Viessmann VITOPLEX 300 Operating instructions

Service instructions
for contractors
VIESMANN
Vitoplex 300
Type TX3A, 620 to 2000 kW
Oil/gas boiler
VITOPLEX 300
5692798 GB 9/2020 Please keep safe.

2
Please follow these safety instruc-
tions closely to prevent accidents
and material losses.
Safety instructions explained
Danger
This symbol warns against the risk
of injury.
!Please note
This symbol warns against the risk
of material losses and environmen-
tal pollution.
Note
Details identified by the word "Note"
contain additional information.
Target group
These instructions are exclusively inten-
ded for qualified contractors.
■Work on gas installations may only be
carried out by a registered gas fitter.
■Work on electrical equipment may only
be carried out by a qualified electrician.
■The system must be commissioned by
the system installer or a qualified per-
son authorised by the installer.
Regulations to be observed
■National installation regulations
■Statutory regulations for the prevention
of accidents
■Statutory regulations for environmental
protection
■Codes of practice of the relevant trade
associations
■Relevant country-specific safety regu-
lations
Safety instructions for working on the system
Working on the system
■Where gas is used as the fuel, close
the main gas shut-off valve and safe-
guard it against unintentional reopen-
ing.
■Isolate the system from the power sup-
ply, e.g. by removing the separate fuse
or by means of a mains isolator, and
check that it is no longer live.
■Safeguard the system against recon-
nection.
■Wear suitable personal protective
equipment when carrying out any work.
Safety instructions
Safety instructions
5692798

3
Danger
Hot surfaces and fluids can lead to
burns or scalding.
■Before maintenance and service
work, switch OFF the appliance
and let it cool down.
■Never touch hot surfaces on the
boiler, burner, flue system or pipe-
work.
!Please note
Electronic assemblies can be dam-
aged by electrostatic discharge.
Prior to commencing work, touch
earthed objects such as heating or
water pipes to discharge static
loads.
Repair work
!Please note
Repairing components that fulfil a
safety function can compromise the
safe operation of the system.
Replace faulty components only
with genuine Viessmann spare
parts.
Auxiliary components, spare and
wearing parts
!Please note
Spare and wearing parts that have
not been tested together with the
system can compromise its func-
tion. Installing non-authorised com-
ponents and making non-approved
modifications or conversions can
compromise safety and may invalid-
ate our warranty.
For replacements, use only original
spare parts supplied or approved by
Viessmann.
Safety instructions
Safety instructions (cont.)
5692798

4
Safety instructions for operating the system
If you smell gas
Danger
Escaping gas can lead to explo-
sions which may result in serious
injury.
■Do not smoke. Prevent naked
flames and sparks. Never switch
lights or electrical appliances on
or off.
■Close the gas shut-off valve.
■Open windows and doors.
■Evacuate any people from the
danger zone.
■Notify your gas or electricity sup-
ply utility from outside the building.
■Have the power supply to the
building shut off from a safe place
(outside the building).
If you smell flue gas
Danger
Flue gas can lead to life threatening
poisoning.
■Shut down the heating system.
■Ventilate the installation site.
■Close doors to living spaces to
prevent flue gases from spread-
ing.
What to do if water escapes from the
appliance
Danger
If water escapes from the appliance
there is a risk of electrocution.
Switch OFF the heating system at
the external isolator (e.g. fuse box,
domestic distribution board).
Danger
If water escapes from the appliance
there is a risk of scalding.
Never touch hot heating water.
Condensate
Danger
Contact with condensate can be
harmful to health.
Never let condensate touch your
skin or eyes and do not swallow it.
Flue systems and combustion air
Ensure that flue systems are clear and
cannot be sealed, for instance due to
accumulation of condensate or other
external causes.
Ensure an adequate supply of combus-
tion air.
Inform system users that subsequent
modifications to the building characteris-
tics are not permissible (e.g. cable/pipe-
work routing, cladding or partitions).
Danger
Leaking or blocked flue systems, or
an inadequate supply of combus-
tion air can cause life threatening
poisoning from carbon monoxide in
the flue gas.
Ensure the flue system is in good
working order. Vents for supplying
combustion air must be non-seala-
ble.
Extractors
Operating appliances that exhaust air to
the outside (extractor hoods, extractors,
air conditioning units, etc.) can create
negative pressure. If the boiler is oper-
ated at the same time, this can lead to a
reverse flow of flue gas.
Safety instructions
Safety instructions (cont.)
5692798

