HTP DB Series User manual

Drain Back Tank
Installation
Start-Up
Maintenance
Parts
Warranty
For Residential and
Commercial Use
DB Series and DBX Models*
*A sux of “X” denotes models with
internal heat exchanger
NOTE TO CONSUMER: PLEASE KEEP ALL INSTRUCTIONS FOR FUTURE REFERENCE.
272 Duchaine Blvd. New Bedford, MA 02745 www.htproducts.com
lp-351b Rev. 11.25.15
This manual must only be used by a qualied installer /
service technician. Read all instructions in this manual
before installing. Perform steps in the given order.
Failure to do so could result in substantial property
damage, severe personal injury, or death.
HTP reserves the right to make product changes or
updates without notice and will not be held liable for
typographical errors in literature.
The surfaces of these products contacted by potable
(consumable) water contain less than 0.25% lead by weight
as required by the Safe Drinking Water Act, Section 1417.

lp-351b Rev. 11.25.15
2
The following dened terms are used throughout this manual
to bring attention to the presence of hazards of various risk
levels or to important product information.
DANGER indicates an imminently hazardous situation which,
if not avoided, will result in serious personal injury or death.
WARNING indicates a potentially hazardous situation which, if
not avoided, could result in personal injury or death.
CAUTION indicates a potentially hazardous situation which, if
not avoided, may result in moderate or minor personal injury.
CAUTION used without the safety alert symbol indicates
a potentially hazardous situation which, if not avoided, may
result in property damage.
NOTICE is used to address practices not related to personal
injury.
Foreword
This manual is intended to be used in conjunction with other
literature provided with your solar water heating system. This
includes all related control information. It is important that this
manual, all other documents included with this system, and
additional publications, such as Solar Water Heating System
Design and Installation Guidelines, SRCC OG-300, be reviewed in
their entirety before beginning any work.
Installation should be made in accordance with the regulations
of the Authority Having Jurisdiction, local code authorities, and
utility companies which pertain to this type of water heating
equipment.
Authority Having Jurisdiction (AHJ) – The Authority Having
Jurisdiction may be a federal, state, local government, or
individual such as a re chief, re marshal, chief of a re
prevention bureau, labor department or health department,
building ocial or electrical inspector, or others having statutory
authority. In some circumstances, the property owner of his/her
agent assumes the role, and at government installations, the
commanding ocer or departmental ocial may be the AHJ.
NOTE: HTP, Inc. reserves the right to modify product technical
specications and components without prior notice.
For the Installer
Table of Contents
Introduction 3
Part 1 - General Safety Information 3
A. When Servicing the Solar Water Heating System 4
B. Local Installation Regulations 4
C. Chemical Vapor Corrosion 4
D. Insulation Blankets 4
E. Water Temperature Adjustment 4
F. Freeze Protection 4
Part 2 - Important Information 5
A. Piping 5
B. Sizing the Drain Back Tank 5
C. Locating the Solar Water Heater 5
D. Specications and Dimensions 6
Part 3 - Piping 8
A. System Piping and Plumbing 8
B. Installation of the Drain Back Tank 8
1. Drain Back Tanks without Heat Exchangers 8
2. Drain Back Tanks with Heat Exchangers 8
C. Solar System Pump 8
D. Electrical Installation 9
E. Fluid Quality Requirements 9
F. Installing the Drain Back Tank Sight Tube 9
G. Applications 10
For your safety, please read through this manual carefully
before installation to minimize the risk of re, property
damage, personal injury, or death. Ensure the solar hot water
system is properly installed in accordance with this manual
before use.
INSTALLATION OR SERVICE OF THIS SOLAR PRODUCT
IS REQUIRED TO BE PERFORMED BY LICENSED
PROFESSIONALS WHERE SOLAR, PLUMBING, AND
ELECTRICAL WORK IS REQUIRED.
The installer should be guided by the instructions furnished
with the tank, as well as local codes and utility company
requirements. Preference should be given to codes
and requirements where they dier from the furnished
instructions. Always use the latest edition of codes.
Additional publications which should guide the installer
include:
Local, state, provincial, and national codes, laws, regulations,
and ordinances.
Solar Water Heating System Design and Installation Guidelines,
SRCC OG-300, available from Solar Rating & Certication
Corporation, 400 High Point Drive, Suite 400, Cocoa, FL
32926-6630, www.solar-rating.org.
Code for the Installation of Heat Producing Appliances (latest
version), available from the American Insurance Association,
85 John Street, New York, NY 11038.
The latest version of the National Electrical Code, NFPA No. 70.
In Canada refer to Canadian Electrical Code C 22.1, from
Canadian Standards Association, 5060 Spectrum Way, Suite
100, Mississauga, Ontario, Canada L4W 5N6.
ForYour Records
Write the Product Model and Serial Numbers:
Model # ___________________________________________
Serial # ____________________________________________
These numbers are listed on the product ratings label.
Keep this manual and information for future reference.

