Why study the KNX Installation block for KNX Basic?

The KNX Installation block covers notions that appear repeatedly in the theory and hands-on parts of the KNX Basic exam. Mastering these questions significantly cuts the risk of stalling on this topic on exam day.

How many KNX Installation questions appear in the KNX Basic exam?

Varies by session — typically 2 to 4 questions per block in the KNX Basic theory exam, plus an applied scenario in the practical part where applicable.

KNX Basic · topic block

KNX Installation KNX Basic: exam questions with worked answers

Practice questions from the KNX Installation block of the KNX Basic Certification certification. Detailed corrections, public sources, free to read without sign-up.

56 questions~ 50 minFree · no sign-up

Questions for the "KNX Installation" topic

Q01
The maximum total cable length of a line segment using certified KNX TP cable is 1000 m.
TrueFalse
4. KNX Installation· bus-cables· Easy
Correct answer
True
Learning tip
Only the standardized green KNX TP cable guarantees reliable transmission over the total cable length of the line segment, up to a maximum of 1000 m.
Source: KNX Basic Course Documentation — 2 — p. 98
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Q02
What is the maximum number of bus devices per line guaranteed by the certified KNX TP cable?
- A.256 devices
- B.128 devices
- C.64 devices
- D.1000 devices
4. KNX Installation· bus-cables· Easy
▸
Correct answer
A — 256 devices
Learning tip
Correct: The standardized cable guarantees a maximum of 256 bus devices per line.
Source: KNX Basic Course Documentation — 2 — p. 98
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Q03
What is the test voltage of the YCYM 2x2x0.8 bus cable according to EN 50090?
- A.2.5 kV
- B.4 kV
- C.6 kV
- D.0.6 kV
4. KNX Installation· bus-cables· Medium
▸
Correct answer
B — 4 kV
Learning tip
Correct: YCYM 2x2x0.8 has a test voltage of 4 kV per EN 50090.
Source: KNX Basic Course Documentation — 2 — p. 98
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Q04
What is the test voltage of the J-Y(St)Y 2x2x0.8 cable according to EN 50090?
- A.4 kV
- B.1.0 kV
- C.2.5 kV
- D.6 kV
4. KNX Installation· bus-cables· Medium
▸
Correct answer
C — 2.5 kV
Learning tip
Correct: J-Y(St)Y 2x2x0.8 has a test voltage of 2.5 kV per EN 50090.
Source: KNX Basic Course Documentation — 2 — p. 98
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Q05
In the used wire pair of the KNX bus cable, red is plus and black is minus.
TrueFalse
4. KNX Installation· bus-cables· Easy
Correct answer
True
Learning tip
The text states the used wire pair is red for plus and black for minus.
Source: KNX Basic Course Documentation — 2 — p. 99
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Q06
The spare wire pair (white/yellow) of the KNX bus cable may be used for which of the following?
- A.A second KNX TP data signal
- B.A DC SELV supply, or left with no connection at all
- C.Voice communication
- D.A 230 V AC mains supply
4. KNX Installation· bus-cables· Medium
▸
Correct answer
B — A DC SELV supply, or left with no connection at all
Learning tip
Correct: Permitted uses are no connection at all or a DC SELV supply.
Source: KNX Basic Course Documentation — 2 — p. 99
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Q07
Which cables can be certified with the KNX logo by KNX Association?
- A.Only cables coloured green, regardless of their electrical properties
- B.Any 230 V mains cable of adequate cross-section
- C.Cables fulfilling the KNX requirements in volume 9 of the KNX Specifications, e.g. YCYM 2x2x0.8 or J-Y(St)Y 2x2x0.8 in TP design
- D.Only cables tested to 6 kV
4. KNX Installation· bus-cables· Medium
▸
Correct answer
C — Cables fulfilling the KNX requirements in volume 9 of the KNX Specifications, e.g. YCYM 2x2x0.8 or J-Y(St)Y 2x2x0.8 in TP design
Learning tip
Correct: These meet the volume 9 requirements and can carry the KNX logo.
Source: KNX Basic Course Documentation — 2 — p. 98
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Q08
How should the shielding of KNX bus cables be treated regarding the equipotential bonding bar?
- A.It must be bonded to the equipotential bar at every device
- B.It must be earthed at the power supply only
- C.It must be connected to the protective earth of the mains
- D.It may not be connected to the equipotential bonding bar
4. KNX Installation· bus-cables· Medium
▸
Correct answer
D — It may not be connected to the equipotential bonding bar
Learning tip
Correct: The shielding of the bus cables may not be connected to the equipotential bonding bar.
Source: KNX Basic Course Documentation — 2 — p. 98
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Q09
A terminating resistor is not required in a KNX TP installation.
TrueFalse
4. KNX Installation· bus-cables· Easy
Correct answer
True
Learning tip
The documentation states plainly that a terminating resistor is not required.
Source: KNX Basic Course Documentation — 3 — p. 101
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Q10
On which DIN rails may KNX TP DIN-rail mounted devices be installed in a distribution board?
