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D E S I G N
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G U I D E
HWAT-Plus System
Design Guide
Contents
Introduction
4
How to use this design guide
6
System description
Application information
7
Design steps
Plumbing design sheet instructions
8
Design Sheet A: Plumbing Design
9
Electrical design sheet instructions
10
Design Sheet B: Electrical Design
11
60-bed nursing home
12
250-bed medium-security prison
14
35-story apartment building
16
500-room hotel
18
Specification
CSI Model Specification
20
Installation
Installation details
22
Design examples
3
HWAT-Plus System
Design Guide
Introduction
This manual presents Raychem’s
recommendations for designing an
HWAT-Plus hot water temperature
maintenance system. Following these
guidelines will result in a reliable,
efficient system. For information
regarding other Raychem heat-tracing
applications, consult your Raychem
representative.
4
HWAT-Plus System
Design Guide
Introduction
Scope
The design information provided is
applicable to the majority of domestic
hot water temperature maintenance
applications, but certain conditions
apply. The heater must be installed
on copper tubes beneath fiberglass
insulation. It must be powered at
208 volts, and the design must fall
within the temperature requirements for one of the typical applications outlined below:
Typical application
Ambient
temperature
Nominal pipe
temperature
Hospitals, nursing
homes
Schools, prisons, some
hospitals
General domestic
(e.g., offices, hotels,
apartments)
Kitchens, laundries
74°F to 79°F (23°C to 26°C)
105°F (40°C)
70°F to 78°F (21°C to 26°C)
115°F (45°C)
70°F to 78°F (21°C to 26°C)
125°F (50°C)
70°F to 78°F (21°C to 26°C)
140°F (60°C)
Pipe temperatures indicated are nominal, and variations will occur. If any of
the following conditions exist, consult
your Raychem representative:
• different nominal pipe temperature
• insulation is not fiberglass
• insulation differs from Plumbing
Design Sheet, Step 6
• ambient temperature range is not as
indicated or may change seasonally
• voltage is different
These nonstandard applications can
be handled with factory assistance.
Approvals and Code Compliance
• UL System Listing
• BOCA
• Uniform Plumbing Code
• National Standard Plumbing Code
• Southern Building Code Congress
• National Electrical Code
Additionally, the HWAT-Plus system is
approved by numerous other state
and local codes and approval agencies. Contact your Raychem representative for more information.
5
HWAT-Plus System
Design Guide
How to use this design
guide
General
Recommended Procedure
This manual provides instructions for
all engineering disciplines involved in
the design of an HWAT-Plus system.
For clarity, the procedure has been
divided into plumbing design and
electrical design. This design guide
provides design and performance
data, recommended design steps,
sample design sheets, and examples
that show typical designs.
1. System description (page 7).
Review the system illustrations to
understand how a typical HWAT-Plus
system operates.
2. Design steps (pages 8 - 11).
Review the design steps to gain a
general understanding of the design
principles.
3. Design examples (pages 12 - 18).
Study the design example which is
similar to your project. Use the
example to gain understanding of the
best design approach for your project.
4. Design sheets (pages 9, 11).
Using the design steps as a guide, fill
in the design sheets located in this
manual. Copies of the original design
sheet may be made for large projects
or for multiple project use.
5. Specification (pages 20, 21).
Use the enclosed sample specification
to specify the HWAT-Plus system you
have designed.
6. Installation details (pages 22, 23).
Include the typical installation details
on your drawings.
6
HWAT-Plus System
Design Guide
System description
The HWAT-Plus system provides temperature maintenance of domestic hot
water lines by tracing the supply pipes
with the HWAT-Plus heating cable.
Because the water in the supply pipe
is directly maintained at temperature,
return lines, pumps, and balancing
valves are all unnecessary. The selfregulating electric heating cable
replaces the small amount of heat
which pipes lose to the environment
through the thermal insulation. The
heating cable automatically compensates for temperature variations. By
changing its power output in response
to the pipe temperature, the HWATPlus heating cable will produce more
power where needed and compensate
for temperature differences
automatically.
Heating cable and glass tape
“Electric traced” label
End seal
Heating cable splice
Heating cable tee
HWATTM
Note:
Pipe insulation shown is incomplete.
Required items not supplied by
Raychem:
• Fiberglass pipe insulation
• 30-mA trip ground-fault protection
device
Power connection
7
HWAT-Plus System
Design Guide
Plumbing design sheet
instructions
Note:
Follow these design steps when filling in copies of the adjacent design sheet.
The design sheet shown on page 9 is
available in tablet form. Contact your
Raychem representative.
1.
Select the appropriate HWAT-Plus heating cable for your application. Verify that
ambient temperatures will be in the range indicated.
Pipe temperatures indicated are nominal, and variations will occur. If the
application requirements are not as indicated, consult your Raychem
representative.
2.
Obtain from the electrical department the maximum available 208-V circuit
breaker size: 15, 20, or 30 amps.
3.
Determine the maximum circuit length. Maximum circuit lengths are based on
system start-up at minimum 60°F (15°C) water temperature.
4.
Lay out the circuits in segments (floors, risers, zones, wings, etc.), staying within
the maximum circuit length. Identify each circuit and measure the circuit length.
See examples on pages 12-19 for additional circuit layout advice.
Note on the drawings the pipes to be traced, and show the circuits using the
following symbols (include circuit no. within symbol):
3
Circuit continued on another sheet
3
End of circuit
Hot water supply pipe traced with HWAT-Plus heating cable
3
Power connection
5.
