Bryant 50YEW, 50PSW, 50GSW, GSW Design Manual

WATER-TO-WATER

SYSTEM DESIGN GUIDE

50YEW, 50PSW, & GSW

WATER-TO-WATER SYSTEMS

WHATEVER IT TAKES.

Water-to-Water System Design Guide Bryant Geothermal Heat Pump Systems

Table of Contents

Water-to-Water System Design Guide

Part 1: System Overview

Why Hydronics .............................................................................................1

Part II: Load Side Design

Heat Gain / Loss Calculations ..............................................................6

System Design & Selection .................................................................10

Piping Design ...............................................................................................22

Source & Load Pump Sizing ...............................................................24

Distribution Design ..................................................................................24

Radiant Floor Heating ............................................................................26

Baseboard Heating ...................................................................................27

Cast Iron Heating .....................................................................................28

Fan Coils ........................................................................................................29

Snow Melt Applications ........................................................................30

Part III: Source Side Design

System Selection ....................................................................................... 31

Open Loop Design ..................................................................................38

Closed Loop Design ............................................................................... 40

Closed Loop Instillation Guidelines ................................................42

Part IV: Controls

50YEW Controls ...................................................................................... 56

Wiring Diagrams .......................................................................................59

Revision Log...............................................................Inside Back Cover

Bryant works continually to improve its products. As a result, the design and specifi cations of each product at the time for order may be changed without notice and may
not be as described herein. Please contact Bryant’s Customer Service Department at 1-405-745-2920 for specifi c information on the current design and spec i fi ca tions, and
placing orders. Statements and other in for ma tion contained herein are not express warranties and do not form the basis of any bargain between the par ties, but are merely
Bryant’s opinion or com men da tion of its products.

Unit Information

50YEW Water-to-Water Series

Features .......................................................................................................... 70

Model Key .....................................................................................................72

Unit Performance ..................................................................................... 74

Physical Data ...............................................................................................75

Unit Dimensions .......................................................................................76

Electrical Data .............................................................................................77

Wiring Diagrams .......................................................................................78

Engineering Specifi cations .................................................................... 82

GSW Water-to-Water Series

Features .......................................................................................................... 86

Model Key .....................................................................................................88

Unit Performance ..................................................................................... 90

Physical Data ...............................................................................................97

Unit Dimensions .......................................................................................98

Electrical Data .......................................................................................... 100

Wiring Diagrams ....................................................................................101

Engineering Specifi cations ................................................................. 103

Bryant Geothermal Heat Pump Systems

1

Water-to-Water System Design Guide

WHY HYDRONICS?

According to Webster’s Dictionary, hydronic heating is “a system of
heating or cooling that involves the transfer of heat by a circulating
fl uid (as water or vapor) in a closed system of pipes.” Because
water is the most effi cient way to move thermal energy, a hydronic
system requires much less transport energy in the process and
takes up far less space. For example, a 1” [25mm] diameter pipe
can carry as much heat as a 10” x 19” [254 x 483 mm] rectangular
duct carrying hot air at 130°F [54°C]. In addition, the mass of
the ground loop [geothermal piping] and/or radiant fl oor piping
provides thermal storage, allowing the system to virtually ignore
large changes in outdoor temperatures. There is no storage benefi t
in most HVAC systems.

Figure 1-1: Thermal Energy Comparison

Hydronics systems, especially systems using radiant fl oor heating,
provide lower operating costs than forced air systems. More Watts
are used to circulate air through ductwork than to circulate water
through piping. For example, a typical 80% effi cient natural gas
residential furnace with an output capacity of 80,000 Btuh [23.4
kW] uses an 850 Watt fan motor. For every Watt used to power
the fan, 94 Btuh [28 Watts] of heat is delivered via the forced air
ductwork. If a boiler or heat pump is used to generate heat, but
the heat is delivered through a radiant fl oor system, the pumping
power would typically be around 300-400 Watts, or 40% to 50%
of the air delivery system Watts, resulting in around 230 Btuh [67
Watts] of heat per Watt of pump power.

Radiant fl oor systems provide heat at occupant level. Hot air rises
to the ceiling (forced air systems), but heat always moves to cold
(radiant system). Therefore, a warm fl oor will heat objects in the
space, not the air directly, resulting in a space that feels warmer at
lower thermostat settings. Occupants will feel more comfor table,
and when the thermostat setting is lowered, the heat loss
decreases, resulting in better comfort at lower operating costs.

Hydronic heating systems can be combined with boilers or heat
pumps to generate hot water for radiant fl oor systems, baseboard
convectors, or radiators. Heat pumps are inherently more effi cient
than fossil fuel (natural gas, oil, or propane) heating systems, and
geothermal heat pumps are more effi cient than air-source heat
pumps, due to the mild heat source of the ground (as compared
to outdoor air temperatures). Water-to-air heat pumps heat the air,

and require a fan to circulate air through ductwork. Water-to-water
heat pumps heat water, allowing the design of a hydronic heating
system with the benefi ts of more effi cient energy distribution,
lower operating costs and better comfort.

Fossil fuel furnaces and boilers are always less than 100% effi cient.
Even the best systems are 95-96% effi cient. Geothermal heat
pumps typically deliver 4 to 6 Watts of heat for every Watt
of energy consumed to run the compressor and ground loop
pump(s). In other words, for each Watt of energy used, 3 to 5
Watts of free energy from the ground is added to provide 4 to
6 Watts of energy to heat the space. The use of a high effi ciency
water-to-water heat pump and a hydronic heating system is an
unbeatable combination.

Water-to-Water Heat Pumps

Bryant water-to-water heat pumps offer high effi ciencies, advanced
features, extremely quiet operation and application fl exibility. As
Bryant’s most adaptable products, water-to-water heat pumps may
be used for radiant fl oor heating, snow/ice melt, domestic hot water
heating, and many other hydronic heating applications.

Bryant’s exclusive double isolation compressor mounting system
provides the quietest water-to-water units on the market.
Compressors are mounted on rubber-grommets or vibration
isolation springs to a heavy gauge mounting plate, which is
then isolated from the cabinet base with rubber grommets for
maximized vibration/sound attenuation. A compressor discharge
muffl er and additional sound attenuation materials further enhance
the quiet operation (50YEW models).

Bryant water-to-water heat pumps are available as heating only
(50YEW series) or with reversible operation for heating and
cooling (50PSW and GSW series). Figure 1-2 shows the simple
refrigerant circuit of the 50YEW series. With only four major
components, the refrigerant circuit is easy to understand and
troubleshoot if necessary.

