Bosch DHW Tank QWST120 O User manual

Installation and Maintenance Instructions
DHW Tank
QWST120 O
6 720 648 100-00.1ITL
6 720 648 071 (2012/03) US

Table of Contents
6 720 648 071 (2012/03)
2
Table of Contents
1 Key to symbols and safety instructions . . . . . . . 3
1.1 Explanation of symbols . . . . . . . . . . . . . . . 3
1.2 Safety instructions . . . . . . . . . . . . . . . . . . 3
2 General points . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Delivered condition . . . . . . . . . . . . . . . . . . 5
2.2 Tank installation . . . . . . . . . . . . . . . . . . . . 5
3 Moving the tank . . . . . . . . . . . . . . . . . . . . . . . . . 6
4 Dimensions and connections . . . . . . . . . . . . . . . 7
5 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1 Safety limits . . . . . . . . . . . . . . . . . . . . . . . 8
5.2 Connections and fittings . . . . . . . . . . . . . . 8
5.3 Temperature monitoring control options . . 9
5.3.1 Installing the temperature sensor . . . . . . . 9
5.3.2 Installing the Aquastat . . . . . . . . . . . . . . 10
6 Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . 11
7 Maintenance and cleaning . . . . . . . . . . . . . . . . 12
7.1 Checking the magnesium anode . . . . . . . 12
7.2 Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.3 Recommissioning after cleaning . . . . . . . 13
8 Spare parts for QWST120 O . . . . . . . . . . . . . . . 14

Key to symbols and safety instructions
6 720 648 071 (2012/03) 3
1 Key to symbols and safety instructions
1.1 Explanation of symbols
Warnings
Signal words at the beginning of a warning are used to
indicate the type and seriousness of the ensuing risk if
measures for minimizing damage are not taken.
•NOTICE indicates that minor damage to property may
occur.
•CAUTION indicates possible minor to medium
personal injury.
•WARNING indicates possible severe personal injury.
•DANGER indicates that fatal injury may occur.
Important information
Additional symbols
1.2 Safety instructions
Safety instructions
Failure to observe the safety instructions can result in
serious injury and a risk of fatal injury as well as damage
to property and the environment.
BRead the safety instructions carefully prior to
commissioning the system.
BEnsure that only a trained and certified contractor
carries out installation, commissioning, maintenance
and service.
BEnsure that the system is approved by the local
jurisdiction.
BClean and perform maintenance at least once a year.
Check that the entire system functions properly at the
same time. Immediately remedy faults.
Danger from failing to consider your own safety in an
emergency such as a fire
BNever put yourself at risk of fatal injury. Your own
safety must always take the highest priority.
Risk of damage from operator error
Operator errors can lead to injuries and/or damage to
property.
BEnsure that only individuals who can operate this
appliance correctly have access to it.
BInstallation and commissioning as well as servicing
and maintenance must be carried out only by a
trained and certified contractor.
Warnings are indicated in the text by a
warning triangle and a gray background.
In case of danger from electric shock, the
exclamation point on the warning triangle is
replaced with a lightning symbol.
Important information that presents no risk
to people or property is indicated with this
symbol. It is separated by horizontal lines
above and below the text.
Symbol Function
BSequence of steps
ÆCross-reference to other points in this
document or to other documents
•Listing/list entry
–Listing/list entry (2nd level)
Table 1

Key to symbols and safety instructions
6 720 648 071 (2012/03)
4
Installation and operation
BHave the appliance installed only by a qualified
contractor.
BEnsure that the hot water tank is completely full prior
to start up.
BTo prevent damage from excess pressure, never
disable the safety valves.
BWater may escape from the safety valve when water is
being heated. Ensure that the safety valve is piped to
within 6 inches of the ground in an area where
property damage will not occur.
BInstall the unit only in a frost-free room.
BNever store or place combustible material or liquids
near the appliance.
BMaintain safe clearances in accordance with local/
national regulations.
Risk of fatal injury from electric shock
BIf an aquastat is used with line voltage, it must be
connected by a licensed electrician. The terminal
wiring diagram must be followed.
BBefore carrying out any work, isolate all phases of the
electrical power using the emergency shut-off switch
or by disengaging the heating system circuit breaker.
Secure against unintentional reconnection.
BDo not install this device in rooms with a high
moisture level (e.g. bathrooms, saunas).
Inspection/maintenance
BRecommendation: sign a maintenance and inspection
contract with a qualified heating contractor and have
the appliance serviced annually.
BThe owner/operator is responsible for the safety and
environmental compatibility of the system.
BRead and follow the safety instructions in the
"Cleaning and maintenance" chapter.
Original spare parts
Damage caused by spare parts not supplied by the
manufacturer are excluded from our warranty.
BUse only original spare parts and accessories from
the manufacturer.
Frost damage
BWhen there is a risk of frost, drain the water from the
DHW tank and the heating system's pipework. The
system is protected from frost only if it is completely
dry.
Instructing the owner/operator
BInstruct the owner/operator in the functionality and
operation of the appliance.
BInform the owner/operator that they must never carry
out any modifications or repairs.
BInform the owner/operator that children
unsupervised by adults should never be in the vicinity
of the heating system.
BComplete the commissioning report in this document
and hand it over to the owner/operator.
BGive the technical documentation to the owner/
operator.
Disposal
BDispose of packaging in an environmentally
responsible manner.
BDispose of the appliance correctly at an authorized
disposal site.
Cleaning
BClean the outside of the appliance with a damp cloth.