5
Danger
The simultaneous operation of the
boiler and appliances that exhausts
air to the outside can result in life
threatening poisoning due to a
reverse flow of flue gas.
Fit an interlock circuit or take suita-
ble steps to ensure an adequate
supply of combustion air.
Safety instructions
Safety instructions (cont.)
5692798

6
1. Information Symbols ................................................................................................. 7
Intended use .......................................................................................... 7
Product information ................................................................................ 8
System examples .................................................................................. 8
Spare parts lists ..................................................................................... 8
2. Commissioning, inspec-
tion, maintenance
Steps - commissioning, inspection and maintenance ............................ 9
3. Water quality Water quality requirements .................................................................... 18
■Heating systems with rated operating temperatures up to 100 °C
(VDI 2035) .......................................................................................... 18
■Prevention of damage through corrosion on the water side ............... 19
Using antifreeze in boilers ..................................................................... 19
4. Commissioning/service
reports
Water quality .......................................................................................... 21
Maintenance/service .............................................................................. 21
5. Specification ................................................................................................................ 23
6. Decommissioning and dis-
posal
Final decommissioning and disposal ..................................................... 24
7. Certificates EU Declaration of Conformity ................................................................ 25
Manufacturer's certificate according to BImSchV .................................. 25
8. Keyword index ................................................................................................................ 26
Index
Index
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7
Symbol Meaning
Reference to other document containing
further information
1.
Step in a diagram:
The numbers correspond to the order in
which the steps are carried out.
Warning of material losses and environ-
mental pollution
Live electrical area
Pay particular attention.
■Component must audibly click into place.
or
■Acoustic signal
■Fit new component.
or
■In conjunction with a tool: Clean the sur-
face.
Dispose of component correctly.
Dispose of component at a suitable collec-
tion point. Do not dispose of component in
domestic waste.
The steps in connection with commissioning, inspec-
tion and maintenance are found in the "Commission-
ing, inspection and maintenance" section and identified
as follows:
Symbol Meaning
Steps required during commissioning
Not required during commissioning
Steps required during inspection
Not required during inspection
Steps required during maintenance
Not required during maintenance
Intended use
The appliance is only intended to be installed and
operated in sealed unvented heating systems that
comply with EN 12828, with due attention paid to the
associated installation, service and operating instruc-
tions as well as the details in the datasheet.
It is only designed for the heating up of heating water.
Commercial or industrial usage for a purpose other
than the heating up of heating water shall be deemed
inappropriate.
Intended use presupposes that a fixed installation in
conjunction with permissible components designed for
this purpose has been carried out.
Every other use will be deemed to be inappropriate.
Any resulting losses are excluded from the manufac-
turer's liability.
Any usage beyond this must be approved by the man-
ufacturer for the individual case.
Intended use also includes the adherence to mainte-
nance and inspection intervals.
Information
Symbols
5692798

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Vitoplex 300, type TX3A
■Fuels: Fuel oil and natural gas
■Permissible operating pressure 6 bar (0.6 MPa)
■Rated heating output 620 to 2000 kW
System examples
Available system examples: See
www.viessmann-schemes.com.
Spare parts lists
Information about spare parts can be found at
www.viessmann.com/etapp or in the Viessmann
spare part app.
Information
Product information
5692798

