Nibe S735 User manual

Installer manual
Exhaust air heat pump
NIBE S735 1x230 V
IHB EN 2220-1
531809

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Setting the indoor temperature.
13.45 3 October
Climate system 1
Offset
Heating
Smartguide
Hi!
Your system is working properly. Do you want help making
changes?
Yes please, take me to Smartguide.
October13.45 3
Here, you can set the temperature in the installation's zones.Smartguide helps you both to view information about the current
status and to make the most common settings easily. The inform-
ation that you see depends on the product you have and the ac-
cessories that are connected to the product.
Product overview
Company AB
Phone number
S735
01234567890123
1.0.0
Product
overview
Product name
Serial number
Software
Service
October13.45 3
Update
Increasing hot water temperature
13.45 3 October
More hot water
Hot water
Here, you can find information about product name, the product's
serial number, the version of the software and service. When there
is new software to download, you can do it here (provided that
S735 is connected to myUplink).
Here, you can start or stop a temporary increase in the hot water
temperature.

41 Important information
4Safety information
4Symbols
4Marking
4Serial number
4Country specific information
6Inspection of the installation
72 Delivery and handling
7Transport
7Assembly
8Supplied components
8Handling panels
10Removing insulation
10Separated/one unit
113 The heat pump design
11General
13Distribution boxes
13Air treatment section
144 Pipe and ventilation connections
14General pipe connections
16Dimensions and pipe connections
17Symbol key
17Climate system
17Cold and hot water
18Installation alternative
19General ventilation connection
19Ventilation flow
20Adjusting ventilation
20Dimension and ventilation connections
215 Electrical connections
21General
23Connections
28Settings
296 Commissioning and adjusting
29Preparations
29Filling and venting
30Start-up and inspection
31Setting the heating curve
347 myUplink
34Specification
34Connection
34Range of services
358 Control - Introduction
35Display unit
36Navigation
36Menu types
38Climate systems and zones
399 Control - Menus
39Menu 1 - Indoor climate
43Menu 2 - Hot water
45Menu 3 - Info
46Menu 4 - My system
49Menu 5 - Connection
50Menu 6 - Scheduling
52Menu 7 - Installer settings
5810 Service
58Maintenance
59Service actions
6211 Disturbances in comfort
62Info-menu
62Manage alarm
62Troubleshooting
6512 Accessories
6613 Technical data
66Dimensions and setting-out coordinates
68Technical specifications
70Energy labelling
72Electrical circuit diagram
79Item register
3Table of ContentsNIBE S735
Table of Contents

Safety information
This manual describes installation and service procedures
for implementation by specialists.
The manual must be left with the customer.
Symbols
Explanation of symbols that may be present in this manual.
WARNING!
This symbol indicates serious danger to person or
machine.
NOTE
This symbol indicates danger to person or machine.
Caution
This symbol indicates important information about
what you should consider when installing or servi-
cing the installation.
TIP
This symbol indicates tips on how to facilitate us-
ing the product.
Marking
Explanation of symbols that may be present on the product’s
label(s).
Fire hazard!
Read the User Manual.
Read the Installer Manual.
Disconnect the voltage supply before starting work.
Dangerous voltage.
Serial number
The serial number can be found at the bottom right on S735,
in the display on the home screen "Product overview" and
on the type plate (PZ1).
Caution
You need the product's (14 digit) serial number for
servicing and support.
Country specific information
UNITED KINGDOM
This installation is subject to building regulation approval,
notify the local Authority of intention to install.
Use only manufacturer’s recommended replacement parts.
For more information see nibe.co.uk.
Benchmark places responsibilities on both manufacturers
and installers. The purpose is to ensure that customers are
provided with the correct equipment for their needs, that it
is installed, commissioned and serviced in accordance with
the manufacturers instructions by competent persons and
that it meets the requirements of the appropriate Building
Regulations. The Benchmark Checklist can be used to
demonstrate compliance with Building Regulations and
should be provided to the customer for future reference.
Installers are required to carry out the installation, commis-
sioning and servicing work in accordance with the Bench-
mark Code of practice which is available from the Heating
and Hotwater Industry Council who manage and promote
the Scheme. Visit centralheating.co.uk for information.
Warranty and insurance information
Thank you for installing a new NIBE heat pump in your home.
NIBE heat pumps are manufactured in Sweden to the very
highest standard so we are pleased to offer our customers
a comprehensive guarantee.
NIBE S735Chapter 1 | Important information4
Important information

