Rotex GCU compact User manual

For certified companies
ROTEX
GCU compact
Installation and maintenance
instructions
Gas Combi Unit compact
Types
GCU compact 315
GCU compact 324
GCU compact 515
GCU compact 524
GCU compact 533
GCU compact 315 Biv
GCU compact 324 Biv
GCU compact 515 Biv
GCU compact 524 Biv
GCU compact 533 Biv
GB
Edition 
0085 CO 0180


List of contents
2ROTEX GCU compact - 
1Guarantee . . . . . . . . . . . . . 4
1.1 Warranty conditions . . . . . . . . . . . . . . . . . . . . . . 4
2 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Observing instructions . . . . . . . . . . . . . . . . . . . . 5
2.2 Warning signs and explanation of symbols . . . . 5
2.3 Avoid danger . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.4 Proper use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.5 Instructions for operating safety . . . . . . . . . . . . . 6
2.5.1 Before working on the heating system . . . . . . . . . .6
2.5.2 Electrical installation . . . . . . . . . . . . . . . . . . . . . . . .6
2.5.3 Installation room . . . . . . . . . . . . . . . . . . . . . . . . . . .6
2.5.4 Requirements for the heating water . . . . . . . . . . . .6
2.5.5 Heating system and sanitary connection . . . . . . . .6
2.5.6 Fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
2.5.7 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
2.5.8 Instructing the user/owner. . . . . . . . . . . . . . . . . . . .6
3 Product description. . . . . . . . . . . . . . . . . . . 7
3.1 Design and components . . . . . . . . . . . . . . . . . . 7
3.1.1 GCU compact 315 / 324 . . . . . . . . . . . . . . . . . . . . .7
3.1.2 GCU compact 515 / 524 / 533. . . . . . . . . . . . . . . . .8
3.2 Brief description . . . . . . . . . . . . . . . . . . . . . . . . . 9
4 Set-up and installation . . . . . . . . . . . . . . . 11
4.1 Dimensions and connection dimensions . . . . . 11
4.1.1 Connection dimensions for the heating and
hot water connections . . . . . . . . . . . . . . . . . . . . . .12
4.2 Installation versions . . . . . . . . . . . . . . . . . . . . . 14
4.2.1 Operation independent of ambient air. . . . . . . . . .15
4.2.2 Operation partially independent of ambient air . . .16
4.2.3 Ambient air dependent operation . . . . . . . . . . . . .16
4.3 Transport and delivery . . . . . . . . . . . . . . . . . . . 16
4.4 Installing the Gas Combi Unit compact . . . . . . 16
4.4.1 Selecting the installation site . . . . . . . . . . . . . . . .16
4.4.2 Setting up the unit . . . . . . . . . . . . . . . . . . . . . . . . .17
4.4.3 Remove the sound insulation hood. . . . . . . . . . . .18
4.5 Air/flue system (LAS) . . . . . . . . . . . . . . . . . . . . 18
4.5.1 General instructions for flue system . . . . . . . . . . .18
4.5.2 Connecting a flue gas line. . . . . . . . . . . . . . . . . . .19
4.5.3 Flue gas system kits . . . . . . . . . . . . . . . . . . . . . . .20
4.6 Water connection . . . . . . . . . . . . . . . . . . . . . . . 21
4.6.1 Connecting the safety group (SBG) . . . . . . . . . . .21
4.6.2 Connecting hydraulic lines . . . . . . . . . . . . . . . . . .22
4.6.3 Connect the condensate drain . . . . . . . . . . . . . . .23
4.7 Connection Control and Electrics. . . . . . . . . . . 23
4.7.1 Instructions concerning electrical connection . . . .23
4.7.2 Establishing the electrical connection . . . . . . . . . .23
4.7.3 Integrated heating circulation pump and
3-way-valve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
4.8 Temperature sensor. . . . . . . . . . . . . . . . . . . . . 25
4.8.1 Connecting the exterior temperature sensor
RoCon OT1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
4.9 Connect the gas line, check the burner
setting for gas type. . . . . . . . . . . . . . . . . . . . . . 26
4.9.1 Important instructions for gas connection . . . . . . .26
4.9.2 Connecting the gas line. . . . . . . . . . . . . . . . . . . . .26
4.9.3 Installing/removing the burner trim . . . . . . . . . . . .26
4.9.4 Checking the gas pre-installation . . . . . . . . . . . . .27
4.10 Optional connections . . . . . . . . . . . . . . . . . . . . 28
4.10.1 Mixer module RoCon M1 . . . . . . . . . . . . . . . . . . .28
4.10.2 Room control RoCon U1 . . . . . . . . . . . . . . . . . . . .28
4.10.3 Internet Gateway RoCon G1 . . . . . . . . . . . . . . . . 28
4.11 Filling the system . . . . . . . . . . . . . . . . . . . . . . 28
4.11.1 Check the water quality and adjust the pressure
gauge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.11.2 Filling the hot water heat exchanger . . . . . . . . . . 28
4.11.3 Filling the storage tank . . . . . . . . . . . . . . . . . . . . 28
4.11.4 Filling the heating system and the storage tank
charging circuit . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5 Start-up. . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
5.1 Initial start-up. . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.1.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.1.2 Checks before start-up . . . . . . . . . . . . . . . . . . . . 31
5.1.3 Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.1.4 After start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.2 Checklists for start-up . . . . . . . . . . . . . . . . . . . 33
6 Control unit . . . . . . . . . . . . . . . . . . . . . . . . .34
6.1 Operating elements on the boiler control
panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
6.2 Replacing the operating section RoCon B1 . . 35
6.3 Changing the sensors . . . . . . . . . . . . . . . . . . . 35
6.3.1 Changing the flow temperature sensor / return
temperature sensor and pressure sensor . . . . . . 36
6.3.2 Changing the internal mixer sensor for heating
support (only GCU compact 5xx) . . . . . . . . . . . . 36
6.3.3 Changing the storage tank temperature sensor . 37
7 Gas burner . . . . . . . . . . . . . . . . . . . . . . . . . .38
7.1 Structure and brief description . . . . . . . . . . . . 38
7.2 Safety function . . . . . . . . . . . . . . . . . . . . . . . . 39
7.3 Burner setting . . . . . . . . . . . . . . . . . . . . . . . . . 39
7.3.1 Setting values . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
7.3.2 Establishing access to the burner . . . . . . . . . . . . 40
7.3.3 Checking and setting the burner . . . . . . . . . . . . . 40
7.3.4 Starting problems - calibrate the firing unit,
starting output burner blower and setting the
gas volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
7.3.5 Setting ignition and Ionisation electrodes . . . . . . 43
7.4 Dismantling the burner . . . . . . . . . . . . . . . . . . 43
8 Hydraulic connection . . . . . . . . . . . . . . . . .45
8.1 Hydraulic system connection . . . . . . . . . . . . . 45
9 Service and maintenance . . . . . . . . . . . . . .47
9.1 General overview of service and maintenance 47
9.2 Service and maintenance tasks . . . . . . . . . . . 47
9.2.1 Checking the connections and pipes. . . . . . . . . . 47
9.2.2 Checking and cleaning the condensate drain. . . 47
9.2.3 Checking and cleaning the burner. . . . . . . . . . . . 48
10 Faults and malfunctions . . . . . . . . . . . . . . .49
10.1 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . 49
10.2 Overview of possible malfunctions . . . . . . . . . 49
10.3 Fault codes . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
10.4 Rectifying burner faults and STB faults. . . . . . 53
10.5 Emergency operation . . . . . . . . . . . . . . . . . . . 54
10.5.1 Parallel operation . . . . . . . . . . . . . . . . . . . . . . . . 54
11 Taking out of service. . . . . . . . . . . . . . . . . .55
11.1 Temporary shutdown . . . . . . . . . . . . . . . . . . . 55
11.2 Final shutdown and disposal. . . . . . . . . . . . . . 55