9
Commissioning steps
Inspection steps
Maintenance steps Page
••• 1. Commissioning the system............................................................................................... 10
• • 2. Shutting down the system................................................................................................. 10
• • 3. Opening the boiler door and cleaning cover................................................................... 11
•4. Cleaning the internal pipes, heating surface, flue outlet and flue pipe........................ 11
• • 5. Checking all gaskets and packing cords on the flue gas side
• • 6. Checking the thermal insulation components on the boiler door................................. 12
•7. Inserting internal pipes; securing the boiler door and cleaning cover......................... 13
• • 8. Checking connections and sensor well on the heating water side for tightness
• • 9. Checking the function of safety equipment..................................................................... 13
••• 10. Checking the function of the pressure switch................................................................ 14
• • 11. Checking the expansion vessel and system pressure................................................... 14
•12. Checking the temperature controller setting if a building management system is
used (DCC system)............................................................................................................ 15
• • 13. Checking the firm seating of electrical plug-in connections and cable grommets
• • 14. Checking the thermal insulation
• • 15. Checking the water quality................................................................................................ 15
• • 16. Cleaning the sight glass in the boiler door...................................................................... 15
•17. Checking the mixer for ease of operation and tightness............................................... 15
•18. Checking the function of the return temperature raising facility (if installed)
• • 19. Checking the installation room ventilation
• • 20. Checking the flue pipe for tightness
•21. Adjusting the burner.......................................................................................................... 16
•22. Instructing the system user.............................................................................................. 17
•23. Operating and service documents................................................................................... 17
Commissioning, inspection, maintenance
Steps - commissioning, inspection and maintenance
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Operating and service instructions for the control
unit and the burner
01. Close the gas shut-off valve and open the boiler
door.
02. Check internal pipes C are correctly inserted into
hot gas flues B. Spring clip D of the internal
pipes must lock into place behind first constriction
E.
Fig. 1
AInternal pipe extractor
03. Check that the ventilation air aperture in the instal-
lation room is open.
04. Fill the heating system with water and vent the
system.
Permissible operating pressure: 6 bar (0.6 MPa)
05. Record the amount of fill water and its hardness in
chapter "Checking the water quality".
!Please note
Unsuitable water quality can damage the
boiler body.
Operate boilers only with softened water.
Observe the instructions in chapter "Water
quality requirements" on page 18.
06. Check the system pressure.
07. Check the oil level or the gas supply pressure.
08. Open the flue gas damper (if installed).
09. Check that the cleaning aperture on the flue outlet
is closed.
10. Open the shut-off valves in the oil or gas line.
11. Switch ON the mains isolator, the switch for the
heating circuit pump and the burner ON/OFF
switch, in that order. Observe the burner manufac-
turer’s operating instructions.
12. The dew point range must be cleared as quickly
as possible. For this reason prevent all heat sup-
ply to consumers when heating the system from
cold. This also applies when restarting after main-
tenance and cleaning work.
!Please note
During boiler heat-up, unpleasant fumes
and odours can result from outgassing from
the thermal insulation, the thermal block
and the paint.
Ventilate the room during commissioning.
13. Once the flow temperature has been reached,
successively switch on the heat consumers.
Switch the burner over to automatic mode.
!Please note
Internal gas emissions from the thermal
block can lead to increased CO values in
the flue gas.
Continue to operate the boiler until a decline
can be clearly recognised.
14. Check all gaskets and plugs, and retighten if nec-
essary.
15. Check the boiler door and cleaning cover after
approx. 50 hours run and retighten all screws.
Shutting down the system
1. Switch OFF the mains isolator or the power supply,
and safeguard against unauthorised reconnection.
2. Interrupt the burner power supply. If installed, pull
plug-in connectors fA and lÖ from the burner.
3. Close the gas shut-off valve.
Danger
Heating water escaping under pressure will
injure bystanders.
Only open the connections on the heating water
side after the boiler has been depressurised.
Commissioning, inspection, maintenance
Commissioning the system
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!Please note
Draining the boiler with a suction pump will cre-
ate negative pressure inside the boiler.
Only drain the boiler with a suction pump when
the air vent valve is open.
Opening the boiler door and cleaning cover
Note
On gas burners, disconnect the gas supply pipe.
4x
Fig. 2
Cleaning the internal pipes, heating surface, flue outlet and flue pipe
Fig. 3
Commissioning, inspection, maintenance
Shutting down the system (cont.)
5692798