The 50YEW series includes a special high temperature scroll
compressor coupled with heat exchangers designed specifi cally
for water heating, which provides unmatched effi ciencies and
performance. The evaporator is a coaxial (tube-in-tube) heat
exchanger that is capable of operation over a wide range
of temperatures, and is more rugged than other types of
evaporators, especially for open loop (well water) systems. The
condenser uses a close approach temperature brazed plate heat
exchanger that is designed for high temperature operation. This
combination of coaxial/brazed plate heat exchangers provides
the best combination of durability and effi ciency. Bryant always
recommends coaxial heat exchangers for evaporators. Brazed
plate heat exchangers may be used for condensers when the unit
is not reversible.

Part I: System Overview

Water Pipe

Air Duct

2

Water-to-Water System Design Guide

Bryant: Whatever It Takes.

Figure 1-2: 50YEW Series Refrigerant Circuit

Figure 1-3: Reversible Water-to-Water Heat Pump, Heating Mode

Figure 1-4: Reversible Water-to-Water Heat Pump, Cooling Mode

To/From

Heating

Distribution

System

To/From

Ground

Loop

Compressor

TXV

Coaxial HX

(Evaporator)

Brazed Plate HX

(Condenser)

Source

Load

To/From

Heating

Distribution

System

To/From

Ground

Loop

Compressor

TXV

Reversing

Valve

Coaxial HX

(Evaporator)

Coaxial HX

(Condenser)

Source

Load

To/From

Chilled Water

Distribution

System

To/From

Ground

Loop

Compressor

TXV

Reversing

Valve

Coaxial HX

(Evaporator)

Coaxial HX

(Condenser)

Source

Load

Part I: System Overview

Bryant Geothermal Heat Pump Systems

3

Water-to-Water System Design Guide

The 50YEW series compressors have a wide operating map, which
allows high temperature operation, up to 145°F [63°C] leaving
water temperature, even at 32°F [0°C] ground loop temperatures.
The ground loop heat exchanger [evaporator] is called the “Source”
heat exchanger in Bryant technical literature, and the heating
system heat exchanger is called the “Load” heat exchanger. The
terminology is not as important for heating only water-to-water
units, since the ground loop heat exchanger is always an evaporator,
but for reversible units, the evaporator and condenser change,
depending upon operating mode, heating or cooling.

Figure 1-3 shows a Bryant reversible water-to-water unit. With the
addition of a reversing valve, the Source and Load heat exchangers
can change functions, depending upon the desired mode of
operation. In the heating mode, the “Load” heat exchanger
functions as the condenser, and the “Source” heat exchanger
functions as the evaporator.

In fi gure 1-4, the reversible water-to-water heat pump now
provides chilled water on the load side instead of hot water. The
load heat exchanger becomes the evaporator, and the source heat
exchanger becomes the condenser. Because the evaporator is
susceptible to freezing under adverse operating conditions (e.g.
failed pump, controls problem, etc.), a coaxial heat exchanger is
used on the load side for reversible units.

When selecting equipment for systems that require cooling, all
aspects of the system design should be considered. In many cases,
a separate water-to-air unit for forced air cooling is more cost
effective than using a chilled water / fan coil application due to the
complication in controls and seasonal change-over. For ground
loop applications, the water-to-water and water-to-air units can
share one ground loop system.

Figure 1-5: COP vs TD

WATER-TO-WATER HEAT PUMP DESIGN

Design Temperatures

Various types of hydronic distribution systems have been used
successfully with geothermal heat pumps. Radiant fl oor systems
use relatively mild water temperatures, whereas baseboard
radiation and other types of heat distribution systems typically
use hotter water temperatures. When designing or retrofi tting
an existing hydronic heating system, it is especially impor tant to
consider maximum heat pump water temperatures as well as the
effect water temperatures have on system effi ciency.

Heat pumps using R-22 refrigerant are not designed to produce
water above 130°F [54°C]. Some heat pumps with R-410A and
R-407C refrigerant are capable of producing water up to 145°F
[63°C]. Regardless of the refrigerant, the effi ciency of the heat pump
decreases as the temperature difference (TD) between the heat
source (generally the earth loop) and the load water (the distribution
system) increases. Figure 1-5 illustrates the effect of source and load
temperatures on the system. The heating capacity of the heat pump
also decreases as the temperature difference increases.

As the temperature difference increases, the Coeffi cient of
Performance (COP) decreases. When the system produces
130°F [54°C] water from a 30° [-1°C] earth loop, the TD is
100°F [55°C], and the COP is approximately 2.5. If the system is
producing water at 90° F [32°C], the TD is 60°F [33°C] and the
COP rises to about 5.0, doubling the effi ciency.

If the water temperature of the earth loop is 90°F [32°C], and
the distribution system requires the same temperature, a heat
pump would not be needed. The system would operate at infi nite
effi ciency, other than the cost of pumping the water through the

Part I: System Overview

4

Water-to-Water System Design Guide

Bryant: Whatever It Takes.

distribution system. When using the various types of hydronic
heat distribution systems, the temperature limits of the geothermal
system must be a major consideration. In new construction, the
distribution system can easily be designed with the temperature
limits in mind. In retrofi ts, care must be taken to address the
operating temperature limits of the existing distribution system.

System Components

The effi ciency, life expectancy and reliability of any hydronic heating
system depends upon how well the various components (heat pump,
distribution system, contols, etc.) work together. The heat pump must
be sized for the building loads; the earth loop must be sized to match
the building loads, ground conditions and climate; the circulating
pumps must be sized for the equipment, piping and ground loop. The
distribution system must be designed to heat and/or cool the building
comfortably. The components must then all be controlled effectively.

Building Heat Loss & Heat Gain

The design must begin with an accurate heating and/or cooling
load of the building. This is the most important step in the design
process. The sizing of the circulation pumps, the distribution
system and the earth loop are all derived directly from the sizing
of the equipment. Overestimating the heat loss or heat gain
means over sizing the system. The extra cost of the oversized
system is unnecessary. In fact, it may result in the selection of a
different type of system. If an oversized system is installed, it may
be ineffi cient and uncomfortable. If the system is undersized it will
not do an adequate job of heating and/or cooling the building.

Loop Design & Installation

Several factors determine the loop design for a specifi c installation.
The energy balance of the building determines how much heat is
taken from and rejected to the earth over the course of a year.
The climate determines the ambient earth temperatures and is a
major factor in the energy needs of the building. The ear th itself
(the conductivity of the soil or rock and the moisture content) are
major factors in calculating the size of the loop. The earth can only
take (heat rejected) or give up (heat extracted/absorbed) a fi xed
amount of Btu/hr [Watts] in a given area. The heat exchanger
must have suffi cient surface area.

The design of the loop itself (the size and type of pipe, the
velocity of the liquid circulating in the pipe and the spacing and
layout of the pipe) has a major effect on the heat absorption and
rejection capabilities of the loop. The depth (ver tical) or trench
length (horizontal) of the loop must be calculated using IGSHPA
(International Ground Source Heat Pump Association) methods
or approved software. In addition, the type and percentage of
antifreeze can have a signifi cant effect on loop performance.