List of contents
ROTEX GCU compact -  3
12 Technical data . . . . . . . . . . . . . . . . . . . . . . . 56
12.1 Basic data . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
12.1.1 GCU compact 3xx . . . . . . . . . . . . . . . . . . . . . . . . 56
12.1.2 GCU compact 5xx . . . . . . . . . . . . . . . . . . . . . . . . 57
12.1.3 Integrated gas burner . . . . . . . . . . . . . . . . . . . . . 58
12.1.4 Integrated heating circulation pump, 3-way valve 58
12.2 Gas type, connection pressures . . . . . . . . . . . .59
12.3 Tightening torque . . . . . . . . . . . . . . . . . . . . . . .60
12.4 Flow rate and residual feed height . . . . . . . . . .60
12.5 Temperature sensor . . . . . . . . . . . . . . . . . . . . .60
12.6 Electrical connection diagram . . . . . . . . . . . . . .61
13 Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
14 List of keywords . . . . . . . . . . . . . . . . . . . . . 63
15 For the chimney sweep . . . . . . . . . . . . . . . 64
15.1 Data for designing the flue gas pipe . . . . . . . . .64
15.2 Emissions measurement. . . . . . . . . . . . . . . . . .64

1xGuarantee
4ROTEX GCU compact - 
1Guarantee
1.1 Warranty conditions
The legal guarantee conditions fundamentally apply. Our war-
ranty conditions beyond that can be found online on your sales
representative's webpage.

2xSafety
ROTEX GCU compact -  5
2Safety
2.1 Observing instructions
This instruction is the >> Original Version << in your language.
Please read this manual carefully and thoroughly before pro-
ceeding with the installation or modification of the heating
system.
These instructions are intended for authorised and trained
heating and sanitation experts who have experience in the proper
installation and maintenance of heating systems and hot water
storage tanks by virtue of their technical training and knowledge.
This manual provides all the necessary information for instal-
lation, start-up and maintenance, as well as basic information on
operation and settings. Please go through the attached docu-
ments for a detailed description of operation and control.
All heating parameters needed for smooth operation are already
factory-set. Please refer to other relevant documents for infor-
mation on setting the control.
Relevant documents
– ROTEX GCU compact:
– For the operator
– Operating manual for the operator.
– ROTEX RoCon BF: Operating instructions.
– When connecting additional ROTEX components; the associ-
ated installation and operating instructions.
The guides are included in the scope of supply for the individual
units.
2.2 Warning signs and explanation of symbols
Meaning of the warnings
Warnings in this manual are classified according into their se-
verity and probability of occurrence.
Special warning signs
Some types of danger are represented by special symbols:
Validity
Some information in this manual has limited validity. The validity
is highlighted by a symbol.
Order number
Information about order numbers are identified with the shopping
basket icon .
Handling instructions
ƔInstructions on actions are shown as a list. Actions of which
the sequential order must be maintained are numbered.
ÎResults of actions are identified with an arrow.
2.3 Avoid danger
ROTEX Gas Combi Unit compact conforms to the state-of-the-art
and meets all recognised technical requirements. However,
improper use may result in serious physical injuries or death, as
well as property damage. Install and operate only ROTEX Gas
Combi Unit compact to avoid danger:
– as stipulated and in perfect condition,
– with an awareness of the safety and hazards involved.
This assumes knowledge and use of the contents of this manual,
the relevant accident prevention regulations and the recognised
safety-related and occupational medical rules.
2.4 Proper use
The ROTEX GCU compact may only be used for the heating of
hot water heating systems. It may only be erected, connected
and operated only according to the indications in this manual.
The ROTEX GCU compact must only be operated with the inte-
grated circulation pump and only in connection with a control
system that has been approved by ROTEX.
Any other use outside the intended use is considered as improper
and leads to a loss of warranty. The operator alone shall bear re-
sponsibility for any resulting damage.
Proper use also includes observing the relevant maintenance
and servicing conditions. Spare parts must at least satisfy the
technical requirements defined by the manufacturer. This is the
case, for example, with original spare parts.
DANGER!
Draws attention to imminent danger.
Disregarding this warning can lead to serious injury or
death.
WARNING!
Indicates a potentially dangerous situation.
Disregarding this warning can result in serious injury
or death.
CAUTION!
Indicates a situation which may cause possible
damage.
Disregarding this warning can lead to damage to
property and the environment.
This symbol identifies user tips and particularly useful
information, but not warnings or hazards.
Electric power
Danger of explosion
Risk of burning or scalding
Risk of poisoning
Pay attention to the stipulated tightening torque
(See chapter 12.3 "Tightening torque")
Only applies for units with unpressurised solar system
connection (Drain Back).
Only applies for units with a bivalent solar system con-
nection (BIV).