Provide equipment to allow for thermal expansion in all closed sections of piping
downstream of check or pressure-reducing valves. For example, in a high-rise
building use an expansion tank or pressure relief valve at each pressure zone.
6.
Specify the correct thicknesses and diameters of fiberglass insulation for each
copper pipe size. Pipe sizes up to 11/4 inch require insulation that is oversized
in diameter by 1/4 inch to allow for installation over the heating cable. For
example, a 1-inch diameter pipe requires 1-inch thick insulation, with a 11/4-inch
inside diameter.
7.
Include clauses in the project specification to provide, install, and test the
HWAT-Plus system. State the appropriate insulation thicknesses. A CSI format
specification is located on page 20.
8.
8
Transmit copies of the plumbing design sheets to the electrical engineer.
HWAT-Plus System
Design Sheet
R
Project name:
Part A:
Plumbing Design
Project No.:
Prepared by:
Area of building:
Checked by:
1. Select the HWAT-Plus heating cable for the application.
Date:
Page no.
of
Application
Ambient
temperature
Nominal pipe
temperature
Heating
cable type
Hospitals, nursing homes
Schools, prisons, some hospitals
General domestic (offices, hotels)
Kitchens, laundries
74°F to 79°F
70°F to 78°F
70°F to 78°F
70°F to 78°F
105°F (40°C)
115°F (45°C)
125°F (50°C)
140°F (60°C)
HWAT-B2
HWAT-G2
HWAT-Y2
HWAT-R2
Use HWAT-
2. Maximum 208-V circuit
breaker size:
15 amp
20 amp
30 amp
Maximum circuit
3. Determine the maximum
circuit length.
Maximum circuit length in feet (meters)
4. Lay out the HWAT-Plus
circuits. Identify and
measure each circuit.
5. Provide for thermal
expansion.
6. Specify the following
thicknesses of fiberglass
insulation:
breaker:
Circuit HWAT-B2
Breaker
HWAT-G2 HWAT-Y2
HWAT-R2
30 amp
20 amp
15 amp
800 (240)
700 (210)
520 (155)
500 (150)
330 (120)
250 (75)
800 (240)
800 (240)
800 (240)
A
Maximum circuit
length:
800 (240)
500 (150)
350 (105)
Circuit Heating
Risers, zones
Drwg. Approx.
no.
cable type or floors served no.
length
Equipment to allow for thermal expansion should be
provided in all closed sections of piping downstream of
check or pressure-reducing valves.
Pipe size
(inches)
Fiberglass insulation
thickness (inches)
1⁄ " - 1"
2
11⁄4" - 2"
21⁄2" - 6"
1"
11⁄2"
2"
Transmit this table to
the electrical engineer.
Provide
in pipe sections
Note: for pipe sizes 11/4" and smaller, use 1/4" larger diameter insulation to allow room for
installation over cable.
7. Include clauses in the project specification to provide, install, and test the HWAT-Plus
system. State appropriate fiberglass insulation thicknesses.
9
HWAT-Plus System
Design Guide
Electrical design sheet
instructions
Note:
Follow these design steps when filling in copies of the adjacent electrical design
sheet.
The design sheet shown on page 11
is available in tablet form. Contact
your Raychem representative.
1.
Based on the information on the plumbing design sheets, note the HWAT-Plus
cable type and fill in the electrical design table. Use Table 1 to determine
breaker size and steady-state current draw. Choose the smallest circuit breaker
size which can accommodate the circuit length.
Junction box and panel locations should be based on circuit layouts provided by
the plumbing engineer.
If desired, steady-state current may be calculated to determine transformer
sizing. Please note that the steady-state current table chart is used to estimate
steady-state current only. Current draw at start-up on a cold pipe will be higher.
The HWAT-Plus system design is based on operation at 208 volts. If different
conditions occur, consult the factory for assistance.
2.
Include the finished table on the electrical drawings.
3.
Call out 30-mA ground-fault protection device in Division 16 of the specification
and on the drawings. These ground fault breakers are a system requirement.
Suitable circuit breakers are available from Westinghouse (types QPGFEP and
QBGFEP) and Square D (types QOEPD and QOBEPD).
10
HWAT-Plus System
Design Sheet
R
Project name:
Part B:
Electrical Design
Project No.:
Prepared by:
Area of building:
Checked by:
1. Fill in the electrical design table below, using the information provided on the plumbing
design sheet.
Date:
Page no.
of
Electrical Design Table
HWAT-Plus cable type:
Circuit Approx. Voltage Breaker
no.
length
Ground
fault
protection
208
30 mA
208
30 mA
208
30 mA
208
30 mA
208
30 mA
Size
(Table 1)
Steadystate
current
(Table 1)
J-box
Panel
location
no.
for power
connection
Include the electrical
design table in the
electrical drawings.
Table 1
Heating
cable type
Circuit length
in feet (meters)
Circuit
breaker*
Steady-state
current draw
HWAT-B2
800 (240)
15 amp
.006 amp / ft @ 105°F
800 (240)
20 amp
(.020 amp / m @ 40°C)
800 (240)
30 amp
520 (155)
15 amp
.008 amp / ft @ 115°F
700 (210)
20 amp
(.026 amp / m @ 45°C)
HWAT-G2
HWAT-Y2
HWAT-R2
800 (240)
30 amp
350 (105)
15 amp
.010 amp / ft @ 125°F
500 (150)
20 amp
(.033 amp / m @ 50°C)
800 (240)
30 amp
250
(75)
15 amp
.015 amp / ft @ 140°F
330 (100)
20 amp
(.049 amp / m @ 60°C)
500 (150)
30 amp
2. Include the finished electrical design
table on the electrical drawings.