The workmanship of the installation also plays a large role in the
effectiveness of the loop. All fusion joints must be done properly.
Vertical loops must be grouted properly for good contact with the
earth. Horizontal loops must be backfi lled with material that will
not cut the pipe, and the soil should be compacted around the
pipe for good contact. All closed loop piping systems should be
hydrostatically pressure tested before burial.

Many factors affect loop performance. Bryant offers training in
loop design and installation, and also provides residential and
commercial loop sizing software.

Controls

The control of a mechanical system determines how it functions. For
the building to work effi ciently and comfortably, the building owner
or manager must understand system functionality and controls.

As Figure 1-5 shows, the effi ciency of a heat pump is a factor
of the difference in temperature between the source and the
load. The heat loss or heat gain of a building varies with the
weather and the use of the building. As the outdoor temperature
decreases, the heat loss of the building increases. When the
ventilation system is operating, the heating or cooling loads
increase. As the occupancy increases, or more lighting is used, or
the solar gain increases, the cooling load increases. At times the
building may require virtually no heating or cooling.

The output of the hydronic heating distribution equipment,
whether it is baseboard radiation, fan coil units or radiant fl oor
heating equipment, is directly related to the temperature and
velocity of the water fl owing through it. Baseboard radiation puts
out approximately 50% less heat with 110°F [43°C] water than
with 130°F [54°C] water. The same is true with fan coil units and
radiant fl oor heating. For example, if a system is designed to meet
the maximum heat loss of a building with 130°F [54°C] water,
it follows that if the heat loss is 50% lower (when the outdoor
temperature is higher), the load can be met with 110°F [43°C]
water. The lower water temperature greatly increases the COP of
the heat pump. Outdoor temperature reset, discussed in part IV of
this manual, is a very cost-effective method of matching the heating
(load side) water temperature with the heat loss of the building.

Other considerations for controls include heating/cooling
switchover, pump control, backup heat (if equipped), distribution
system or zone controls, and priority assignments (e.g. determining
if radiant fl oor heating or domestic hot water will take priority).
The 50YEW series includes internal controls, which makes system
installation much easier. Other Bryant water-to-water heat pumps
must be controlled via external controls.

Part I: System Overview

Bryant Geothermal Heat Pump Systems

5

Water-to-Water System Design Guide

SUMMARY

Hydronic geothermal systems can be used very effectively in new
installations, as well as in many retrofi t applications. Effi cient systems
can be designed for residential, commercial and industrial applications.

To make a system as effi cient as possible, it is important to follow
good design criteria. Some of the factors to consider are listed below:

• An accurate heat loss and heat gain must be calculated to
properly size the system.

• The system must meet the application requirements. In other
words, the design of the system must take into consideration
the type of distribution system and the needs of the customer.
For example, baseboard radiation designed for 180°F [82°C]
water should not be used with 130°F [54°C] water without
careful consideration and design analysis.

• The components of the system must be designed to work
together. The earth loop must be designed to work with the
heat pump; the pumping system must work effectively with the
earth loop and the heat distribution system; and the distribution
system must be chosen to work properly with the water
temperatures available from the heat pump.

• The system must be controlled to operate as effi ciently
as possible. It is important to operate the system to take
variations in the building loads into account. For example,
the heat loss of the building is reduced when the outdoor
temperature climbs, and the temperature of the water
circulated through the distribution system can be lowered,
allowing the heat pumps to operate more effi ciently. It is
possible to integrate the functions of the mechanical systems in
a building.

Part I: System Overview

6

Water-to-Water System Design Guide

Bryant: Whatever It Takes.

HEAT LOSS / HEAT GAIN CALCULATIONS

Heat loss loss/gain calculations for any residential HVAC design
should be performed using standard industry practices. Br yant
accepted calculations include methods developed by ACCA (Air
Conditioning Contractors of America) used in Manual J, HRAI
(Heating, Refrigeration and Air Conditioning Institute of Canada)
and ASHRAE (American Society of Heating Refrigerating and Air
Conditioning Engineers). Light commercial load calculations should
be performed using ACCA Manual N or the ASHRAE method.
Other methods for load calculations outside of North America are
acceptable providing the methodology is recognized by the local
HVAC industry.

Heat Loss Calculations for Radiant Floor or Zoned
Baseboard Systems

A room-by-room calculation must be performed for all radiant
fl oor or zoned baseboard systems in order to determine the
design of the radiation system. Once the heat loss has been
calculated and the decision on fl ooring material has been made
for each room, the amount of radiant fl oor tubing, pipe spacing,
water temperature and layout can be determined, based upon the
Btuh/square foot [Watts/square meter] requirements. Similarly,
the amount of heat loss will allow the designer to determine the
length of baseboard convector required based upon the design
water temperature.

Outdoor design temperatures should be obtained from the
appropriate ACCA, ASHRAE or HRAI manual at the 99.6% condition
or local requirements, whichever is most severe. Indoor design
temperatures vary, based upon the type of system and customer
preference. Following are some minimum design guidelines:

*The nature of radiant fl oor heating tends to allow occupants
to feel the same comfort level with radiant fl oor heating at 65°F
[18°C] as with a forced air system at 70°F [21°C].

It is important to remember that a radiant fl oor system heats
objects, not the air. In turn, these objects radiate heat, which
heat people and furnishings to a comfortable temperature. Air
temperature remains near 65°F [18°C], and is approximately equal
from ceiling to fl oor. Forced air heating, by comparison, heats the
air, which heats the people and objects. Therefore, a higher air
temperature is required in order to bring people and objects up to
the same temperature as in a radiant heating system.

When calculating the heat loss of a structure, the nature of radiant
heating should be considered to allow for a more appropriately
sized system. As mentioned above, a thermostat setting of 65°F
[18°C] for a radiant fl oor system is comparable to a forced air
system with a thermostat setting of 70°F [21°C]. This principle
affects the heat loss in two ways:

1. The lower temperature difference [between indoor and
outdoor temperatures] causes the heat loss to be lower.

2. The lack of air movement lowers the infi ltration rate of
the structure.

Following is an example of the differences in load calculations for
radiant fl oor systems and forced air systems:

System A: Forced Air System

ACCA Manual J heat loss calculation
2,000 sq. ft. [186 sq. meter] residential structure
Outside design temperature = 0°F [-18°C]
Indoor design temperature = 70°F [21°C]
Temperature difference = 70°F [39°C]
Air changes per hour = 0.60 AC/H
Heat loss = 50,000 Btu/hr [14,654 Watts]

System B: Radiant Floor System

ACCA Manual J heat loss calculation
2,000 sq. ft. [186 sq. meter] residential structure
Outside design temperature = 0°F [-18°C]
Indoor design temperature = 65°F [18°C]
Temperature difference = 65°F [36°C]
Air changes per hour = 0.50 AC/H
Heat loss = 44,423 Btu/hr [13,020 Watts]

When the characteristics of a radiant fl oor system are considered,
equipment sizing can be signifi cantly impacted. In the example
above, the heat loss for the structure decreases by 5,577 Btu/hr
[1,635 Watts], or 11%. Industry estimates are as high as 20%.
However, Bryant encourages the use of load calculations at actual
temperature differences and infi ltration rates for equipment sizing,
rather than “rules of thumb.”