6ROTEX GCU compact - 
2xSafety
2.5 Instructions for operating safety
2.5.1 Before working on the heating system
ƔWork on the heating system (such as installation, connection
and initial start-up) may only be carried out by authorised,
trained heating technicians.
ƔSwitch off the main switch and secure it against unintended
switching on when carrying out any work on the heating
system.
ƔSeals must not be damaged or removed.
ƔMake sure that the safety valves comply with the require-
ments of EN 12828 when connecting on the heating side, and
with the requirements of EN 12897 when connecting on the
domestic water side.
2.5.2 Electrical installation
ƔElectrical installations must only be conducted by electrical
engineers and in compliance with valid electrical guidelines
as well as the specifications of the energy supply company.
ƔBefore completing the mains connection, compare the mains
voltage, indicated on the type plate (230 V, 50 Hz) with the
supply voltage.
ƔBefore beginning work on live parts, disconnect them from the
power supply (switch off main switch, remove fuse) and
secure against unintentional restart.
ƔEquipment covers and service panels must be replaced as
soon as the work is completed.
2.5.3 Installation room
ƔOperate ROTEX GCU compact only if sufficient combustion
air supply is ensured. If you operate the ROTEX GCU
compact in a room-air independent manner with a concentric
air/flue gas system (LAS) dimensioned as per ROTEX
standard, this is fulfilled automatically and there are no other
conditions for the equipment erection room. With installation
in residential rooms, this method of operation applies exclu-
sively.
ƔMake sure that, with installation in a room-air dependent or
limited room-air independent manner, an inlet air opening to
the outside of at least 150 cm2is provided.
ƔDo not operate the ROTEX GCU compact by the ambient air
dependent method in rooms with aggressive vapours (e.g.
hair spray, perchloroethylene, carbon tetrachloride), strong
dust formation (e.g. workshop) or high humidity (e.g. laundry).
ƔStrictly keep the minimum distances to walls and other
objects (see chapter 4.1).
2.5.4 Requirements for the heating water
Avoid damage caused by deposits and corrosion: Observe
the relevant regulations of technology to prevent creation of cor-
rosion products and deposits.
Measures for desalination, softening or hardness stabilization are
necessary, if the filling and top-up water have a high total
hardness (>3 mmol/l - sum of the calcium and magnesium con-
centrations, calculated as calcium carbonate.
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 is entirely
that of the operator.
2.5.5 Heating system and sanitary connection
ƔCreate a heating system according to the safety requirements
of EN 12828.
ƔWith sanitary connection, you must observe;
– EN 1717 - Protection of potable water from contamination
in domestic water installations and general requirements
concerning safety equipment for the prevention of domes-
tic water contamination by back-flow
– EN 806 - Technical regulations for domestic water instal-
lations (TRWI)
– and, in addition, the country-specific legal regulations.
During operation of the ROTEX GCU compact with hot water
storage, the storage tank temperature may exceed 60°C, partic-
ularly when solar power is used.
ƔTherefore, incorporate scald protection during the installation
of the system (domestic hot water mixing construcion, e.g.
VTA32, 15 60 16).
2.5.6 Fuel
The ROTEX GCU compact is factory set to the gas type indicated
on the burner sticker and on the settings type plate and adjusted
to the gas pressure indicated on the burner sticker.
ƔOperate the unit only with the gas type and gas pressure
indicated on these stickers.
ƔInstallation and adaptation of the gas system must only be
conducted by personnel qualified for this work and in
compliance with valid gas installation related guidelines as
well as the applicable regulations of the gas supply company.
2.5.7 Operation
ƔOperate ROTEX GCU compact only with closed silencer
hoods.
ƔOnly operate the ROTEX GCU compact if all the require-
ments as per the checklist in chapter 5.2 are fulfilled.
2.5.8 Instructing the user/owner
ƔBefore you hand over the heating system, explain to the
owner how he/she can operate and check the heating
system.
ƔHand over the technical documentation (at least the operating
instruction manual and operating handbook) to the user and
advise him that these documents must be made available at
all times and be stored in the immediate vicinity of the unit.
ƔMake a record of the handover by filling out and signing the
installation and instruction forms jointly with the user/owner.