12
1. Pull internal pipes B out towards the front with a
quick tug. For this, use internal pipe extractor A
from the cleaning equipment.
2. Clean flues C and combustion chamber D with
the brush.
Remove combustion residues with a vacuum
cleaner.
3. Remove combustion residues from the flue pipe
and the flue outlet through cleaning aperture E in
the flue outlet using a vacuum cleaner.
Checking all gaskets and packing cords on the flue gas side
Checking the thermal insulation components on the boiler door
Danger
When working with high temperature insulation
materials that contain zirconium or aluminium
silicate ceramic fibres, fibre dust may
develop. This fibre dust can be harmful to
health.
Only trained personnel may adjust or replace
the insulation. Wear suitable protective clothing,
especially breathing equipment and safety gog-
gles.
Commissioning, inspection, maintenance
Cleaning the internal pipes, heating surface,… (cont.)
5692798

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Note
On gas burners, mount the gas supply pipe.
Danger
Escaping gas leads to a risk of explosion.
Check all gas connections for tightness.
4x
25 Nm
5 Nm
B C DE
A
1 2 3
F
Fig. 4
1. Push internal pipes C far into hot gas flues B.
Spring clip E must snap into place behind
first constriction D.
Note
This snapping into place prevents the internal
pipes from slipping forward during boiler operation.
2. Tighten boiler door screws A crosswise (torque
25 Nm).
Tighten cleaning cover screws F (5 Nm).
Danger
Leaks can result in a risk of poisoning
through escaping gas.
Check gaskets carefully.
Checking connections and sensor well on the heating water side for tight-
ness
Checking the function of safety equipment
Check safety valves, water level and pressure limiter in
accordance with manufacturer's details.
Commissioning, inspection, maintenance
Inserting internal pipes; securing the boiler door and cleaning cover
5692798

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Installation instructions in the "pressure switch
set"
Checking the expansion vessel and system pressure
Observe the manufacturer's documentation for
the expansion vessel.
Note
Check when system is cold.
Expansion vessel
1. Drain the system until the pressure gauge shows
"0". Alternatively: close the cap valve on the
expansion vessel and reduce the pressure in the
expansion vessel.
Note
The pre-charge pressure of the expansion vessel
(p0) is made up of the static system pressure (pSt)
(= static head) and a supplement: p0 = pSt + sup-
plement.
The supplement depends on the high limit safety
cut-out setting. The following applies:
■100 °C: 0.2 bar (0.02 MPa)
■110 °C: 0.7 bar (0.07 MPa).
2. If the pre-charge pressure of the expansion vessel
is lower than the static system pressure: top up
with nitrogen until the pre-charge pressure is 0.1 to
0.2 bar (0.01 to 0.02 MPa) higher.
The static pressure corresponds to the static head.
3. Top up with softened water*1 until the charge pres-
sure of the cooled system is 0.1 to 0.2 bar (0.01 to
0.02 MPa) higher than the pre-charge pressure of
the expansion vessel.
Permiss. operating pressure: 6 bar (0.6 MPa)
Pump controlled pressure maintaining systems
In heating systems with automatic pressure maintain-
ing systems also provide individual protection by instal-
ling an expansion vessel for each boiler. This applies
in particular to pump controlled systems with integral
deaeration.
Boiler output kW Up to 1000 Up to 2100
Expansion
vessel
l 140 300
The individual protection reduces the frequency and
level of pressure fluctuations. This significantly increa-
ses the operational reliability and service life of the
system components. Failure to observe these recom-
mendations may result in damage to the boiler or to
other system components.
Only use pump controlled pressure maintaining sys-
tems that are sealed to prevent corrosion. The pres-
sure maintaining systems must be protected against
oxygen ingress into the heating water. Otherwise dam-
age to the system through oxygen corrosion can result.
Pump controlled pressure maintaining systems with
atmospheric deaeration through cyclical pressure
release effect a central post-ventilation of the heating
system. They do not provide oxygen removal in the
sense of corrosion protection as described in VDI 2035
Part 2.
Note
Check the pressure maintaining system in line with the
manufacturer's instructions.
!Please note
Cyclical pressure fluctuations and more signifi-
cant pressure differentials point towards a sys-
tem fault. Such faults result in damage to other
heating system components.
Limit pressure fluctuations to the lowest possible
differential.
*1 See chapter "Water quality requirements".
Commissioning, inspection, maintenance
Checking the function of the pressure switch
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!Please note
Shutting down from full load can result in high
material stress and material damage.
If a system with a higher ranking building man-
agement system takes over the temperature
control of the boiler, adjust the settings at the
temperature controller TR. Set the electronic
temperature controller to at least 10 K below the
mechanical temperature controller.
Checking the firm seating of electrical plug-in connections and cable
grommets
Checking the thermal insulation
Checking the water quality
Observe the instructions in chapter "Water quality
requirements" on page 18 onwards.
The total hardness of the feed and top-up water must
not exceed 0.11 °dH (sum of all alkaline earths ≤ 0.02
mol/m3). The pH value should be between 9 and 10.5.
Enter the amount of top-up water and the total hard-
ness of the feed and boiler water into the table on
page 21.
Cleaning the sight glass in the boiler door
Fig. 5
Note
Check the gaskets and hose connection for tightness.
Checking the mixer for ease of operation and tightness
1. Remove the motorised lever from the mixer han-
dle.
2. Check the mixer for ease of operation.
Commissioning, inspection, maintenance
Checking the temperature controller setting if a building management system
is used (DCC system)
5692798