The product is guaranteed for 24 months for parts and la-
bour from the date of installation or 33 months from the
date of manufacture, whichever is the shorter.
The NIBE guarantee is based on the unit being installed and
commissioned by a NIBE accredited installer, serviced every
year and the Benchmark documents completed. Where this
condition is not met, any chargeable spare parts or compon-
ents issued within the applicable guarantee period still be-
nefit from a 12 month warranty from the date of issue by
the manufacturer.
We recommend the installer completes and returns as soon
as possible, your guarantee registration card or completes
the guarantee form on the NIBE website www.nibe.co.uk
Electrical Supply
The heat pump must be permanently connected to a 230 V
~ 50 Hz supply.
All system components shall be of an approved type and all
wiring to current I.E.E wiring regulations.
External wiring must be correctly earthed, polarised and in
accordance with the relevant standards: Currently this is
BS 7671.
Domestic Hot Water
All domestic hot water circuits, connections and fittings
must be in accordance with the relevant standards and
water supply regulations. It should also be in accordance
with the relevant requirements of the Local Authority and
the Building Regulations relevant to the location of installa-
tion.
BS 8558:2015 Services supplying water for domestic use
within buildings and their cartilages.
Water Supply (Water Fitting) Regulations 1999 or The Water
Bylaws 2000 (Scotland).
Heating System
The installation of the heat pump should follow best practice
as covered in the following:
BS 5449 Forced circulation hot water central heating sys-
tems for domestic premises.
BS 15450 Heating systems in buildings – Design of heat
pump heating systems.
Ventilation System
Any ventilation system should be designed and installed in
accordance with Building Regulations, England & Wales Ap-
proved Document F1 and Scotland Technical Standard
Section 3.14 Ventilation. Only this will ensure hygienic room
air and prevent any dampness to the building structure.
To be able to ensure a high degree of efficiency and an ex-
tremely comfortable living environment, we recommend
that the installation of any ventilation system should be
planned and this plan be strictly followed by the ventilation
engineer.
The discharge air duct work to outside must be insulated to
ensure condensation does not form in the duct work.
5Chapter 1 | Important informationNIBE S735

Inspection of the installation
Current regulations require the heating installation to be inspected before it is commissioned. The inspection must be
carried out by a suitably qualified person. In addition, fill in the page for the installation data in the User Manual.
DateSignatureNotesDescription
✔
Ventilation (page 19)
Outdoor air damper
Setting ventilation flow exhaust air
Setting the ventilation flow outdoor air
Connecting ground cables
Heating medium (page 17)
System flushed
System vented
Pressure in the climate system
Hot water (page 17)
Mixing valve
Expansion vessel
Tundish
Electricity (page 21)
Connections
Main voltage
Phase voltage
Fuses heat pump
Fuses property
Outside sensor
Room sensor
Safety breaker
Earth circuit-breaker
Miscellaneous
Benchmark checklist
NIBE S735Chapter 1 | Important information6

Transport
S735 should be transported and stored vertically in a dry
place.
Ensure that the heat pump cannot fall over during transport.
R
0
R
0
Check that S735 has not been damaged during transport.
However, the S735 can be carefully laid on its back when
being moved into the building. The centre of gravity is in the
upper part.
Assembly
•Place S735 on a solid foundation indoors that can take the
heat pump’s weight.
Use the product’s adjustable feet to attain a horizontal
and stable set-up.
30 - 50 mm
30 - 50 mm
15 - 40 mm
20-55 mm
•Because water comes from S735, the floor coating is im-
portant. A waterproof floor or floor membrane is recom-
mended.
•Because water comes from S735, it is good if the area
where the heating pump is located is provided with floor
drainage.
•Install with its back to an outside wall, ideally in a room
where noise does not matter, in order to eliminate noise
problems. If this is not possible, avoid placing it against a
wall behind a bedroom or other room where noise may be
a problem.
•Wherever the unit is located, walls to sound sensitive
rooms should be fitted with sound insulation.
•Route pipes so they are not fixed to an internal wall that
backs on to a bedroom or living room.
•The heat pump's installation area should always have a
temperature of at least 10 °C and max 30 °C.
INSTALLATION AREA
Leave a free space of 800 mm in front of the product. Leave
free space between S735 and wall/other machinery/fit-
tings/cables/pipes etc. It is recommended that a space of
at least 10 mm is left to reduce the risk of noise and of any
vibrations being propagated.
800
NOTE
Ensure that there is sufficient space (300 mm)
above S735 for connecting ventilation ducts.
7Chapter 2 | Delivery and handlingNIBE S735
Delivery and handling