3xProduct description
ROTEX GCU compact -  7
3 Product description
3.1 Design and components
3.1.1 GCU compact 315 / 324
Fig. 3-1 Structure and components GCU compact 315/324 -
plan view (for legend designations, see tab. 3-1)
Fig. 3-2 Structure and components GCU compact 315 / 324 -
front view (for legend designations, see tab. 3-1)
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Fig. 3-3 Structure and components GCU compact 315 / 324 -
Schematic view (for legend designations, see tab. 3-1)
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8ROTEX GCU compact - 
3xProduct description
3.1.2 GCU compact 515 / 524 / 533
Fig. 3-4 Structure and components GCU compact 515 / 524 / 533 -
plan view (for legend designations, see tab. 3-1)
Fig. 3-5 Structure and components GCU compact 515 / 524 / 533 -
front view (for legend designations, see tab. 3-1)
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Fig. 3-6 Structure and components GCU compact 515 / 524 / 533 -
Schematic view (for legend designations, see tab. 3-1)
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3xProduct description
ROTEX GCU compact -  9
Tab. 3-1 Legend from fig. 3-1 to fig. 3-6
3.2 Brief description
Die ROTEX Gas Combi Unit compact (GCU compact) is a fully
preassembled gas condenser unit., which is built into a water
storage tank. The excellent heat insulation properties of the
plastic storage tank ensure that heat losses are kept to a
minimum. The aluminium boiler body is inserted in a metal
housing in the cover of the storage tank. The complete flue gas
unit is surrounded by fresh air.
Operating mode
The ROTEX GCU compact is designed such that it can be
operated independently of the ambient air (concentric flue gas/air
inlet piping). The burner suctions the combustion air directly in
through an installation shaft or a double-walled flue gas pipe. This
procedure is recommended by ROTEX and has many advan-
tages:
– 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 pre-
heating the combustion air.
– Contamination from the environment of the burner are not
suctioned in. The heating room can thus be used as a
work-space, laundry room etc. at the same time.
– Possible to set up in loft areas or attic.
The condensate which arises is collected in the flue gas collector
and transported into the storage tank via a plastic pipe where it is
neutralised.
The pressureless storage water serves as heat storage medium.
Useful heat is supplied and led out by completely submerged,
helically intertwined stainless steel corrugated tubes (1.4404).
The hot water zone in the storage tank works as a combination of
heat storage and geyser (see fig. 3-3 and fig. 3-6).
The cold water which flows out when the hot water is removed is
first routed to the storage tank at the very bottom of the heat ex-
changer, where it cools the lower area of the storage tank down
as much as possible. The readiness zone is heated by a heat ex-
changer for charging storage tank (SL-WT) which is heated
using the gas burner, heated from top to bottom where the water
also flows.
On its way to the top, the domestic water continuously absorbs
the heat of the storage tank water. The flow direction, operating
on the principle of counter-flow, and the coil-shaped heat ex-
changer create a pronounced temperature layering in 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.
– On the GCU compact 515/515-BIV, 524/524-BIV models, the
SL-WT ends approx. 40 cm above the floor of the container.
Only the hot water zone about it is heated by the boiler. The
tank volume below it is heated only on using the solar energy.
– On the GCU compact 315/315-BIV, 324/324-BIV, 533/533-
BIV models, the SL-WT is pulled down all the way to the con-
tainer floor. The entire storage volume is heated by the boiler
(greater hot water output readiness).
Optimum water hygiene
Low flow or unheated zones on the domestic water side are com-
pletely excluded with the ROTEX GCU compact. It is impossible
for sludge, rust or other sediments to be deposited, as can be the
case with other large volume tanks. The water which is fed into
the system first is also discharged first (first in, first out principle).
1 Cold water connection (1" AG) 2)
2 Hot water (1" AG) 2)
3 Storage charge - flow (1" AG)
4 Storage charge - return flow (1" AG)
5 Heater- flow (1" AG)* 2)
6 Heater- return flow (1" AG)*
7 Solar - flow (1" IG)
8 Draining connection or solar return
flow
9 Exhaust
10 Supply air
11 Sensor immersion sleeve for storage
temperature sensor tDHW
12 Upper filling connection and condensate
overflow connection
13 Condensation drain pipe
14 Condensate pipe
15 Heating heat exchanger (boiler body)
16 Heat exchanger (stainless steel) for drink-
ing water heating
17 Heat exchanger (stainless steel) for stor-
age tank charging or heating support
18 Heat exchanger (stainless steel) for biva-
lent storage charge 1)
19 BIV storage charge - flow 1)2) (1" AG)
20 BIV storage charge - return flow 1)
(1" AG)
21 Solar inflow layering pipe
22 Heating circulation pump
23 Burner blower
24 Safety overpressure valve (heating circuit)
3)
25 Connection for SBG GCU compact 3)
26 Gas connection (G ½" IG) with connected
gas hose
27 Boiler control panel with RoCon BF control
28 Heat insulation
29 Burner trim
30 Silencer hood
31 Insertion mount, sound insulation hood
32 Type plate
33 Setting type plate
34 Threaded insert for carrying loop
35 Cover screen boiler control panel
3UV DHW
3-way change valve (distribution valve
KRWZDWHUKHDWLQJKHDWLQJVXSSRUW)
3-way change valve (mixer valve)
tDHW Storage temperature sensor
tRReturn temperature sensor 1 in FLS1
(boiler circuit)
tRReturn temperature sensor 2 (boiler
circuit)
tV1 Flow temperature sensor (boiler circuit)
tV2 Internal mixer sensor (boiler circuit)
A Gas boiler
B Storage tank (polypropylene double walled
jacket with PUR hard foam heat insulation)
CU
npressurised storage tank water
D Hot water zone
DS Pressure sensor
E Solar zone
FLS1
Flow sensor with return temperature sen-
sor tR1 (boiler
circuit) 536
Optional: ROTEX Solaris R3 regulation
and pump unit
AG Male thread
IG Female thread
ÜM Union nut
Safety devices
Observe tightening torque!
* Ball cock (1" IG) is supplied with the equip-
ment
1) Only valid for types with BIV configuration
2) Recommended accessories:
Non-return valves (2 pcs.), 16 50 70
3) Recommended accessories:
Safety group SBG GCU compact,
15 70 46
3UV%