General points
6 720 648 071 (2012/03) 5
2 General points
2.1 Delivered condition
The DHW tank QWST120 O Is delivered as a fully
assembled unit.
Additional components supplied with the tank:
1 125 psi P and T valve
3 3/4" brass couplings
1 3/4" brass tee
1 Honeywell L4006 adjustable differential tank
aquastat
1 Aquastat mounting bracket and 4 mounting screws
3 Adjustable tank leg leveling bolts
1 Roll of high quality Teflon tape
2.2 Tank installation
Select a dry, frost free room for installation. The tank
must not be allowed to freeze, or it must be drained or
protected appropriately when not in operation. The floor
must be level and able to carry the weight of the unit.
When installing the heating boiler and DHW tank,
observe the minimum clearance requirements for
assembly and service (ÆFig. 1).
Fig. 1 Minimum space requirements for installation
and maintenance
6 720 648 100-14.1ITL
16"
16"
min. 4"
(406 mm)
(406 mm)
(102 mm)

Moving the tank
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6
3 Moving the tank
The DHW tank can be moved by means of a hand truck
(accessory, ÆFig. 2) while still packaged or after
removal of the packaging.
BPosition the tank on the hand truck, secure with a
strap if necessary, and transport safely to the
installation location.
BRemove the strap.
Fig. 2 Hand truck (illustrative)
BRemove the plastic wrapping.
BRemove the polystyrene cover pad and 4 wooden
boards.
BLay the polystyrene cover [1] on the ground and
carefully lay the DHW tank [2] on its side.
BRemove bottom polystyrene pad and pallet. Install the
adjustable feet M10 x 30 [3].
Fig. 3 DHW tank on polystyrene cover pad (illustrative)
1Polystyrene cover pad
2DHW Tank
3Adjustable feet
BPlace the DHW tank upright.
BDispose of the DHW tank packaging in an
environmentally responsible manner.
NOTICE: Take care not to damage the tank
when moving it.
BObserve the handling instructions on the
packaging.
BUse suitable means of transportation,
e.g. a hand truck with strap, to handle
this product.
BMove this product upright.
BPrevent impact and shock.
6 720 648 100-02.1ITL
6 720 648 100-15.1ITL
ca. 0.78"
2 3
1
3/4 - 1"
(19 - 25 mm)

Dimensions and connections
6 720 648 071 (2012/03) 7
4 Dimensions and connections
Fig. 4 Dimensions and connections
1Magnesium anode
AB Hot water outlet
EK Cold water inlet
VS Tank coil supply
RS Tank coil return
MB Hot water temperature sensor or Aquastat
EL Drain
6 720 648 100-13.1ITL
MB
EKRSVS
1
MB
EL
EL
AB
20"
37"
3/4" - 1"
20"
(508 mm)
37"
(940 mm)
3/4" - 1"
(19 - 25 mm)
Type VS RS EK/AB Sacrificial
anode
Weight (empty)
Lbs (kg)
120 NPT ¾ " NPT ¾ " NPT ¾ " G 1" 158 (72)
Table 2 Dimensions and connections