*Use a ground-fault protection device
with a nominal 30-mA trip level in each
circuit.
3. Call out 30-mA ground-fault protection
device in Division 16 of the specification
and on the drawings.
11
HWAT-Plus System
Design Guide
Design example:
60-bed nursing home*
*Design example has been simplified for clarity.
The Decision
The plumbing engineer was laying out
the piping for the domestic hot water
system for St. Mary’s Nursing Home, a
three-story, sixty-bed, long-term health
care facility. The engineer did not
believe it necessary to recirculate the
risers and was going to run two recirculation loops, one for each wing, in
the ground floor ceiling space. However, the engineer decided that the
return lines would have to take the
same route as the supply lines. In this
situation, the engineer knew the
HWAT-Plus system would provide the
more economical design. Furthermore, the client had indicated the
possibility of extending either wing at
some time in the future. The engineer
knew that by using HWAT-Plus
products, the system could be easily
expanded if and when the client decided to do so.
Plumbing Design
The plumbing engineer began to fill in
an “HWAT-Plus System Design Sheet,
Part A: Plumbing Design.” The nursing
home required a nominal temperature
of 105°F, and HWAT-B2 was chosen.
The engineer thought it would be
useful to be able to isolate either wing
for maintenance, so it was decided to
run two separate circuits. Using 15amp circuit breakers, a maximum
circuit length of 800 feet could be run,
which was sufficient for either wing.
Alternatively, just one circuit could
have been run, with a tee connection
at the intersection of the pipes from
the two wings. The plumbing engineer
filled in the table on the design sheet
and handed it over to the electrical
engineer.
HWAT-Plus System
Design Sheet
R
Refer to the HWAT-Plus Design Guide for complete design instructions.
Project name:
Area of building:
St. Mary's Nursing Home
All
Project No.:
E10
Prepared by:
Checked by:
Date:
1. Select the HWAT-Plus heating cable for the application.
DG
KC
11/4/90
80
Page no. 23 of
Application
Ambient
temperature
Nominal pipe
temperature
Heating
cable type
Hospitals, nursing homes
Schools, prisons, some hospitals
General domestic (offices, hotels)
Kitchens, laundries
74°F to 79°F
70°F to 78°F
70°F to 78°F
70°F to 78°F
105°F (40°C)
115°F (45°C)
125°F (50°C)
140°F (60°C)
HWAT-B2
HWAT-G2
HWAT-Y2
HWAT-R2
Use HWAT-
15 amp
20 amp
30 amp
Maximum circuit
2. Maximum 208-V circuit
breaker size:
3. Determine the maximum
circuit length.
4. Lay out the HWAT-Plus
circuits. Identify and
measure each circuit.
breaker:
B2
15
A
Maximum circuit length in feet (meters)
Circuit HWAT-B2
breaker
HWAT-G2 HWAT-Y2
HWAT-R2
30 amp
20 amp
15 amp
800 (240)
700 (210)
520 (155)
500 (150)
330 (120)
250 (75)
800 (240)
800 (240)
800 (240)
800 (240)
500 (150)
350 (105)
Circuit Heating
Risers, zones,
Drwg. Approx.
no.
cable type or floors served no.
length
1
2
See reverse to make
additional Circuit Design
Table entries.
B2
B2
EW Wing
NS Wing
13
13
280'
180'
5. Provide for thermal
expansion.
Equipment to allow for thermal expansion should be
provided in all closed sections of piping downstream of
check or pressure-reducing valves.
6. Specify the following
thicknesses of fiberglass
insulation:
Pipe size
(inches)
Fiberglass insulation
thickness (inches)
1⁄2"
1"
- 1"
11⁄4" - 2"
11⁄2"
21⁄2" - 6"
2"
Maximum circuit
length:
800 ft
Transmit this table to
the electrical engineer.
Check here if additional circuits are listed on
reverse.
Provide
in pipe sections
Note: for pipe sizes 11/4" and smaller, use 1/4" larger diameter insulation to allow room for
installation over cable.
7. Include clauses in the project specification to provide, install, and test the HWAT-Plus
system. State appropriate fiberglass insulation thicknesses.
Completed HWAT-Plus System
Design Sheet, Part A: Plumbing
Design
The plumbing engineer noted the
pipes to be traced with HWAT-Plus
heating cables on the drawings. He
then inserted the standard clauses to
provide, install and test the HWATPlus system, and called out the correct thicknesses of fiberglass insulation, in Division 15 of the specification.
12
Part A:
Plumbing Design
Isometric of building
HWAT-Plus System
Design Guide
Design example:
60-bed nursing home*
*Design example has been simplified for clarity.
Electrical Design
Upon receiving the HWAT-Plus
Plumbing Design Sheet, the electrical
engineer took out an “HWAT-Plus
System Design Sheet, Part B:
Electrical Design.” In the electrical
drawings, junction boxes were located
near each power connection. It was
decided to power both circuits from
the same panel. Circuit breaker sizes
and steady-state current were
calculated and included on a table in
the electrical drawings. The need for a
ground-fault protection device in each
circuit was noted on the electrical
drawings.
HWAT-Plus System
Design Sheet
R
Part B:
Electrical Design
Refer to the HWAT-Plus Design Guide for complete design instructions.
Project name:
Area of building:
St. Mary's Nursing Home
All
Project No.:
E10
Prepared by:
Checked by:
Date:
1. Fill in the electrical design table below, using the information provided on the plumbing
design sheet.