10 ROTEX GCU compact - 
3xProduct description
Low scaling
On the storage tank side only one deposition of scale is possible.
All the stainless steel heat exchanger pipes in the storage tank
water largely remain without fixed coverings. This means that no
scale can build up which would continuously reduce the effi-
ciency of heat transfer in the course of operation.
The thermal and pressure expansion and high flow rates in the
domestic water heat exchanger release any possible scale de-
posits, which are then flushed away.
Solar utilisation
The hot water storage tank of ROTEX GCU compact can also be
used by solar energy. Depending on the available heat from the
sun, the entire hot water storage tank can be heated up. The
stored heat is used for hot water generation and also for heating
support on types GCU compact 5xx. The ISM ("Intelligent
Storage Manager") controls the integrated 3-way valves in such
a way that the solar heat yield is optimally divided up and used
for the hot water generation and heating support. The high total
storage capacity allows for bridging of the periods without any
solar yield.
If a ROTEX pressurised solar system or an external heating
boiler is used as an external heat generator, this means that only
one of the - listed in section 3.1 - GCU compact with BIV config-
uration is permitted as the primary hot water storage unit.
On the models GCU compact BIV, the complete storage tank is
designed as a hot water zone. It is possible to make thermal use
of solar energy for hot water preparation. In connection with a
ROTEX Solaris plant connected in series (preheating stage), the
solar proportion is optimised.
Safety management
The entire safety management of the ROTEX GCU compact is
entrusted to electronic control. This effects a safety switch-off in
the event of water shortage, gas shortage or undefined operating
states. A corresponding fault signal provides an engineer with all
the necessary information for troubleshooting.
Electronic control
An electronic digital controller combined with the "intelligent" au-
tomatic firing unit of the burner controls all heating and hot water
functions automatically for the direct heating circuit and a storage
tank charging circuit.
Optionally, connected mixer modules RoCon M1 ( 15 70 68)
can be used to connect and regulate one or more mixed circuits.
All settings, displays and functions are made via the integrated
RoCon BF control. The display and operating elements offer con-
venient operating possibilities.
As an option, for increased convenience, a digital room controller
(RoCon U1,15 70 34) is available as an option. This can be
used as a remote control and a room thermostat.
Using the optional gateway (RoCon G1,15 70 56), the con-
troller can be connected to the internet. This means that the
ROTEX GCU compact can be controlled remotely via mobile
phone (using an App).
Condensing technology
The calorific value engineering makes optimum use of the energy
contained in the heating gas. The flue gas is cooled down in the
boiler and in the flue system - when operated independently of
ambient air - such that the temperature is below the dew point.
A part of the water vapour generated on combustion of the gas
thus condenses. The condensation heat is fed to the heating,
unlike low temperature boilers, which makes efficiencies of over
100 % possible (in relation to the lower heating value).

4xSet-up and installation
ROTEX GCU compact -  11
4 Set-up and installation
Incorrect set-up and installation would render the manufacturer's
guarantee for the unit void. If you have questions, please contact
our Technical Customer Service.
4.1 Dimensions and connection dimensions
WARNING!
Incorrectly erected and installed gas devices may not
operate properly and are dangerous for the health and
safety of individuals.
ƔThe ROTEX GCU compact must be installed only
by heating engineers authorised and trained by
gas or energy supply companies.
ASide view
BFront view
CTop view
Fig. 4-1 Installation dimensions for flue gas pipe at the rear (for values see tab. 4-1)
ASide view
BFront view
CTop view
Fig. 4-2Installation dimensions for flue gas pipe at the side (for values see tab. 4-1)
K
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K
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V
U
W
K
U
Z
AB
C
V
'
K
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V
U
W
K
U
Z
AB
V
V
C
V
C
V
'
K
5
V

12 ROTEX GCU compact - 
4xSet-up and installation
Tab. 4-1 Connection- and set-up dimensions GCU compact in mm
(in relation to fig. 4-1, fig. 4-2, fig. 4-10, fig. 4-13, fig. 4-14)
4.1.1 Connection dimensions for the heating and hot water connections
GCU compact 3xx
Dim. GCU compact 3xx GCU compact 5xx
h1 1380
h2 1920 1950
h3 1560
hR2070 2100
r1 110 250
r2 380 540
s1 345
s2 350, 4701) 200, 3201)
s3 535, 3651), 2852) 500, 3301), 2502)
s4 370, 2001), 210, 401),
s5 750, 6301), 5002)
s6 750, 6301), 5002) 750, 6301)
sD150
t615 790
w595 790
1) When installing the test adapter to the rear.
2) When using a shorter exhaust pipe D8 L25 ( 15 50 79.0102) instead of
the exhaust pipe D8 L50 contained in SET.
Dim. GCU compact 3xx GCU compact 5xx
Fig. 4-3 Connection dimensions GCU compact 3xx (view from behind)









A Front side
B Rear side
Gc GCU compact
Fig. 4-4 Connection dimensions GCU compact 3xx (plan view)
%
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



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
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A
B
Gc 3xx

4xSet-up and installation
ROTEX GCU compact -  13
GCU compact 5xx
Fig. 4-5 Connection dimensions GCU compact 5xx (view from behind)









A Front side
B Rear side
Gc GCU compact
Fig. 4-6 Connection dimensions GCU compact 5xx (plan view)
ROTEX recommends the installation of gravity brakes
(16 50 70) or syphoning (lead the connection lines
straight downward) of the potable water connections to
avoid an increased loss through cooling.
Gc 5xx




