Nibe S1256PC User guide

Installer manual
Ground source heat pump
NIBE S1256PC
IHB EN 2305-1
631161

Quick guide
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are more pages.
If the menu has several
sub-menus, you can
see more information
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with your finger.
Most options and func-
tions are activated by
lightly pressing on the
display with your finger.
Drag to the right or left
with your finger to
browse between the
pages.
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
S1256PC
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
S1256PC 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
5Inspection of the installation
62 Delivery and handling
6Transport
6Assembly
7Supplied components
7Handling panels
9Removing insulation
103 The heat pump design
10General
11Distribution boxes
11Cooling module
124 Pipe connections
12General
13Dimensions and pipe connections
14Brine side
15Climate system
15Cold and hot water
15Installation alternative
175 Electrical connections
17General
19Connections
24Settings
266 Commissioning and adjusting
26Preparations
26Filling and venting
27Start-up and inspection
29Setting the cooling/heating curve
317 myUplink
31Specification
31Connection
31Range of services
328 Control - Introduction
32Display unit
33Navigation
33Menu types
35Climate systems and zones
369 Control - Menus
36Menu 1 - Indoor climate
40Menu 2 - Hot water
42Menu 3 - Info
43Menu 4 - My system
47Menu 5 - Connection
48Menu 6 - Scheduling
49Menu 7 - Installer settings
5710 Service
57Service actions
6211 Disturbances in comfort
62Info-menu
62Manage alarm
62Troubleshooting
6412 Accessories
6513 Technical data
65Dimensions
66Electrical data
67Technical specifications
70Energy labelling
73Item register
75Contact information
3Table of ContentsNIBE S1256PC
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.
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).
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
S1256PC, in the display on the home screen "Product over-
view" and on the type plate (PZ1).
Caution
You need the product's (14 digit) serial number for
servicing and support.
NIBE S1256PCChapter 1 | Important information4
Important information

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
✔
Brine side
System flushed
System vented
Antifreeze
Level/Expansion vessel
Filterball (particle filter)
Safety valve
Shut off valves
Circulation pump setting
Climate system
System flushed
System vented
Expansion vessel
Filterball (particle filter)
Safety valve
Shut off valves
Circulation pump setting
Electricity
Connections
Main voltage
Phase voltage
Fuses heat pump
Fuses property
Outside sensor
Room sensor
Current sensor
Safety breaker
Earth circuit-breaker
Set emergency mode in menu 7.1.8.2
5Chapter 1 | Important informationNIBE S1256PC

Transport
S1256PC should be transported and stored vertically in a
dry place. When being moved into a building, S1256PC may
be leant back 45 °.
Ensure that S1256PC has not been damaged during trans-
port.
Caution
The product can be tail heavy.
Remove the outer panels in order to protect them when
moving in confined spaces inside buildings.
R
0
R
0
EXTRACTING THE COOLING MODULE
To simplify transport and service, the heat pump can be
separated by pulling the cooling module out from the cabin-
et.
See page 59 for instructions about the separation.
Assembly
•Position S1256PC on a solid foundation indoors that
withstands water and the weight of the product.
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
•Since water comes from S1256PC, the area where S1256PC
is located must be equipped 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.
INSTALLATION AREA
Leave a free space of 800 mm in front of the product. Ap-
prox. 50 mm free space is required on each side, to allow
the side panels to be removed (see image). All service on
S1256PC can be carried out from the front, however the
right-hand panel may need to be removed. Leave free space
between the heat pump and the wall behind (and any routing
of supply cables and pipes), to reduce the risk of any vibra-
tions being propagated.
(50) (50)
800
*
*
* A normal installation needs 300 – 400 mm (any side) for
connection equipment, e.g. level vessel, valves and electrical
equipment.
NIBE S1256PCChapter 2 | Delivery and handling6
Delivery and handling

Supplied components
LEK
Current sensor1
3 x
Room
sensor(BT50)
1 x
Outdoor temperat-
ure sensor (BT1)
1 x
LEK
Safety valve (FL3)
0.3 MPa (3 bar)1
1 x
LEK
Level vessel
(CM2)1
1 x
O-rings
8 x
Label for external
control voltage for
the control system
1 x
Compression ring
couplings
8 kW
2 x (ø28 x G25)
Filterball (QZ2)
8 kW
1 x G1
1 x G3/4
LOCATION
The kit of supplied items is placed in packaging on top of
the heat pump.
Handling panels
OPEN FRONT HATCH
Press the hatch's top left corner to open it.
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
7Chapter 2 | Delivery and handlingNIBE S1256PC
2 x (ø22 x G20)
1 Not Denmark, Italy and the DACH countries.