Heat Gain Calculations

Most space cooling is accomplished through the use of forced air.
Heat gain calculations must be performed on a room-by-room or
zoned basis. Although load calculations for single zone systems
may consider the whole house or building as one zone, a room-by­room calculation will facilitate air duct sizing.

Outdoor design temperatures should be obtained from the
appropriate ACCA, ASHRAE or HRAI manual at the 0.4%
condition or local requirements, whichever is most severe. Indoor
design temperatures for cooling typically range from 70-78°F [21­25°C], with most designed at 75°F [24°C].

System Type

Indoor

Design Range

Minimum

Indoor Design
100% Radiant Floor* 65-70°F [18-21°C] 65°F [18°C]
Mixed Radiant/Forced Air 68-72°F [20-22°C] 68°F [20°C]
Baseboard 68-72°F [20-22°C] 68°F [20°C]

Part II: Load Side Design

Bryant Geothermal Heat Pump Systems

7

Water-to-Water System Design Guide

SIZING WATER-TO-WATER EQUIPMENT /
BUFFER TANKS

Water-to-Water Equipment Sizing

Water-to-water equipment sizing is dependent upon the type of
hydronic system application (load side – indoor) and the type of
ground loop system (source side – outdoor). Since the capacity
and effi ciency of the water-to-water unit is directly related to the
entering source temperature, care must be taken to insure that
the unit will provide adequate capacity at design conditions. The
complexity of the ground loop sizing can be simplifi ed with the
use of software, like Bryant’s GeoDesigner. GeoDesigner allows
the user to enter the heat loss/heat gain, the water-to-water unit
size, and the ground loop parameters. An analysis based upon bin
weather data allows the user to size the equipment/ground loop
and obtain annual operating costs. Below is a typical screen shot.

Figure 2-1: GeoDesigner Heat Pump / Loop Sizing

Part II: Load Side Design / Equipment Sizing

8

Water-to-Water System Design Guide

Bryant: Whatever It Takes.

Backup Heat

Just like water-to-air systems, which typically have some type
of backup heating capability, water-to-water systems can also
benefi t from the use of supplemental heating to help lower initial
installation costs. Design temperatures are usually chosen for
1%. In other words, 99% of the time, the outdoor temperature
is above the design temperature. If the heat pump is designed to
handle 100% of the load, it is larger than required 99% of the time.
GeoDesigner can determine an economical balance point that will
allow the water-to-water unit to be downsized when a backup
boiler or water heater is used for supplemental heat.

For example, suppose a home in Chicago has a heat loss the same as
the example above [44,423 Btuh, 13,019 Watts]. One 50YEW010
unit has a heating capacity of approximately 10kW [33,000 Btuh] at
32°F [0°C] entering source (ground loop) temperature. According
to GeoDesigner, the water-to-water unit could handle the heating
load 98% of the time. A backup electric boiler would consume
about 326 kWh annually for back up heat [$33 per year at $0.10/
kWh]. Two 50YEW010 units could handle the heating load no
matter what the outdoor temperature is (100% heating – no backup
required). However, this combination would only save about 239
kWh per year [$24 per year at $0.10/kWh], yet the additional
installation cost for a second unit and signifi cantly more ground loop
would never pay back in operating cost savings. In most cases, sizing
for 100% of the heating load is not cost effective.

Cooling

Cooling is not always desired with radiant heating systems. A
water-to-water heat pump system can provide chilled water to
ducted or non-ducted fan coil units. A reversible water-to-water
heat pump can provide chilled water to cool the building, as well
as hot water for the heating system. Buildings with fan coil units
can generally be retrofi tted for cooling quite easily. The diffi culty, as
mentioned in part I, is using existing fan coils for heating, especially
if they were originally sized for high water temperatures.

For optimal cooling and dehumidifi cation, Br yant recommends a
separate water-to-air heat pump for cooling. Controls are much
simpler when a water-to-water unit is used for space heating
and/or domestic water heating, and a water-to-air unit is used for
cooling. Since the water-to-water and water-to-air units can share
one ground loop, the installation cost of using a water-to-air unit
for cooling is simply the incremental cost of the unit. Generally, no
additional ground loop is required (in Northern climates), and the
cost of the water-to-air unit is usually less than the cost of chilled
water/fan coil units, especially if the cost of additional piping/
valving/controls and labor is considered. The cost of a water-to­air unit is approximately the same as a ductless mini split, and is
much more effi cient. The advantages of geothermal heat pumps
for cooling (no outdoor unit, no refrigerant line sets, longevity, etc.)
should be considered when cooling is required.

Buffer Tank Sizing / Application

All water-to-water units used in heating applications require a
buffer tank to prevent equipment short cycling and to allow
different fl ow rates through the water-to-water unit than through

the hydronic heating delivery system. A buffer tank is also required
for chilled water cooling applications if the water-to-water unit(s)
is more than 20% larger than the cooling load and/or multiple fan
coil units will be used. Water-to-water units sized for the cooling
load in applications with only ONE fan coil unit may be able
to operate without a buffer tank, but this would be an unusual
situation, since the cooling load is normally much smaller than
the heating load. The best approach is to plan for a buffer tank in
every application.

The size of the buffer tank should be determined based upon
the predominant use of the water-to-water equipment (heating
or cooling). For heating, buffer tanks should be sized at one U.S.
gallon per 1,000 Btuh [13 Liters per kW] of heating capacity at
the maximum entering source water temperature (EST) and the
minimum entering load water temperature (ELT), the point at
which the water-to-water unit has the highest heating capacity,
usually 50-70°F [10-21°C] EST and 80-90°F [26-32°C] ELT. For
cooling, buffer tanks should be sized at one U.S. gallon per 1,000
Btuh [13 Liters per kW] of cooling capacity at the minimum EST
and the maximum ELT, the point at which the water-to-water unit
has the highest cooling capacity, usually 50-70°F [10-21°C] EST and
50-60°F [10-16°C] ELT. Select the size of the tank based upon the
larger of the calculations (heating or cooling). The minimum buffer
tank size is 40 U.S. gallons [150 Liters] for any system.

Electric water heaters typically make good buffer tanks because of
the availability and relatively low cost. However, the water heater
must be A.S.M.E. rated (rated for heating) in order to qualify as a
buffer tank. Attention should be paid to insulation values of the
tank, especially when a buffer tank is used to store chilled water
due to the potential for condensation. A minimum insulation value
of R-12 [2.11 K-m2/W] is recommended for storage tanks.