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
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
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A
B

14 ROTEX GCU compact - 
4xSet-up and installation
4.2 Installation versions
The ROTEX GCU compact are designed basically for operation
independent of the ambient air. They are fitted with a con-
centric flue gas /air supply pipe DN 60/100.
The SET GCU1 ( 15 50 79.17) kit can be used to flexibly ar-
range the flue gas /air supply pipe for the connection directions to
the rear or upwards and extended to DN 80/125.
1-6 Different set-ups (For a description, see
section 4.2.1 to 4.2.3)
CA Inlet air (combustion air)
FG Flue gas
RV Rear ventilation
aSet up variant for room-air independent
operation (flue gas/inlet air concentric)
bSet up variant for limited room-air inde-
pendent operation (flue gas/air inlet sepa-
rate)
cSet up variant for room-air dependent op-
eration
dLongitudinally ventilated shaft with fire re-
sistance duration of 90 min (in residential
buildings with low headroom 30 min).
Observe country-specific regulations for
fire-resistance periods!
eVentilation opening (1x150 cm² or
2x75 cm²)
fRear ventilation opening (150 cm²)
Fig. 4-7 Installation variants for the GCU compact
In some cases, the resonance in the flue system can
amplify the noise at the mouth of the flue gas pipe. The
noise level can be effectively reduced with the applica-
tion of a silencer (E8 MSD, 15 45 78 or E11 MSD,
15 45 79).
Using the ROTEX GCU compact in room-air inde-
pendent operation with a concentric flue gas/air supply
pipe is recommended by ROTEX. If possible, choose
this set-up!
In the event of limited room-air independent (separate
flue gas/air supply pipes with a single-walled con-
necting pipe) and in the event of room-air dependent
operation, the installation room must have a ventilation
opening of at least 150 cm2into the outdoors.
This reduces the overall energy efficiency of the
building in the framework of the European Guideline
2010/31/EU: EPBD.

4xSet-up and installation
ROTEX GCU compact -  15
4.2.1 Operation independent of ambient air
Set-up version 1
The ROTEX GCU compact with the SET GCU1 and the
concentric LAS connection line SET H or SET K is connected to
the chimney or an installation shaft.
– The combustible air supply from the outside runs through the
chimney or through an installation shaft.
– The flue gas discharge using a flue gas pipe to the outside
runs through the same shaft as the air supply.
– Minimum vertical distance between flue gas exit and roof
ridge: 40 cm.
Set-up version 2
The ROTEX GCU compact is placed directly below the roof.
Connection with SET GCU1 und 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 tube and the flue gas dis-
charge to the outside runs through the inner tube.
– Minimum vertical distance between flue gas exit and roof sur-
face: 40 cm.
– Minimum height of the flue gas pipe: 2m.
Set-up version 3
The ROTEX GCU compact is not placed directly below the roof.
The dual tube for the combustible air supply and flue gas pipe
runs through the roof truss.
– The combustible air supply and the flue gas discharge run
through a concentric dual pipe (as in Installation version 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 protec-
tive pipe with sufficient fire resistance or be structurally sepa-
rated from the roof truss.
Set-up version 4
The ROTEX 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 (suc-
tion from below).
– The flue gas discharge to the outside runs through a concen-
tric 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.
Set-up version 5
If, for constructional or legal/regulatory reasons, the shaft used
for the flue gas routing is not suited for sending the combustion
air through it at the same time, the combustion air must be sent
through a separate line.
If the flue gas connection line to the shaft is double-walled and is
surrounded by the combustion air, there are no additional venti-
lation requirements on the installation room.
– Combustion air inlet is routed from the outside via the ade-
quately sealed inlet air which is connected directly to the con-
centric exterior pipe of the connection line. The air inlet line
should be sized so that the suction resistance at nominal
power is less than 50 Pa.
– The connection line between the ROTEX GCU compact and
the installation shaft is completely concentric and surrounded
by combustion air.
With equipment erection in residential rooms, only one
of the set up variants 1 to 4 is permissible.
If the wall feed through has a height of less than one
meter above the plot, ROTEX recommends sending the
combustible air through a separate air supply pipe
(mounting height: about 2 m). W8 ZR, 15 50 79.00
66 or W11 ZR, 15 50 77.00 30