lp-351b Rev. 11.25.15
3
Introduction
Drain back tanks are designed to allow solar collectors and related
piping to drain heat transfer uid into the drain back reservoir
when not in use.
Drain back systems are versatile: ideally suited for both cold
and warm regions. The drain back process protects solar system
components from both freezing and overheating, and saves
power by shutting down the solar system when there is no
longer a demand for hot water. Drain back systems have fewer
components than pressurized systems, making drain back
systems easier to use, service, and maintain. Your drain back tank
may come with an internal heat exchanger (for use with a storage
tank), or without a heat exchanger (for use with either a solar
water heater with an internal heat exchanger or a storage tank
with an external plate and frame heat exchanger).
Job site conditions will require your installation contractor to
supply some or all of the following:
• Plumbing connections
• Piping and insulation
• Valves between the existing domestic water system and
the drain back solar system
NOTE: Solar system performance and eciency varies with
factors such as: household hot water load, ambient air
temperature, collector/roof pitch, collector orientation, and
seasonal intensity.
NOTE: Failure to follow the procedures and instructions in this
manual WILL VOID the warranty.
Part 1 - General Safety Information
Installer - Read all instructions in this manual before installing.
Perform steps in the given order.
User - This manual is for use only by a qualied heating installer /
service technician. Have this solar water heating system serviced
/ inspected annually by a qualied service technician.
Failure to adhere to these guidelines can result in substantial
property damage, severe personal injury, or death.
NOTE: Obey all local codes. Obtain all applicable permits before
installing the solar system.
NOTE: Install all solar system components and piping in such a
manner that does not reduce the performance of any re rated
assembly.
Part 4 - Start-Up Preparation 11
A. Fill the Drain Back Reservoir 11
B. Start-Up Procedure 12
Part 5 - Service / Maintenance Procedures 12
A. Shutdown Procedures 12
B. Draining the Drain Back Reservoir 12
C. Routine Maintenance 12
D. Vacation Shutdown Procedure 12
Part 6 - Troubleshooting 12
A. Leaks 12
B. Other Problems 12
Limited Warranty 13
Customer Installation Record Form 15
DO NOT USE THE SOLAR SYSTEM IF ANY PART HAS BEEN
SUBMERGED IN WATER. Immediately call a qualied service
technician. Components may need to be replaced. Attempting
to operate components that have been submerged could create
numerous harmful conditions, such as a potential gas leakage
causing a re and/or explosion, or the release of mold, bacteria,
or other harmful particulates into the air. Operating a previously
submerged water heater could result in property damage,
severe personal injury, or death.
NOTE: Damage due to ood or submersion is considered an Act
of God, and IS NOT covered under product warranty.
NOTE: If the solar water heating system is exposed to the
following, do not operate. Immediately call a qualied service
technician.
1. Fire
2. Damage
3. Submersion in Water
Failure to adhere to these guidelines can result in substantial
property damage, severe personal injury, or death.
Only use this solar hot water system as intended and described
in this installation manual. Any use other than described will
void warranty and may lead to re, property damage, personal
injury, or death.
UNCRATING THE WATER HEATER - Any claims for damage
or shortage in shipment must be led immediately against the
transportation company by the consignee.
High heat sources (sources generating heat 100oF / 37oC or
greater, such as stove pipes, space heaters, etc.) may damage
plastic components of the water heater as well as plastic vent
pipe materials. Such damages ARE NOT covered by warranty. It
is recommended to keep a minimum clearance of 8” from high
heat sources. Observe heat source manufacturer instructions,
as well as local, state, provincial, and national codes, laws,
regulations and ordinances when installing this water heater
and related components near high heat sources.
Improper installation or use may result in property damage.
Such damages ARE NOT covered by warranty.
Ensure there are no low points or dips in sloped non-vertical
supply and return pipe runs from the solar collectors to the drain
back tank. Low points and improperly designed solar piping
can trap water and possibly rupture in freezing weather. Pitch
non-vertical piping ¼” per foot towards the drain back tank
to facilitate proper drainage, and take care to properly layout
piping to ensure there are no low points.
In addition, the drain back tank and solar storage tank must
be protected from freezing temperatures. Care must be taken
when lling the system to avoid overlling and exposing pipes
to a freezing condition.
ALL PIPING AND PLUMBING CONNECTIONS SHOULD
BE MADE WITH COPPER PIPE ONLY. No less than ¾” I.D.
copper tube of the type meeting local codes must be used for
piping. Pipe runs must be solidly attached with proper clamping
methods. Soldered connections should be secured with 95/5
lead-free solder. Use only pipe rated for 250oF minimum on both
the collector return and supply piping.