Installation
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8
5 Installation
BLevel the DHW tank by adjusting the feet (ÆFig. 5).
Fig. 5 Adjusting the feet (illustrative)
5.1 Safety limits
Maximum Temperature:
•Heating water (boiler) 230 °F (110 °C)
•Domestic water (DHW tank) 203 °F (95 °C)
Operating pressure:
•Heating water (boiler) 87 psi 1
•Domestic water (DHW tank) 145 psi (10 bar)
5.2 Connections and fittings
It is the installer's responsibility to follow national and
local code when installing this tank (ÆFig. 6).
BConnect all piping to the DHW tank by means of
threaded fittings. For easy service and maintenance,
each connection should be equipped with a shutoff
valve. Install a drain valve [2] in the hot water pipe
upstream and downstream of the shut-off valve [3].
Attach a tag with the following statement to the safety
valve [4]: "Do not close drain line. During heating,
water may be released for safety reasons."
Fig. 6 Installation (illustrative)
1Storage tank
2Purge valve
3Shut-off valve with drain
4Pressure and temperature safety valve
5Flow check valve
6Shut-off valve
7DHW recirculation pump (optional)
8Pressure reducer (if required)
9Purge valve
10 Backflow preventer
11 Pressure gauge connection
12 Drain
AB Hot water outlet
EK Cold water inlet
EZ Recirculation inlet
EL Drain
WARNING: Risk of damage to property and
personal injury if temperature / pressure
limits exceeded.
BFor safety reasons, never exceed the
following limits.
1. From the heating system, individual safety equipment
required (safety valve, expansion vessel).
6 720 648 100-05.1ITL
6 720 648 100-06.1ITL
15
11 10 9 8 6
4
2
12
3
6 7 6

Installation
6 720 648 071 (2012/03) 9
BA listed pressure and temperature relief valve (PTRV)
must be installed at the time of installation. No valve
is to be placed between the PTRV and the heater. No
reducing coupling or other restriction may be
installed in the discharge line. The discharge line must
be a minimum of 6" (153 mm) above a drain and
installed such that it allows complete drainage of
both the PTRV and the line. The discharge line must
be placed where it will not cause any water damage.
The location of the PTRV must be readily accessible
for servicing or replacement, and be mounted as close
to the water heater as possible.
BManually activate the TPRV annually to ensure proper
operation. If the TPRV does not activate it must be
replaced.
BMake sure that the installed pipework and
connections are free of stress.
BCheck all connections for leaks! Do not kink or twist
hoses.
Safety valve
Only use approved and listed pressure and temperature
relief valves of the proper size for the output of the tank.
5.3 Temperature monitoring control
options
Install a temperature sensor or an Aquastat on the DHW
tank to measure and monitor the hot water temperature.
5.3.1 Installing the temperature sensor
BFeed the temperature sensor [2] with the spring [1]
into the sensor well [3].
Fig. 7 Installing the temperature sensor
1Spring clip
2Temperature sensor
3Sensor well
WARNING: Precautions must be taken prior
to manually operating the relief valve to
avoid contact with hot water being released
and to prevent water damage.
WARNING: If a relief valve discharges
periodically, this may be due to thermal
expansion in a closed water supply system.
Contact the installer to correct this
situation. Do not plug the relief valve.
Minimum
connection
diameter
Nominal capacity
of the water
chamber (gal)
Max. heating
capacity
[kBtu/hr]
3/4" 32 (120 liters) 255
Table 3 Safety valve
Ensure that the sensor surface has contact
with the sensor well surface over its full
length, and that it cannot accidentally be
pulled out.
6 720 648 100-07.1ITL
2
1
3

Installation
6 720 648 071 (2012/03)
10
5.3.2 Installing the Aquastat
BRemove cover from the Aquastat.
BIf necessary, remove any unnecessary attachments.
Attach bracket [3] to Aquastat [2] by means of 2 self-
tapping screws [1].
Fig. 8 Attaching the Aquastat to the bracket
1Self-tapping screws C-ST 4.2x13 mm
2Aquastat
3Bracket
BFeed the temperature probe [4] with the spring [5]
into the sensor well [3]. Ensure that the probe makes
contact with the well wall over its entire length.
BAttach Aquastat [2] to the DHW tank by means of
2 self-tapping screws [1].
Fig. 9 Installing the Aquastat
1Self-tapping screws C-ST 4.2x13 mm
2Aquastat
3Sensor well
4Temperature sensor
5Spring
BReplace the cover of the Aquastat.
DANGER: Risk of fatal injury from electric
shock.
BDisconnect all electrical power before
working on the system.
6 720 648 100-08.1ITL
2
1
3
Connect the electrical power and set the
temperature as shown in the manual
supplied with the Aquastat.
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2
1
3
5
4