Part II: Load Side Design / Equipment Sizing

CAUTION:

Maximum leaving water temperature of the 50YEW series
equipment is 145°F [63°C]. For domestic hot water tank
temperatures or heating buffer tank temperatures above
130°F [54°C], pump and pipe sizing is critical to insure that
the fl ow rate through the heat pump is suffi cient to maintain
leaving water temperatures below the maximum temperature,
and to provide water fl ow rates within the ranges shown in
the performance section of this manual.

Bryant Geothermal Heat Pump Systems

9

Water-to-Water System Design Guide

Figure 2-2: Connections – Electric Water Heater /
Buffer Tank

When using an electric water heat as a buffer tank, there are
fewer water connections. Alternate piping arrangements may be
required to make up for the lack of water connections. Schematics
are shown in the next section. Above is an illustration showing the
water connection differences between a buffer tank and an electric
water heater.

Typical Electric

Water Heater

HC

Drain (3)

Connection for
Press Relief Valve

Hot/Cold Water

Connections

(1) (2)

Typical

Buffer Tank

Connection for
Press Relief Valve

Load & Source
Connections

(1)

(2)

(3)

(4)

Drain (5)

Part II: Load Side Design / Equipment Sizing

10

Water-to-Water System Design Guide

Bryant: Whatever It Takes.

SYSTEM DESIGN

As mentioned in part I, hydronics applications offer a wide range
of application fl exibility, so much in fact, that it is necessary to
narrow down the choices in order to start designing the system.
As with any heating and cooling design, there is never a perfect
solution, but rather a compromise between installation costs,
operating costs, desired features and comfort. Once the system is
selected, design of the distribution system, pumps, piping and other
components can be considered.

Figure 2-3a: System Selection Flow Chart (Part 1)

SYSTEM SELECTION

Figures 2-3a and 2-3b present system selection in fl ow chart
format for the load side of the water-to-water unit. There are
six piping schematics following the fl ow charts that illustrate each
of the possible choices. There are also two additional piping
schematics, one for alternate buffer tank piping, and one for using a
backup boiler for supplemental heat. To select the correct drawing,
begin in fi gure 2-3a, and fi nish the selection process in fi gure 2-3b.

Start

(Load Side Applications)

Heating

System?

Radiant Floor

Baseboard Convection

Radiator
Fan Coil

Cooling

System?

Cooling

System?

Chilled Water / Fan Coil

Chilled Radiant Floor

Chilled Water / Fan Coil

Chilled Radiant Floor

See drawing 2-5 (

50PSW

/

GSW + sep htg /clg buffer

tanks)

No Cooling or Separate

Cooling System

No Cooling or Separate

Cooling System

Use 50PSW or GSW series

Reversible Model

Buffer

Tanks?

Buffer tank for heating and

a separate buffer tank for

cooling

One buffer tank for both

heating and cooling

Use 50YEW (high temp) or
50PSW/GSW ( med temp)

series

Use 50YEW (high temp)

series

1

2

(required)

NOTE: Green arrows indicate Bryant
recommended applications.

High temp (

50YEW

) unit is

not reversible.

See drawing 2-6 (

50PSW

/

GSW +

one htg

/clg buffer

tank)

Part II: Load Side Design / System Design & Selection

Bryant Geothermal Heat Pump Systems

11

Water-to-Water System Design Guide

Figure 2-3b: System Selection Flow Chart (Part 2)

1

Buffer
Tank?

Buffer tank is required

No

Ye s

Domestic

Hot

Wat er ?

No

Ye s

50YEW?

Ye s

No

50YEW has integrated

controls. Choose 50YEW

(other choices are possible,

but not shown in

drawings).

Indirect

Water

Heater?

Ye s

No

NOTE: Green arrows indicate Bryant
recommended applications.

See drawing 2-1 (50YEW +

Indirect Water Heater)

Secondary Heat Exchanger / Pump

is required. See drawing 2-2 (50YEW

+HX + Pump + Water Heater)

2

Buffer
Tank?

No

Ye s

Domestic

Hot

Wat er ?

No

Ye s

Indirect

Wat er

Heater?

Ye s

No

See drawing 2-1 (50YEW +

Indirect Water Heater)

Secondary Heat Exchanger / Pump

is required. See drawing 2-2

(50YEW + HX + Pump +

Water Heat)

See drawing 2-3 (

50YEW

)

or drawing 2-4 (

50PSW

/

GSW

)

See drawing 2-3 (

50YEW

)

Buffer tank is required

Part II: Load Side Design / System Design & Selection

12

Water-to-Water System Design Guide

Bryant: Whatever It Takes.

System Descriptions

Figure 2-4: Component Legend for Drawings 2-1 to
2-9

Drawing 2-1 – 50YEW Typical Load Piping Indirect Water Heater
/ No Cooling or Separate Cooling System: System #1 uses one
or more water-to-water units and a buffer tank for each unit.
Drawing 2-1 shows a typical piping arrangement for this system.
A thermistor mounted in an immersion well senses buffer tank
temperature, which allows the internal controls (50YEW units
only) to engage the water-to-water unit compressor, load pump
and source pump(s) when the tank temperature drops below
the set point, typically 120°F [49°C] or less. The radiant fl oor (or
baseboard, radiator, fan coil, etc.) system therefore is completely
isolated from the water-to-water unit. The controls for the
hydronic distribution system energize pumps and/or zone valves to
allow heated water in the buffer tank to fl ow through the heating
distribution system. Potable water is heated via an indirect water
heater, so that heating system water and potable water do not mix.
The 50YEW unit has an internal motorized valve, which allows
the load pump to send heated water to the buffer tank or the
indirect water heater. A thermistor mounted in an immersion well
senses DHW tank temperature, which allows the internal controls
(50YEW units only) to engage the water-to-water unit compressor,
load pump and source pump(s) when the DHW tank temperature
drops below the set point, typically 130°F [54°C]. If desired,
cooling is accomplished with a separate system.

Component Legend

3-Way Valve - Manually Operated

3-Way Valve - Motorized

Mixing Valve

Ball Valve

Gate Valve

Pressure Reducing Valve

Pressure Relief ("Pop-Off") Valve

Union

Pressure/Temperature (P/T) Port

Circulator Pump

Heat Exchanger

T

Check Valve

M

Indirect

Water Heater

Heating

Buffer Tank

NOTES:

1. Place air vent at the highest point in the system. If
internal expansion tanks are installed, only an air
vent is required.

2. Thermistors should be installed in an immersion well.

Locate thermistor in the bottom half of the tank.

3. If electric water heat is used instead of buffer tank, see
drawing 2-7.

4. P/T (pressure/temperature) ports are internal for
50YEW units on load and source connections.

5. Other components (additional ball valves, unions, etc.)
may be required for ease of service. This drawing
shows only minimum requirements. Your specific
installation will dictate final component selections.