16 ROTEX GCU compact - 
4xSet-up and installation
4.2.2 Operation partially independent of ambient air
Alternative to set-up variant 5
The ROTEX GCU compact is operated with separately routed
inlet air/ flue gas lines (2 line system).
– Combustion air inlet is routed from the outside via the ade-
quately sealed inlet air through the external wall. The air inlet
line should be sized so that the suction resistance at nomi-
nal power is less than 50 Pa.
–F
lue gas dissipation to the outdoors is via the chimney or an
installation shaft. If the connection line between the ROTEX
GCU compact and the installation shaft is single-walled or is
not completely surrounded by combustion air, a ventilation
opening of at least 150 cm2is 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. In the lower area there must be a rear ventilation
opening of at least 150 cm2must be provided.
The cross-section of the installation shaft must be sized so
that between the external wall of the flue gas line and the
internal face of the installation shaft the following mini-
mum distance must be maintained:
– with a rectangular shaft cross-section: 2cm
– with round shaft cross-section: 3cm.
The rear ventilation opening must not be in rooms where a
positive pressure is generated (e.g. by controlled apartment
ventilation, a tumble-drier etc.).
4.2.3 Ambient air dependent operation
Set-up version 6
The ROTEX GCU compact can be connected even with venti-
lation and air-conditioning. Thereby, only the inner flue gas pipe
(plastic pipe Ø 60 mm) of the concentric air-flue gas pipe is con-
nected to the flue gas line. The device sucks the combustible air
from the installation room through the ring-shaped gap of the
jacket pipe.
For the flue gas routing to the outdoors, the shaft sizing and the
rear ventilation, the same conditions apply as in section 4.2.2.
Aventilation opening to the outside of 150 cm2is imperative.
4.3 Transport and delivery
The ROTEX GCU compact is delivered on a pallet. All industrial
trucks, such as lifting trucks and forklift trucks, are suitable for
transporting it.
Scope of delivery
– ROTEX GCU compact (preassembled),
– Bag of accessories (see fig. 4-8),
– Outside temperature sensor (RoCon OT1), for weather-con-
trolled regulation.
– Document pack.
Recommended accessory
– Safety group (SGB GCU compact, 15 70 46) with pres-
sure gauge, safety valve, automatic bleeding, filling cock,
connection fittings).
Additional accessories see ROTEX price list.
4.4 Installing the Gas Combi Unit compact
4.4.1 Selecting the installation site
The place of installation for the ROTEX GCU compact must meet
the following minimum requirements.
Installation surface
– The base must be level and smooth and have a sufficient
ground load-bearing capacity, of 1050 kg/m² plus safety
factor. Install a pedestal if necessary.
– Observe the set-up dimensions (see section 4.1).
Installation room
– There are no special conditions for ventilation of the installa-
tion room for operation independent of the ambient air (using
a concentric air/flue system).
– In the event of limited room-air independent operation and in
the event of room-air dependent operation, the installation
room must have a ventilation opening of at least 150 cm2to
the outside. If the flue gas line goes via an installation shaft to
the outside, it must be rear ventilated (see section 4.2.2).
– For partial ambient air-independent and for ambient air-
dependent mode, the installation room must be free from
aggressive vapours (e.g. hair spray, perchloroethylene, car-
bon tetrachloride), heavy dust formation and high atmos-
pheric humidity (e.g. washhouse).
–Outdoor installation is only possible to a limited extent. The
storage tank must not be exposed to continuous direct
sunlight, as the UV radiation and the effects of the weather
will damage the plastic.
– Installation room must be continuously protected from frost.
In some cases, the resonance in the flue system can
amplify the noise at the mouth of the flue gas pipe. The
noise level can be effectively reduced with the applica-
tion of a silencer (E8 MSD, 15 45 78 bzw.
E11 MSD, 15 45 79).
WARNING!
The ROTEX GCU compact is top heavy when not
filled, it can tilt over during transport. This can pose a
risk to persons or damage the machine.
ƔCorrectly secure the ROTEX GCU compact,
transport carefully, use the handles.
A Handles (only required for
transport)
B Cover screen
C Hose connection piece for
safety overflow
D Spanner
Fig. 4-Contents of bag of accessories
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4xSet-up and installation
ROTEX GCU compact -  17
Surface temperatures, minimum distance
– When operating independently of the ambient air with nomi-
nal output, the design does not allow temperatures > 70 °C on
any component outside the unit panels. Therefore, no mini-
mum distance is required to components made with flamma-
ble materials.
– A minimum distance of 50 mm between the flue gas duct and
flammable components should be maintained in a partial
room air-independent and ambient air-dependent mode (sep-
arate flue gas/air intake line).
– Do not use or store easily inflammable and easily combustible
substances directly next to the ROTEX GCU compact (mini-
mum distance 1 m, see fig. 4-10).
4.4.2 Setting up the unit
Precondition
– The installation site complies with the respective country-spe-
cific regulations, as well as the minimum requirements
described in section 4.4.1.
Set-up
ƔRemove the packaging and dispose of it in an environmen-
tally sound manner.
ƔUnscrew the threaded inserts (fig. 4-9, item G), onto which
the carrier loops are to be attached, from the hot water
storage tank.
ƔThread the carrier loops (item A) through the threaded pieces
(item G) and mount onto the available connections on the
front and back of the hot water storage tank.
ƔCarefully transport the ROTEX GCU compact to the erection
site, use the handles.
ƔInstall ROTEX GCU compact at the place of installation.
–Recommended distances:
to the wall (s1/s2/s3/s4): see tab. 4-1
To the ceiling (sD): 150 mm.
–Installclose to the discharge point.
ƔInstall the connection lines to allow for the removal of the
sound insulation hood (fig. 4-11).
WARNING!
The plastic wall of the storage tank of the ROTEX GCU
compact can melt under the effects of external heat
(80°C) and, in the extreme case, can catch fire.
ƔOnly install the ROTEX GCU compact with a
minimum distance of 1 m to other heat sources
(>80°C) (e.g. electrical heater, oil heater, chimney)
and the material to be combusted.
CAUTION!
Wird die ROTEX GCU compact is not erected
adequately lower the flat solar panels (the top edge
of the storage tank is higher than the bottom edge of
the solar panels), the unpressurised solar system in
the outdoor area will be unable to drain completely.
ƔErect the GCU compact low enough, with a solar
connection, with regard to the flat solar panels
(observe minimum gradient in the solar connecting
lines)
WARNING!
The ROTEX GCU compact is top heavy when not
filled, it can tilt over during transport. This can pose a
risk to persons or damage the machine.
ƔCorrectly secure the ROTEX GCU compact,
transport carefully, use the handles.
Fig. 4-9 Assemble the handles (for legend, see fig. 4-8)
Fig. 4-10 Minimum distances for the erection of the GCU compact
(for dimensions, see tab. 4-1)
V VV
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18 ROTEX GCU compact - 
4xSet-up and installation
4.4.3 Remove the sound insulation hood
4.5 Air/flue system (LAS)
4.5.1 General instructions for flue system
Minimum requirements
Observe country-specific regulations and EN 15287 for the
design and measurement of the flue gas system.
Basically, for the flue gas system, you can use each flue gas pipe
according to EN 14471 with EU label, which meets the following
minimum requirements:
– Suitable for gas.
– Suitable for flue gas temperatures of at least 120°C (temper-
ature class T120 or higher).
– Suitable for at least 200 Pa overpressure (pressure class P1
or H1).
– Humidity-resistant (condensation resistance class W).
– Sufficiently corrosion-resistant (corrosion resistance class 1
or 2).
The properties of the flue gas system must be identifiable on the
installed system (nameplate in the installation room).
Type of connections
– Directly backwards (fig. 4-1: SET H, 15 50 79.08).
– At the side towards the back (fig. 4-2: SET K,
15 50 79.09).
– Direct roof penetration (fig. 4-7, variant 2 and 3: SET L,
15 50 79.10).
For other details and connection dimensions for the three ver-
sions of the flue gas pipe, see section 4.5.3.
– Each flue gas line must be installed with a suitable test
adapter for checking and setting the combustion values. The
ROTEX LAS construction sets each include a test adapter
(D8PA, 15 50 79.00 93).
Installation position and line height
– The maximum permitted flue gas counter pressure is 200 Pa.
The pressure loss in the supply line must not exceed 50 Pa.
– Angle of entry of the flue gas pipe into the chimney or instal-
lation shaft: at least 3°.
– Slope for horizontal parts of the flue gas pipe: at least 3°.
Counter-slopes are not allowed at any point in the flue gas
pipe.
– If the flue gas duct needs more than 3 deflections >45° for the
flue gas duct, the maximum height for the flue gas duct
reduces by at least 1 m per deflection (flue gas calculations
may be needed).
– If the horizontal connecting piece is extended, the maximum
permitted height of the flue gas pipe is reduced by exactly that
length.
– Flexible flue gas lines must not be used in horizontal connec-
tion sections.
Flue gas system resistance
For a safe burner start and stable flue gas values in the lower
output range, a minimum resistance in the flue gas line is nec-
essary, especially for liquid gas units.
After the initial burner start, the ROTEX GCU compact switches
at first into the storage tank charging mode. In this mode, the
burner blower runs with max. speed.
ƔSwitch the burner on (see chapter 15.2 "Emissions
measurement").
ƔMeasure the resistance with a differential pressure
measurement unit on the flue gas measurement location
between the flue gas and intake air measurement openings
(differential pressure for the ROTEX GCU compact at least
0.45 mbar).
ÎIf the differential pressure is not reached when the burner
blower is at maximum speed, a silencer will need to be fit-
ted (E8 MSD, 15 45 78 or E11 MSD, 15 45 79)
The tab. 4-2 shows the maximum permissible height of the flue
gas line to ensure that the ROTEX GCU compact can be op-
erated in the rated power range.
Tab. 4-2 Maximum height for the flue gas duct in m
The characteristics for the flue gas calculation can be obtained
from fig. 4-12 and chapter 15.1 "Data for designing the flue gas
pipe".
WARNING!
There will be a risk of poisoning caused by flue gas
escaping within enclosed rooms that are inadequately
ventilated.
ƔInstall only approved flue gas systems.
ƔThe stipulated ventilation and rear ventilation must
be ensured, depending on the set up variant.
ƔCoverings of the flue gas mouth are not allowed.
Installation
version
(according to
fig. 4-7)
Max. permissible height of the flue
gas line)
GCU compact
315 / 515 324 / 524 533
11), 2, 3, 4 123) 153) 193)
5, 6 253) 273) 293)
1) Shaft cross-section at DN80: 135 mm x 135 mm
) Concentric flue gas-/supply line: DN80/125
 Design for natural gas (G20)
Fig. 4-1Unscrew/loosen screws, lift the cover at the back and remove
in a forwards direction.