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4
A. When Servicing the Solar Water Heating System
To avoid electric shock, disconnect electrical supply before
performing maintenance.
To avoid severe burns, allow solar collector and associated
equipment to cool before servicing.
B. Local Installation Regulations
Installation of this solar water heating system may be governed
by individual local rules and regulations for this type of system,
which must be observed. Always use the latest edition of codes.
The installation, adjustment, service, and maintenance of the
solar water heater must be done by a licensed professional who
is qualied and experienced in the installation, service, and
maintenance of solar hot water systems.
C. Chemical Vapor Corrosion
Products to Avoid Areas Likely to Have
Contaminants
Spray cans containing
uorocarbons
Dry cleaning / laundry areas
and establishments
Permanent wave solutions Swimming pools
Chlorinated waxes / cleaners Metal fabrication plants
Chlorine-based swimming pool
chemicals Beauty shops
Calcium chloride used for thawing Refrigeration repair shops
Sodium chloride used for water
softening Photo processing plants
Refrigerant leaks Auto body shops
Paint or varnish removers Plastic manufacturing plants
Hydrochloric or Muriatic acid Furniture renishing areas and
establishments
Cements and glues New building construction
Antistatic fabric softeners used in
clothes dryers Remodeling areas
Chlorine-type bleaches, laundry
detergents, and cleaning solvents Garages and workshops
Adhesives used to fasten building
products
Table 1 - Products and Areas Likely to Have Contaminants
NOTE: DAMAGE TO THE DRAIN BACK TANK, SOLAR
SYSTEM, OR RELATED COMPONENTS CAUSED BY
EXPOSURE TO CORROSIVE VAPORS IS NOT COVERED BY
WARRANTY. (Refer to the limited warranty for complete terms
and conditions.)
D. Insulation Blankets
For installation of insulation blankets, refer to Solar Water
Heating System Design and Installation Guidelines, SRCC OG-300.
E. Water Temperature Adjustment
An ASSE 1017 rated mixing valve to avoid severe burns or death
from scalding temperatures IS REQUIRED PER SRCC OG-300.
Approximate Time / Temperature Relationships in Scalds
120oFMore than 5 minutes
125oF1 1/2 to 2 minutes
130oFAbout 30 seconds
135oFAbout 10 seconds
140oFLess than 5 seconds
145oFLess than 3 seconds
150oFAbout 1 1/2 seconds
155oFAbout 1 second
Table 2 - Approximate Time / Temperature Relationships in Scalds
Households with small children, disabled, or elderly persons
may require a 120oF or lower temperature setting to prevent
severe personal injury or death due to scalding.
In addition, to prevent scalding, the high temperature of
the potable water must be limited using an ASSE 1016
tempering valve. This valve is usually located between the
hot water storage tank and faucets in bathrooms, kitchens,
etc. Tempering valves are mandatory under most codes and
usually set to a maximum of 120oF. Tempering valves must be
rated for high-temperature solar use.
F. Freeze Protection
NOTE: Consider piping and installation when determining
drain back tank location. Place tank in a location not prone
to freezing.
Failure of the drain back tank, solar system, or components
due to freeze related damage IS NOT covered by product
warranty.
In order to meet health and safety regulations, solar system
antifreeze uid should be food grade polypropylene glycol,

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5
Part 2 - Important Information
A. Piping
Collector piping requires the use of copper and brass ttings
in the collector loop. To avoid leaks and uid loss, copper
and brass ground joint unions should be used to join the
collectors. Use only lead-free solder. Engelhard Silvabrite 100
or equivalent is the required soldering material. Use of 50/50
lead solder is expressly prohibited. Use of galvanized steel,
CPVC, PVC or any other non-rated plastic pipe is prohibited.
Piping in new solar installations may have dirt, grease, solder
ux, or other impurities that will aect the quality of glycol
heat transfer uid over time. Thorough cleaning is required
before charging new solar installations with glycol.
All vertical piping between the drain back tank and collector(s)
shall be supported at each story or at maximum intervals
of ten feet (10’). In addition, all non-vertical solar collector
piping should pitch ¼” per foot down to the drain back tank to
facilitate proper drainage. Ensure that there are no dips or low
points in solar piping that could trap uid and possibly rupture
in freezing conditions. Copper plumbers tape or tube strap is
the required strapping material. The pipe insulation may not
be compressed or crimped by the strapping material.
The installation of all piping may not reduce the performance
or rating of structural members or re rated assemblies and
must adhere to all applicable local codes and ordinances.
B. Sizing the Drain Back Tank
To ensure proper operation of the drain back solar system,
the drain back tank volume should be sized with double the
volume capacity of the total volume of the solar collectors and
all solar piping above the drain back tank.
For example:
An HP-30SC Evacuated tube solar collector has a .3 gallon
capacity.
100 feet of 1” copper pipe has a 4.6 gallon capacity.
The capacity of the collector and piping equals 4.9 gallons.
The system requires a 10 gallon drain back tank.
NOTE (Drain Back Tanks with Heat Exchangers ONLY):
Drain back tanks with heat exchangers have pressure drop
which must be considered in system design. Refer to Figure
1 for pressure drop through the heat exchanger of the various
gallon sizes. The chart represents ow and friction loss
through the heat exchanger, and will aid circulator selection.
Figure 2 - Pressure Drop through Heat Exchanger
FDA rated as “generally recognized as safe” (GRAS). The
recommended glycol is DOWFROST or equivalent. Using
proper concentrations of glycol, solar systems can be operated
at ambient temperatures as low as -60oF. Freeze tolerance
limits are based upon an assumed set of environmental
conditions. Refer to the specication sheet included with the
glycol for recommended concentrations. A glycol/water mix
must not exceed 50%, unless the manufacture species that
a dierent ratio is recommended for use with solar water
heaters. Glycol may need to be changed periodically (every
3-5 years) to prevent it from becoming acidic; please refer to
the guidelines provided by the glycol manufacturer regarding
replacement.
C. Locating the Solar Water Heater
To minimize expense and heat loss, locate the drain back tank
as centrally to the solar tank and near the solar collectors as
possible. The tank must also be located in as warm a location as
possible, away from areas which would subject the drain back
reservoir to freezing temperatures. The drain back tank has no
controls, but the sight tube must have clearance for inspection
and service.
In addition, the solar water heater should be installed with
plenty of clearance for service. If minimum clearances are
not met, it may not be possible to service the heater without
removing it from its location.
The drain back tank should also be installed in a place where T&P
discharge or a leak will not result in damage to the surrounding
area. Install a 2” high catch pan with a minimum of ¾” drain line
to prevent water damage if leakage should occur (See Figure 2).
Figure 1 - Catch Pan Dimensions
Filled hot water storage tanks are very heavy, and should be
located in areas that can structurally support such weight.
Failure to properly locate water storage tanks could result in
property damage, personal injury, or death.
This tank must be installed upright in the vertical position as
described in this manual. DO NOT attempt to install this tank
in any other orientation. Doing so will result in improper tank
operation and property damage, and could result in serious
personal injury or death.