16
3. Check the mixer for leaks. Replace the O-rings if
the mixer is leaking.
4. Snap the motorised lever into place.
Checking the function of the return temperature raising facility (if
installed)
Checking the installation room ventilation
Checking the flue pipe for tightness
Adjusting the burner
Adjust the maximum oil or gas throughput of the
burner to the rated boiler heating output.
Rated heating out-
put
Pressure drop on the hot gas
side
kW Pa mbar
620 350 3.5
780 400 4.0
1000 400 4.0
1250 500 5.0
Rated heating out-
put
Pressure drop on the hot gas
side
kW Pa mbar
1600 850 8.5
2000 800 8.0
To protect the system against dew point corrosion,
burner stage 2 (full heating output) must be set to the
rated boiler heating output. It must remain switched on,
even during the summer months (burner stage 2 on
constant standby).
Partial load operation
Set the minimum heating output for the base load
stage in accordance with the flue system. The flue sys-
tem must be suitable for the low flue gas temperatures.
In the case of frequent cycling in standby mode and for
partial loads below 40 % we recommend that you:
■Insulate the flue gas collector
■Install a motorised flue gas damper
■Set the minimum runtime of the boiler to 10 min
This extends the service life and reduces running
costs.
Operation with burner load ≥ 60 %
The minimum boiler water temperature for oil operation
is 40 °C and for gas operation 50 °C.
To protect the boiler, the minimum heating output in the
base load stage is set to 60 % of the rated heating out-
put (see table).
Rated heating out-
put
Minimum heating output to
be set (burner stage 1)
kW kW
620 372
780 468
1000 600
1250 750
1600 960
2000 1200
Commissioning, inspection, maintenance
Checking the mixer for ease of operation and… (cont.)
5692798

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The base load stage requires a minimum flue gas tem-
perature, the value of which is subject to the design of
the flue system.
Operation with burner load ≥ 40 % and < 60 %
The minimum system temperatures (flow/return) are
60/50 °C for oil operation and 70/60 °C for gas opera-
tion.
Operation with burner load < 40 %
The minimum system temperatures (flow/return) are
60/55 °C for oil operation and 70/65 °C for gas opera-
tion.
Instructing the system user
The installer should instruct the user in the operation of
the system.
Operating and service documents
1. Complete and detach the customer registration
card:
■Hand the system user their section for safekeep-
ing.
■Retain the heating contractor's section.
2. File all parts lists, operating and service instruc-
tions in the folder and hand this over to the system
user.
The installation instructions are no longer required
after the appliance has been installed. They do not
need to be retained.
Commissioning, inspection, maintenance
Adjusting the burner (cont.)
5692798

