Daikin GCU compact Series User manual

Installation and operating instructions
Floor-standing gas condensing boiler with integrated heat storage English
Installation and operating instructions
GCU compact
GCU compact 315
GCU compact 320
GCU compact 515
GCU compact 520
GCU compact 524
GCU compact 528
GCU compact 315 Biv
GCU compact 320 Biv
GCU compact 515 Biv
GCU compact 520 Biv
GCU compact 524 Biv
GCU compact 528 Biv
04/2019

List of contents
Installation and operating instructions
3
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
List of contents
1 General safety precautions 5
1.1 Particular safety instructions ..................................................... 5
1.1.1 Observing the instructions .......................................... 6
1.1.2 Meaning of warnings and symbols.............................. 6
1.2 Safety instructions for installation and operation....................... 6
1.2.1 General ....................................................................... 6
1.2.2 Intended use ............................................................... 7
1.2.3 Installation room.......................................................... 7
1.2.4 Electrical installation ................................................... 7
1.2.5 Requirements for the heating water............................ 7
1.2.6 Heating system and sanitary connection .................... 8
1.2.7 Operation .................................................................... 8
2 Handover to operator and warranty 9
2.1 Instruct the owner...................................................................... 9
2.2 Warranty conditions................................................................... 9
3 Product description 10
3.1 Design and components............................................................ 10
3.1.1 GCU compact 315 / 320 (Biv)..................................... 10
3.1.2 GCU compact 515 / 520 / 524 / 528 (Biv)................... 11
3.2 Brief description......................................................................... 13
4 Set-up and installation 15
4.1 Dimensions and connection dimensions ................................... 15
4.1.1 Connecting dimensions for the heating and hot water
connections................................................................. 16
4.2 Different set-ups ........................................................................ 17
4.2.1 Room-air independent operation ................................ 18
4.2.2 Partial ambient air-independent mode........................ 18
4.2.3 Ambient air-dependent mode...................................... 19
4.2.4 Additional information on the device type in
accordance with CEN/TR1749................................... 19
4.3 Transport and delivery............................................................... 20
4.4 Installing the GCU compact....................................................... 20
4.4.1 Selecting the installation site....................................... 20
4.4.2 Installing the device .................................................... 21
4.4.3 Removing the cover and thermal insulation................ 22
4.5 Air/flue gas system (LAS).......................................................... 23
4.5.1 General instructions for the flue gas system............... 23
4.5.2 Connecting a flue gas line........................................... 24
4.5.3 Flue gas system kits ................................................... 25
4.6 Water connection ...................................................................... 26
4.6.1 Aligning the connections of the heating inflow and
return flow ................................................................... 27
4.6.2 Connecting hydraulic lines.......................................... 28
4.6.3 Connecting the condensate drain and storage tank
overflow....................................................................... 29
4.6.4 Installation of the DB connection kit............................ 29
4.6.5 Installation of the P connection kit .............................. 29
4.7 Electrical connection ................................................................. 30
4.7.1 Opening the control unit housing and establishing
electric connections .................................................... 30
4.7.2 Integrated heating circulation pump and 3-way valve. 33
4.7.3 Temperature sensors and further electrical
components ................................................................ 33
4.7.4 Connecting the RoCon OT1 outside temperature
sensor ......................................................................... 34
4.7.5 RoConM1 mixer module ............................................ 35
4.7.6 RoCon U1 room controller .......................................... 35
4.7.7 RoCon G1 Internet gateway ....................................... 35
4.7.8 Room thermostat ........................................................ 35
4.7.9 External switching contact .......................................... 35
4.8 Connect the gas line, check the burner setting for gas type ..... 36
4.8.1 Important instructions for gas connection ................... 36
4.8.2 Connecting the gas line .............................................. 36
4.8.3 Removing/attaching the heat cell panelling ................ 36
4.8.4 Checking the gas presetting ........................................ 36
4.9 Filling the system........................................................................ 37
4.9.1 Checking the water quality and adjusting the
pressure gauge ............................................................ 37
4.9.2 Filling the hot water heat exchanger............................ 37
4.9.3 Filling the condensate siphon ...................................... 37
4.9.4 Filling the storage tank................................................. 37
4.9.5 Filling the heating system ............................................ 37
5 Commissioning 38
5.1 Initial commissioning .................................................................. 38
5.1.1 Requirements............................................................... 38
5.1.2 Checks before commissioning..................................... 38
5.1.3 Commissioning ............................................................ 38
5.1.4 After commissioning..................................................... 39
5.2 Checklists for commissioning ..................................................... 40
6 Controller and electronic components 41
6.1 Operating elements on the boiler control panel.......................... 41
6.2 Replacing the RoCon B1 control panel ...................................... 41
6.3 Changing sensors ...................................................................... 42
6.3.1 Replacing the inflow temperature sensor / return flow
temperature sensor and pressure sensor .................... 43
6.3.2 Replacing the internal mixer sensor for heating
support ......................................................................... 43
6.3.3 Changing the storage tank temperature sensor........... 43
7 Heat cell with gas burner 44
7.1 Design and brief description....................................................... 44
7.2 Safety function............................................................................ 45
7.3 Burner setting ............................................................................. 45
7.3.1 Setting values .............................................................. 46
7.3.2 Establishing access to the burner................................ 46
7.3.3 Checking and setting the burner.................................. 46
7.3.4 Starting problems – calibrating the combustion
control, setting the burner blower starting output and
gas volume................................................................... 47
7.3.5 Setting ignition and ionisation electrodes..................... 48
7.4 Dismantling the burner ............................................................... 49
8 Hydraulic connection 51
8.1 Hydraulic system connection...................................................... 51
9 Service and maintenance 53
9.1 General information regarding inspection and maintenance...... 53
9.2 Inspection and maintenance tasks ............................................. 53
9.2.1 Checking the connections and pipes ........................... 53
9.2.2 Check and clean combustion chamber and
condensate drain ......................................................... 53
9.2.3 Checking the storage tank fill level .............................. 55
9.2.4 Check and clean the burner......................................... 55
9.2.5 Filling, topping up the storage tank.............................. 55
9.2.6 Filling, topping up the heating system and storage
tank charging circuit ..................................................... 56
9.2.7 Venting the hydraulic block.......................................... 57
10 Errors and faults 59
10.1 Troubleshooting.......................................................................... 59
10.2 Overview of possible faults......................................................... 59
10.3 Error codes................................................................................. 61
10.4 Rectifying burner faults and STB faults ...................................... 63
10.5 Emergency operation ................................................................. 63
11 Taking out of operation 64
11.1 Temporary shutdown.................................................................. 64
11.1.1 Draining the storage tank............................................. 64
11.1.2 Draining the heating circuit and hot water circuit ......... 65
11.2 Final shutdown and disposal ...................................................... 66
12 Technical data 67
12.1 Basic data................................................................................... 67
12.1.1 GCU compact 3xx........................................................ 67
12.1.2 GCU compact 5xx........................................................ 68

