HEAT CONTROLLER, INC.
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
Hot Water Generator
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 field. 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
The temperature set point of the HWG is field 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
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 efficient 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.
Figure 15: Typical HWG Installation (Indoor Compressor Section)
Hot Outlet | Cold |
Figure 16: HWG Double Tank Installation (Indoor Compressor Section)
Hot Outlet to
house
to home | Inlet |
| Shut Off |
| Valve #1 |
| Shut Off |
| Valve #4 |
| Upper |
Cold Inlet from
Domestic supply
Hot Outlet
Cold Inlet
|
| element to |
|
| 120 - 130°F |
|
| [49 - 54°C] |
|
| Lower |
| Powered | element to |
| Water | 100 - 110°F |
Heater | [38 - 43°C] | |
|
| |
Valve #3 |
|
|
Shut Off |
|
|
Valve #2 |
|
|
| Field supplied 3/4’ brass nipple and ‘T’ | |
Insulated water lines -
5/8” OD, 50 ft maximum (one way) [16mm OD, 15 meters maximum]
| Upper element to 130°F [54°C] | |
| Valve #1 | (or owner preference) |
|
| |
|
| |
| Valve #4 |
|
| Powered |
|
| Water Heater | Lower element to 120°F [49°C] |
| Unpowered |
|
Water Heater |
| |
|
| |
Valve #3 |
|
|
Shut Off |
|
|
Valve #2 |
|
|
| Field Supplied 3/4” brass nipple and “T” | |
Insulated water lines - 5/8” OD, 50 ft maximum (one way) | ||
| [16mm OD, 15 meters maximum] |
|
20 | Heat Controller, Inc. |