BW
JJ
11/5/90
83
Page no. 13 of
Electrical Design Table
HWAT-Plus cable type:
HWAT-B2
Circuit Approx. Voltage Breaker
no.
length
Groundfault
protection
1
2
280'
180'
208
30 mA
208
30 mA
208
30 mA
208
30 mA
208
30 mA
Size
(Table 1)
15
15
Steadystate
current
(Table 1)
1.7 A
1 A
J-box
Panel
location
no.
for power
connection
J-17
J-21
Include the electrical
design table in the
electrical drawings.
Check here if additional circuits are listed on
reverse.
P-3
P-3
Completed See
HWAT-Plus
System
reverse for additional
circuit entries
Design Sheet, Part B: Electrical
Design
2
1
H
1
PLAN OF GROUND FLOOR HOT WATER PIPING
NOTE
LEGEND
1
1
H
Beginning and end of HWATPlus heat-tracing circuit
2
All heat-tracing
cable to be HWAT-B2
Water heater
Riser up
HWAT-Plus heat-tracing layout
shown on plumbing drawing
13
HWAT-Plus System
Design Guide
Design example:
250-bed, mediumsecurity prison*
*Design example has been simplified for clarity.
The Decision
Reviewing the architectural drawings,
the plumbing engineer observed that
the design consisted of about a dozen
two-story “pods” arranged around an
expanse of open space. For security
reasons, the County had requested
that mechanical equipment and piping,
and the associated pipe openings, be
kept to an absolute minimum. The
layout of the cells in each pod did not
allow any “shortcut” for return piping
for a recirculation loop; it would have
to follow the same corridor as the
supply piping. The plumbing engineer
knew from experience that in these
kinds of situations, the HWAT-Plus
system would be more economical
than recirculation.
Plumbing Design
For the prison application, HWAT-G2
was selected to maintain nominal temperature of 115°F. Each pod would be
provided with a separate water heater
and it was not considered necessary
to heat trace the risers. Upon measuring the length of the ground floor
piping, the plumbing engineer found it
was possible to trace the entire piping
in each pod with a single HWAT-G2
circuit and stay within the capacity of a
15-amp ground-fault circuit breaker.
This would allow the heating cable to
be conveniently powered from the
electrical panel in the mechanical
room. The plumbing engineer decided
that the situation was sufficiently simple to ignore marking on the plumbing
drawing the lines to be heat traced.
Instead, the extent of the heat tracing
could be called out in the notes. The
plumbing engineer filled in the table on
the design sheet and faxed it to the
electrical engineer.
The plumbing engineer then inserted
the standard clauses to provide,
install, and test the HWAT-Plus system, and called out the correct thicknesses of fiberglass insulation, in
Division 15 of the specification.
14
HWAT-Plus System
Design Sheet
R
Part A:
Plumbing Design
Refer to the HWAT-Plus Design Guide for complete design instructions.
Project name:
Area of building:
Sherwood County Prison
Typical Pod
Project No.:
C-15
Prepared by:
Checked by:
Date:
1. Select the HWAT-Plus heating cable for the application.
MW
AJ
4/30/91
34
Page no. 12 of
Application
Ambient
temperature
Nominal pipe
temperature
Heating
cable type
Hospitals, nursing homes
Schools, prisons, some hospitals
General domestic (offices, hotels)
Kitchens, laundries
74°F to 79°F
70°F to 78°F
70°F to 78°F
70°F to 78°F
105°F (40°C)
115°F (45°C)
125°F (50°C)
140°F (60°C)
HWAT-B2
HWAT-G2
HWAT-Y2
HWAT-R2
Use HWAT-
15 amp
20 amp
30 amp
Maximum circuit
2. Maximum 208-V circuit
breaker size:
3. Determine the maximum
circuit length.
4. Lay out the HWAT-Plus
circuits. Identify and
measure each circuit.
breaker:
HWAT-G2 HWAT-Y2
HWAT-R2
30 amp
20 amp
15 amp
800 (240)
700 (210)
520 (155)
500 (150)
330 (120)
250 (75)
800 (240)
800 (240)
800 (240)
A
G2
All h.w.
piping
P5
270'
Equipment to allow for thermal expansion should be
provided in all closed sections of piping downstream of
check or pressure-reducing valves.
Pipe size
(inches)
Fiberglass insulation
thickness (inches)
1⁄2"
1"
- 1"
11⁄4" - 2"
11⁄2"
21⁄2" - 6"
2"
Maximum circuit
length:
800 (240)
500 (150)
350 (105)
Circuit Heating
Risers, zones,
Drwg. Approx.
no.
cable type or floors served no.
length
1
6. Specify the following
thicknesses of fiberglass
insulation:
15
Maximum circuit length in feet (meters)
Circuit HWAT-B2
breaker
See reverse to make
additional Circuit Design
Table entries.
5. Provide for thermal
expansion.
G2
520 ft
Transmit this table to
the electrical engineer.
Check here if additional circuits are listed on
reverse.
Provide
None required
in pipe sections
Note: for pipe sizes 11/4" and smaller, use 1/4" larger diameter insulation to allow room for
installation over cable.
7. Include clauses in the project specification to provide, install, and test the HWAT-Plus
system. State appropriate fiberglass insulation thicknesses.
Completed HWAT-Plus System
Design Sheet, Part A: Plumbing
Design
HWAT-Plus System
Design Guide
Design example:
250-bed, mediumsecurity prison*
*Design example has been simplified for clarity.