6. Buffer tank must be approved as a heating vessel.

7. Local code supercedes any piping arrangements or
components shown on this drawing.

To/From

Radiant Floor,

Radiator,

Baseboard,

or Fan Coil

Heating System

HC

HC

Exp

Ta nk

Note 1

Air Vent

See drawings in section 3 for Source connections

03Oct07

Note 3

50YEW

Unit

Source HX

(coaxial)

Load HX

(brz plt)

INOUTIN OUTOUT

HTG DHW

M

DHW

IN

HTG

P. R. V .

Thermistor

Note 2

If heat exchanger
of indirect water
heater does not
have enough
mass, see
drawing 2-9

Thermistor

Note 2

Drawing 2-1: 50YEW Typical Load Piping ­Indirect Water Heater / No Cooling or Separate
Cooling System

Part II: Load Side Design / System Design & Selection

Bryant Geothermal Heat Pump Systems

13

Water-to-Water System Design Guide

Drawing 2-2 – 50YEW Typical Load Piping Water Heater with
Secondary Heat Exchanger / No Cooling or Separate Cooling
System: System #2 uses one or more water-to-water units
and a buffer tank for each unit. Drawing 2-2 shows a typical
piping arrangement for this system. A thermistor mounted in
an immersion well senses tank temperature, which allows the
internal controls (50YEW units only) to engage the water-to-water
unit compressor, load pump and source pump(s) when the tank
temperature drops below the set point, typically 120°F [49°C]
or less. The radiant fl oor (or baseboard, radiator, fan coil, etc.)
system therefore is completely isolated from the water-to-water
unit. The controls for the hydronic distribution system energize
pumps and/or zone valves to allow heated water in the buffer
tank to fl ow through the heating distribution system. Potable
water is heated via a direct water heater (typically an electric
water heater) and a secondary heat exchanger (typically a brazed
plate heat exchanger), so that heating system water and potable
water do not mix. The 50YEW unit has an internal motorized
valve, which allows the load pump to send heated water to the
buffer tank or the secondary heat exchanger for heating potable
water. A thermistor mounted in an immersion well senses tank

temperature, which allows the internal controls (50YEW units
only) to engage the water-to-water unit compressor, load pump
and source pump(s) when the tank temperature drops below
the set point, typically 130°F [54°C]. The use of a direct water
heat and secondary heat exchanger requires a pump between
the secondary heat exchanger and the water heater. The addition
of a pump contactor near the water heater will be necessary to
energize the pump any time the 50YEW load pump is energized
for potable water heating. If desired, the 50YEW controls allow
emergency water heating via electric elements if the 50YEW unit
is locked out. This requires a contactor at the water heater to
energize the electric elements when the heat pump is locked out.
Cooling is accomplished with a separate system.

Secondary Heat Exchanger Sizing: Due to the
lower water temperatures associated with heat
pumps (as compared to 180-200°F [82-93°C] boiler
temperatures), heat exchanger sizing is critical.
Bryant recommends the use of sizing software
provided by the heat exchanger manufacturer. An
example is shown in fi gure 2-5. NOTE: Even though
the maximum leaving water temperature of the
50YEW series equipment is 145°F [63°C], some
room for piping changes, pump performance, and/
or pressure switch tolerance, should be considered
via slightly lower design temperatures (143°F [62°C]
is shown in fi gure 2-5 example). Refrigerant high
pressure switches typically have a tolerance of ± 15
psi [±1 Bar], potentially resulting in nuisance faults if
the switch tolerance is on the lower side of the range.
The compressor is rated for 145-149°F [63-65°C]
operation, but if the switch is marginal, a slightly
conservative design temperature will help avoid
nuisance faults.

Drawing 2-2: 50YEW Typical Load Piping ­Water Heater with Secondary Heat Exchanger /
No Cooling or Separate Cooling System

Thermistor

Note 2

Heating

Buffer Tank

NOTES:

1. Place air vent at the highest point in the system. If
internal expansion tanks are installed, only an air
vent is required.

2. Thermistors should be installed in an immersion well.

Locate thermistor in the bottom half of the tank.

3. If electric water heat is used instead of buffer tank, see
drawing 7.

4. P/T (pressure/temperature) ports are internal for
50YEW units on load and source connections.

5. Other components (additional ball valves, unions, etc.)
may be required for ease of service. This drawing
shows only minimum requirements. Your specific
installation will dictate final component selections.

6. Buffer tank must be approved as a heating vessel.

7. Local code supercedes any piping arrangements or
components shown on this drawing.

To/From

Radiant Floor,

Radiator,

Baseboard,

or Fan Coil

Heating System

HC

See drawings in section 3 for Source connections

03Oct07

Note 3

Direct

Water Heater

HC

Exp

Ta nk

Note 2

Air Vent

Plate Heat
Exchanger

Secondary

Pump

50YEW

Unit

Source HX

(coaxial)

Load HX

(brz plt)

INOUTIN OUTOUT

HTG DHW

M

DHW

IN

HTG

P. R. V .

Thermistor

Note 2

Part II: Load Side Design / System Design & Selection

14

Water-to-Water System Design Guide

Bryant: Whatever It Takes.

CAUTION:

Maximum leaving water temperature of the 50YEW series
equipment is 145°F [63°C]. For domestic hot water tank
temperatures or heating buffer tank temperatures above 130°F
[54°C], pump and pipe sizing is critical to insure that the fl ow
rate through the heat pump is suffi cient to maintain leaving water
temperatures below the maximum temperature, and to provide
water fl ow rates within the ranges shown in the performance
section of this manual.

SWEP INTERNATIONAL

v.1.5.6 SWEP North America, Inc.

3483 Satellite Blvd., Suite 210

Duluth, GA 30096

SWEP SSP CBE

HEAT EXCHANGER: B10Tx30H/1P (1” fittings)
SINGLE PHASE - Rating

7002PES41:etaDelpmaxE:remotsuC

WHDrofXHyradnoces)zH06(010WE50Y:ecnerefeR

2EDIS1EDISSTNEMERIUQERYTUD

)%0.02(retaW-locylGenelyporP1ediSdiulF

retaW2ediSdiulF

]76.15[00.521]76.16[00.341:]C°[F°erutarepmettelnI
]40.65[78.231]22.75[00.531:]C°[F°erutarepmetteltuO

]34.54[00.21]34.54[00.21:]m/l[mpgSUetarwolF

:porderusserp.xaM

287.0597.0:UTNhtgnellamrehT

PHYSICAL PROPERTIES

]68.35[49.821]44.95[00.931:]C°[F°erutarepmetecnerefeR

415.0477.0:PcytisocsivcimanyD

694.0718.0:Pcllaw-ytisocsivcimanyD

75.1674.26:tfuc/blytisneD

1999.09969.0:F°,bl/utByticapactaehcificepS

4473.06503.0:F°,h,tf/utBytivitcudnoclamrehT

PLATE HEAT EXCHANGER

]27631[05664:]W[h/utBdaoltaeH

m[tfrqsaerarefsnarttaehlatoT

2

] : 9.34 [0.868]