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D. Specications and Dimensions
Figure 3 - Drain Back Tank without Heat Exchanger Specications and Dimensions

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7
Figure 4 - Drain Back Tank with Heat Exchanger Specications and Dimensions

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8
Part 3 - Piping
The design and installation of the solar water heating system
should be done by qualied individuals. It is important that
good design and installation practices be followed to assure that
your system will operate properly. Failure to follow installation
guidelines for your solar water heating system could cause
component failure and possible safety issues.
NOTE: To ensure proper drainage, consider system piping
BEFORE making a nal decision on collector mounting.
A. System Piping and Plumbing
It is very important that you do the potable piping before you
pipe into your solar system. Failure to do so may damage your
water heater.
Do not introduce HTF into any ttings on the heater except
those clearly marked for that purpose.
It is mandatory that plumbing be done in accordance with all
local and state plumbing codes. FAILURE TO DO SO WILL VOID
THE WARRANTY.
All solar collectors must be installed level. All non-vertical supply
and return solar piping must be pitched at a minimum of ¼”
per foot for drainage and must drain without any uid traps
to prevent freezing. Ensure there are no dips, low points, or
piping congurations that may trap uid and rupture in freezing
conditions.
ALL PIPING AND PLUMBING CONNECTIONS SHOULD BE
MADE WITH COPPER PIPE ONLY. No less than ¾” I.D. copper
tube of the type meeting local codes must be used for piping.
Pipe runs must be solidly attached with proper clamping
methods. Soldered connections should be secured with 95/5
lead-free solder. No check valves are allowed within the solar
piping loop. Remove integral check from pump if so equipped.
Insulate pipe with ¾” pipe insulation rated for 250oF minimum.
Insulate all hot water piping and all exposed cold water piping at
the entrance to the solar tank. Paint pipe insulation exposed to
ultraviolet radiation with insulation manufacturer approved UV
resistant latex based paint, or wrap with PVC pipe wrap. Support
piping with plumbers straps or pipe hangers and install in such a
manner as to not crush the insulation.
Never use dielectric unions or galvanized steel ttings on any
domestic water connections or auxiliary connections. ONLY use
copper or brass ttings. Teon thread sealant must be used on
all connections.
B. Installation of the Drain Back Tank
1. Drain Back Tanks without Heat Exchangers
a. Pipe solar collector return to the inlet tting located on the
top of the drain back tank.
b. Pipe drain back tank outlet (located near the bottom of
the tank) to the solar heat exchanger inlet.
c. Pipe solar heat exchanger outlet to the solar collector
supply tting.
(See installation diagrams in Part 5 for piping details.)
2. Drain Back Tanks with Heat Exchangers
a. Pipe solar collector return to the inlet tting located on the
top of the drain back tank.
b. Pipe drain back tank outlet to the solar collector supply
tting.
c. Pipe cold supply water from the solar storage tank to the
heat exchanger inlet tting located on the drain back tank.
d. Pipe heat exchanger outlet to hot return tting on solar
storage tank.
(See installation diagrams in Part 5 for piping details.)
Insulate all hot water lines, as well as the nal 5’ of cold water
supply pipe leading to the system, with at least ¾” thick heat
resistant rubber tubing insulation.
Before commissioning the system, install the sight tube and
an ASME/ANSI rated 30 PSI pressure relief valve into the
appropriate ttings on the drain back tank using pipe dope.
Follow further pressure relief valve installation information
listed below.
To avoid water damage or scalding due to relief valve
operation:
• Discharge line must be connected to relief valve outlet
and run to a safe place of disposal. Terminate the
discharge line in a manner that will prevent possibility
of severe burns or property damage should the relief
valve discharge.
• Discharge line must be as short as possible and
the same size as the valve discharge connection
throughout its entire length.
• Discharge line must pitch downward from the valve
and terminate at least 6” above the oor drain, making
discharge clearly visible.
• The discharge line shall terminate plain, not threaded,
with a material serviceable for temperatures of 375oF
or greater.
• Do not pipe discharge to any location where freezing
could occur.
• No valve may be installed between the relief valve and
heater or in the discharge line. Do not plug or place
any obstruction in the discharge line.
• Test the operation of the relief valve after lling and
pressurizing the system by lifting the lever. Make sure
the valve discharges freely. If the valve fails to operate
correctly, immediately replace with a new, properly
rated relief valve.
• Test relief valve at least once annually to ensure the
waterway is clear. If valve does not operate, turn the
heater “o” and call a plumber immediately.
• Take care whenever operating relief valve to avoid
scalding injury or property damage.
FAILURE TO COMPLY WITH THE ABOVE GUIDELINES
COULDRESULTINFAILUREOFRELIEFVALVEOPERATION,
RESULTING IN POSSIBILITYOF SUBSTANTIAL PROPERTY
DAMAGE, SEVERE PERSONAL INJURY, OR DEATH.
The circulating pump becomes very hot when running. Allow
sucient time to cool before touching. Failure to do so can
lead to personal injury.
C. Solar System Pump