Electrical Design
The electrical engineer took out the
“HWAT-Plus System Design Sheet,
Part B: Electrical Design” and filled in
the table from the data on the plumbing engineer’s transmittal.The electrical engineer confirmed that a 15-amp
breaker was adequate, and calculated
the steady-state current. A junction
box was located adjacent to the beginning of the heating cable circuit, and
its number and the number of the
electrical panel in the table were
noted. A draftsperson copied the table
onto the electrical drawings, along
with a note calling out the need for a
ground-fault protection device in each
circuit.
HWAT-Plus System
Design Sheet
R
Part B:
Electrical Design
Refer to the HWAT-Plus Design Guide for complete design instructions.
Project name:
Area of building:
Sherwood County Prison
Typical Pod
Project No.:
C-15
Prepared by:
Checked by:
1. Fill in the electrical design table below, using the information provided on the plumbing
design sheet.
Date:
HB
BF
5/4/1
40
Page no. 14 of
Electrical Design Table
HWAT-Plus cable type:
HWAT-G2
Circuit Approx. Voltage Breaker
no.
length
Groundfault
protection
1
270'
208
30 mA
208
30 mA
208
30 mA
208
30 mA
208
30 mA
Size
(Table 1)
15 A
Steadystate
current
(Table 1)
2.2 A
J-box
Panel
location
no.
for power
connection
A-5
Include the electrical
design table in the
electrical drawings.
Check here if additional circuits are listed on
reverse.
P-1
Completed See
HWAT-Plus
System
reverse for additional
circuit entries
Design Sheet, Part B: Electrical
Design
H
LEGEND
H
Water
heater
Riser up
HW supply
piping
NOTE
Heat-trace all HW
distribution piping with
HWAT-G2 heating cable.
Do not trace branches or
risers.
Ground floor hot water piping
diagram
15
HWAT-Plus System
Design Guide
Design example:
35-story apartment
building*
*Design example has been simplified for clarity.
horizontal supply and return lines necessary in each zone, given the very
limited space provided above the
dropped ceilings. And there was not
any room for the booster heaters and
pumps for the recirculation system.
The Decision
The plumbing engineer was faced with
laying out the hot water piping for the
35-story Washington Towers. The piping was relatively complex, making it
especially important to balance the
system adequately. As requested by
the developer, the architect had
squeezed in the maximum number of
residential floors by working to the
minimum headroom allowed by code.
The plumbing engineer was required
by code to divide the building into
three pressure zones. However, there
would be great difficulty in running the
HWAT-Plus System
Design Sheet
R
The plumbing engineer decided that
an HWAT-Plus system would eliminate the need for horizontal piping and
additional heaters or pumps. The
risers could run continuously from top
to bottom, broken only by pressurereducing valves at the 11th and 23rd
floors. The plumbing engineer noted
that the need for flow balancing was
completely eliminated by using the
HWAT-Plus system.
Plumbing Design
Following the plumbing design sheet,
the plumbing engineer selected
HWAT-Y2. Having estimated that a
single circuit length on a 20-amp circuit breaker could run the complete
height of the building, the engineer
marked an HWAT-Plus circuit on each
of the four risers and sent copies of
the plumbing drawing and the design
sheet to the electrical engineer.
Standard clauses to provide, install,
and test the HWAT-Plus system were
included in Division 15 of the specification. To provide pressure relief in
the piping during system startup, an
expansion tank was indicated on each
riser at each PRV.
Part A:
Plumbing Design
H
Refer to the HWAT-Plus Design Guide for complete design instructions.
Project name:
Area of building:
Washington Towers
Block A
Project No.: F21
Prepared by:
Checked by:
Date:
1. Select the HWAT-Plus heating cable for the application.
Page no.
JB
MP
Application
Ambient
temperature
Nominal pipe
temperature
Heating
cable type
Hospitals, nursing homes
Schools, prisons, some hospitals
General domestic (offices, hotels)
Kitchens, laundries
74°F to 79°F
70°F to 78°F
70°F to 78°F
70°F to 78°F
105°F (40°C)
115°F (45°C)
125°F (50°C)
140°F (60°C)
HWAT-B2
HWAT-G2
HWAT-Y2
HWAT-R2
Use HWAT-
15 amp
20 amp
30 amp
Maximum circuit
2. Maximum 208-V circuit
breaker size:
3. Determine the maximum
circuit length.
4. Lay out the HWAT-Plus
circuits. Identify and
measure each circuit.
See reverse to make
additional Circuit Design
Table entries.
5. Provide for thermal
expansion.
6. Specify the following
thicknesses of fiberglass
insulation:
LEGEND
1/10/91
41 of 80
H
breaker:
Water
heater
20
Pressurereducing
valve
A
Maximum circuit length in feet (meters)
Circuit HWAT-B2
breaker
HWAT-G2 HWAT-Y2
HWAT-R2
30 amp
20 amp
15 amp
800 (240)
700 (210)
520 (155)
500 (150)
330 (120)
250 (75)
800 (240)
800 (240)
800 (240)
Circuit Heating
Risers, zones,
Drwg. Approx.
no.
cable type or floors served no.
length
1
P5
2
HWAT-Y2
370'
HWAT-Y2
P5
370'
riser 1
Pipe size
(inches)
Fiberglass insulation
thickness (inches)
1⁄2"
1"
- 1"
11⁄2"
21⁄2" - 6"
2"
Balancing
valve
500 ft
Transmit this table to
the electrical engineer.
Check here if additional circuits are listed on
reverse.
riser 2
Equipment to allow for thermal expansion should be
provided in all closed sections of piping downstream of
check or pressure-reducing valves.
