HEAT CONTROLLER, INC. WATER-SOURCE HEAT PUMPS
R e s i d e n t i a l S p l i t - 6 0 H z R 4 1 0 A
R e v. : 0 3 A u g u s t , 2 0 1 2
Heat Controller, Inc. Water-Source Heating and Cooling Systems
20
Hot Outlet
to home
Insulated water lines -
5/8” OD, 50 ft maximum (one way)
[16mm OD, 15 meters maximum]
Powered
Water
Heater
Upper
element to
120 - 130°F
[49 - 54°C]
Lower
element to
100 - 110°F
[38 - 43°C]
Shut-off
Valve #3
Shut Off
Valve #2
Field supplied 3/4’ brass nipple and ‘T’
Cold
Inlet
Shut Off
Valve #4
Shut Off
Valve #1
Insulated water lines - 5/8” OD, 50 ft maximum (one way)
[16mm OD, 15 meters maximum]
Upper element to 130°F [54°C]
(or owner preference)
Cold Inlet
Hot Outlet to
house
Powered
Water Heater
Cold Inlet from
Domestic supply
Hot Outlet
Unpowered
Water Heater
Field Supplied 3/4” brass nipple and “T”
Lower element to 120°F [49°C]
Shut-off
Valve #1
Shut-off
Valve #4
Shut-off
Valve #3
Shut Off
Valve #2
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 18 shows a typical example of HWG water
piping connections on a unit with built-in circulating pump.
This piping layout reduces scaling potential.
The temperature set point of the HWG is
fi
eld selectable
to 125°F or 150°F . The 150°F setpoint allows more heat
storage from the HWG. For example, consider the amount
of heat that can be generated by the HWG when using
the 125°F set point, versus the amount of heat that can be
generated by the HWG when using the 150°F set point.
In a typical 50 gallon two-element electric water heater
the lower element should be turned down to 100°F, or the
lowest setting, to get the most from the HWG. The tank will
eventually stratify so that the lower 80% of the tank, or 40
gallons, becomes 100°F (controlled by the lower element).
The upper 20% of the tank, or 10 gallons, will be maintained
at 125°F (controlled by the upper element).
Using a 125°F set point, the HWG can heat the lower 40
gallons of water from 100°F to 125°F, providing up to 8,330
btu’s of heat. Using the 150°F set point, the HWG can heat
the same 40 gallons of water from 100°F to 150°F and the
remaining 10 gallons of water from 125°F to 150°F, providing
a total of up to 18,743 btu’s of heat, or more than twice as
much heat as when using the 125°F set point.
This example ignored standby losses of the tank. When
those losses are considered the additional savings are even
greater.
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 50 gallons (189 liters) is
used to limit installation costs and space. However, a dual
tank, as shown in Figure 16, is the most ef
fi
cient system,
providing the maximum storage and temperate source water
to the HWG.
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. Consult Table 4 for scaling potential tests.
Hot Water Generator
Figure 15: Typical HWG Installation
(Indoor Compressor Section)
Figure 16: HWG Double Tank Installation
(Indoor Compressor Section)
