Buderus Logalux ST400/3 US User manual

6304 0112 – 07/2005 US For heating contractors
Please read carefully prior to installation and maintenance.
Installation and maintenance
instructions
Indirect Fired domestic hot water tank
Logalux ST400/3 "US", 500/3 "US",
750/3 "US" and 1000/3 "US"

Contents
2Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
We reserve the right to make any changes due to technical modifications.
1 General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Standards and guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Tools, materials and accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Correct use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Notes structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3 Please observe these notes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.4 Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Product description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1 Dimensions and connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2 Safety limits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Transporting and installing DHW tank. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1 DHW tank handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.2 Positioning the DHW tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6 DHW tank installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1 Installing the DHW pipework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.2 Checking the magnesium anode connection . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.3 Installing the hot-water temperature sensor (Logamatic or SP34D Control) . . . . . . . 9
6.4 Installing Honeywell Aquastat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.5 Install thermal insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7 Start-up and shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1 Starting the DHW tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.2 Shutdown tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8 Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.1 Preparing the DHW tank for maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.2 Cleaning the DHW tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8.3 Checking the magnesium anode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.4 Replacing the magnesium anode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.5 Returning the DHW tank into use after cleaning . . . . . . . . . . . . . . . . . . . . . . . 19

General information 1
3
We reserve the right to make any changes due to technical modifications.
Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
1 General information
1.1 Standards and guidelines
1.2 Tools, materials and accessories
You need standard tools for the installation and
maintenance of the DHW tank, as those typically used in
gas and water installations.
A transport dolly is also useful.
USER NOTE
Observe all standards and guidelines
applicable to the installation and operation
of this heating system in your country.
USER NOTE
If the storage tank will be installed in
Massachusetts, it must be installed by an
installer or dealer who is registered there.

Safety2
4Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
We reserve the right to make any changes due to technical modifications.
2 Safety
These installation and maintenance instructions contain
important information for the safe and appropriate
installation, initial start-up and maintenance of the
Logalux ST400/3 -1000/3 DHW tanks (in the following
"DHW tank").
These installation and maintenance instructions are
designed for specialists, who – through their vocational
training and experience –are knowledgeable in handling
heating systems and DHW installations.
zInform the user about the operation of the DHW tank,
with a particular emphasis on safety aspects.
zHand over the installation and maintenance
instructions to the user to be retained near the
heating system.
2.1 Correct use
Logalux ST400/3 -1000/3 DHW tanks are designed for
heating and storing potable water. The requirements of
the Potable Water Order (or local regulations) apply to
potable water.
Only heat these DHW tanks with heating water in sealed
systems.
2.2 Notes structure
Two levels of danger are identified and signified by the
following terms:
2.3 Please observe these notes
2.4 Disposal
zDispose of the DHW tank packaging in an
environmentally responsible manner.
zDispose of old DHW tanks in an environmentally
responsible manner through an approved
organization.
WARNING!
RISK TO LIFE
Identifies possible dangers emanating
from a product, which might lead to
serious injury or death if appropriate care
is not taken.
CAUTION!
RISK OF INJURY/
SYSTEM DAMAGE
Identifies potentially dangerous situations,
which might lead to medium or slight
injuries or to material losses.
USER NOTE
Tip for the optimum utilization and setting
of the control(s) plus other useful
information.
WARNING!
RISK TO HEALTH
Improper installation and maintenance
work can contaminate the potable water.
zInstall and clean the DHW tank
hygienically and thoroughly and in
accordance with current standards.
CAUTION!
TANK DAMAGE
due to unsatisfactory cleaning and
maintenance.
zCarry out cleaning and maintenance at
least every two years.
zImmediately remedy all faults to
prevent system damage.
USER NOTE
Only use original Buderus spare parts.
Losses caused by the use of parts not
supplied by Buderus are excluded from the
Buderus warranty.