List of contents
Installation and operating instructions
4
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
12.1.3 Integrated gas boiler ................................................... 69
12.1.4 Integrated heating circulation pump, 3-way valves..... 69
12.1.5 Information on the type plate ...................................... 70
12.1.6 Data sheets according to Ecolabel and Ecodesign
regulation (EU)811/2013 and (EU)813/2013 ............ 70
12.2 Gas type, connection pressures................................................ 72
12.3 Tightening torques..................................................................... 72
12.4 Flow rate and residual feed height ............................................ 73
12.5 Temperature sensor .................................................................. 73
12.6 Electrical connection diagram ................................................... 74
13 Notes 76
List of keywords 79
14 For the chimney sweep 80
14.1 Data for designing the flue gas pipe.......................................... 80
14.2 Emissions measurement ........................................................... 80

1 General safety precautions
Installation and operating instructions
5
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
1 General safety precautions
1.1 Particular safety instructions
WARNING
Heaters that have not been set up and
installed correctly can impair the func-
tion of the heater and/or cause serious
or fatal injuries to the user.
▪ Work on the device (such as set-up,
servicing, connection and initial com-
missioning) must only be carried out
by persons who are authorised and
have successfully completed quali-
fying technical or vocational train-
ing and who have taken part in ad-
vanced training sessions recognised
by the relevant responsible authorit-
ies for the specific activity. These in-
clude, in particular, certified heating
engineers, qualified electricians
and HVAC specialists who, be-
cause of their professional training
and expert knowledge, have exper-
ience in the professional installation
and maintenance of heating sys-
tems, gas installations and hot water
storage tanks.
WARNING
Disregarding the following safety in-
structions may result in serious phys-
ical injury or death.
▪ This device may only be used by
children aged 8 and above and by
persons with restricted physical,
sensory or mental capabilities or with
a lack of experience and knowledge
if they are under supervision or if
they have been instructed in the safe
use of the equipment and under-
stand the dangers arising therefrom.
Children must not play with the
device. Cleaning and user mainten-
ance must not be carried out by
children without supervision.
▪ Establish the power supply in ac-
cordance with IEC60335-1, via a
separate isolator which separates all
poles with a contact opening dis-
tance that provides full disconnection
in accordance with overvoltage cat-
egory III.
▪ All the electrical work must only be
carried out by electrically qualified
experts and with consideration of the
local and national regulations, and
the instructions in this manual.
Ensure that a suitable electrical cir-
cuit is used.
Insufficient load capacity of the elec-
trical circuit or improperly executed
connections can result in electric
shock or fire.
▪ The customer must install a pressure
relief device with a rated over-pres-
sure of less than 0.6MPa (6bar).
The connected drain line must have
a continuous gradient and a free out-
let into a frost-free environment
(seeChap. 4.4).
▪ Water may drip out of the drain line
of the pressure relief device. The
drain opening must be left open to
atmosphere.
▪ The pressure relief device must be
operated regularly in order to re-
move scale deposits and to make
sure it is not blocked.
▪ The storage tank and hot water cir-
cuit can be drained. The instructions
in Chap. 11.1 must be observed.
▪ All work on gas-carrying parts must
only be carried out by gas-related
qualified experts and with considera-
tion of local and national regulations
and the instructions in this manual.
▪ Improperly performed work on gas or
gas-carrying lines can endanger life
and health and hinder the operation
of the heater.