Supplied components
Room sensor(BT50)Outdoor temperature sensor
(BT1)
LEK
Vent hose
(length 4 m)
Earth cabling (2 pcs)
Label for external control
voltage for the control sys-
tem
Extra air filter
LEK
LEK
Gasket2 x tundish (WM3)
LEK
LEK
Outdoor air mixing OEK S20Expansion vessel (CM4) with
holder
(enclosed separately)
(supplied separately)
LOCATION
The kit of supplied items is placed on top of the product.
Handling panels
OPEN FRONT HATCH
Press the hatch's top left corner to open it.
REMOVE THE AIR TREATMENT UNIT’S HATCH
Remove the upper panel by pulling it straight out.
REMOVE THE FRONT
1. Remove the screw in the hole next to the on/off button
(SF1).
2. Pull the panel's top edge towards you and lift diagonally
upwards to remove it from the frame.
UN
NIBE S735Chapter 2 | Delivery and handling8

ASSEMBLE THE FRONT
1. Hook one bottom corner of the front onto the frame.
2. Hook the other corner in place.
3. Check the display is straight. Adjust if necessary.
4. Press the top of the front section against the frame and
screw it into place.
REMOVE SIDE PANEL
The side panels can be removed to facilitate the installation.
1. Remove the screws from the upper and lower edges.
UN
2. Twist the panel slightly outwards.
UN
9Chapter 2 | Delivery and handlingNIBE S735

3. Move the panel outwards and backwards.
UN
4. Assembly takes place in the reverse order.
Removing insulation
The insulation can be removed to make installation easier.
Separated/one unit
S735 is delivered as a unit and can be installed as one unit
or separately. For separate installation, the accessory DKI
S10 is required.
The images in this manual show S735 installed as one unit.
UN
Separated installationOne unit
NIBE S735Chapter 2 | Delivery and handling10

General
XL3 XL1GP1 XL2 QM22QM26 QM20
WP3
FL1QZ2
FL2
QM13
QM11
WP1
WM2
WM1
RM1
CM1XL10
WM6
QN10
BT2
EB1
BT6
UB1
AA4
SF1
UB2
FC1
XF8
BT7
BT5
PZ1
PZ3
XF3
XL4
BP5
WP2
BL3
QN17
XL29
FL5
11Chapter 3 | The heat pump designNIBE S735
The heat pump design

PIPE CONNECTIONS
Connection, heating medium flow lineXL1
Connection, heating medium return lineXL2
Connection, cold waterXL3
Connection, hot waterXL4
Connection, draining heating mediumXL10
Connection, T&P valveXL29
HVAC COMPONENTS
Expansion vesselCM1
Expansion relief valve, water heaterFL1
Safety valve, climate systemFL2
T&P valveFL5
Circulation pumpGP1
Filler valve, climate systemQM11
Filling valve 2, climate systemQM13
Venting, heating mediumQM20
Venting, coilQM22
Venting, heating medium 2QM26
Shuttle valve, climate system/water heaterQN10
Pressure reduction valve with integrated check valveQN17
FilterballQZ2
Non-return valveRM1
Overflow cupWM1
Overflow water dischargeWM2
Water sealWM6
Overflow pipe, safety valve hot water heaterWP1
Overflow pipe, safety valve climate systemWP2
Overflow pipe, condensationWP3
SENSORS ETC.
Flow sensor (located on the rear of the product)BF1
Level monitor for the overflow cupBL3
Pressure gauge, heating systemBP5
Temperature sensors, heating medium flowBT2
Temperature sensor, hot water, controlBT5
Temperature sensor, hot water, controlBT6
Temperature sensor, hot water, displayBT7
ELECTRICAL COMPONENTS
Display unitAA4
Immersion heaterEB1
Miniature circuit-breakerFC1
On/off buttonSF1
USB socketXF3
Network connection for myUplinkXF8
MISCELLANEOUS
Rating platePZ1
Serial number platePZ3
Cable glandUB1-2
Designations according to standard EN 81346-2.
NIBE S735Chapter 3 | The heat pump design12

