Installation
Start-Up
Maintenance
Parts
Warranty
Drain Back Tank
For Residential and
Commercial Use
DB Series and DBX Models*
*A sux of “X” denotes models with
internal heat exchanger
This manual must only be used by a qualied 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.
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
2
The following dened 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 ocial 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 ocer or departmental ocial may be the AHJ.
NOTE: HTP, Inc. reserves the right to modify product technical
specications and components without prior notice.
For Your 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.
For the Installer
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 dier 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 & Certication
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.
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. Specications 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
lp-351b Rev. 11.25.15
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
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 eciency 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 qualied heating installer /
service technician. Have this solar water heating system serviced
/ inspected annually by a qualied 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.
3
DO NOT USE THE SOLAR SYSTEM IF ANY PART HAS BEEN
SUBMERGED IN WATER. Immediately call a qualied 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 qualied 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.
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.
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 overlling and exposing pipes
to a freezing condition.
Improper installation or use may result in property damage.
Such damages ARE NOT covered by warranty.
UNCRATING THE WATER HEATER - Any claims for damage
or shortage in shipment must be led immediately against the
transportation company by the consignee.
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.
lp-351b Rev. 11.25.15
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 qualied and experienced in the installation, service, and
maintenance of solar hot water systems.
C. Chemical Vapor Corrosion
Products to Avoid
Spray cans containing
uorocarbons
Permanent wave solutions Swimming pools
Chlorinated waxes / cleaners Metal fabrication plants
Chlorine-based swimming pool
chemicals
Calcium chloride used for thawing Refrigeration repair shops
Sodium chloride used for water
softening
Refrigerant leaks Auto body shops
Paint or varnish removers Plastic manufacturing plants
Hydrochloric or Muriatic acid
Cements and glues New building construction
Antistatic fabric softeners used in
clothes dryers
Chlorine-type bleaches, laundry
detergents, and cleaning solvents
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.)
Areas Likely to Have
Contaminants
Dry cleaning / laundry areas
and establishments
Beauty shops
Photo processing plants
Furniture renishing areas and
establishments
Remodeling areas
Garages and workshops
Approximate Time / Temperature Relationships in Scalds
o
120
F More than 5 minutes
o
F 1 1/2 to 2 minutes
125
o
F About 30 seconds
130
o
F About 10 seconds
135
o
F Less than 5 seconds
140
o
F Less than 3 seconds
145
o
F About 1 1/2 seconds
150
o
F About 1 second
155
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.
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.
lp-351b Rev. 11.25.15
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,
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 specication sheet included with the
glycol for recommended concentrations. A glycol/water mix
must not exceed 50%, unless the manufacture species that
a dierent 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.
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 aect 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.
5
Figure 2 - Pressure Drop through Heat Exchanger
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).
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.
Figure 1 - Catch Pan Dimensions
lp-351b Rev. 11.25.15
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