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9
E. Fluid Quality Requirements
Two heat transfer uids may be used in drain back systems:
Distilled water or glycol/water mix.
In order to meet health and safety regulations, drain back
system antifreeze uid should be food grade polypropylene
glycol, FDA rated as “generally recognized as safe” (GRAS).
Using proper concentrations of glycol, solar systems can
be operated at ambient temperatures as low as -60oF.
Freeze tolerance limits are based upon an assumed set of
environmental conditions. Refer to the glycol manufacturer’s
specication sheet for recommended concentrations.
If using a glycol/water mix, the water must meet the above
requirements, and the glycol content of the liquid must not
exceed 50%, unless the manufacture species that a dierent
ratio is recommended for use with solar water heaters. HTP
recommends using a pre-blended solution. Glycol/water mix
should be tested for pH and freeze protection annually, and
may need to be changed periodically (every 3-5 years) to
prevent it from becoming acidic. Please refer to the guidelines
provided by the glycol manufacturer regarding replacement
and balancing additives.
NOTE: The drain back tank IS NOT WARRANTED against
freeze related damage.
Solar pumps must be installed at least 3’ below drain back tank
level. Remove integral check if so equipped. The solar system
pump must be sized to lift water to the top of the collector
array. The solar pump must be sized for proper ow and head
loss. Friction losses must also be considered when sizing a
pump and solar system piping.
When sizing the pump, determine the head losses (also called
psi, head feet, and foot lift). Determine head loss through
piping and the heat exchanger using the solar collector
manufacturer’s recommended ow rates. Consider the
vertical lift from the drain back tank to the top of the solar
panels. Size the pump for whichever is greater: Head loss
pumping through the system, or vertical lift, not both. A solar
modulating pump control is highly recommended on a drain
back system.
If the pump continues pumping at full speed rate after the
system is primed, the solar loop will often be over-pumped and
the recommended velocity will be exceeded. This condition
will lead to premature failure and reduced performance of the
solar system.
D. Electrical Installation
ALL CONNECTIONS MUST BE MADE IN ACCORDANCE
WITH LOCAL ELECTRICAL CODES. A qualied electrician
or contractor is required to install a 115-120VAC duplex
receptacle adjacent to the solar storage tank. This receptacle
is used to supply power to the pump/control combo.
F. Installing the Drain Back Tank Sight Tube
IMPORTANT NOTE: A sight tube has been included with the
solar drain back tank. The sight tube allows service technicians,
installers, and users to quickly determine proper drain back
system drainage and solar system heat transfer uid level.
It is extremely important that this sight tube be installed
BEFORE lling the solar water heating system. Failure to install
the sight tube will result in a spillage of heat transfer uid,
which, depending on your system, may or may not contain
antifreeze. Property damages due to failure to install the sight
tube ARE NOT covered by product warranty.
1. Remove the two brass ttings, washers, and rubber gaskets
from the brass sight tube ttings installed on the solar drain
back tank.
2. Place a brass nut (threaded end facing out), washer, and
rubber gasket on each end of the sight tube. See Figure 5.
Figure 5 - Installing the Brass Fitting, Washer, and Gasket
3. Use an adjustable wrench to install the sight tube by tightening
each brass nut onto the brass ttings on the drain back tank. DO
NOT OVER-TIGHTEN. See Figure 6.
NOTE: If installing a drain back tank smaller than 30 gallons,
skip to step 6. Steps 4 and 5 refer to drain back tanks sized 30
gallons and larger.
Figure 6 - Sight Tube Connected to Brass Fitting
4. Using the sight tube as a guide,
use a drill with a Phillips Head bit
to install the included snap ttings
into the tank with the included 6 X
1 screws. The snap ttings should
be spaced roughly one foot from
each tting, and the sight tube
should run as straight as possible
when installed into the snap
ttings. 30, 40, and 60 gallon drain
back tanks are provided with two
snap ttings; 80 gallon tanks are
provided with three.
5. Snap the sight tube into the snap
ttings. See Figure 10. Sight tube
installation is complete.
6. After solar water heating
installation is complete, ll the
system and check the sight tube
for any leaks. Repair as necessary.
Figure 7 - Installed Sight
Tube With Snap Fittings