Distribution boxes
-X29
-X28
1 0-5V 2 +5V
3 AUX1 4 AUX2 5 AUX3 6 AUX4 7 AUX5 8 AUX6 9 AUX7
10AUX8 11AUX9 12 BT25
1
1
2
3
2 3 4 5 6 7 8 9
10
11
12
GND
+12V
B
A
OT+ OT−
0-5V
PWM0 PWM1
CPU
EXT COM
INT COM
ERROR
POWER
+5V
GND
BE1 BE2 BE3
K10
-X27
NO
O
NC
AUX-RELAY
13 BT50 14 BT1
-X30
FQ10
AA2
RF2 FQ10-S2
ELECTRICAL COMPONENTS
Base cardAA2
Temperature limiterFQ10
FQ10-S2 Reset button for temperature limiter
EMC cardRF2
Air treatment section
BT21
BT3
QM24
GQ2
GQ10
BT14
QN1
BT17
BT20
HQ10
CA1
QA40
RA1
XL31
XL32
HZ2
BT15
BT12
EP2
EP1
AA3
AA30
FQ14
AA36
VENTILATION CONNECTIONS
Ventilation connection, exhaust airXL31
Ventilation connection, extract airXL32
HVAC COMPONENTS
Vent valve, heat exchangerQM24
SENSORS ETC.
Temperature sensors, heating medium returnBT3
Temperature sensor, heating medium flow after condens-
er
BT12
Temperature sensor, hot gasBT14
Temperature sensor, fluid pipeBT15
Temperature sensor, suction gasBT17
Temperature sensor, exhaust airBT20
Temperature sensor, extract airBT21
ELECTRICAL COMPONENTS
ZAB board1 AA3
SFT board1 AA30
Measurement board1 AA36
CapacitorCA1
Temperature limiter, compressorFQ14
InverterQA40
ChokeRA1
1Not visible in the image
COOLING COMPONENTS
EvaporatorEP1
CondenserEP2
CompressorGQ10
Drying filterHZ2
Expansion valveQN1
VENTILATION
Exhaust air fanGQ2
Exhaust air filter1 HQ10
1Not visible in the image
13Chapter 3 | The heat pump designNIBE S735

General pipe connections
Pipe installation must be carried out in accordance with
current norms and directives.
The system requires the radiator circuit to be designed for
a low temperature heating medium. At the lowest dimen-
sioned outdoor temperature (DOT) the highest recommended
temperatures are 55 °C on the supply line and 45 °C on the
return line.
Caution
Ensure that incoming water is clean. When using
a private well, it may be necessary to supplement
with an extra water filter.
NOTE
The pipe systems need to be flushed out before
the heat pump is connected so debris cannot
damage component parts.
NOTE
Water may drip from the safety valve. A factory-
fitted overflow pipe runs from the safety valve to
an overflow cup. An overflow pipe has to be routed
from the overflow cup to a suitable drain. The en-
tire length of this overflow pipe is inclined to pre-
vent water pockets, and it must also be frost-
proof.
NOTE
This installation is subject to building regulation
approval, notify the local Authority of intention to
install.
NOTE
Use only manufacturer’s recommended replace-
ment parts.
Waste water from the evaporator’s collection tray and from
safety valves is led via an unpressurised overflow pipe to
the drain, so that hot water splashes cannot cause damage.
The mouth of the overflow pipe must be visible and not
placed close to electrical components. In addition, the mouth
of the overflow pipe (tundish), drain valves and motorised
valves should also be positioned well away from all electrical
components. This is the only permitted use of unpressurised
overflow pipes. Overflow pipes from tundish (WM3) connec-
ted to the expansion relief valve (FL1) must also be connec-
ted to the drain in the same way.
The connection for the T&P valve (XL29) must not be used
for any other purpose. Valves may not be positioned between
the T&P valve (FL5) and the water heater.
Overflow pipes from tundish must be routed with a fall and
be at least 300 mm long, before bends or angles in the
pipework (see image) and must also be frost-proof.
Matal discharge pipe
from tundish, with
continous fall.
Min. 300 mm
Tundish
Safety device
(e.g. temperature
relief valve)
Metal discharge pipe
from temperature relief
valve to tundish
Possible
wall
Discharge
below fixed
grating
Fixed
grating
Trapped
gulley
Max 600 mm
NIBE S735Chapter 4 | Pipe and ventilation connections14
Pipe and ventilation connections