1 General safety precautions
Installation and operating instructions
6
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
1.1.1 Observing the instructions
▪ The original documentation is written in German. All other lan-
guages are translations.
▪ Please read this manual carefully and thoroughly before proceed-
ing with the installation or modification of the heating system.
▪ The precautionary measures described in this document cover
very important topics. Follow them meticulously.
▪ The installation of the system, and all activities described in this
manual and the applicable documents for the installer must be
carried out by an approved installer.
This manual provides all the necessary information for installation,
commissioning and maintenance, as well as basic information on op-
eration and settings. Please see the attached documents for a de-
tailed description of operation and control.
All heating parameters needed for smooth operation are already
factory-set. Please refer to other relevant documents for information
on setting the control.
Relevant documents
▪ GCUcompact:
▪ Operating instructions for the operator.
▪ Operating manual for the operator
▪ RoConBF: Operating instructions.
▪ When additional components are connected; the associated in-
stallation and operating instructions.
The instructions are included in the scope of supply for the individual
devices.
1.1.2 Meaning of warnings and symbols
Warnings in this manual are classified according into their severity
and probability of occurrence.
DANGER
Indicates an immediate danger.
Disregarding this warning can lead to serious injury or
death
WARNING
Indicates a potentially dangerous situation
Disregarding this warning may result in serious physical in-
jury or death.
CAUTION
Indicates a situation which may cause possible damage
Disregarding this warning can cause damage to property
and the environment and result in minor injuries.
This symbol identifies user tips and particularly useful in-
formation, but not warnings or hazards
Special warning signs
Some types of danger are represented by special symbols.
Electric current
Danger of explosion
Risk of burns or scalds
Risk of poisoning
Validity
Some information in this manual has limited validity. The validity is
highlighted by a symbol.
Observe the specified tightening torque (see Chap. 12.3)
Only applies to devices with unpressurised solar system
connection (DrainBack).
Only applies to devices with a bivalent solar system connec-
tion (Biv).
Handling instructions
1Handling instructions are shown as a list. Actions where the se-
quential order must be maintained are numbered.
èResults of actions are identified with an arrow.
1.2 Safety instructions for installation
and operation
1.2.1 General
WARNING
Heaters that have not been set up and installed correctly
can impair the function of the heater and/or cause serious
or fatal injuries to the user.
▪ Work on the GCUcompact (such as set-up, inspection,
connection and initial commissioning) must only be car-
ried out by persons who are authorised and who have
successfully completed qualifying technical or voca-
tional training and who have taken part in advanced
training sessions recognised by the relevant authorities
responsible for the specific activity. These include, in
particular, certified heating engineers, qualified elec-
tricians and HVAC specialists who, , because of their
professional training and their expertise, have experi-
ence with the professional installation and maintenance
of heating systems, gas installations and hot water stor-
age tanks.
▪ Switch off the external main switch before starting any
work on the GCUcompact and secure it against uninten-
tional switch-on.
▪ Do not leave any tools or other objects below the hood
of the device after finishing installation or maintenance
work.
Avoiding danger
The GCUcompact conforms to the state of the art and meets all re-
cognised technical requirements. However, improper use may result
in serious physical injuries or death as well as property damage. To
prevent such risks, only install and operate the devices:
▪ as stipulated and in perfect condition,
▪ with an awareness of safety and the dangers involved.
This assumes knowledge and use of the contents of this manual, the
relevant accident prevention regulations and the recognised safety-
related and occupational health rules.
Before working on the heating system
▪ Only authorised and trained heating technicians may work on the
heating system (such as installation, connection and initial com-
missioning).
▪ Switch off the main switch and secure it against unintended
switch-on when carrying out any work on the heating system.
▪ Seals must not be damaged or removed.
▪ Make sure that the safety valves comply with the requirements of
EN12828 when connecting on the heating side and with the re-
quirements of EN12897 when connecting on the domestic water
side.

1 General safety precautions
Installation and operating instructions
7
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
1.2.2 Intended use
The GCUcompact may only be used for the heating of hot water
heating systems. It may only be installed, connected and operated in
accordance with the information in this manual.
The GCUcompact may only be operated with the integrated circula-
tion pump and only in conjunction with a controller system approved
by us.
Any other use beyond the intended use is considered as improper
and will result in a loss of warranty. The operator alone shall bear re-
sponsibility for any resulting damage.
The GCUcompact is suitable for operation with natural gas E, nat-
ural gas LL and liquid gas (propane).
Gases from regenerative sources (e.g. biogas) may contain sub-
stances that cause corrosion of the gas valve and can impair its
function.
The gas composition must comply with the requirements on condi-
tions for feeding into the gas distribution grid (low-pressure
pipelines) of the public standard gas supply. Gases from regenerat-
ive sources (e.g. biogas) may only be used when they have been
previously prepared so that they can be fed into the public natural
gas grid in accordance with regional regulations.
Intended use also includes compliance with the maintenance and
service conditions. Replacement parts must at least satisfy the tech-
nical requirements defined by the manufacturer. This is the case,
forexample, with original spare parts.
1.2.3 Installation room
WARNING
The plastic wall of the storage tank of the GCUcompact
can melt under the effects of external heat (>80°C) and, in
extreme cases, can catch fire.
▪ Only install the GCUcompact at a minimum distance of
1m to other heat sources (>80°C) (e.g. electrical
heater, gas heater, chimney) and combustible materials.
CAUTION
▪ Only install the GCUcompact if sufficient load-carrying
capacity of the ground of 1050kg/m2 plus safety margin
is ensured. The ground must be flat, horizontal and
level.
▪Outdoor installation is not permissible.
▪ Installation in an explosion-risk environment is not per-
missible.
▪ The electronic control system must not be exposed to
weather effects such as rain and snow under any cir-
cumstances.
▪ The storage tank may not be exposed to continuous dir-
ect sunlight, as the UV radiation and the effects of the
weather will damage the plastic.
▪ The GCUcompact must be installed protected from
frost.
▪ Operate the GCUcompact only if sufficient combustion air supply
is ensured. If the GCUcompact is operated as an ambient air-in-
dependent device with a concentric air/flue gas system (LAS) di-
mensioned according to our standard, this is automatically en-
sured and there are no further conditions regarding the installation
room. Only this method of operation is permissible for installation
in residential rooms.
▪ Make sure that there is an outside air opening of at least 150cm2
for ambient-air dependent or partial ambient-air independent oper-
ation.
▪ Do not operate the GCUcompact in ambient-air dependent opera-
tion in rooms with aggressive vapours (e.g. hair spray, perchloro-
ethylene, carbon tetrachloride), strong dust formation (e.g. work-
shop) or high humidity (e.g. laundry).
▪ Avoid operating conditions that can cause heavy soiling of the
burner. Do not operate the device if temporary heavy dust depos-
its occur in the area of the air extraction system.
▪ Always ensure the minimum distances from walls and other ob-
jects ( Chap. 4.1).
CAUTION
▪ If a DrainBack solar heating system is connected,
install the GCUcompact far enough under the solar pan-
els to allow complete emptying of the solar heating sys-
tem. (Follow instructions in the DrainBack solar heating
system manual). An insufficient height difference may
lead to destruction of the DrainBack solar heating sys-
tem.
▪ The GCUcompact must not be operated in rooms with
ambient temperatures above 40°C.
1.2.4 Electrical installation
▪ Electrical installations may only be carried out by electrical techni-
cians and in compliance with valid electrical guidelines as well as
the specifications of the responsible energy supply company.
▪ Compare the mains voltage (230V, 50Hz) indicated on the name-
plate with the supply voltage before connecting to the mains.
▪ Before beginning work on live parts, disconnect them from the
power supply (switch off main switch, remove fuse) and secure
against unintentional restart.
▪ Device covers and service panels must be replaced as soon as
the work is completed.
1.2.5 Requirements for the heating water
Damage due to deposits and corrosion: To avoid corrosion products
and deposits, observe the relevant technical regulations and locally
applicable requirements.
Measures for desalination, softening or hardness stabilisation are
necessary if the filling and top-up water have a high total hardness
(>3mmol/l - total of the calcium and magnesium concentrations, cal-
culated as calcium carbonate).
Minimum requirements regarding the quality of filling and supple-
mentary water:
▪ Water hardness (calcium and magnesium, calculated as calcium
carbonate): ≤3mmol/l
▪ Conductivity: ≤1500 (ideal: ≤100) μS/cm
▪ Chloride: ≤250mg/l
▪ Sulphate: ≤250mg/l
▪ pH-values (heating water): 6.5 - 8.5
Measures for desalination, softening or hardness stabilisation or
other suitable conditioning measures are necessary to maintain the
required water quality if the filling and top-up water have a high total
hardness or other properties divergent from the minimum require-
ments.
Using filling water and top-up water which does not meet the stated
quality requirements can cause a considerably reduced service life
of the equipment. The responsibility for this lies solely with the oper-
ator.