11⁄4" - 2"
Maximum circuit
length:
800 (240)
500 (150)
350 (105)
Provide
Expansion tank
in pipe sections
All risers at
floors 11 and
23
BH
Booster
heater
Supply
piping
Return
piping
7. Include clauses in the project specification to provide, install, and test the HWAT-Plus
system. State appropriate fiberglass insulation thicknesses.
Completed HWAT-Plus System
Design Sheet, Part A: Plumbing
Design
BH
Recirc.
pump
Note: for pipe sizes 11/4" and smaller, use 1/4" larger diameter insulation to allow room for
installation over cable.
16
BH
Y2
Riser diagram showing
originally proposed
recirculation system
BH
HWAT-Plus System
Design Guide
Design example:
35-story apartment
building*
*Design example has been simplified for clarity.
Electrical Design
HWAT-Plus System
Design Sheet
R
The electrical engineer looked at the
plumbing drawing, and at the “HWATPlus System Design Sheet, Part A:
Plumbing Design,” and determined
that it was most convenient to power
all the circuits from the penthouse
mechanical room. Junction boxes
would be located at the beginning of
each circuit and power run from a
single panel. The electrical engineer
completed the “HWAT-Plus System
Design Sheet, Part B: Electrical
Design” by calculating the breaker
sizes and the steady-state currents.
The finished table was included in the
electrical drawings, along with a note
calling for a ground-fault protection
device in each circuit.
Part B:
Electrical Design
Refer to the HWAT-Plus Design Guide for complete design instructions.
Project name:
Area of building:
Washington Towers
Block A
Project No.:
F21
Prepared by:
Checked by:
1. Fill in the electrical design table below, using the information provided on the plumbing
design sheet.
Date:
VL
PB
1/20/92
40
Page no. 26 of
Electrical Design Table
HWAT-Plus cable type:
HWAT-Y2
Circuit Approx. Voltage Breaker
no.
length
Groundfault
protection
1
2
3
370'
370'
370'
208
30 mA
208
30 mA
208
30 mA
208
30 mA
208
30 mA
Size
(Table 1)
20
20
20
20
A
A
A
A
Steadystate
current
(Table 1)
4 A
4 A
4 A
4.3 A
J-box
Panel
location
no.
for power
connection
A-5
A-8
A-18
A-19
Include the electrical
design table in the
electrical drawings.
Check here if additional circuits are listed on
reverse.
R2-4
R2-4
R2-4
R2-4
See reverse for additional circuit entries.
Completed HWAT-Plus System
Design Sheet, Part B: Electrical
Design
H
4
LEGEND
H
1
2
3
1
2
3
Water
heater
Pressurereducing
valve
Expansion
tank
Riser diagram using HWATPlus system
3
3
Beginning
and end
of HWATPlus
heating
cable
installed
on supply
piping
NOTE
All heat-tracing
to be HWAT-Y2
4
17
HWAT-Plus System
Design Guide
Design example:
500-room hotel*
*Design example has been simplified for clarity.
The Decision
The plumbing engineer reviewed the
architectural drawings for a new hotel
planned by National Resorts. The
building consisted of six floors of guest
rooms over a commercial area containing a health club, restaurants, conference rooms, shops, offices, and a
laundry. The plumbing engineer decided to deliver water from the boiler at
140°F directly to the kitchens and
laundry, and to mix to 125°F for
domestic hot water.
The HWAT-Plus system was chosen
rather than recirculation because
National Resorts insisted that there be
no delay in getting hot water from any
fixture. An HWAT-Plus system was
chosen to accommodate all the architectural and construction changes that
were bound to occur before the
system was operating.
Plumbing Design
Following the “HWAT-Plus System
Design Sheet, Part A: Plumbing
Design,” HWAT-R2 was selected for
the 140°F line running out of the boiler
to the kitchens and laundry, and
HWAT-Y2 for the domestic hot water
system. Separate design sheets were
used for each HWAT-Plus cable type.
After reviewing the circuit length table,
it was determined that the entire
domestic hot water piping could be
traced with only two HWAT-Y2 circuits
by utilizing a 30-amp circuit breaker.
However, the plumbing engineer
decided to lay out the heating cable in
smaller discrete zones to facilitate
partial shutdown of the system for
maintenance. Circuits staying within
the maximum length for a 15-amp
breaker were indicated on the
drawing, and the table in the design
sheets was completed. A copy of the
drawing and the design sheets were
sent to the electrical engineer.
Division 15 of the specification for the
domestic hot water lines called out
standard clauses to provide, install,
and test the HWAT-Plus system.
18
HWAT-Plus System
Design Sheet
R
Part A:
Plumbing Design
Refer to the HWAT-Plus Design Guide for complete design instructions.
Project name:
Area of building:
National Resorts Hotel
Tower 1
Project No.:
P19
Prepared by:
Checked by:
Date:
1. Select the HWAT-Plus heating cable for the application.
SK
JS
7/21/90
60
Page no. 42 of
Application
Ambient
temperature
Nominal pipe
temperature
Heating
cable type
Hospitals, nursing homes
Schools, prisons, some hospitals
General domestic (offices, hotels)
Kitchens, laundries
74°F to 79°F
70°F to 78°F
70°F to 78°F
70°F to 78°F
105°F (40°C)
115°F (45°C)
125°F (50°C)
140°F (60°C)
HWAT-B2
HWAT-G2
HWAT-Y2
HWAT-R2
Use HWAT-
15 amp
20 amp
30 amp
Maximum circuit
2. Maximum 208-V circuit
breaker size:
3. Determine the maximum
circuit length.