Resistance created by
each elbow or bend
Maximum resistance al-
lowed, expressed as a
lenght of straight pipe
(i.e. no elbows or bends)
Minimum size of dis-
charge pipe from tundish
Minimum size of dis-
charge pipe
Valve outlet size
0.8 mmup to 9 m22 mm15 mmG1/2
1.0 mmup to 18 m28 mm15 mmG1/2
1.4 mmup to 27 m35 mm15 mmG1/2
1.0 mmup to 9 m28 mm22 mm<G3>/4
1.4 mmup to 18 m35 mm22 mm<G3>/4
1.7 mmup to 27 m42 mm22 mm<G3>/4
1.4 mmup to 9 m35 mm28 mmG1
1.7 mmup to 18 m42 mm28 mmG1
2.3 mmup to 27 m54 mm28 mmG1
Table sizing of copper discharge pipe for common temperature relief valve outlet sizes.
HARD WATER AREAS
Normally, there should not normally be any problem installing
S735 in hard water areas, as the operating temperature is
50–60°C.
CLEANING THE CLIMATE SYSTEM
When the water heater and the climate system have been
filled with water, S735 must operate at maximum normal
temperature for at least one hour. Thereafter the system
must be drained of water and refilled.
Before installing the heat pump in an existing system, it is
important that the system is properly flushed through.
Even if the heat pump is to be installed in a new system, the
heat pump and system should be flushed.
NOTE
Ensure that cleaning agent has been removed from
the entire system before adding inhibitor.
After flushing an inhibitor should be used for long-term anti-
corrosion protection.
NIBE Energy Systems Limited recommends water treatments
(supplied by e.g. Fernox and Sentinel) specifically designed
for heat pumps.
SYSTEM VOLUME
H
S735 is equipped with an expansion
vessel (CM1).
The volume of the expansion vessel
is 10 litres and it is pre-pressurised as
standard to 0.5 bar. As a result, the
maximum permitted height "H"
between the expansion vessel and the
highest installed radiator is 5 m, see
figure.
If the pre-pressure is not high enough,
it can be increased by filling with air
via the valve in the expansion vessel. Any change in the pre-
pressure affects the ability of the expansion vessel to handle
the expansion of the water.
The maximum system volume, excluding S735, is 285 litres
at the above-mentioned pre-pressure.
15Chapter 4 | Pipe and ventilation connectionsNIBE S735