4xSet-up and installation
ROTEX GCU compact -  19
The flue gas mass flow of the plant depends on the burner output
of the ROTEX GCU compact.
4.5.2 Connecting a flue gas line
Requirements
– The flue system fulfils the requirements described in
section 4.5.1.
– The flue system fulfils any other required national or regional
safety requirements.
– The ROTEX GCU compact is installed correctly.
Connection
ƔConnect the ROTEX GCU compact to the flue gas system
inside the installation room (fig. 4-1 / fig. 4-2).
For dimensions, see tab. 4-1.
ƔPlace the nameplate of the flue gas pipe in the installation
room.
a
ANatural gas E/H (G20)
BNatural gas LL/L (G25)
CLiquid gas
mET Flue gas mass flow
PBurner load
Fig. 4-12 Flue gas mass flow in dependence of the burner load ROTEX
GCU compact (all types)
We recommend to use the associated ROTEX LAS-
sets (see fig. 4-15). They satisfy all requirements and
are also fitted with special acid-proof seals.
Fig. 4-13 Plan view GCU compact Flue gas connection to the rear with
SET H (see section 4.5.3) - (for dimensions, see tab. 4-1)
V
A
W
Z
Fig. 4-14 Plan view GCU compact Flue gas connection to the side with
SET K (see section 4.5.3) - (for dimensions, see tab. 4-1)
In some cases, the resonance in the flue system can
amplify the noise at the mouth of the flue gas pipe. The
noise level can be effectively reduced with the applica-
tion of a silencer (E8 MSD, 15 45 78 bzw.
E11 MSD, 15 45 79).
V
W
A
V
Z
A
V
V
Z
V

20 ROTEX GCU compact - 
4xSet-up and installation
4.5.3 Flue gas system kits
Fig. 4-15 Flue system kits *If needed
** See tab. 4-1
(L)Flue gas connection left
(R) Flue gas connection right
(H) Flue gas connection rear
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