1 General safety precautions
Installation and operating instructions
8
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
1.2.6 Heating system and sanitary connection
▪ Create a heating system according to the safety requirements of
EN12828.
▪ The plumbing connection must comply with the requirements of
EN12897. The requirements of the following must also be ob-
served:
▪ EN1717 – Protection against pollution of potable water installa-
tions and general requirements of devices to prevent pollution
by backflow
▪ EN61770 – Electric appliances connected to the water mains –
Avoidance of backsiphonage and failure of hose-sets
▪ EN806 – Specifications for installations inside buildings con-
veying water for human consumption
▪ and, in addition, the country-specific legislation.
During operation of the GCUcompact with additional heat source,
the storage tank temperature may exceed 60°C, above all when
solar energy is used.
▪ For this reason, some form of scalding protection needs to be in-
cluded when you install the system (hot water mixing device, e.g.
VTA32).
1.2.7 Operation
▪ Do not operate the GCUcompact if the protective cover is open.
▪ Only operate the GCUcompact if all requirements according to
the checklist in Chap. 5.2 are satisfied.

2 Handover to operator and warranty
Installation and operating instructions
9
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
2 Handover to operator and
warranty
2.1 Instruct the owner
▪ Before you hand over the heating system, explain to the owner
how he/she can operate and check the heating system.
▪ Hand over the technical documentation (at least the operating in-
structions and operating manual) to the operator and advise him
that these documents must be made available at all times and be
stored in the immediate vicinity of the device.
▪ Document the handover by filling out the installation and instruc-
tion forms together with the owner and sign them.
2.2 Warranty conditions
The legal guarantee conditions fundamentally apply. Our more ex-
tensive warranty conditions can be found in the Internet. Ask your
suppliers if necessary.
There is only an entitlement to warranty services when it can be cer-
tified that the annual maintenance work according to Chap. 9 has
been regularly completed.

3 Product description
Installation and operating instructions
10
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
3 Product description
3.1 Design and components
3.1.1 GCU compact 315 / 320 (Biv)
Fig.3-1 Design and components of GCUcompact315 / 320
(Biv)
(for legend designations, seeTab. 3-1)
Fig.3-2 Design and components of GCUcompact315 / 320
(Biv) – schematic drawing
(for legend designations, see Tab. 3-1)

3 Product description
Installation and operating instructions
11
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
3.1.2 GCU compact 515 / 520 / 524 / 528 (Biv)
Fig.3-3 Design and components of GCUcompact515 / 520 /
524 / 528 (Biv)
(for legend designations, see Tab. 3-1)
Fig.3-4 Design and components of GCUcompact515 / 520 /
524 / 528 (Biv) – schematic drawing
(for legend designations, see Tab. 3-1)

3 Product description
Installation and operating instructions
12
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
Fig.3-5 Design and components of – illustration for GCUcom-
pact515 / 520 / 524 / 528 (Biv)
(for legend designations, see Tab. 3-1)
Item Name
1Cold water connection (1" AG) (1)
2Hot water connection (1" AG) (1)
3Storage tank - inflow (1" AG)
4Storage tank - return flow (1" AG)
5Heating - inflow (1" AG)(2) (1)
6Heating - return flow (1" AG)(2)
7 Solar - inflow (1" IG)
8Draining connection or Solar - return flow
9 Flue gas
10 Supply air
11 Sensor pocket for tank temperature sensor tDHW
12 Upper filling and overflow connection
14 Condensate drain
15 Heat exchanger (boiler body)
16 Heat exchanger (stainless steel) for domestic hot wa-
ter heating
17 Heat exchanger (stainless steel) for storage tank
charging or heating support
18 Heat exchanger (stainless steel) for bivalent storage
charging(3)
19 Bivalent storage charging - inflow(1), (3) (1" IG)
20 Bivalent storage charging - return flow(1), (3) (1"
IG)
21 Solar - inflow layering pipe
22 Heating circulation pump
23 Burner fan
24 Safety-pressure relief valve (heating circuit)
25 Vent valve (manual)
26 Gas connection (G ½" IG) with connected gas hose
27 Boiler control panel with controller RoConBF
28 Heat insulation
29 Panelling of the heat cell
30 Protective cover
31 Holding burls for protective cover
32 Type plate
33 Settings type plate
34 Threaded insert for carrying handle
35 Combined filling and draining valve (heating circuit)
36 Automatic vent valve
37 Fill level indicator for storage tank water
39 Ball valve (heating circuit)
40 MAG connection
41 Optional: R3 control and pump unit
3UVDHW 3-way valve (distribution valve, hot water/heating/
heating support)
3UVB1 3-way mixer valve
tDHW Storage tank temperature sensor
tRReturn flow temperature sensor (boiler circuit)
(1) Recommended accessories: SKB circulation stop valves (2 pcs. each)
(2) Ball cock (1" IG) is supplied.
(3) Only valid for types with Biv configuration