4. Lay out the HWAT-Plus
circuits. Identify and
measure each circuit.
breaker:
6. Specify the following
thicknesses of fiberglass
insulation:
15
A
Maximum circuit length in feet (meters)
Circuit HWAT-B2
breaker
HWAT-G2 HWAT-Y2
HWAT-R2
30 amp
20 amp
15 amp
800 (240)
700 (210)
520 (155)
500 (150)
330 (120)
250 (75)
800 (240)
800 (240)
800 (240)
1
2
3
4
horiz. dist
main riser
risers B,C,D
risers F,G,H
Y2
Y2
Y2
Y2
H3
H3
H3
H3
95'
110'
240'
230'
Equipment to allow for thermal expansion should be
provided in all closed sections of piping downstream of
check or pressure-reducing valves.
Pipe size
(inches)
Fiberglass insulation
thickness (inches)
1⁄2"
1"
- 1"
11⁄4" - 2"
11⁄2"
21⁄2" - 6"
2"
Maximum circuit
length:
800 (240)
500 (150)
350 (105)
Circuit Heating
Risers, zones,
Drwg. Approx.
no.
cable type or floors served no.
length
See reverse to make
additional Circuit Design
Table entries.
5. Provide for thermal
expansion.
Y2
350 ft
Transmit this table to
the electrical engineer.
✓ Check here if additional circuits are listed on
reverse.
Provide
None required
in pipe sections
Note: for pipe sizes 11/4" and smaller, use 1/4" larger diameter insulation to allow room for
installation over cable.
7. Include clauses in the project specification to provide, install, and test the HWAT-Plus
system. State appropriate fiberglass insulation thicknesses.
Completed HWAT-Plus System
Design Sheet, Part A: Plumbing
Design (for HWAT-Y2 only;
design sheet for HWAT-R2 not
shown)
HWAT-Plus System
Design Guide
Design example:
500-room hotel*
*Design example has been simplified for clarity.
Electrical Design
HWAT-Plus System
Design Sheet
R
The electrical engineer looked at the
layout of the circuits and assigned
junction-box and panel locations for
each circuit according to the electrical
drawings. Filling in the information on
the “HWAT-Plus System Design
Sheet, Part B: Electrical Design,” the
engineer calculated the breaker size
and the steady-state current for each
circuit. The completed table, with a
note that the circuit breakers would
incorporate 30-mA ground-fault protection, was then transferred to the
electrical drawing.
Part B:
Electrical Design
Refer to the HWAT-Plus Design Guide for complete design instructions.
Project name:
Area of building:
National Resorts Hotel
1
P19
Project No.:
Prepared by:
Checked by:
Date:
1. Fill in the electrical design table below, using the information provided on the plumbing
design sheet.
GL
BF
7/25/90
45
Page no. 18 of
Electrical Design Table
HWAT-Plus cable type:
HWAT-Y2
Circuit Approx. Voltage Breaker
no.
length
Groundfault
protection
1
2
3
4
5
95'
110'
240'
230'
260'
208
30 mA
208
30 mA
208
30 mA
208
30 mA
208
30 mA
Size
(Table 1)
15
15
15
15
15
A
A
A
A
A
Steadystate
current
(Table 1)
1
1.1
2.4
2.3
2.6
A
A
A
A
A
Include the electrical
design table in the
electrical drawings.
J-box
Panel
location
no.
for power
connection
CF-3
J-21
T-6
T-32
CR-6
✓ Check here if additional circuits are listed on
reverse.
R-3
M-4
S-8
S-14
R-6
See reverse for additional circuit entries.
Table 1
Completed Heating
HWAT-PLUS
Circuit length
cable type
feet (meters)
System Design
Sheet,inPart
B:
Electrical Design
2
3
3
4
3
4
Circuit
breaker*
Steady-state
current draw
4
*Use a ground-fault protection device
with a nominal 30-mA trip level in each
circuit.
LEGEND
H
2
2
4
3
6
6
Beginning
and end
of HWATPlus
heating
cable
circuit
installed
on supply
piping
5
NOTE
5
6
5
6
1
Water
heater
2
5
1
5
5
All heating
cables to be
HWAT-Y2 except
circuit no. 1
which shall be
HWAT-R2
H
HWAT-Plus heat-tracing layout
shown on plumbing drawing
19
HWAT-Plus System
Design Guide
CSI Model
Specification
Raychem HWAT-Plus
Hot Water Temperature
Maintenance System
Part 1 - General
2. Mechanical:
The cable shall have a minimum
cut-through resistance of 600 lb per
CSA 22.2 0.3 Cutting Test 4.14.
The cable shall have a minimum
impact resistance of 25 ft•lb per UL
1588.11. The cable shall withstand
a glancing impact of 22 ft•lb per UL
1581.590. The cable shall have a
minimum abrasion resistance of
7000 cycles per UL 719.19. The
cable shall withstand a crush resistance of 4500 N per IEEE 515
Deformation Test 5.1.5.
1. Furnish and install a UL-listed
system of electric self-regulating
heating cable and components for
maintaining the water temperature
in the hot water lines as indicated
on the drawings. The cable shall
utilize a radiation-crosslinked conductive polymer as the heating
element, and the cable shall be
specifically designed, manufactured, and UL listed for domestic
hot water temperature
maintenance.
Part 3 - Performance
2. Submittals:
i) Copy of UL file indicating the
heating cable is specifically
listed to provide supplementary
heating to hot water service
supply systems utilizing thermally insulated metal or plastic
pipe.
ii) Manufacturer’s catalog cuts
showing materials and performance data.
iii) Project list of at least 20 projects, installed for at least 5
years, with at least 2000 ft
(600 m) of heating cable in each
project.