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Heating systems with rated operating temperatures up to 100 °C (VDI 2035)
The water used in heating systems must comply with
the chemical values of the Drinking Water Ordinance
[Germany]. If well water or similar is used, check its
suitability before filling the system.
Avoid excessive scale deposits (calcium carbonate) on
the heating surfaces. For heating systems with operat-
ing temperatures up to 100 °C, Guideline VDI 2035
Part 1 "Prevention of damage in water heating installa-
tions - Scaling in domestic hot water supply installa-
tions and water heating installations" applies together
with the following standard values. For more informa-
tion, see the explanations for guideline VDI 2035.
Total heating out-
put in kW
> 50 to
≤ 200
> 200 to
≤ 600
> 600
Total alkaline
earths in mol/m3
≤ 2.0 ≤ 1.5 < 0.02
Total hardness in
°dH
≤ 11.2 ≤ 8.4 < 0.11
The standard values assume the following conditions:
■The total volume of fill and top-up water will not
exceed three times the water content of the heating
system during its service life.
■The specific system volume is less than 20 l/kW
heating output. In multi boiler systems, apply the out-
put of the smallest boiler.
■All measures to prevent corrosion on the water side
in accordance with VDI 2035 Part 2 have been
implemented.
Soften the fill and top-up water in heating systems with
the following conditions:
■The total of alkaline earths in the fill and top-up water
exceeds the standard value.
■Higher fill and top-up water volumes are expected.
■The specific system volume is greater than 20 l/kW
heating output. In multi boiler systems, apply the out-
put of the smallest boiler.
When designing the system, observe the following:
■Install shut-off valves in each section. This prevents
the need for draining all the heating water in the case
of repairs or system expansion.
■Install a water meter to record the volume of fill and
top-up water. The volumes and hardness of the top-
ped-up water volumes must be entered in the boiler
service instructions.
■For systems with a specific volume greater than
20 litres/kW heating output (for multi boiler systems,
the output of the smallest boiler should be used), the
requirements of the next highest total heating output
group should be applied (using the table). If even
bigger (> 50 litres/kW), soften the water down to a
total of alkaline earths of ≤ 0.02 mol/m3.
Operating information:
■Start the system gradually at a high heating water
flow rate, starting with the lowest boiler output. This
prevents localised concentration of limescale depos-
its on the heating surfaces.
■For multi boiler systems, all boilers should be started
at the same time to prevent the entire volume of
limescale settling on the heat transfer surface of only
one boiler.
■During expansion or repair work, only drain the nec-
essary sections.
■Where water treatment is required, treat even the
first fill of the heating system prior to commissioning.
This also applies to any subsequent filling, e.g. when
adding top-up water or after a repair, or for any sys-
tem expansion.
■Periodically inspect, clean and activate all filters, dirt
traps or other blow-down or separating facilities in
the heating water circuit after reinstalling or installing
for the first time. Thereafter, this may be one as
required, depending on the type of water treatment
applied (e.g. water softening).
The build-up of limescale deposits on the heating sur-
faces will be minimised if these instructions are fol-
lowed.
If failure to observe guideline VDI 2035 results in
harmful limescale deposits, the service life of the
installed boilers will in most cases have already been
reduced. Removing limescale deposits may be an
option to restore the operating capability. This must be
carried out by Viessmann Industrieservice or a special-
ist contractor. Inspect the heating system for possible
damage prior to returning it into use. The faulty operat-
ing parameters must be corrected in order to prevent
excessive scale build-up from reoccurring.
Water quality
Water quality requirements
5692798
Appendix