5994:tfrqs/h/utBxulftaeH
Log mean temperature difference °F [°C] : 10.06 [5.59]
Overall H.T.C. (available/required) Btu/sqrft,h,°F : 950/496

]85.11[86.1]71.11[26.1:]aPk[isplatot-sporderusserP
]23.1[191.0]43.1[491.0:]aPk[ispstropni-

549.0549.0:niretemaidtroP

4151:slennahcforebmuN

03:setalpforebmuN

19:%gnicafrusrevO

100.0:utB/F°,h,tfrqsrotcafgniluoF

Note:

Disclaimer: Data used in this calculation is subject to change without notice. "SWEP may have patents, trademarks, copyrightsor otherintellectual property rights
covering subject matter in this document." "Except as expressly provided in any writtenlicense agreementfrom SWEP," "the furnishing of thisdocument does not give
you any license to these patents, trademarks, copyrights, or other intellectual property."

Sized to
deliver
130°F
[54°C]
at the
DHW
tank.

DHW tank

Heat Pump

DATE 14SEP07 PAGE 1 OF1

Part II: Load Side Design / System Design & Selection

Bryant Geothermal Heat Pump Systems

15

Water-to-Water System Design Guide

Figure 2-5: Example Secondary Heat Exchanger Sizing

Drawing 2-3 – 50YEW Typical Load Piping / No DHW Heating
or Separate DHW System / No Cooling or Separate Cooling
System: System #3 uses one or more water-to-water units
and a buffer tank for each unit. Drawing 2-3 shows a typical
piping arrangement for this system. A thermistor mounted in
an immersion well senses tank temperature, which allows the
internal controls (50YEW units only) to engage the water-to-water
unit compressor, load pump and source pump(s) when the tank
temperature drops below the set point, typically 120°F [49°C] or
less. The radiant fl oor (or baseboard, radiator, fan coil, etc.) system
therefore is completely isolated from the water-to-water unit.
The controls for the hydronic distribution system energize pumps
and/or zone valves to allow heated water in the buffer tank to fl ow
through the heating distribution system. Potable water is heated
with a separate system. If desired, cooling is accomplished with a
separate system.

Heating

Buffer Tank

NOTES:

1. Place air vent at the highest point in the system. If
internal expansion tanks are installed, only an air
vent is required.

2. Thermistor should be installed in an immersion well.

Locate thermistor in the bottom half of the tank.

3. If DHW option is not used, DHW supply connection MUST
be plugged.

4. If electric water heat is used instead of buffer tank, see
drawing 2-7.

5. P/T (pressure/temperature) ports are internal for
50YEW units on load and source connections.

6. Other components (additional ball valves, unions, etc.)
may be required for ease of service. This drawing
shows only minimum requirements. Your specific
installation will dictate final component selections.

7. Buffer tank must be approved as a heating vessel.

8. Local code supercedes any piping arrangements or
components shown on this drawing.

To/From

Radiant Floor,

Radiator,

Baseboard,

or Fan Coil

Heating System

HC

See drawings in section 3 for Source connections

03Oct07

Note 4

50YEW

Unit

Source HX

(coaxial)

Load HX
(brz plt)

INOUT

OUT

OUT
HTG

DHW

M

IN

HTG

IN

DHW

Exp

Tank

Air Vent

Note 1

Note 3

P. R. V .

Cold Water Supply

Thermistor

Note 2

Drawing 2-3: 50YEW Typical Load Piping ­No DHW Heating or Separate DHW System / No
Cooling or Separate Cooling System

Part II: Load Side Design / System Design & Selection

16

Water-to-Water System Design Guide

Bryant: Whatever It Takes.

Drawing 2-4 – 50PSW/GSW Typical Load Piping / No DHW
Heating or Separate DHW System / No Cooling or Separate
Cooling System: System #4 uses one or more water-to-water
units and a buffer tank for each unit. Drawing 2-4 shows a typical
piping arrangement for this system. A thermistor mounted in an
immersion well senses tank temperature, which allows the water­to-water unit to engage the compressor, load pump and source
pump(s) when the tank temperature drops below the set point,
typically 120°F [49°C] or less. The radiant fl oor (or baseboard,
radiator, fan coil, etc.) system therefore is completely isolated from
the water-to-water unit. The controls for the hydronic distribution
system energize pumps and/or zone valves to allow heated water
in the buffer tank to fl ow through the heating distribution system.
Potable water is heated with a separate system. If desired, cooling
is accomplished with a separate system.

Heating

Buffer Tank

NOTES:

1. Place air vent at the highest point in the system.

2. Aqua-stat should be installed in an immersion well.

Locate aqua-stat in the bottom half of the tank.

3. If electric water heat is used instead of buffer tank, see
drawing 2-7.

4. Other components (additional ball valves, unions, etc.)
may be required for ease of service. This drawing
shows only minimum requirements. Your specific
installation will dictate final component selections.

5. Buffer tank must be approved as a heating vessel.

6. Local code supercedes any piping arrangements or
components shown on this drawing.

To/From

Radiant Floor

HC

See drawings in section 3 for Source connections

03Oct07

Notes 2,3

50PSW

or GSW

Unit

Source HX

(coaxial)

Load HX

(coaxial)

INOUTOUTIN

Exp

Tank

Air Vent

Note 1

P. R. V .

Cold Water Supply

P/T port (50PSW / GSW units only)

Aqua-stat

Drawing 2-4: 50PSW / GSW Typical Load Piping ­No DHW Heating or Separate DHW System / No
Cooling or Separate Cooling System

Part II: Load Side Design / System Design & Selection

Bryant Geothermal Heat Pump Systems

17

Water-to-Water System Design Guide

Drawing 2-5 – 50PSW/GSW Typical Load Piping - Chilled Water
Cooling System / Separate Heating & Cooling Buffer Tanks / No
DHW Heating or Separate DHW System: System #5 uses one
or more water-to-water units and two buffer tanks, one for heated
water, and one for chilled water. Drawing 2-5 shows a typical
piping arrangement for this system. An aqua-stat (well-mounted if
possible) in each tank senses tank temperature, which allows the
water-to-water unit to engage the compressor, load pump and
source pump(s) when the heating tank temperature drops below
the set point [typically 120°F [49°C] or less], or when the chilled
water tank temperature rises above the set point (typically 45­50°F [7-10°C]). The radiant fl oor (or baseboard, radiator, fan coil,
etc.) heating system and the chilled water cooling system (typically

Drawing 2-5: 50PSW / GSW Typical Load Piping ­Chilled Water Cooling System / Separate Heating
and Cooling Buffer Tanks - No DHW Heating or
Separate DHW System

Chilled Water

Buffer Tank

NOTES:

1. Place air vent at the highest point in the system.

2. Aqua-stat should be installed in an immersion well.

Locate aqua-stat in the bottom half of the tank.