Product description 3
5
We reserve the right to make any changes due to technical modifications.
Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
3 Product description
The Logalux ST400/3 – 1000/3 DHW tanks are mounted
on a pallet at the factory. Covers and accessories are in
a separate carton package.
The main components of the DHW tank are:
–DHW tank (Fig. 1, Item 5) with corrosion protection.
The cathodic corrosion protection is the hygienic
DUOCLEAN MKT thermo-glazing from Buderus and
the magnesium anode mounted on the top access
port (Fig. 2, Item 1).
–Tank jacket
The removable cover components are the lid (Fig. 1,
Item 1), the access port cover (Fig. 1, Item 8), the
two-piece cover strip (Fig. 1, Item 6) at the front and
the three-piece cover strip at the back (Fig. 1,
Item 3).
–Thermal insulation jacketing (Fig. 1, Item 4)
The thermal insulation mat is flexible foam with an
outer cover of plastic.
–Top and bottom thermal insulation (Fig. 1, Item 2)
–Front thermal insulating disk (access port) (Fig. 1,
Item 7)
–Front access port (Fig. 1, Item 9)
The manual access cover is an opening for
maintenance inspection and cleaning.
–Sensor well for installation of a DHW temperature
sensor (Fig. 2, page 6, M)
The boiler DHW thermostat regulates the set DHW
temperature using this DHW temperature sensor
(port).
–Coiled heat exchanger
The coil type heat exchanger (Fig. 2, Item 3,page6)
transfers the energy from the heating water to the
DHW inside the tank. The tank content is evenly
heated through.
Fig. 1 Logalux ST400/3 –1000/3 DHW tank
Item 1: Tank cover
Item 2: Thermal insulation disks
Item 3: Back cover strips
Item 4: Thermal insulation jacket
Item 5: DHW tank
Item 6: Front cover strip
Item 7: Access port in thermal insulation
Item 8: Access port cover
Item 9: Front access tank hand hole
3
4
2
6
1
2
333
3
6
8
7
5
9
9

6Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
We reserve the right to make any changes due to technical modifications.
Specifications4
4 Specifications
4.1 Dimensions and connections
Fig. 2 Sectional view of DHW tanks
Tab. 1 Technical specification of the Logalux ST DHW tank
4.2 Safety limits
3
2
1
Item 1: Magnesium anode Item 2: Nameplate
Item 3: Coil type heat exchanger
M1= sensing port DHW tank EZ = recirculation inlet
AW = hot water outlet EK/EL = cold water inlet and tank drain
VS = boiler supply
RS = boiler return
Type ØD
[in.]
H
[in.]
Capacity
[Gal.]
Weight
[lbs.]
AW VS
RS
EK
EL
EZ Max. headtransfer
capacity CM
ST 400/3 "US" 33½ 61 103 407 1¼" 1¼" 1¼" ¾" 225
ST 500/3 "US" 33½ 73 129 486 1¼" 1¼" 1¼" ¾" 260
ST 750/3 "US" 39¼ 73 194 702 1¼" 1¼" 1½" ¾" 350
ST 1000/3 "US" 43¼ 75½ 258 893 1½" 1¼" 1½" ¾" 425
Approved
maximum values
Temperatur
e
Operating
pressure
On-site test
pressure 2
°C (°F) bar (psi) bar (psi)
Heating water 100 (212) 6 (80)1N/A1
DHW 95 (203) 10 (1453)10 (1453)
Tab. 2 DHW tank safety limits
1Subject to the individual heating system protection (e.g. boiler
relief valve and diaphragm expansion vessel).
2Operating and test pressure are overpressure.
3Maximum 100 psi in Massachusetts.
CAUTION!
TANK DAMAGE
through exceeding limits.
zFor safety reasons DO NOT exceed
the limits stated in "Tab 3".

Transporting and installing DHW tank 5
7
We reserve the right to make any changes due to technical modifications.
Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
5 Transporting and installing DHW tank
5.1 DHW tank handling
Use suitable equipment to move the DHW tank. Secure
the DHW tank against slipping.
5.2 Positioning the DHW tank
The DHW tank may be placed either on the right or left
side of the boiler.
Observe the minimum clearances recommended for
installation and maintenance when installing the DHW
tank (Fig. 4). Maintain at least 6" clearance from
combustible surfaces.
The floor must be level and able to support a full tank.
Fig. 3 Moving DHW tank on pallet (general layout)
USER NOTE
zTransport the DHW tank fastened to
the pallet on a transport dolly.
Fig. 4 Positioning the DHW tank (general layout)
(dimensions in inches)
CAUTION!
TANK DAMAGE
through frost.
zThe boiler room must be dry and safe
from the risk of frost.

8Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
We reserve the right to make any changes due to technical modifications.
DHW tank installation6
6 DHW tank installation
6.1 Installing the DHW pipework
Please observe the following note regarding the
connection of the DHW tank to the pipework. These
notes are important for trouble free operation.
Fig. 5 Installation diagram (general layout)
Item 1: DHW tank
Item 2: Inlet and outlet valve
Item 3: Stop valve with drain valve
Item 4: P & T valve
Item 5: Check valve
Item 6: Isolation valve
Item 7: Circulation pump
Item 8: Pressure reducer valve (optional)
Item 9: Purge valve
Item 10: Non-return valve
Item 11: Pressure gauge (optional)
Item 12: Tank drain
Legend:
AW: Domestic hot water outlet
EZ: DHW recirculation inlet
EK: Cold water inlet
zAttach the included brass tees to the DHW outlet
and cold water inlet/drain connections. Install the
included pressure & temperature valve on the
NPT¾ connection of the brass tee on the DHW
outlet connection. Install the included drain valve on
the NPT¾ connection of the brass tee on the cold
water inlet/drain connection.
zIf a Logamatic or Goldline SP30D control is used,
the installation is described in Section 6.3, page 9.
zIf a Honeywell Aquastat is used as the DHW control,
the installation is described in Section 6.4, page 10.
zRefer to Table 1 and select a P & T valve with a
rating at least equal to the maximum heat transfer
capacity of the tank
CAUTION!
TANK DAMAGE
Protective sleeves are inserted in the AW,
EZ and EK connectors. They protect the
enameled faces of the connectors from
corrosion.
zKeep these protective sleeves inserted.
WARNING!
RISK TO HEALTH
Improper installation work can
contaminate the potable water.
zInstall the DHW tank hygienically in
accordance with current standards.
zRinse the DHW tank and pipework
thoroughly with potable water.
USER NOTE
If a back flow prewater is required per local
code, an expansion vessel thermal on the
DHW piping must be installed.
CAUTION!
SYSTEM DAMAGE
due to incorrect installation.
zObserve all current standards and
guidelines applicable to the installation
and operation of this DHW tank as
applicable in your state or per local
jurisdiction.
USER NOTE
The safety equipment on the DHW tank
must be adapted to the output of the boiler
if the boiler exceeds 100.000 Btu/hr.

DHW tank installation 6
9
We reserve the right to make any changes due to technical modifications.
Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
zEquip and install the DHW pipework in accordance
with state.
6.2 Checking the magnesium anode connection
zCheck that the ground wire (Fig. 6, Item 1) for the
magnesium anode (Fig. 6, Item 2) is correctly
connected.
6.3 Installing the hot-water temperature sensor (Logamatic or SP34D Control)
If a Buderus Logamatic control or Goldline SP34D
control is used, install the DHW temperature sensor
supplied with the Logamatic or SP34D as follows:
zInsert the sensor pack including the blank spacers
and wavy compensating spring (Fig. 7, Item 1 to 4)
until it bottoms out inside the sensor well (Fig. 7,
Item 5).
During insertion the plastic spiral (Fig. 7, Item 3),
which holds the sensor together, slides back
automatically.
The spring (Fig. 7, Item 4) ensures contact between the
sensor well and the sensor surfaces and so a reliable
temperature transfer.
CAUTION!
SYSTEM DAMAGE
through leaking connections.
zConnect all connection pipes free from
stress.
Fig. 6 Checking the magnesium anode connection
Item 1: Magnesium anode
Item 2: Ground wire
1
2
Fig. 7 Installing the DHW temperature sensor package
Item 1: Blanking piece
Item 2: Quadrant temperature sensor (or SP34D sensor)
Item 3: Plastic spiral
Item 4: Compensating spring
Item 5: Immersion well (M1)
12
4
5
3