19
Prevention of damage through corrosion on the water side
The corrosion resistance of ferrous materials on the
heating water side of heating systems and boilers
depends on the absence of oxygen in the heating
water.
The oxygen introduced into the heating system with
the first fill and the top-up water reacts with the system
materials without causing damage.
The characteristic blackening of the water after some
time in use indicates that free oxygen is no longer
present.
The technical rules and in particular VDI Directive
2035-2 therefore recommend that heating systems are
designed and operated so that a constant ingress of
oxygen into the heating water is prevented.
Opportunities for oxygen ingress during the operation:
■Through overflowing open expansion vessels
■Through negative pressure in the system
■Through gas-permeable components
Sealed unvented systems, e.g. with a diaphragm
expansion vessel, offer good protection against the
ingress of airborne oxygen into the system, if correctly
sized and operating at the correct pressure.
At every part of the heating system, even at the suc-
tion side of the pump and under all operating condi-
tions, the system pressure should be above ambient
atmospheric pressure.
The pre-charge pressure of the diaphragm expansion
vessel should be checked at least during the annual
service.
The use of permeable components, e.g. plastic pipes
that are permeable to gas in underfloor heating sys-
tems, should be avoided. Provide system separation if
such components are nevertheless used. This must
separate the water flowing through the plastic pipes
from other heating circuits, e.g. from the heat source,
by the provision of a heat exchanger made of corro-
sion-resistant material.
No further anti-corrosion measures are required for
sealed hot water heating systems subject to the above
points being observed.
However, take additional precautions where there is a
risk of oxygen ingress, for example by adding oxygen
binder sodium sulphite (5 - 10 mg/litre into the excess).
The heating water should have a pH value between
9.0 and 10.5.
Different conditions apply to systems that contain alu-
minium components.
Where chemicals are used as part of the corrosion
protection, we recommend that the manufacturer of the
chemicals issues a certificate of suitability of the addi-
tives with regard to the boiler materials and the materi-
als of the other heating equipment components.
We recommend you refer questions of water treatment
to Viessmann industrial services or an appropriate
specialist.
Further details can be found in VDI Directive 2035-2
and EN 14868.
Using antifreeze in boilers
Viessmann boilers are designed and built for water as
a heat transfer medium. To protect boiler systems from
frost, it may be necessary to treat the boiler water or
circulating water with antifreeze.
When doing so, observe the following:
■In general, follow the specifications given by the anti-
freeze manufacturer.
■The properties of antifreeze and water are very dif-
ferent.
■The temperature stability of the antifreeze must be
sufficient for the particular application.
■Check the compatibility with sealing materials. If
other sealing materials are used, take this into
account when designing the system.
■Antifreeze developed especially for heating systems
contains inhibitors and buffer substances for corro-
sion protection as well as glycol. When using anti-
freeze, always observe the manufacturer's instruc-
tions regarding minimum and maximum concentra-
tions.
■The concentration must never fall below the prescri-
bed minimum level, subject to the required frost pro-
tection temperature. Check and adjust the pH value
and frost protection (measure the density) regularly,
at least once a year, according to the manufacturer's
instructions.
■Check with the relevant supplier whether antifreeze
may affect system components that are not part of
the boiler, such as pumps, electrically and pneumati-
cally driven valves, other types of valves, gaskets,
etc.
■If the system is filled with antifreeze, it must be
marked accordingly.
■If a boiler system is changed to operate without anti-
freeze, flush the system in order to remove all traces
of the antifreeze.
■The quality of the boiler water and feedwater must
meet the requirements of Directive VDI 2035.
■The systems must be designed as sealed unvented
systems, as the antifreeze inhibitors decrease rapidly
if airborne oxygen is allowed to enter.
Water quality
Water quality requirements (cont.)
5692798
Appendix

20
■Diaphragm expansion vessels must comply with
DIN 4807 [or local regulations].
■Solder connections should preferably be made with
Ag or Cu hard solder. If liquids containing chlorides
are used for soft soldering, any deposits must be
removed from the circuit afterwards through thor-
ough flushing. A higher chloride content in the heat
transfer medium can cause corrosion damage.
■Only use oxygen diffusion-resistant hoses or metal
hoses for flexible connections.
■Never equip the system on the primary side with
zinc-plated heat exchangers, containers or pipes as
zinc can be corroded by glycol/water mixtures.
■To avoid the risk of corrosion, ensure that there is no
difference in electrical potential between system
components that are in contact with antifreeze.
■Route all pipes in such a way that circulation cannot
be interrupted by gas cushions or deposits.
■The water circuit must always be filled up to the high-
est point with the heat transfer medium.
■After filling, ensure there are no more air cushions in
the system. When the temperature falls, gas cush-
ions form negative pressure and this can draw air
into the system.
■After initial filling and commissioning, but after 14
days at the latest, clean the integral dirt trap so the
heat transfer medium can flow freely.
■Following any losses through leaks or drawing off,
top up the antifreeze solution according to the con-
centration already in place. Establish the volume of
antifreeze as a check.
Water quality
Using antifreeze in boilers (cont.)
5692798
Appendix