SYSTEM DIAGRAM
S735 consists of a heat pump, water heater, immersion
heater, fan, circulation pump and control system.S735 is
connected to the ventilation system and heating medium
circuits.
When the room temperature exhaust air, and in certain cases
outdoor air, passes through the evaporator, the refrigerant
evaporates because of its low boiling point. In this way the
energy in the room air is transferred to the refrigerant.
The refrigerant is then compressed in a compressor, causing
the temperature to rise considerably.
The warm refrigerant is led to the condenser. Here the refri-
gerant gives off its energy to the heating system water,
whereupon the refrigerant changes state from gas to liquid.
The refrigerant then goes via filters to the expansion valve,
where the pressure and temperature are reduced.
The refrigerant has now completed its circulation and re-
turns to the evaporator.
431
XL 2
Connection, heating medium flowXL1
Connection, heating medium returnXL2
Cold water connectionXL3
Hot water connectionXL4
Caution
This is a principle of operation. For more detailed
information about S735, see section "The heat
pump design".
Dimensions and pipe
connections
XL2 XL4 XL3 XL1 WM1
The overflow cup (WM1) can be turned, allowing the pipe to
be pointed forwards or backwards to simplify connection to
the drain.
SETTING OUT DIMENSIONS
440
A
B
C
440
A
B
C
CBAConnection
105280115(mm)XL1 Heating medium supply
370275180(mm)XL2 Heating medium return
195445190(mm)XL3 Cold water
250400255(mm)XL4 Hot water
6003402005(mm)XL29 T&P connection
50275185(mm)WM1 Overflow cup
PIPE DIMENSIONS
Connection
22(mm)XL1-XL2 Heating medium ext Ø
22(mm)XL3 Cold water ext Ø
22(mm)XL4 Hot water ext Ø
15(mm)XL29 Connection, T&P valve
32(mm)WM2 Overflow water discharge
NIBE S735Chapter 4 | Pipe and ventilation connections16

Symbol key
MeaningSymbol
Unit box
Non-return valve
Mixing valve
Circulation pump
Immersion heater
Temperature sensor
Trim valve
Reversing valve/shunt
Overflow valve
Under floor heating systems
Radiator system
Domestic hot water
Hot water circulation
Heat pump
Climate system
A climate system is a system that regulates the indoor
temperature with the help of the control system in S735
and, for example, radiators, underfloor heating, fan coils,
etc.
CONNECTING THE CLIMATE SYSTEM
Install as follows:
•When connecting to a system with thermostats on all ra-
diators/underfloor heating coils, either a bypass valve
must be fitted or some of the thermostats must be re-
moved to ensure there is sufficient flow and heat emission.
XL1
XL2
Cold and hot water
The settings for hot water are made in menu 7.1.1 - "Hot
water".
Stop temperature for hot water must be at least 60°C.
CONNECTING COLD AND HOT WATER
Install as follows:
•shut-off valve
•mixing valve
A mixing valve must be installed when the factory setting
for hot water is changed. National regulations must be
observed.
•enclosed expansion vessel (CM4)
The expansion vessel (CM4) accommodates expansion
that results from heating the water inside the unit. The
expansion vessel must be connected between the expan-
sion relief valve (FL1) and the water heater. The location
of the expansion vessel should allow access to recharge
the pressure when neccessary.
•enclosed tundish (WM3)
XL3
XL4
XL29
17Chapter 4 | Pipe and ventilation connectionsNIBE S735

Installation alternative
S735 can be installed in several different ways, some of
which are shown here.
Further option information is available at nibe.co.uk and in
the respective assembly instructions for the accessories
used. See page 65 for a list of the accessories that can be
used with S735.
EXTRA CLIMATE SYSTEM
In buildings with several climate systems that require differ-
ent supply temperatures, the accessory ECS 40/ECS 41 can
be connected.
A shunt valve then lowers the temperature to the underfloor
heating system, for example.
-EP21-GP10-EP21-BT2
-EP21-AA25
-EP21-BT3
-EP21-QN25
-EP21
EXTRA HOT WATER HEATERS
The system should be supplemented with an extra water
heater, if a large bath tub or other significant consumer of
hot water is installed.
Water heater without immersion heater
In water heaters without an immersion heater, the water is
heated by the heat pump.
The water heater’s flow is connected before S735.
Some water heaters require pipe routing behind the units,
which requires 60 mm of free space to the wall.
For connection, a docking kit DEW is required.
DEW S42 means that S735 can be connected to the water
heater VPB S200.
DEW S43 means that S735 can be connected to the water
heater AHPH S/AHPS S.
Water heater with immersion heater
In a water heater with an immersion heater, the water is
initially heated by the heat pump. The immersion heater in
the water heater is used for keeping warm and when the
heat pump does not have sufficient power.
The water heater’s flow is connected after S735.
HOT WATER CIRCULATION
A circulation pump can be controlled by S735 to circulate
the hot water. The circulating water must have a temperat-
ure that prevents bacterial growth and scalding, and national
standards must be satisfied.
The HWC return is connected to a freestanding water heater.
The expansion vessel (CM4) that is enclosed S735 may need
to be replaced with a larger one.
The circulation pump is activated via the AUX output in menu
7.4 -"Selectable in/outputs".
-QZ1-FQ3
-QZ1-GP11
-QZ1-RM1
-QZ1-RN1
-QZ1
NIBE S735Chapter 4 | Pipe and ventilation connections18