10 Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
We reserve the right to make any changes due to technical modifications.
DHW tank installation6
zPush the sensor holder clip (Fig. 8, Item 1) from the
side over the sensor well (Fig. 8, Item 2).
zRoute the sensor lead to the boiler or control panel
(Logamatic or SP34D control) and ensure the lead is
not strained. This lead must not be in contact with
any hot boiler parts.
6.4 Installing Honeywell Aquastat
zRemove cover from Aquastat (Fig. 9, Item 2).
Slacken the hex bolt on the top.
zScrew retainer (Fig. 9, Item 6) on Aquastat with two
self-tapping screws (remove existing fastener if
necessary).
zInsert temperature capillary with clamping spring and
possibly blank spacers (Fig. 9, Item 4 and 5) fully
into the sensor well (M) (Fig. 9, Item 3).
zScrew Aquastat (Fig. 9, Item 2) to DHW tank with
two self-tapping screws (Fig. 9, Item 1). First drill two
small holes in the cover beside the M1connection.
zReplace cover in Aquastat.
Fig. 8 Installing the sensor holder clip
Item 1: Sensor holder clip
Item 2: Immersion well
1
2
USER NOTE
See the wiring diagram supplied for the
electrical connection of the temperature
sensor.
Fig. 9 Installing Aquastat
Item 1: Self-tapping screws C-ST 4.2 × 13 mm
Item 2: Aquastat
Item 3: Sensor well (M1 connection)
Item 4: Temperature capillary
Item 5: Clamping spring
Item 6: Holder/retainer
1
2
3
4
5
6
WARNING!
RISK TO LIFE
from electric shock.
zBefore you work on the system:
Isolate the system from the electrical
system.
USER NOTE
Connect the electrical power and set the
temperature as shown in the manual
supplied with the Aquastat.

DHW tank installation 6
11
We reserve the right to make any changes due to technical modifications.
Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
6.5 Install thermal insulation
The thermal insulating jacket is best installed at
approximately room temperature conditions. Lightly tap
the thermal insulating jackets towards the two ends to
make it easier to pull the ends together.
First attach the sealing strip to the connection lines and
secure with installation aid (U-bar) (Fig. 10, Item 1) if
necessary.
zPlace slotted thermal insulating disk on the floor with
the slots near the tank feet (Fig. 10).
zPlace the perforated thermal insulating jackets
around the tank so the holes fit the connections
(Fig. 10).
zPull the ends of the thermal insulating jackets
together and close them (Fig. 10).
zPosition thermal insulating disk before front access
port (Fig. 11).
zPlace 4 snap nuts over the holes in the thermal
insulating foil (Fig. 11, Item 2).
zScrew cover over access port with 4 sheet metal
screws (Fig. 11, Item 1).
Fig. 10 Position thermal insulating disk and thermal
insulating jackets
Item 1: Installation aid
1
USER NOTE
The thermal insulating jacket comes in two
parts.
Fig. 11 Attaching thermal insulating disk and thermal
insulating jacket
Item 1: Sheet metal screw
Item 2: Snap nut
Item 3: Thermal insulation disk
Item 4: Access hand hole cover
Item 5: Outer tank cover
1
2
5
3
4

12 Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
We reserve the right to make any changes due to technical modifications.
DHW tank installation6
zPlace cover strip (Fig. 12, Item 4) on the sealing strip
of the thermal insulating jacket.
zPosition rectangular thermal insulating plug (Fig. 12,
Item 3) in the cutout from the inside.
zPosition round thermal insulating plugs in the holes
for the connections that are not required in the
thermal insulating jacket.
zPlace thermal insulating disk (Fig. 12, Item 1) on the
top access port so it contacts the edge of the thermal
insulating jacket.
zPlace tank cover (plastic cover, Fig. 12, Item 2)over
the thermal insulating disk and the edge of the
thermal insulating jacket.
zRemove the nameplate from the envelope with the
technical documentation.
zPull protective foil off the back of the nameplate and
stick the nameplate under the existing smaller
nameplate (Fig. 13).
Fig. 12 Thermal insulation – top access port
Item 1: Thermal insulation disk
Item 2: Tank cover
Item 3: Thermal insulating plug
Item 4: Cover strip
1
2
3
4
Fig. 13 Attaching nameplate

Start-up and shutdown 7
13
We reserve the right to make any changes due to technical modifications.
Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
7 Start-up and shutdown
7.1 Starting the DHW tank
Before placing the DHW tank into use, check it for
soundness to avoid leaks occurring during operation.
zOpen the highest faucet to vent the DHW tank.
zOpen the shut-off valve for the cold water inlet EK
(Fig. 14, Item 1) to fill the DHW tank.
zBefore heating up check whether the boiler, DHW
tank and pipework are filled with water. Open the
highest faucet for this.
zCheck all connections, pipework and the access port
for leaks.
7.1.1 Operating tips
Inform the user that:
–The local heating contractor should be notified if the
high limit safety trips on the boiler frequently
responds.
–The pressure and temperature valve function should
be checked annualy by manually opening it.
–The P & T valve blow-off line (Fig. 14, Item 2) must
always be kept open and piped full port to a nearby
floor drain.
Fig. 14 Installation diagram (general layout)
Item 1: Shut-off valve for cold water inlet
Item 2: Blow-off line of the P & T valve
AW: Domestic hot water outlet
EZ: DHW recirculation inlet
EK: Cold water inlet
2
1
USER NOTE
zCarry out the leak test exclusively with
potable water. The on-site test
pressure on the DHW side must not be
higher than 10 bar (145 psi).
CAUTION
TANK DAMAGE
The DHW tank may be destroyed by
unacceptably high pressure if the safety
valve is closed.
zAlways keep the blow-off line of the
P & T valve (Fig. 14, Item 2) open and
unobstructed and piped to nearby floor
drain .
USER NOTE
For operating information (e.g. setting the
DHW temperature) check the control panel
operating instructions.