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10
G. Applications
Figure 8 - Drain Back Tank without Heat Exchanger
FIGURE NOTES:
1. This drawing is meant to demonstrate system piping concept only. The installer is responsible for all equipment and detailing by local codes.
2. Non-potable HTF shall only be used for the solar heat exchanger circuit. Never introduce non-potable HTF to any connection other than the
solar loop.
3. If there is a check valve on the cold water feed line, a thermal expansion tank suitable for potable water must be sized and installed within
this piping system between the check valve and cold water inlet of the solar water heater. The expansion tank should be properly sized for the
volume of stored hot water and maximum tank temperature. Normal solar control settings may be between 120o and 160o. Do not exceed 160o
on the solar control setting.
4. A solar rated mixing valve is recommended if the domestic hot water setting is above 120oF. A standard mixing valve generally cannot deliver
the temperature protection range at which a solar system operates.
5. A minimum of 12 diameters of straight pipe must be installed upstream of all circulators.
6. Make sure solar storage tank is fully purged of air before power is turned on to the backup heat source.
7. Due to extreme temperatures, circulators with integral ow checks are not to be used in solar systems. If circulator comes equipped
with an integral ow check, remove it.
8. Non-vertical drain back solar system piping should pitch ¼” per foot back to the tank to facilitate draining.
9. No check valves are allowed in the solar loop.
10. Solar pumps must be installed 3’ below the drain back tank.

lp-351b Rev. 11.25.15
11
Figure 9 - Drain Back Tank with Heat Exchanger
FIGURE NOTES:
1. This drawing is meant to demonstrate system piping concept only. The installer is responsible for all equipment and detailing by local codes.
2. Non-potable HTF shall only be used for the solar heat exchanger circuit. Never introduce non-potable HTF to any connection other than the
solar loop.
3. If there is a check valve on the cold water feed line, a thermal expansion tank suitable for potable water must be sized and installed within
this piping system between the check valve and cold water inlet of the solar water heater. The expansion tank should be properly sized for the
volume of stored hot water and maximum tank temperature. Normal solar control settings may be between 120o and 160o. Do not exceed 160o
on the solar control setting.
4. A solar rated mixing valve is recommended if the domestic hot water setting is above 120oF. A standard mixing valve generally cannot deliver
the temperature protection range at which a solar system operates.
5. A minimum of 12 diameters of straight pipe must be installed upstream of all circulators.
6. Make sure solar storage tank is fully purged of air before power is turned on to the backup heat source.
7. Due to extreme temperatures, circulators with integral ow checks are not to be used in solar systems. If circulator comes equipped with an
integral ow check, remove it.
8. Non-vertical drain back solar system piping should pitch ¼” per foot back to the tank to facilitate draining.
9. No check valves are allowed in the solar loop.
10. Solar pumps must be installed 3’ below the drain back tank.
11. The drain back tank must be properly supported to account for the weight of the tank when lled with HTF.
Part 4 - Start-Up Preparation
DO NOT MOVE ON TO THESE STEPS UNTIL THE ENTIRE
SOLAR SYSTEM, INCLUDING ALL PIPING, SOLAR
COLLECTORS, SENSORS, PUMP, CONTROLS, AND
ELECTRICAL CONNECTIONS, ARE PROPERLY SECURED,
INSULATED, LABELED AND INSTALLED.
A. Fill the Drain Back Reservoir
1. Attach hose to solar loop ll valve. The location of the ll
valve varies depending on numerous factors, including
whether the drain back tank has a heat exchanger.
2. Open ll valve and the bleed valve on the drain back tank
sight tube (see Specication drawing for location, this
manual).
3. Slowly ll the drain back reservoir to the top of the sight
tube.
4. When nearly full, close bleed valve, and add between 2
and 5 PSI head pressure to the system. When system is
full and at desired head pressure, shut o ll valve.
5. Remove ll hose.

lp-351b Rev. 11.25.15
12
B. Start-Up Procedure
Once the system is lled as prescribed above:
1. Apply power to the solar controller.
2. Set controller to operate pump manually. Let pump run
for 5 minutes.
3. Check for leaks at collectors and in attic, if applicable.
4. If no leaks are found, program controller for your
drain back system (see solar controller programming
instructions).
If the sun is shining and the tank is cool, the pump should turn on
and begin circulating water. Check control settings to maximize
your system performance.
Take care not to overll the drain back solar system. Overlling
will cause a potentially dangerous condition that could lead to
freezing and failure of the solar system.
Part 5 - Service / Maintenance Procedures
A. Shutdown Procedures
To shut down the drain back system, simply unplug the
dierential controller. The pump will stop and water will drain
out of the collectors into the reservoir.
D. Vacation Shutdown Procedure
If hot water is not to be used for an extended period of time,
unplug the controller and allow the solar collectors and piping to
drain into the drain back reservoir. To re-energize, simply plug in
the controller.
Never open the pressure relief valve while the system is in
operation or hot water is present. Allow to cool prior to opening.
B. Draining the Drain Back Reservoir
1. Unplug the controller and wait until all water returns to
the reservoir.
2. Attach hose to ll valve.
3. Open the pressure relief valve.
4. Open ll valve.
5. Allow the system to completely drain.
6. Close ll valve and the pressure relief valve.
7. Remove drain hose.
C. Routine Maintenance
The heat transfer uid level in the drain back reservoir should be
checked twice a year. With the system turned o, make sure that
the water level in the reservoir reaches the top of the sight tube.
If not, follow the instructions in “Fill the Drain Back Reservoir”,
this manual.
Periodically check the temperature dierence between the
collector supply (from the tank to the collector) and collector
return lines (from the collector to the tank). As a rule, an 8 –
12° temperature gain should be expected across a collector, in
bright sun, at the proper ow rate. Larger systems may have a
greater temperature dierence.
Part 6 - Troubleshooting
Owners are advised to contact the installer whenever in-depth
interaction with the solar system is required.
A. Leaks
For leaks in the solar system, shut down the system by pulling
B. Other Problems
A noisy pump could be an indication of worn bearings,
obstructions, or a leak in your system. Call your installer
for diagnosis of the problem, repair of the system, and/or
replacement of components.
For your safety, DO NOT attempt repair of electrical wiring
or other operating controls. Refer repairs to qualied service
personnel. Failure to do so could result in serious personal
injury or death.
Figure 10 - Drain Back Tank Replacement Parts
the plug on the solar controller and call a plumber.