General ventilation connection
•Ventilation installation must be carried out in accordance
with current norms and directives.
•Provision must be made for inspection and cleaning of
the duct.
•Make sure that there are no reductions of cross-sectional
area in the form of creases, tight bends, etc., since this
will reduce the ventilation capacity.
•The air duct system must be a minimum of air tightness
class B.
•To prevent fan noise being transferred to the ventilation
devices, install silencers in suitable locations in the duct
system.
•The extract air and outdoor air ducts are insulated using
diffusion-proof material along their entire lengths.
•Ensure that the condensation insulation is thoroughly
sealed at any joints and/or at lead-in nipples, silencers,
roof cowls, outdoor air dampers or similar.
•The extract air duct should, if possible, be routed up
through the roof.
•The extract air duct must be a maximum of 20 m long with
a maximum of six bends.
•Because the heat pump contains a flammable refrigerant,
the air ducting system must be earthed. This is done by
making a good electrical connection to the air ducts using
the enclosed earth cables (2). The cables must then be
connected to the earth pins on top of the top cover.
•A duct in a masonry chimney stack must not be used for
extract air.
NOTE
S735 occasionally has a very low extract air and
outdoor air temperature. To avoid damaging the
product and/or the building, it is therefore import-
ant that the extract and outdoor air ducts, the
damper section and the motor shelf are insulated
with diffusion-proof material along their entire
length.
TIP
If additional condensation insulation dimension
Ø 200 is installed on the outside of the existing
exhaust line between the heat pump and the inner
roof, the noise in the installation area is reduced
by 1-2 dB(A).
VENTILATION CONNECTIONS
S735 has two sizes of ventilation connection, 125 mm or 160
mm.
On delivery, the ventilation connections have the smaller
dimension; if the larger dimension is required, the insulation
rings placed in the connections must be removed.
Connect the heat pump to the duct system by installing a
nipple (not enclosed) or other ventilation component in the
ventilation connections.
EXHAUST AIR DUCT /KITCHEN FAN
Exhaust air duct (kitchen fan) must not be connected to
S735.
To prevent cooking odours from being led to the S735, the
distance between the kitchen fan and the exhaust air valve
must be observed. The distance should not be less than 1.5
m.
Always use a kitchen fan when cooking.
Ventilation flow
Connect S735 so that all the exhaust air, except kitchen
duct air (kitchen fan), passes through the evaporator (EP1)
in the heat pump.
19Chapter 4 | Pipe and ventilation connectionsNIBE S735

The ventilation flow must comply with the applicable national
standards.
For optimum heat pump performance, the ventilation flow
should not be less than 25 l/s (90 m³/h).
The ventilation capacity is set in the heat pump’s menu
system (menu 7.1.4 - "Ventilation").
If the exhaust air temperature falls below 10 °C, the com-
pressor is blocked and electric additional heat is permitted.
No energy is recovered from the exhaust air when the
compressor is blocked.
Adjusting ventilation
To obtain the necessary air exchange in every room of the
house, the exhaust air devices must be correctly positioned
and adjusted and the fan in the heat pump adjusted.
Immediately after installation adjust the ventilation so that
it is set according to the projected value of the house.
Incorrect adjustment of the ventilation may lead to reduced
installation efficiency and thus poorer operating economy,
a poorer indoor climate and moisture damage in the building.
Dimension and ventilation
connections
Exhaust air
Extract air
Ø125
620
430
Ø160
560
2005
20-50
440
180
445
600
315
120
60
35
600
NIBE S735Chapter 4 | Pipe and ventilation connections20