14 Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
We reserve the right to make any changes due to technical modifications.
Start-up and shutdown7
7.2 Shutdown tips
In case of longer periods away from home (e.g. during a
holiday) we recommend the following:
zKeep the DHW tank in use.
zActivate the holiday function on the control panel or
select the lowest possible DHW temperature.
Should it be necessary to take the DHW tank out of use,
observe the hygiene requirements for DHW system
(flushing of pipework) currently applicable in your state
or jurisdiction.
CAUTION
TANK DAMAGE
Corrosion damage may occur if the DHW
tank has to remain empty for several days.
zDry the inside of the DHW tank well
(e.g. with hot air) and keep the manual
access cover open.

Maintenance 8
15
We reserve the right to make any changes due to technical modifications.
Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
8 Maintenance
Generally, we recommend having the DHW tank
checked and cleaned by a qualified contractor at
least every two years. Please inform the user
accordingly.
Shorter cleaning intervals should be chosen under
unfavorable operating conditions, such as hard or
very hard water and/or high operating temperatures.
8.1 Preparing the DHW tank for maintenance
zDisconnect your heating system from the electricity
supply.
zDrain the DHW tank. Shut off so the cold water feed
and open the drain EL. Open the air vent valve or the
highest tap to vent the system.
zRemove the top cover (Fig. 15, Item 2). Remove the
four screws on the side.
zRemove the thermal insulating disk (Fig. 15, Item 1)
from the front of the access cover.
CAUTION!
TANK DAMAGE
due to unsatisfactory cleaning and
maintenance.
zCarry out cleaning and maintenance at
least every two years.
zRemedy all faults immediately to
prevent possible damage.
Fig. 15 Thermal insulation – top access port
Item 1: Thermal insulation disk
Item 2: Tank cover
1
2

16 Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
We reserve the right to make any changes due to technical
Maintenance8
zRemove hexagon bolts (Fig. 16, Item 1) from the
manual access cover (Fig. 16, Item 3).
zRemove the access cover, transport handle (Fig. 16,
Item 2) and access cover gasket (Fig. 16, Item 4)
from the DHW tank.
8.2 Cleaning the DHW tank
zCheck the DHW tank interior for scale deposits
(calcium).
Should scale deposits be discovered inside the DHW
tank, proceed as follows:
zHose down the interior of the DHW tank with a "hard"
cold water jet (approx. 58 – 72 psi pressure)
(Fig. 17).
You can increase the cleaning effect of the jet by
heating up the DHW tank before cleaning. The
thermo-shock effect releases scale deposits more
easily from the coil type heat exchanger. Remove the
residues with a wet & dry vacuum cleaner with plastic
suction tube or flush debris through the tank drain.
Fig. 16 Removing the access cover
Item 1: Hexagon bolts
Item 2: Transport handle
Item 3: Hand hole cover
Item 4: Manual access cover gasket
Item 5: Magnesium anode
3
2
1
4
5
CAUTION!
SYSTEM DAMAGE
through damaged surface finish.
zNever use hard objects or objects with
sharp edges to clean the interior walls
of the DHW tank.
Fig. 17 Hosing down the inside of the DHW tank