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.
NIBE S1256PCChapter 2 | Delivery and handling8

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
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.
UN
9Chapter 2 | Delivery and handlingNIBE S1256PC

General
UN
BT7
QN10
BT2
EB1
PZ1
EP14-QM34
EP14-QM31
BT6
EP14-QM32
EP14-QM33
PZ2
QM22 UB1
AA4
SF1
XL1
XL6
XL4 XL3
XL7
XL2
BF1
UB2
FC1
XL5
XF8
FR1
XF3
EP14
BT5
PIPE CONNECTIONS
Connection, heating medium flowXL1
Connection, heating medium returnXL2
Connection, cold waterXL3
Connection, hot waterXL4
Connection, HWCXL5
Connection, brine supplyXL6
Connection, brine returnXL7
HVAC COMPONENTS
Cooling moduleEP14
EP14-QM31 Shut-off valve, heating medium supply
EP14-QM32 Shut off valve, heating medium return
EP14-QM33 Shut-off valve, brine supply
EP14-QM34 Shut-off valve, brine return
Venting, coilQM22
Shuttle valve, climate system/water heaterQN10
SENSORS ETC.
Flow meterBF1
Temperature sensors, heating medium flowBT2
Temperature sensor, hot water charging startBT5
Temperature sensor, hot water chargingBT6
Temperature sensor, hot water topBT7
ELECTRICAL COMPONENTS
Display unitAA4
Immersion heaterEB1
Miniature circuit breaker1 FC1
Electrical anode2 FR1
On/off buttonSF1
USB socketXF3
Network connection for myUplinkXF8
1S1256PC-8 3x400 V is not equipped with miniature circuit breakers (FC1).
2Only heat pump with enamelled vessel.
MISCELLANEOUS
Rating platePZ1
Identification plate, cooling modulePZ2
Cable glandUB1
Cable glandUB2
Designations according to standard EN 81346-2.
NIBE S1256PCChapter 3 | The heat pump design10
The heat pump design

Distribution boxes
UN
-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-S2
FQ10
AA2
ELECTRICAL COMPONENTS
Base cardAA2
Electrical anode board1 AA8
Temperature limiterFQ10
FQ10-S2 Reset button for temperature limiter
1Only heat pump with enamelled vessel.
Cooling module
QN18
BT12
AA3
BT11
GP2
GP1
QM2 QM1
BT10
EP6
BT3
RF2
EP2
RA1
BT15
XL21
QA40
BT17
BP1
BT14
HS1
XL20
EB10
EP1
GQ10
QN1
BP2
CA1
BT84
FQ14
BP8
BP9
PIPE CONNECTIONS
Service connection, high pressureXL20
Service connection, low pressureXL21
HVAC COMPONENTS
Circulation pumpGP1
Brine pumpGP2
Drainage, climate systemQM1
Draining, brine sideQM2
Mixing valve, coolingQN18
SENSORS ETC.
High pressure pressostatBP1
Low pressure pressostatBP2
Low pressure transmitterBP8
High pressure sensorBP9
Temperature sensors, heating medium returnBT3
Temperature sensor, brine supplyBT10
Temperature sensor, brine returnBT11
Temperature sensor, condenser supply lineBT12
Temperature sensor, hot gasBT14
Temperature sensor, fluid pipeBT15
Temperature sensor, suction gasBT17
Temperature sensor, suction gas evaporatorBT84
ELECTRICAL COMPONENTS
Input circuit boardAA3
CapacitorCA1
Compressor heaterEB10
Temperature limiter, compressorFQ14
InverterQA40
ChokeRA1
EMC-filterRF2
COOLING COMPONENTS
EvaporatorEP1
CondenserEP2
Heat exchanger, coolingEP6
CompressorGQ10
Drying filterHS1
Expansion valveQN1
11Chapter 3 | The heat pump designNIBE S1256PC