3 Product description
Installation and operating instructions
13
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
Item Name
tV1 Inflow temperature sensor (boiler circuit)
tV2 Internal mixer sensor = inflow temperature sensor
(heating circuit)
AGas boiler
B Storage tank (polypropylene, double-walled jacket
with PUR hard foam heat insulation)
C Pressure-free storage water
D Hot water zone
DS Pressure sensor
E Solar zone
FLS (V1) Flow sensor (boiler circuit)
MAG Diaphragm expansion vessel (on the building side)
STBK Safety temperature limiter
AG Outer thread
IG Inner thread
ÜM Union nut
Safety devices
Observe tightening torque!
Tab.3-1 Legend for Fig. 3-1 to Fig. 3-5
3.2 Brief description
The Gas Combi Unit 2 (GCU compact) is a fully preassembled gas
condenser unit integrated in a hot water storage tank. The very good
thermal insulation properties of the plastic storage tank ensure that
heat losses are kept to a minimum. The aluminium boiler body is in a
metal housing installed on the cover of the storage tank. The com-
plete flue gas unit is surrounded by fresh air.
Operating mode
The GCU compact is designed so that it can be operated independ-
ently of the ambient air (concentric flue gas/supply air pipes). The
burner suctions the combustion air directly in through an installation
shaft or a double-walled flue gas pipe. We recommend this operating
mode which has many advantages:
▪ The heating room does not need any ventilation opening into the
open air and therefore does not cool down.
▪ Lower energy consumption.
▪ Additional energy recovery in the flue gas pipe through preheating
the combustion air.
▪ Contamination from the environment of the burner is not suctioned
in. This means that the heating room can be used as a work-
space, laundry room, etc. at the same time.
▪ Can be installed in loft areas or attic.
The condensate is collected in the flue gas collector, led to the rear
via a condensate pipe integrated in the storage cover and then dis-
charged into the drainage system.
The unpressurised storage tank water acts as the heat storage me-
dium. Useful heat is supplied and removed via the spiral heat ex-
changer, which is made from a stainless steel corrugated pipe
(1.4404), and is completely immersed in the storage tank water.
The hot water zone in the storage tank works as a combination of
heat storage and geyser (see Fig. 3-2 and Fig. 3-4).
The cold water that flows out when the hot water is removed is first
routed to the storage tank at the very bottom of the heat exchanger,
where it cools the lower area of the storage tank down as much as
possible. The readiness zone is flowed through and heated from top
to bottom by the heat exchanger for the storage tank charging
(SL-WT), which is heated by the gas burner.
On its way to the top, the domestic water continuously absorbs the
heat of the storage tank water. As the flow direction makes use of
the counter flow principle and the heat exchanger has a spiral
shape, there is definite temperature stratification within the hot water
storage tank. As high temperatures can be maintained for a very
long time in the upper section of the storage tank, a high hot water
output is achieved even if water is drawn off over a long period of
time.
▪ In the GCUcompact5xx (Biv) models, the SL-WT ends approx.
25cm above the floor of the container. Only the hot water zone
above that point is heated by the boiler. The water below that
point in the tank is heated by solar power alone.
▪ In the GCUcompact3xx (Biv) models, the SL-WT descends to the
floor of the container. The entire storage volume is heated by the
boiler (greater hot water output readiness).
Optimum water hygiene
There are no low-flow or unheated zones on the domestic water side
with the GCU compact. It is not possible for sludge, rust or other
sediments to be deposited, as can be the case with other large
volume tanks. The water that is fed into the system first is also dis-
charged first (first in, first out principle).
Low scaling
On the storage tank side, scale can only be deposited once. All the
stainless steel heat exchanger pipes in the storage tank water
largely remain virtually free of solid deposits. This means that the
scale cannot build up, which would continuously reduce the effi-
ciency of heat transfer (as is the case for other storage designs) dur-
ing the operation time.
The thermal and pressure expansion and high flow rates in the do-
mestic water heat exchanger cause any scale deposits to be re-
leased, which are then flushed away.
Using solar power
The hot water storage tank of GCU compact can also be heated by
solar energy. The entire hot water storage tank can be heated up de-
pending on the heat available from the sun. The stored heat is used
for the hot water preparation and for heating system support. The
ISM ("Intelligent Storage Manager") controls the integrated 3-way
valves in such a way that the solar heat yield is optimally divided and
used for domestic hot water preparation and heating support. The
high total storage capacity enables the bridging of periods without
solar yield.
When a pressurised solar system or an external heating boiler is
used as an external heat generator, only one of the GCU compact
with Biv configuration – listed in chap.Chap. 3.1 – is permitted as
the primary hot water storage unit.
In the GCUcompactBiv models, the complete storage tank is de-
signed as a hot water zone. It is possible to make thermal use of
solar energy for domestic hot water preparation. The solar compon-
ent is optimised in combination with an upstream Solaris system
(pre-heating stage).
Safety management
The entire safety management of the GCU compact is managed by
electronic control. It performs a safety switch-off in the event of water
shortage, gas shortage or undefined operating states. A correspond-
ing fault signal provides an engineer with all the information neces-
sary for troubleshooting.
Electronic controller
An electronic digital controller combined with the burner "intelligent"
combustion control automatically controls all heating and hot water
functions for the direct heating circuit and a storage tank charging
circuit.