Maintenance 8
17
We reserve the right to make any changes due to technical modifications.
Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
8.3 Checking the magnesium anode
The magnesium anode is a sacrificial anode, which
is consumed by its use during the operation of the
DHW tank. Check the magnesium anode diameter
annually.
Warranty claims for the DHW tank will not be
accepted if the magnesium anode is not serviced on
an annual basis.
zCheck magnesium anode (Fig. 18, Item 1) for decay.
Replace the magnesium anode if the diameter has
become reduced to approx. 1/2" to 3/4".
8.4 Replacing the magnesium anode
zRemove the M8 nut (Fig. 18, Item 10), to release the
ground wire eyelet (Fig. 18, Item 8).
zRemove M8 nut (Fig. 18, Item 7).
zRemove the manual access cover (Fig. 18, Item 3)
from the magnesiumanode (Fig. 18, Item 1).
zReplace the magnesium anode.
zFit the new magnesium anode with its associated
small parts, see Fig. 18.
Fig. 18 Replacing the magnesium anode
Item 1: Magnesium anode
Item 2: Gasket
Item 3: Access port cover
Item 4: Insulating sleeve
Item 5: Washer
Item 6: Lock washer
Item 7: M8 nut
Item 8: Grounding wire eyelet
Item 9: Lock washer
Item 10: M8 nut
1
2
3
4
5
6
7
8
9
10
USER NOTE
Never bring the magnesium anode surface
into contact with oil or grease. Keep
everything clean.

18 Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
We reserve the right to make any changes due to technical
Maintenance8
8.4.1 Checking magnesium anode with a
multimeter on annual basis
Proceed as follows to check the magnesium anode:
zDisconnect ground wire (Fig. 19, Item 3) on the
magnesium anode or on the DHW tank.
zSet multimeter to DcmA (milliamperes).
zConnect black multimeter measuring wire (Fig. 19,
Item 6) to the threaded pin on the DHW tank (Fig. 19,
Item 7).
zConnect red multimeter measuring wire (Fig. 19,
Item 5) to the magnesium anode.
zMake sure that all connections have good metal-to-
metal contact.
zIf the anode current is 0.3 mA to 30 mA, the anode is
working correctly.
zNote the annual measurements in Table 3.
Enter the measured values into the table:
zReconnect the wiring after every test.
Fig. 19 Check magnesium anode with multimeter
Item 1: Magnesium anode
Item 2: M8 threaded pin
Item 3: Ground wire
Item 4: Access port cover
Item 5: Red multimeter measurement wire
Item 6: Black multimeter measurement wire
Item 7: Threaded pin on DHW tank
Item 8: Digital multimeter
2
1
3
4
6
7
5
8
USER NOTE
The DHW tank must be full of water while
testing the anode.
Date Measurement Service Company/Signature
7DE 0HDVXUHPHQWUHVXOWV
USER NOTE
If the anode current changes by none than
10 % (up or down) from the previous test,
open up tank access cover and visually
inspeet the anode rod.

Maintenance 8
19
We reserve the right to make any changes due to technical modifications.
Installation and maintenance instructions Logalux ST400/3, 500/3, 750/3 and 1000/3 "US" • Issue 07/2005
8.5 Returning the DHW tank into use after cleaning
zRe-insert manual access cover.
While doing this, observe the correct orientation of
the manual access cover gasket: The imprint
"Deckelseite" must point towards the manual access
cover.
zScrew in hexagon bolts (Fig. 20, Item 1) hand tight in
the access port cover and install the transport handle
(Fig. 20, Item 2).
zTighten hexagon bolts (Fig. 20, Item 1) with a
wrench by a three quarter turn (equal to the
recommended torque of 40 Nm).
zFill the DHW tank and restart the heating system.
zCheck all connections and the manual access cover
for leaks.
zInsert the thermal insulating disk (Fig. 21, Item 1) in
front of the access cover.
zPosition top cover (Fig. 21, Item 2) on the DHW tank
and screw in place with four screws from the side.
Fig. 20 Inserting top access cover
Item 1: Hexagon bolts
Item 2: Transport handle
Item 3: Access port cover
Item 4: Manual access cover gasket
Item 5: Magnesium anode
3
2
1
45
CAUTION!
SYSTEM DAMAGE
through faulty gasket.
zAfter cleaning, we recommend you use
a new manual access cover gasket
(Fig. 20, Item 4) to prevent the DHW
tank from leaking.
Fig. 21 Thermal insulation – top access port
Item 1: Thermal insulation disk
Item 2: Tank cover
1
2

Your local heating contractor:
BBT North America Inc.
50 Wentwort Avenue
NH 03053 Londonderry
Tel: [phone]
Fax: [phone]
Toll Free: 1-800-BUDERUS
www.buderus.net