General
Pipe installation must be carried out in accordance with
current norms and directives. S1256PC can operate with a
return temperature of up to 58 °C and an outgoing temper-
ature from the heat pump of 70 (65 °C with only the com-
pressor).
S1256PC is not equipped with external shut off valves; these
must be installed to facilitate any future servicing.
Caution
Ensure that incoming water is clean. When using
a private well, it may be necessary to supplement
with an extra water filter.
Caution
Any high points in the climate system, must be
equipped with air vents.
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’s overflow
pipe. The overflow pipe must be routed to a suit-
able drain, to prevent hot water splashes from
causing harm. The overflow pipe must be inclined
along its entire length to prevent pockets where
water can accumulate, and must be frost-proof.
The overflow pipe must be at least the same size
as the safety valve. The overflow pipe must be
visible and its mouth must be open and not placed
close to electrical components.
NOTE
The climate system must be adjusted for both
heating and cooling operation.
SYMBOL KEY
MeaningSymbol
Unit box
Shut-off valve
Non-return valve
Mixing valve
Circulation pump
Expansion vessel
Filterball
Fan
Pressure gauge
Level vessel
Control valve
Particle filter
Safety valve
Temperature sensor
Trim valve
Reversing valve/shunt
Manual reversing valve/shunt
Heat exchanger
Overflow valve
Bore hole
Ground collector
Pool
Domestic hot water
Hot water circulation
Heat pump
Heating system
Heating system with lower temperature
NIBE S1256PCChapter 4 | Pipe connections12
Pipe connections

SYSTEM DIAGRAM
S1256PC consists of heat pump, water heater, immersion
heater, circulation pumps and control system. S1256PC is
connected to the brine and heating medium circuits.
In the heat pump evaporator, the brine (water mixed with
anti-freeze, glycol or ethanol) releases its energy to the re-
frigerant, which is vaporised in order to be compressed in
the compressor. The refrigerant, of which the temperature
has now been raised, is passed to the condenser where it
gives off its energy to the heating medium circuit and, if
necessary, to the water heater. If there is a greater need for
heating/hot water than the compressor can provide there
is an integrated immersion heater.
The brine can also be circulated via a mixing valve to a heat
exchanger. There the brine cools the heating system's water
so that comfort cooling can be maintained during the hotter
periods of the year.
XL 1 6 3 7
42
Connection, heating medium flowXL1
Connection, heating medium returnXL2
Connection, cold waterXL3
Connection, hot waterXL4
Connection, brine supplyXL6
Connection, brine returnXL7
Dimensions and pipe
connections
560 440
70
1800
650*
20-50
650*
600
60
135
210
390
465
540
25
622
622
600
560 440
70
1800
650*
20-50
25
60
135
210
390
465
540
650*
XL1 XL6 XL7XL4 XL3 XL2
PIPE DIMENSIONS
8 kWConnection
22(mm)(XL1)/(XL2) Heating medium supply/return ext. Ø
22(mm)(XL3)/(XL4) Cold/hot water Ø
28(mm)(XL6)/(XL7) Brine supply/return ext. Ø
* Can be angled for side connection.
13Chapter 4 | Pipe connectionsNIBE S1256PC