lp-351b Rev. 11.25.15
13
Drain Back Tank
Limited Warranty
Five year warranty to assure your complete satisfaction.
For Residential and Commercial Use
HTP warrants to the original retailer purchaser that HTP will furnish
a replacement Drain Back Tank in the event of tank leakage due to
defects in material or workmanship; or repair same at our option,
at no cost to the original retail purchaser except as set forth in
this warranty. HTP SHALL NOT, UNDER ANY CIRCUMSTANCES,
BE HELD LIABLE FOR INCIDENTAL, CONSEQUENTIAL OR
SECONDARY DAMAGES AND EXPENSES RESULTING FROM
ALLEGED DEFECTS UNDER THIS WARRANTY.
WARRANTY
1. Drain Back Tank assembly – consists of a stainless steel storage
tank, and heat exchanger (when applicable), warranted for five (5)
years.
2. Parts are warranted by original manufacturer for a period of one
(1) year. These can consist of fittings, glass, pressure relief valve,
and other such components that are not part of the tank assembly.
COVERAGE
A. HTP warrants that it will repair or replace, at its option, any
defective or malfunctioning component of the drain back tank with
a component of equivalent size and current model. Replacement
components will be warranted for ninety (90) days. It is expressly
agreed between HTP and the original consumer purchaser that
repair or replacement are the exclusive remedies of the original
consumer purchaser.
B. Through five (5) years after the original date of installation, HTP
will repair or replace, at its option, any drain back tank having a
defect or malfunction that results in a water leak from the outside
jacket or inner tank as a result of normal use and service. The
replacement drain back tank will be warranted for only the unexpired
portion of the original warranty. It is expressly agreed between HTP
and the original consumer purchaser that repair or replacement are
the exclusive remedies of the original consumer purchaser.
C. If HTP is unable to repair or replace the drain back tank so as
to conform to this warranty after a reasonable number of attempts,
HTP will provide, at its option, a replacement product. These
remedies are the consumer purchaser’s exclusive remedies for
breach of warranty.
D. If government regulations, industry certification, or similar
standards require the replacement drain back tank or part(s) to
have features not found in the defective drain back tank or part(s),
you will be charged for the difference in price represented by those
required features. If you pay the price difference for those required
features and/or to upgrade the size and/or other features available
on a new replacement drain back tank or part(s), you will also
receive a complete new limited warranty for that replacement drain
back tank or part(s).
E. If at the time of a request for service the original consumer
purchaser cannot provide a copy of the original sales receipt or the
warranty card registration, the warranty period for the drain back
tank shall then be the date of manufacture of drain back tank and
NOT the date of installation of the drain back tank.
F. This warranty extends only to drain back tanks utilized in
heating applications that have been properly installed by qualified
professionals based upon manufacturer’s installation instructions.
OWNER RESPONSIBILITIES
To avoid the exclusion list in this warranty, the owner or installer
must:
1. Keep the drain back tank free of damaging scale deposits.
2. Keep the drain back tank in an area not prone to freezing.
3. Make provisions so if the drain back tank or any component
part or connection should leak, the resulting flow of water will
not cause damage to the area in which it is installed. A water
heater temperature and pressure relief valve should be piped to
the nearest drain in order to avoid damage in the event the valve
is activated.
4. Periodic maintenance of glycol must be performed to assure pH
levels do not exceed 10 or drop below 8. Failure to do so will cause
damage to tank or components of the solar system.
5. Operate the drain back tank assembly at pressure below that
shown on the rating plate on the pressure relief valve.
WARRANTY EXCLUSIONS
This limited warranty shall not cover:
1. Breaches of warranty that result (a) from any use of a drain
back tank for any purpose other than its ordinary purpose, as well
as any neglect, accident, or ordinary wear and tear; or (b) from
damage from transport, shipping, handling, or any act of God or
other Force Majeure;
2. Breaches of warranty resulting from a) freezing; or (b) excessive
pressure or leaks at water connections or any other similar case;
3. Breaches of warranty resulting from installation that is not in
accordance with (a) HTP installation and operation manual in
effect on the date when the Product is sold to the Customer; or
(b) instructions and/or all relevant standards, codes of practice,
electrical wiring and safety regulations and any regional authority
regulations;
4. Failure of a component, control, or component part other than a
component part manufactured solely by HTP;
5. Any cause similar to any of the above, not resulting solely due
to defective material and/or workmanship;
6. Any damage or failure resulting from improper water chemistry.
WATER CHEMISTRY REQUIREMENTS – Sodium less than
20mGL. Water pH between 6.0 and 8.0. Hardness less than 7
grains. Chlorine concentration less than 100 ppm;
7. Condition resulting from exposure to foreign particles in the tank
and exposure to chlorine content higher than 100 parts per million,
or other corroding substances;
8. Connecting materials other than copper, brass, or stainless
steel. (Use of galvanized piping or dielectric unions is expressly
forbidden.)
9. Damages, malfunctions, or failures resulting from failure to
operate and maintain the drain back tank in accordance with the
manufacturer’s provided instructions.
10. Units installed outside the fifty states (and the District of
Columbia) of the United States of America and Canada.
NOTE: HTP WILL NOT WARRANT ANY UNIT PURCHASED
FROM AN UNAUTHORIZED DEALER.
PROCEDURES FOR WARRANTY SERVICE REQUESTS
Any claim for warranty assistance must be made promptly.
Determine if the drain back tank is “in-warranty” (that is, within
the applicable warranty period) by reviewing a copy of the original
sales receipt. You must present a copy of the original sales receipt
for a warranty service request.
If your drain back tank is “in-warranty”, contact the retailer from
whom the tank was purchased (or the installer) for assistance.
Be prepared to provide the retailer or installer with a copy of your
original receipt, complete model and serial numbers, and the date
of installation, in addition to explanation of your drain back tank
problem.
Warranty coverage is subject to validation of “in-warranty” coverage
by HTP claims department personnel. All alleged defective
or malfunctioning parts must be returned to HTP via the local
distribution channels where original purchase was made. NOTE:
Any parts or tanks returned to HTP for warranty analysis will
become the property of HTP and will not be returned, even if credit
is denied.