3 Product description
Installation and operating instructions
14
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
One or more mixed circuits can be connected and controlled via op-
tionally connected mixer modules RoConM1.
All settings, displays and functions are carried out by the integrated
RoConBF controller. The display and the operating elements make
operation easy.
A digital room controller (RoConU1) is optionally available for
greater comfort. It can be used as a remote control and room ther-
mostat.
The controller can be connected to the Internet via the optional gate-
way (RoConG1). This enables remote control of the GCU compact
by mobile phone (using an app).
Calorific value engineering
Calorific value engineering makes optimum use of the energy con-
tained in the heating gas. The flue gas is cooled down in the boiler –
and in the flue system with ambient air-independent operation in the
concentric flue gas system – to the extent that the temperature is be-
low the dew point. Part of the water vapour generated by the com-
bustion of the gas thus condenses. The condensation heat is fed to
the heating, as opposed to low-temperature boilers, which enables
efficiency rates of more than 100% (based on the lower heating
value).

4 Set-up and installation
Installation and operating instructions
15
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
4 Set-up and installation
WARNING
Incorrectly erected and installed gas appliances may not
operate properly and are dangerous for the health and
safety of individuals.
▪ The GCUcompact must only be set up and installed by
heating engineers authorised and trained by gas or en-
ergy supply companies.
Incorrect set-up and installation would render the manufacturer's
guarantee void. If you have questions, please contact our Technical
Customer Service.
4.1 Dimensions and connection
dimensions
Fig.4-1 Installation dimensions for flue gas connection on the
rear (for values, see Tab. 4-1)
ASide view
BFront view
CTop view
Fig.4-2 Installation dimensions for flue gas connection on the
side or upwards (for values, see Tab. 4-1)
ASide view
BFront view
CTop view
Dim. GCUcompact3xx GCUcompact5xx
h1 1380
h2 1895
h3 1745 1740
hR2095
r1 165 130
s1 440 370
s2 200
s3 300
s4 435 335
sD200
t 615 790
w 595 790
Tab.4-1 Connection and installation dimensions of the GCU com-
pact in mm (based on Fig. 4-1, Fig. 4-2, Fig. 4-10,
Fig. 4-16 to Fig. 4-20)

4 Set-up and installation
Installation and operating instructions
16
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
4.1.1 Connecting dimensions for the heating
and hot water connections
GCUcompact3xx
Fig.4-3 GCUcompact3xx connection dimensions (view from the
back)
For legend of position numbers, see Tab. 3-1
Fig.4-4 Connection dimensions of the GCUcompact3xx (top
view)
For legend of position numbers, see Tab. 3-1
AFront side
BRear side

4 Set-up and installation
Installation and operating instructions
17
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
GCUcompact5xx
Fig.4-5 Connection dimensions GCUcompact5xx (view from
the back)
For legend of position numbers, see Tab. 3-1
Fig.4-6 Connection dimensions GCUcompact5xx (top view)
For legend of position numbers, see Tab. 3-1
AFront side
BRear side
INFORMATION
To avoid increased cooling losses, we recommend the in-
stallation of SKB gravity brakes or the syphoning (connect-
ing lines leading directly downwards) of the drinking water
connection.
4.2 Different set-ups
Fig.4-7 Installation variants for the GCUcompact
1-6 Installation variant (for a description, see Chap. 4.2.1 to
Chap. 4.2.3)
CA Supply air (combustion air)
FG Flue gas
RV Rear ventilation
aInstallation variant for ambient air-independent operation
(flue gas/supply air concentric)
bInstallation variant for conditional ambient air-independent
operation (separate flue gas/supply air)
cInstallation variant for ambient air-dependent mode
dLongitudinally ventilated shaft with a fire-resistance period
of 90minutes (30minutes in low height residential build-
ings). Observe country-specific regulations for fire-resist-
ance periods.
eVentilation opening (1×150cm2 or 2×75cm²)
fRear ventilation opening (150cm2)
The GCUcompact are designed basically for the ambient air inde-
pendent operation. They are fitted with a concentric flue gas /air
supply pipe DN 60/100 as standard.
The SETGCU1 kit can be used to flexibly arrange the flue gas /air
supply line for the connection directions to the rear, to the side or up-
wards and extended to DN 80/125.