Brine side
COLLECTOR
Caution
The length of the collector hose varies depending
on the rock/soil conditions, climate zone and on
the climate system (radiators or underfloor heat-
ing) and the building’s power requirement. Each
installation must be sized individually. The brine
pump’s capacity must be taken into consideration
when sizing the collector.
In those cases where it is necessary to have several collect-
ors, these should be connected in parallel with the possibility
for adjusting the flow of the relevant coil.
For surface soil heat, the hose should be buried at a depth
determined by local conditions and the distance between
the hoses should be at least 1 metre.
For several bore holes, the distance between the holes must
be determined according to local conditions.
Ensure the collector hose rises constantly towards the heat
pump to avoid air pockets. If this is not possible, airvents
should be used.
Because the temperature of the brine system can fall below
0 °C, it must be protected against freezing down to -15 °C.
When making the volume calculation, use 1 litres of ready
mixed brine per metre of collector hose (applies when using
PEM-hose 40x2.4 PN 6.3) as a guide value.
SIDE CONNECTION
It is possible to angle the brine connections, for connection
to the side instead of top connection.
To angle out a connection:
1. Disconnect the pipe at the top connection.
2. Angle the pipe in the desired direction.
3. If necessary, cut the pipe to the desired length.
CONNECTING THE BRINE SIDE
Insulate all indoor brine pipes against condensation.
Mark the brine system with the antifreeze that is used.
Install as follows:
•enclosed level vessel (CM2)/expansion vessel
The level vessel must be installed as the highest point in
the brine system on the incoming pipe before the brine
pump (Alternative 1). If the level vessel cannot be placed
at the highest point, an expansion vessel must be used
(Alternative 2).
NOTE
Note that condensation may drip from the level
vessel. Position the vessel so that this does not
harm other equipment.
•enclosed safety valve (FL3)
Install the safety valve under the level vessel as illustrated.
•pressure gauge
The pressure gauge is only required if an expansion vessel
is used.
•shut-off valve
Install the shut-off valve as close to S1256PC as possible.
•enclosed filterball (QZ2)
Install the filterball as close to S1256PC as possible.
TIP
If filling connection KB25/KB32 is used, the en-
closed filterball does not need to be fitted.
•vent valve
When necessary you should install venting valves in the
brine system.
In the case of connection to an open groundwater system,
an intermediate frost-protected circuit must be provided,
because of the risk of dirt and freezing in the evaporator.
This requires an extra heat exchanger.
P
-QZ20
Alt. 1 Alt. 2
XL6
XL7
NIBE S1256PCChapter 4 | Pipe connections14

Climate system
A climate system is a system that regulates the indoor
temperature with the help of the control system in S1256PC
and, for example, radiators, underfloor heating, underfloor
cooling, fan coils, etc.
CONNECTING THE CLIMATE SYSTEM
Install as follows:
•expansion vessel
•pressure gauge
•pressure relief valve
Recommended opening pressure is 0.25 MPa (2.5 bar).
For information about max opening pressure, see technical
data. Install the safety valve as illustrated.
Install the safety valve as illustrated.
•enclosed filterball (QZ2)
Install the filterball as close to S1256PC as possible.
•shut-off valve
Install the shut-off valve as close to S1256PC as possible.
•When connecting to a system with thermostats, either a
bypass valve must be fitted or, alternatively, some of the
thermostats must be removed to ensure there is sufficient
flow and heat emission.
P
XL1
XL2
Cold and hot water
The settings for hot water are made in menu 7.1.1 - "Hot
water".
CONNECTING COLD AND HOT WATER
Install as follows:
•shut-off valve
•non-return valve
•pressure relief valve
The safety valve must have an opening pressure of max.
1.0 MPa (10.0 bar).
•mixing valve
A mixer valve must also be installed, if the factory setting
for hot water is changed. National regulations must be
observed.
XL3
XL4
Installation alternative
S1256PC can be installed in several different ways, some of
which are shown here.
Further option information is available at nibe.eu and in the
respective assembly instructions for the accessories used.
See page 64 for a list of the accessories that can be used
with S1256PC.
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 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 S1256PC.
HOT WATER CIRCULATION
A circulation pump can be controlled by S1256PC 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 can be connected to XL5 or a freestanding
water heater. If an electric water heater is connected after
the heat pump, the HWC return must be connected to the
water heater.
The circulation pump is activated via the AUX output in menu
7.4 -"Selectable in/outputs".
HWC can be supplemented with a hot water sensor for HWC
(BT70) and (BT82), which is connected via the AUX input in
menu 7.4 -"Selectable in/outputs".
-QZ1-FQ3
-QZ1-GP11
-QZ1-RM1
-QZ1-RN1
-QZ1
15Chapter 4 | Pipe connectionsNIBE S1256PC