Part 2 - Materials
1. Construction:
The self-regulating heating cable
shall consist of two (2) 16-AWG
(1.2-mm2) nickel-coated copper bus
wires embedded in a radiationcrosslinked conductive polymer
core. It shall be covered by a
radiation-crosslinked, polyolefin,
dielectric jacket surrounded by a
polymer-coated aluminum wrap,
and enclosed in a tinned copper
braid of 14 AWG (2.5 mm2) equivalent wire size. The braid shall be
covered with a (nominal) 40-mil (1mm) polyolefin outer jacket, color
coded for easy identification.
20
1. Operating temperatures:
The system shall maintain a nominal temperature of [105°F (40°C),
115°F (45°C), 125°F (50°C), 140°F
(60°C)] as noted on the drawings,
at 208 V.
2. Maintenance temperature:
Each hot water system temperature
shall be maintained using only one
product. Temperatures shall be
maintained with straight runs of
heating cable on the pipe.
3. Power control (self-regulating
index):
The slope of the power/temperature curve shall be such that the
power of the heating cable shall
increase with decreasing temperature at a rate of at least 0.028
W/ft•°F (0.16 W/m•°C) from 50°F
(10°C) to 100°F (38°C).
4. Long-term thermal stability (as
determined by accelerated
testing):
The power retention of the heating
cable shall be at least 90% after
300 cycles between 50°F (10°C)
and 212°F (100°C).
5. High temperature withstand:
The heater shall not decrease in
resistance, overheat, or burn when
powered at 208 V and exposed to
400°F (205°C) in an oven for 30
minutes.
HWAT-Plus System
Design Guide
CSI Model
Specification
Raychem HWAT-Plus
Hot Water Temperature
Maintenance System
Part 4 - Manufacturer
1. Experience:
The manufacturer shall have more
than ten years experience with selfregulating heating cables for temperature maintenance of domestic
hot water.
2. Acceptable manufacturer:
Raychem Corporation
Part 5 - Execution
1. Installation:
The system shall be installed
according to the drawings and the
manufacturer’s instructions. The
installer shall be responsible for
providing a functional system,
installed in accordance with applicable national and local code
requirements. Each circuit shall be
protected with a 30-mA groundfault protection device.
2. Testing
i) Procedure: Measure the heater
circuit continuity and the insulation resistance between the
braid and bus wires with a 2500Vdc megohmmeter (megger).
ii) Timing: The tests should be performed after the pipe insulation
has been installed and prior to
installation of wall or ceiling
panels, and shall be witnessed
by the Construction Manager
and the manufacturer or the
manufacturer’s representative.
iii) Acceptable results: The heater
circuit shall be continuous and
megger readings shall be at
least 20 megohms regardless of
heater length. Circuits yielding
unacceptable readings must be
repaired or replaced.
iv) Submittal of results: Submit
records of the test data to the
Construction Manager.
21
HWAT-Plus System
Design Guide
Installation details
HWK-XE end seal.
Use one per circuit plus one
per tee. No service loop
required.
ETL “electric traced” label.
Place at 10-ft (3-m) intervals
on alternating sides of
insulation.
GT-66 glass tape.
Use tape to attach heating
cable to pipe every 2 ft (.6 m).
One roll will handle
approximately 50 ft (15 m).
ELECTRIC
TRACED
HWK-XP power connection kit
(junction box not included).
Use one per circuit. Allow for a
2-ft (.6-m) service loop.*
HWK-XS splice kit.
Use as needed. Allow for a 2- ft
(.6-m) service loop.
HWK-XT tee kit.
Use at tees in traced piping.
Allow for a 3-ft (1-m) service
loop.
Note:
Required items not supplied by Raychem:
• Fiberglass pipe insulation
• 30-mA ground-fault protection device
Component
Usage
Heater Allowance*
Power Connection Kit
Splice Connection Kit
Tee Connection Kit
End Seal Kit
Glass Tape
One per circuit
As required
At tees in traced piping
One per circuit and one per tee
Use tape to attach heating cable
to pipe every 2 ft (.6 m)
Place at 10-ft (3-m) intervals on
alternating sides of insulation
2 ft (.6 m)
2 ft (.6 m)
3 ft (1 m)
–
–
“Electric Traced” Labels
22
–
*Raychem recommends a “service loop” (not
shown) in the HWAT-Plus heating cables at connections or places in the piping where future service is expected. This extra length of cable will
make any maintenance easier to accomplish. Be
sure to consider service loops when calculating the
total length required for an HWAT-Plus system.
HWAT-Plus System
Design Guide
Installation details
HWATTM
Power connection
Heating cable splice
Heating cable tee
End seal
Heating cable and glass tape
“Electric traced” label
23
Raychem Corporation
Construction Products Group
300 Constitution Drive
Menlo Park, California 94025-1164
(800) 542-8936
Fax (650) 361-6036
Raychem Canada Ltd.
3245 American Drive
Mississauga
Ontario, Canada LV4 1N4
(800) 387-3993
Fax (416) 671-0972
6/92
H54227
(Y8645)
1992 Raychem Corporation
Printed in USA
All of the information in this booklet, including illustrations, is believed to be
reliable. Users, however, should independently evaluate the suitability of each
product for their application. Raychem makes no warranties as to the accuracy
or completeness of the information, and disclaims any liability regarding its use.
Raychem’s only obligations are those in the Standard Terms and Conditions of
Sale for this product, and in no case will Raychem be liable for any incidental,
indirect, or consequential damages from the sale, resale, use, or misuse of the
product.