4 Set-up and installation
Installation and operating instructions
18
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
INFORMATION
In some cases, the resonance in the flue gas system can
amplify the noise at the mouth of the flue gas duct. The
noise level can be effectively reduced by using a silencer
(DN80: E8MSD or DN110: E11MSD).
INFORMATION
We recommend using the GCUcompact in ambient air-in-
dependent operation with a concentric flue gas/air supply
line. If possible, choose this installation variant.
In partial ambient air-independent operation (separate flue
gas/air supply lines with a single-walled connecting pipe)
and ambient air-dependent operation, the installation room
must have a ventilation opening of at least 150cm2 to the
outside.
This reduces the overall energy efficiency of the building
according to European Directive 2010/31/EU: EPBD.
The following descriptions of the different set-ups include
information regarding the possible classification of the
devices based on the type of flue gas routing (device type)
in accordance with CEN/TR1749. Chap. 4.2.4 and
Chap. 4.5 must also be observed in this regard.
The SETs (see Fig. 4-18) mentioned below are recom-
mendations for the appropriate combination of the required
individual components for the typical installation variants.
4.2.1 Room-air independent operation
INFORMATION
When devices are installed in residential rooms only one of
the installation variants 1 to 4 is permissible.
Installation variant 1
The GCUcompact with the SETGCU1 and the concentric LAS con-
nection line SETH or SETK is connected to the chimney or an in-
stallation shaft.
▪ The combustible air supply from the outside runs through the
chimney or through an installation shaft.
▪ The flue gas discharge to the outside runs through the same shaft
as the air supply.
▪ Minimum vertical distance between the flue gas exit and roof
ridge: 40cm.
▪ Device type C93
Installation variant 2
The GCUcompact is placed directly below the roof. Connection with
SETGCU1 and SETL.
▪ The combustible air supply and flue gas discharge run through a
concentric dual pipe.
▪ The combustible air supply from the outside runs through the
outer ring-shaped gap of the dual pipe, and the flue gas discharge
to the outside runs through the inner tube.
▪ Minimum vertical distance between the flue gas exit and roof sur-
face: 40cm.
▪ Minimum height of the flue gas pipe: 2m.
▪ Device type C33
Installation variant 3
The GCUcompact is not placed directly below the roof. The dual
pipe for the combustible air supply and flue gas duct runs through
the roof truss.
▪ The combustible air supply and the flue gas discharge run through
a concentric dual pipe (as in Installation variant 2).
▪ In the area of the roof truss, the dual pipe for the combustible air
supply and the flue gas duct must be laid through a protective pipe
with sufficient fire resistance or be structurally separated from the
roof truss.
▪ Device type C33
Installation variant 4
The GCUcompact with the SETGCU1 and the LAS connection line
SETH or SETK is connected to the exterior wall system SETG.
▪ The combustible air supply from the outside runs through the ring-
shaped gap in the dual pipe through the outer wall (suction from
below).
▪ The flue gas discharge to the outside runs through a concentric
pipe, through the outer wall and then up to at least 40cm over the
roof surface. In the external area, the outer air gap serves as heat
insulation for the flue gas pipe.
▪ Device type C53
INFORMATION
If the wall feed through is at a height of less than one
meter above the ground, we recommend routing the com-
bustion air through a separate air supply pipe (mounting
height: approx. 2m). W8ZR or W11ZR
Installation variant 5
If, for constructional or legal/regulatory reasons, the shaft used for
the flue gas routing is not suited for also routing the combustion air
at the same time, the combustion air must be routed through a sep-
arate line.
If the flue gas connection line to the shaft is double-walled and is
surrounded by the combustion air, there are no additional ventilation
requirements on the installation room.
▪ The combustion air supply is routed from the outside via the ad-
equately sealed supply line that is connected directly to the con-
centric exterior pipe of the connection line. The supply line should
be dimensioned so that the suction resistance at nominal out-
put is less than 50Pa.
▪ The connection line between the GCUcompact and the installa-
tion shaft is completely concentric and surrounded by combustion
air.
▪ Device type C53, C83
Installation variant 7 (not shown)
If permitted by local regulations, the GCUcompact can be connec-
ted to SETW2 to the horizontal flue gas outlet.
▪ The combustible air supply and flue gas discharge run through a
concentric dual pipe.
▪ The combustible air supply runs from the outside through the
outer ring-shaped gap of the dual pipe (supply air inlet via the in-
take grille of the wall feedthrough) and the flue gas discharge to
the outside runs through the inner tube.
▪ Minimum height of the flue gas pipe: 2m
▪ Observe the local regulations regarding minimum distances of
windows or other building openings.
▪ Device type C13
4.2.2 Partial ambient air-independent mode
Alternative to installation variant 5
The GCUcompact is operated with separately routed supply air/flue
gas lines (2-pipe system).
▪ The combustion air supply from the outside runs through an ad-
equately sealed air supply line through the external wall. The sup-
ply line should be dimensioned so that the suction resistance at
nominal output is less than 50Pa.