BUFFER VESSEL (UKV)
UKV is an accumulator tank that is suitable for connection
to a heat pump or another external heat source, and can
have several different applications.
For further information, see the Installer Manual for the ac-
cessory.
Volume
A 2-pipe-connected buffer vessel is used when the system
volume in the climate system is less than the minimum re-
commended volume for the heat pump.
GROUND WATER SYSTEM
An intermediate heat exchanger is used to protect the heat
pump’s exchanger from dirt. The water is released into a
buried infiltration unit or a drilled well. See page Possible
selections for AUX output for more information about con-
necting a groundwater pump.
If this docking alternative is used, "min. brine out" in menu
7.1.2.8 "br pmp al set." must be changed to a suitable value
to prevent freezing of the heat exchanger.
-EP12-GP3
-EP12-HQ40
-EP12-EP4
-EP12-AA25
-EP12
VENTILATION RECOVERY
The installation can be supplemented with the exhaust air
module NIBE FLM S45 to provide ventilation recovery.
•Pipes and other cold surfaces must be insulated with dif-
fusion-proof material to prevent condensation.
•The brine system must be supplied with a pressure expan-
sion vessel. If there is a level vessel this should be re-
placed.
P
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
POOL
With the POOL 40 accessory, you can heat the pool with
your system.
During pool heating, the heating medium circulates between
the S1256PC and the pool exchanger using the heat pump’s
internal circulation pump.
-CL11-HQ4-CL11-BT51-CL11-GP9
-CL11-EP5
-CL11-AA25
-CL11
NIBE S1256PCChapter 4 | Pipe connections16

General
All electrical equipment, except the outdoor sensors, room
sensors and the current sensors are ready connected at the
factory.
•Electrical installation and wiring must be carried out in
accordance with national provisions.
•Disconnect S1256PC before insulation testing the house
wiring.
•If the building is equipped with an earth-fault breaker,
S1256PC should be equipped with a separate one.
•S1256PC must be installed via an isolator switch. The cable
area has to be dimensioned based on the fuse rating used.
•If a miniature circuit breaker is used, this must have at
least triggering characteristic "C". See section "Technical
specifications" for fuse size.
•To prevent interference, sensor cables to external connec-
tions must not be laid close to high voltage cables.
•The minimum area of communication and sensor cables
to external connections must be 0.5 mm² up to 50 m, for
example EKKX, LiYY or equivalent.
•Electrical wiring diagram for S1256PC, see separate
handbook (WHB).
•When routing a cable into S1256PC, the cable grommets
UB1 and UB2 must be used.
UB1
UB2
FC1
NOTE
Electrical installation and any servicing must be
carried out under the supervision of a qualified
electrician. Disconnect the current using the cir-
cuit breaker before carrying out any servicing.
NOTE
If the supply cable is damaged, only NIBE, its ser-
vice representative or similar authorised person
may replace it to prevent any danger and damage.
NOTE
Check the connections, main voltage and phase
voltage before the product is started, to prevent
damage to the heat pump electronics.
NOTE
Do not start the system before filling up with wa-
ter. Components in the system could be damaged.
MINIATURE CIRCUIT-BREAKER
The operating circuit in S1256PC and some of its internal
components are fused internally by a miniature circuit
breaker (FC1).
S1256PC-8 3x400 V is not equipped with miniature circuit
breakers (FC1).
17Chapter 5 | Electrical connectionsNIBE S1256PC
Electrical connections

ACCESSIBILITY, ELECTRICAL CONNECTION
Removing the cover
The cover is opened using a screwdriver.
Removing the covers
The cover is opened using a screwdriver.
CABLE LOCK
Use a suitable tool to release/lock cables in the heat pump
terminal blocks.
Terminal block
1.
2.
TEMPERATURE LIMITER
-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-S2
The temperature limiter (FQ10) cuts the power supply to the
electric additional heat if the temperature rises above 89 °C
and it is reset manually.
Resetting
The temperature limiter (FQ10) is accessed behind the front
cover. Reset the temperature limiter by pressing its button
(FQ10-S2).
NIBE S1256PCChapter 5 | Electrical connections18

