Domestic supply
Upper element to 130°F [54°C]
Shut-off
Valve #1
(or owner preference)
Shut-off
Valve #4
Powered
Lower element to 120°F [49°C]
Water Heater
Unpowered
Water Heater
Field Supplied 3/4" brass nipple and "T"
[16mm OD, 15 meters maximum]
23