4 Set-up and installation
Installation and operating instructions
19
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
▪ The flue gas discharge to the outside runs through the chimney or
an installation shaft. If the connection line between the GCUcom-
pact and the installation shaft is single-walled or not completely
surrounded by combustion air, a ventilation opening to the out-
side of at least 150cm2 is required.
Appropriate measures must be taken to ensure that the burner
cannot be operated if the ventilation opening is closed.
▪ The installation shaft where the flue gas line runs must be rear
ventilated. There must be a rear ventilation opening of at least
150cm2 in the lower area.
The cross-section of this installation shaft must be dimensioned so
that the following minimum distance is maintained between the
external wall of the flue gas line and the internal face of the in-
stallation shaft:
▪ with a rectangular shaft cross-section: 2cm
▪ with a round shaft cross-section: 3cm.
The rear ventilation opening must not be located in rooms where a
negative pressure is generated (e.g. by controlled apartment vent-
ilation, a tumble dryer, etc.).
▪ Device type C53, C83
4.2.3 Ambient air-dependent mode
Installation variant 6
The GCUcompact can also be connected with ambient air. Thereby,
only the inner flue gas pipe (plastic pipe Ø60mm) of the concentric
air/flue gas pipe is connected to the flue gas line. The device sucks
the combustible air from the installation room through the ring-
shaped gap of the jacket pipe.
The same conditions apply to the flue gas routing into the open air,
shaft dimensioning and rear ventilation as in Chap. 4.2.2. A ventila-
tion opening into the open air of at least 150cm2 is mandatory.
▪ Device type B23, B23P, B33, B53, B53P
INFORMATION
In some cases, the resonance in the flue gas system can
amplify the noise at the mouth of the flue gas duct. The
noise level can be effectively reduced by using a silencer
(DN80: E8MSD or DN110: E11MSD).
4.2.4 Additional information on the device type
in accordance with CEN/TR1749
INFORMATION
We basically recommend installing the GCUcompact re-
gardless of the ambient air (device type C) and with con-
centric air/flue gas guides (see Chap. 4.2.1). Other per-
missible applications of the air intake and flue gas dis-
charge are not described in detail in these instructions.
Special requirements that exist for such systems based on
EN15502 -2-1 are listed below.
C13:
▪ Horizontal openings for flue gas outlet and supply air inlet
▪ Openings within a square of 50cm×50cm
C33:
▪ Vertical openings for flue gas outlet and supply air inlet
▪ Openings within a square of 50cm×50cm
▪ Spacing of opening levels <50cm
C43:
▪ Connection of more than one device to a common air/flue gas sys-
tem that is part of the building
▪ Vertical opening for the flue gas outlet and supply air inlet
▪ Openings within a square of 50cm×50cm
▪ Spacing of opening levels <50cm
▪ Suitable calculated dimensioning verification required because va-
cuum prevails in the case of the flue gas inlet into the common air/
flue gas system. The flue gas must be discharged with a natural
draught.
▪ For data on dimensioning, see Tab. 14-1.
▪ Condensate flow from the common air/flue gas system must not
be discharged through the device.
C53:
▪ Vertical opening for the flue gas outlet
▪ Opening for the supply air inlet into different pressure area pos-
sible.
▪ Openings must not be installed on opposite walls of the building
C63:
▪ Connection to a separately approved and marketed flue gas/sup-
ply air system if allowed by national law.
▪ This allows all other described installation forms to the realised for
device type C if the conditions of the respective installation form
are met.
▪ If the dimensions of the system used differ from those described in
this manual (seeChap. 4.5.1), a suitable arithmetical dimension-
ing verification is required.
▪ For data on dimensioning, see Tab. 14-1.
▪ Properties and possible applications of the pipe system:
▪ Minimum requirements according toChap. 4.5.1 fulfilled
▪ Condensate flow into the device allowed with single assign-
ment, not allowed with multiple assignment.
▪ Maximum combustion air temperature: 60°C
▪ Maximum allowed flue gas recirculation current under wind con-
ditions: 10%
C83:
▪ Connection of one or more devices to an underpressure flue gas
system that is part of the building.
▪ Vertical opening for the flue gas outlet
▪ Air supply feed via the associated second (4) pipe
▪ Opening for the supply air inlet into a different pressure area pos-
sible.
▪ Suitable arithmetical dimensioning verification required because
vacuum prevails in the case of the flue gas inlet into the common
air/flue gas system.
▪ For data on dimensioning, see Tab. 14-1.
▪ Properties and application options of the flue gas system:
▪ Minimum requirements according toChap. 4.5.1 fulfilled (except
for pressure class)
▪ Condensate flow into the device allowed with single assign-
ment, not allowed with multiple assignment.
C93:
▪ as for C33, but
▪ Connection of the supply air pipe to an existing vertical shaft (e.g.
chimney) that is part of the building.
▪ The cross-section of this installation shaft must be dimensioned so
that the following minimum distance must be maintained
between the external wall of the flue gas line and the internal
face of the installation shaft:
▪ with a rectangular shaft cross-section: 2cm
▪ with a round shaft cross-section: 3cm
(4) If the air supply pipe was used beforehand as a flue gas pipe or chimney of an oil or solid fuel furnace, it should be cleaned
prior to use as an air supply pipe.

4 Set-up and installation
Installation and operating instructions
20
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
B23:
▪ Flue gas pipe without flow safeguard – underpressure operation
▪ Properties and application options of the flue gas pipe:
▪ Minimum requirements according toChap. 4.5.1 fulfilled
▪ Opening for the flue gas outlet to the outside
▪ Supply air directly from the installation room (seeChap. 4.2.3).
▪ If the dimensions of the flue gas pipe differ from those described
in these instructions (see Tab. 4-2), a suitable calculated dimen-
sioning verification is required.
▪ For data on dimensioning, see Tab. 14-1.
B23P:
▪ as for B23, but underpressure operation
B33:
▪ Connection of more than one device to a common flue gas system
(underpressure flue gas shaft)
▪ Vertical opening for the flue gas outlet
▪ Supply air directly from the installation room (seeChap. 4.2.3).
▪ Suitable arithmetical dimensioning verification required because
vacuum prevails in the case of the flue gas inlet into the common
air/flue gas system.
▪ For data on dimensioning, see Tab. 14-1.
▪ Parts under overpressure of the connection pipe must be conduc-
ted as a concentric pipe system.
B53:
▪ as for B33, but connection to associated flue gas pipe system in-
cluding flue gas opening
B53P:
▪ as for B53, but overpressure operation
4.3 Transport and delivery
WARNING
The GCUcompact is top-heavy in the unfilled state and
could tip over during transport, which could put persons in
danger or damage the device.
▪ Secure the GCUcompact well, transport carefully, use
handles.
The GCUcompact is delivered on a pallet. All industrial trucks, such
as lifting trucks and forklift trucks, are suitable for transport.
Scope of delivery
▪ GCUcompact (preassembled),
▪ Bag of accessories (see Fig. 4-8),
▪ Outside temperature sensor (RoConOT1), for weather-com-
pensated regulation
▪ Document pack.
Fig.4-8 Contents of bag of accessories
AHandles (only required for transport)
BCover panel
CHose connecting piece for safety overflow
DAssembly wrench
EBallcock
FFlat gasket
GO-ring
HCable tie
ISecuring clip
JVenting hose
KOutside temperature sensor
For additional accessories, see the price list.
4.4 Installing the GCU compact
4.4.1 Selecting the installation site
The installation site of the GCUcompact must meet the minimum re-
quirements below (see alsoChap. 1.2.3).
Installation area
▪ The base must be level and smooth and have sufficient ground
load-bearing capacity of 1050kg/m² plus safety factor. Install a
pedestal if necessary.
▪ Observe the installation dimensions (see Chap. 4.1).
Installation room
▪ There are no special conditions for ventilation of the installation
room for ambient air-independent operation (using a concentric
air/flue gas system).
▪ In partial ambient air-independent and ambient-dependent mode,
the installation room must have a ventilation opening of at least
150cm2 to the outside. If the flue gas line is routed to the outside
through an installation shaft, it must be rear-ventilated
(seeChap. 4.2.2).