Connections
TERMINAL BLOCKS
The following terminal blocks are used on the base board
(AA2).
-X29
-X28
1 0-5V 2 +5V
3 AUX1 4 AUX2 5 AUX3 6 AUX4 7 AUX5 8 AUX6 9 AUX7
10 AUX8 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
AA2
X1
X5X6-2X6-1
X7-2
X9
POWER CONNECTION
Supply voltage
Enclosed cable for incoming supply electricity is connected
to terminal block X1 and X6-1 on the PCB (AA2).
Connection 3x400V
AA2-X1
AA2-X6-1
PE N L1 L2 L3
1234
Connection 1x230V
AA2-X1
PE N L (L) (L)
1234
AA2-X6-1
External control voltage for the control
system
If the control system is to be powered separately from the
other components in the heat pump (e.g. for tariff control),
a separate operating cable must be connected.
NOTE
During service, all supply circuits must be discon-
nected.
Remove the bridges from terminal block X5.
Control voltage (230 V ~ 50Hz) connects to AA2:X5:N, X5:L
and X6-2 (PE).
L
N
1. 2.
3. 4.
X5
Enclosed label
The enclosed label is placed on the electrical connection’s
cover.
Tariff control
If the voltage to the immersion heater and/or compressor
is lost for a period, "Tariff blocking" must be selected at the
same time via the selectable inputs, see section "Selectable
inputs".
19Chapter 5 | Electrical connectionsNIBE S1256PC

EXTERNAL CONNECTIONS
Connect external connections on terminal blocks X28, X29
and X30 on the base board (AA2).
-X29
-X28
1 0-5V 2 +5V
3 AUX1 4 AUX2 5 AUX3 6 AUX4 7 AUX5 8 AUX6 9 AUX7
10 AUX8 11 AUX9 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
X28
X29
X30
AA2
X27
Sensors
Outside sensor
The outdoor temperature sensor (BT1) is placed in the shade
on a wall facing north or north-west, so it is unaffected, for
example, by the morning sun.
Connect the outdoor temperature sensor to terminal block
AA2-X28:14 and AA2-X29:GND.
If a conduit is used it must be sealed to prevent condensa-
tion in the sensor capsule.
13
1211
109 14
BT1
BT1
BT50
GND
BT25
AUX9 AUX8 AUX7
AA2-X28
AA2-X29
External supply temperature sensor
If an external supply temperature sensor (BT25) needs to
be used, connect it to terminal block AA2-X28:12 and to
terminal block AA2-X29:GND.
1211109
BT25
GND
BT25
AUX9 AUX8 AUX7
AA2-X28
AA2-X29
Room sensor
S1256PC is supplied with an enclosed room sensor (BT50)
that makes it possible to display and control the room tem-
perature in the display on S1256PC.
Fit the room sensor in a neutral position where a set temper-
ature is required. A suitable location might be, for example,
on a free inner wall in a hall approx. 1.5 m above the floor. It
is important that the room sensor is not obstructed from
measuring the correct room temperature, for example by
being located in a recess, between shelves, behind a curtain,
above or close to a heat source, in a draught from an external
door or in direct sunlight. Closed radiator thermostats can
also cause problems.
S1256PC operates without room sensor, but if you want to
read the home’s indoor temperature from the display on
S1256PC, the room sensor must be fitted. Connect the room
sensor to terminal block X28:13 and AA2-X29:GND.
If a room sensor is to be used to change the room temperat-
ure in °C and/or to fine-tune the room temperature, the
sensor must be activated in menu 1.3 - "Room sensor set-
tings".
If a room sensor is used in a room with underfloor heating,
it should only have an indicatory function, not control of the
room temperature.
13121110
BT50
GND
BT50 BT25
AUX9 AUX8
AA2-X28
AA2-X29
Caution
Changes of temperature in accommodation take
time. For example, short time periods in combina-
tion with underfloor heating will not give a notice-
able difference in room temperature.
Pulse energy meter
Up to two electricity meters or energy meters for heating
(BE6, BE7) can be connected to S1256PC via terminal blocks
AA2-X28:1-2 and AA2-X30:7-8.
S1256PC External
BE7
+OT
+OT
0-5V
+5V
GND
95 6 7 8
AA2-X28
+5V
+5V
0-5V
+5V
AUX 1 AUX 2 AUX 3
AA2-X30
51234
BE6
NIBE S1256PCChapter 5 | Electrical connections20