3. If electric water heat is used instead of buffer tank, see
drawing 2-7.

4. Motorized valve to be activated by unit RV solenoid
coil (24VAC).

5. Chilled water tank must be insulated to avoid condensation.

6. Other components (additional ball valves, unions, etc.)
may be required for ease of service. This drawing
shows only minimum requirements. Your specific
installation will dictate final component selections.

7. Buffer tank must be approved as a heating vessel.

8. Local code supercedes any piping arrangements or
components shown on this drawing.

To/From

Radiant Floor

HC

See drawings in section 3 for Source connections

03Oct07

50PSW

or GSW

Unit

Source HX

(coaxial)

Load HX
(coaxial)

INOUTOUTIN

Exp

Ta nk

Air Vent

Note 1

Heating

Buffer Tank

HC

To/From

Fan Coil Units

M

Notes 2,3

Note 4

Notes 2,3,5

Cold Water Supply

P. R. V .

P/T port (50PSW / GSW units only)

Aqua-stat

Aqua-stat

Note 2

Note 2

fan coil units) therefore are completely isolated from the water­to-water unit. The controls for the hydronic distribution system
energize pumps and/or zone valves to allow heated/chilled water
in the buffer tanks to fl ow through the heating/cooling distribution
systems. The motorized valve is used to switch between the
two tanks based upon heating or cooling season. Due to the
complexity of the controls, a manual seasonal changeover switch is
the best way to determine heated or chilled water operation. The
switch (typically a light switch) switches the unit reversing valve and
motorized valve. A reversible unit is required for this application
(50YEW is heating only – 50PSW/GSW units are reversible).
Potable water is heated with a separate system.

Part II: Load Side Design / System Design & Selection

18

Water-to-Water System Design Guide

Bryant: Whatever It Takes.

Drawing 2-6 – 50PSW/GSW Typical Load Piping - Chilled Water
Cooling / Single Buffer Tank / No DHW Heating or Separate
DHW System: System #6 uses one or more water-to-water
units and a buffer tank for each unit. Drawing 2-6 shows a
typical piping arrangement for this system. Two aqua-stats (well­mounted if possible) sense tank temperature, one for heating and
one for cooling, which allows the water-to-water unit to engage
the compressor, load pump and source pump(s) when the tank
temperature drops below the set point (typically 120°F [49°C]
or less] in the heating mode, or when the tank temperature rises
above the set point [typically 45-50°F [7-10°C]) in the cooling
mode. The radiant fl oor (or baseboard, radiator, fan coil, etc.)
heating system and the chilled water cooling system (typically
fan coil units) therefore are completely isolated from the water­to-water unit. The controls for the hydronic distribution system
energize pumps and/or zone valves to allow heated/chilled water

in the buffer tank to fl ow through the heating/cooling distribution
systems. The motorized valves are used to switch between the
two distribution systems (and aqua-stats) based upon heating or
cooling season. Due to the complexity of the controls, a manual
seasonal changeover switch is the best way to determine heated
or chilled water operation. The switch (typically a light switch)
switches the unit reversing valve, motorized valves, and aqua-stats
(additional relays are required for determining heating/cooling
logic). A reversible unit is required for this application (50YEW
is heating only – 50PSW/GSW units are reversible). When using
one tank for both heated and chilled water, a buffer tank (not an
electric water heater) is recommended, since water heaters do not
have enough connections to facilitate all of the water connections
and the two well-mounted aqua-stats. Potable water is heated
with a separate system.

NOTES:

1. Motorized valves to be activated by unit RV solenoid
coil (24VAC).

2. Aqua-stat should be installed in an immersion well.

Locate heating aqua-stat in the bottom half of the tank.

Locate cooling aqua-stat in the top half of the tank.

3. Chilled water tank must be insulated to avoid condensation.

4. Place air vent at the highest point in the system.

5. Other components (additional ball valves, unions, etc.)
may be required for ease of service. This drawing
shows only minimum requirements. Your specific
installation will dictate final component selections.

6. Buffer tank must be approved as a heating vessel.

7. Local code supercedes any piping arrangements or
components shown on this drawing.

Heating / Chilling

Buffer Tank

To/ Fro m

Radiant Floor

HC

See drawings in section 3 for Source connections

03Oct07

Notes 2,3

50PSW

or GSW

Unit

Source HX

(coaxial)

Load HX
(coaxial)

INOUTOUTIN

Exp

Tank

Air Vent

Note 4

M

Note 1

To/ Fro m

Fan Coil Units

P. R. V .

Cold Water Supply

P/T port (50PSW / GSW only)

Aqua-stat

Aqua-stat

Cooling

Heating

Drawing 2-6: 50PSW / GSW Typical Load Piping ­Chilled Water Cooling System / Single Buffer Tank

- No DHW Heating or Separate DHW System

Part II: Load Side Design / System Design & Selection

Bryant Geothermal Heat Pump Systems

19

Water-to-Water System Design Guide

Drawing 2-7 – Alternate Buffer Tank (Electric Water Heater)
Typical Piping: A “true” buffer tank is the best approach for control
of a hydronic system using a heat pump. Tanks are usually well
insulated, and there are typically a number of water connections
(6 or more in many cases), so that plumbing is easier and water
fl ows are not restricted. However, due to the cost of buffer tanks,
some installers use an electric water heater for the buffer tank. An
electric water heater is much less expensive, but may not have
enough water connections, and may require external installation.
Drawing 2-7 may be used as an alternate piping schematic for
drawings 2-1 through 2-5 when an electric water heater is used.
Drawing 2-6 requires a buffer tank due to the need for two aqua­stats. If a water heater is used, it must be approved as a heating
vessel (A.S.M.E. approval in the U.S.).

Drawing 2-7: Alternate Buffer Tank (Electric
Water Heater) Typical Piping

Part II: Load Side Design / System Design & Selection

Electric

Water Heater

NOTES:

1. Not all components shown (expansion tank, air vent, etc.).
Drawing is for buffer tank connections only.

2. Pump not needed for 50YEW unit with internal load pump option.

3. Thermistor or aqua-stat should be installed in an immersion
well. If water heater does not have well, one of the
heating elements should be removed, and a well adapter

4. Other components (additional ball valves, unions, etc.)
may be required for ease of service. This drawing
shows only minimum requirements. Your specific
installation will dictate final component selections.

5. Buffer tank must be approved as a heating vessel.

6. Local code supercedes any piping arrangements or
components shown on this drawing.

HC

Thermistor or Aqua-stat

Note 3

03Oct07

Note 3

Radiant

Floor

System

From Water-to-Water Unit

Note 1

Notes 1,2

To Water-to-Water Unit

(ASME Approved)

should be installed. Locate thermistor/aqua-stat in the
bottom half of the tank.