Bryant 50YEW Design Manual page 23

Drawing 2-9 – Piping for Indirect Water Heaters with Insuffi cient
Heat Exchanger Mass: Drawing 2-9 may be used for indirect
water heaters that lack a heat exchanger of suffi cient mass (see
fi gure 2-9 later in this section). Most indirect water heaters are
designed for 180°F [82°C] or hotter water. Using lower water
temperatures could cause the heat pump to short cycle and the
tank temperatures to remain below set point. When the piping
is arranged as shown in drawing 2-9, the mass is increased. The
disadvantages of this arrangement are higher installation costs,
more mechanical room space, and an additional pump (plus the
additional Watts associated with the pump). It is always best to use
an indirect water heater with more heat exchanger mass that is
designed for operation with lower water temperatures.
Drawing 2-9: Alternate DHW Piping - Indirect
Water Heater with Low Mass Heat Exchanger
Domestic Cold
Water
Hot
Water Supply
H C
Direct
Water Heater
(optional backup
electric elements)
Notes 1,2
Aqua-stat
Bryant Geothermal Heat Pump Systems
Part II: Load Side Design / System Design & Selection
P.R.V.
H C
Indirect
Water Heater
Note 1
Secondary Pump
Water-to-Water System Design Guide
Air Vent
Note 3
Exp
Tank
NOTES:
1. Aqua-stat controls secondary pump.
2. Thermistor/aqua-stat should be installed in an immersion well.
Locate thermistor/aqua-stat in the bottom half of the tank.
3. Place air vent at the highest point in the system. If internal
expansion tanks are installed, only an air vent is required.
4. If optional 50YEW pump is used, this pump is not necessary.
5. Other components (additional ball valves, unions, etc.)
may be required for ease of service. This drawing
shows only minimum requirements. Your specific
Note 2
installation will dictate final component selections.
Thermistor or aqua-stat
6. Local code supercedes any piping arrangements or
components shown on this drawing.
To Water-to-Water Heat Pump
Note 4
From Water-to-Water Heat Pump
03Oct07
21