lp-351b Rev. 11.25.15
14
If all warranty conditions are satisfied, HTP will provide replacement
parts to the retailer.
If you have questions about the coverage of this warranty, please
contact HTP at the address or phone number stated below:
HTP
272 Duchaine Blvd.
New Bedford, MA 02745
Attention: Warranty Service Department
1(800) 323-9651
SERVICE, LABOR AND SHIPPING COSTS
This limited warranty does not extend to any shipping charges,
delivery expenses, or administrative fees incurred by the purchaser
in repairing or replacing the drain back tank or part(s). This warranty
does not extend to labor costs beyond the coverage specified in this
warranty document. All such expenses are your responsibility.
LIMITATIONS OF YOUR HTP WARRANTY AND REMEDIES
THE FOREGOING WARRANTIES ARE EXCLUSIVE AND ARE
GIVEN AND ACCEPTED IN LIEU OF ANY AND ALL OTHER
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT
LIMITATION THE IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS FOR A PARTICULAR PURPOSE AND ANY
OBLIGATION, LIABILITY, RIGHT, CLAIM OR REMEDY IN
CONTRACT OR TORT, WHETHER OR NOT ARISING FROM HTP’S
NEGLIGENCE, ACTUAL OR IMPUTED. THE REMEDIES OF THE
PURCHASER SHALL BE LIMITED TO THOSE PROVIDED HEREIN
TO THE EXCLUSION OF ANY OTHER REMEDIES INCLUDING
WITHOUT LIMITATION, INCIDENTAL OR CONSEQUENTIAL
DAMAGES, SAID INCIDENTAL AND CONSEQUENTIAL DAMAGES
INCLUDING, BUT NOT LIMITED TO, PROPERTY DAMAGE, LOST
PROFIT OR DAMAGES ALLEGED TO HAVE BEEN CAUSED BY
ANY FAILURE OF HTP TO MEET ANY OBLIGATION UNDER
THIS AGREEMENT INCLUDING THE OBLIGATION TO REPAIR
AND REPLACE SET FORTH ABOVE. NO AGREEMENT VARYING
OR EXTENDING THE FOREGOING WARRANTIES, REMEDIES
OR THIS LIMITATION WILL BE BINDING UPON HTP. UNLESS
IN WRITING AND SIGNED BY A DULY AUTHORIZED OFFICER
OF HTP. THE WARRANTIES STATED HEREIN ARE NOT
TRANSFERABLE AND SHALL BE FOR THE BENEFIT OF THE
ORIGINAL PURCHASER ONLY.
NO OTHER WARRANTIES
Your HTP warranty gives you specific legal rights, and you may
also have other rights that vary from state to state. Some states do
not allow the exclusion or limitation of incidental or consequential
damages so this limitation or exclusion may not apply to you.
These are the only written warranties applicable to the drain back
tank manufactured and sold by HTP. HTP neither assumes nor
authorizes anyone to assume for it any other obligation or liability in
connection with said drain back tanks.
HTP reserves the right to change specifications or discontinue
models without notice.

lp-351b Rev. 11.25.15
15
IMPORTANT
Customer: Please only sign after the installer has fully reviewed the installation, safety, proper operation, and maintenance of the system.
If the system has any problems please call the installer. If you are unable to make contact, please call your sales representative.
Distributor / Dealer: Please insert contact details.
Customer Installation Record Form
The following form should be completed by the installer for you to keep as a record of the installation in case of a warranty
claim. After reading the important notes at the bottom of the page, please also sign this document.
Customer’s Name
Date of Installation
Installation Address
Product Name / Serial Number(s)
Comments
Installer’s Code / Name
Installers Phone Number
Signed by Installer
Signed by Customer
Installation Notes