- A.Standardized EN 50022 35x7.5 mm DIN rails
- B.Only proprietary KNX rails supplied by the manufacturer
- C.EN 50090 15x5 mm rails
- D.Only earthed metal rails used as the SELV return
4. KNX Installation· bus-cables· Medium
▸
Correct answer
A — Standardized EN 50022 35x7.5 mm DIN rails
Learning tip
Correct: Any commercial board with EN 50022 35x7.5 mm DIN rails may be used.
Source: KNX Basic Course Documentation — 4 — p. 101
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Q11
In a KNX TP installation, the maximum permitted length of a single line segment is 1000 m.
TrueFalse
4. KNX Installation· installation-check· Easy
Correct answer
True
Learning tip
Correct. The physical limits of a KNX TP installation set the maximum length of a line segment at 1000 m.
Source: KNX Basic Course Documentation — 17.1 — p. 118
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Q12
In a KNX TP line, what is the maximum permitted distance between the power supply unit and a bus device?
- A.700 m
- B.1000 m
- C.350 m
- D.As specified by the manufacturer
4. KNX Installation· installation-check· Medium
▸
Correct answer
C — 350 m
Learning tip
Correct: The distance between the power supply unit and a bus device may not exceed 350 m.
Source: KNX Basic Course Documentation — 17.1 — p. 118
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Q13
During the installation check, how should the ends of the bus cables be marked?
- A.'KNX TP' or 'BUS'
- B.With '230 V' to warn of the operating voltage
- C.No marking is required at the cable ends
- D.With the manufacturer's serial number only
4. KNX Installation· installation-check· Easy
▸
Correct answer
A — 'KNX TP' or 'BUS'
Learning tip
Correct: Bus cable ends should be clearly identified as KNX TP by marking them 'KNX TP' or 'BUS'.
Source: KNX Basic Course Documentation — 17.2 — p. 118
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Q14
Which statement about connecting the bus cables of different lines is correct?
- A.Bus cables from different lines may be connected at the line coupler.
- B.Bus cables from different lines may never be connected together.
- C.Bus cables from different lines may be connected if the total length stays under 1000 m.
- D.Bus cables from different lines must be connected to form a single segment.
4. KNX Installation· installation-check· Easy
▸
Correct answer
B — Bus cables from different lines may never be connected together.
Learning tip
Correct: Bus cables from different lines may never be connected together; the check looks for such inadmissible connections.
Source: KNX Basic Course Documentation — 17.3 — p. 118
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Q15
The insulation resistance of the bus cable shall be at least 500 kΩ.
TrueFalse
4. KNX Installation· installation-check· Easy
Correct answer
True
Learning tip
Correct. The insulation resistance of the bus cable shall be at least 500 kΩ.
Source: KNX Basic Course Documentation — 17.4 — p. 119
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Q16
At what test voltage should the insulation resistance of the bus cable be measured?
- A.250 V DC
- B.230 V DC
- C.500 V DC
- D.21 V DC
4. KNX Installation· installation-check· Medium
▸
Correct answer
A — 250 V DC
Learning tip
Correct: The insulation resistance measurement should be carried out at 250 V DC.
Source: KNX Basic Course Documentation — 17.4 — p. 119
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Q17
Why should overvoltage protectors be removed before measuring the insulation resistance of the bus cable?
- A.Because overvoltage protectors are only fitted on mains cables, never on bus cables.
- B.So the measurement is not influenced and the overvoltage protector is not damaged.
- C.To raise the test voltage above 250 V DC.
- D.Because the protectors must be replaced after every insulation test.
4. KNX Installation· installation-check· Medium
▸
Correct answer
B — So the measurement is not influenced and the overvoltage protector is not damaged.
Learning tip
Correct: Overvoltage protectors should always be removed before the test so that the measurement is not influenced and the protector is not damaged.
Source: KNX Basic Course Documentation — 17.4 — p. 119
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Q18
What is the minimum bus voltage that must be measured at the end of each bus cable?
- A.24 V DC
- B.29 V DC
- C.20 V DC
- D.21 V DC
4. KNX Installation· installation-check· Medium
▸
Correct answer
D — 21 V DC
Learning tip
Correct: The bus voltage at each bus cable end should be at least 21 V DC.
Source: KNX Basic Course Documentation — 17.6 — p. 119
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Q19
When the ETS project is handed over, the customer's signature confirms agreement with which of the following?
- A.Only the total price of the installation.
- B.All the realized functions, and that the installer's warranty expires with any change to the realized KNX installation.
- C.That the installer stays liable for any future changes made by others.
- D.That no project documentation needs to be provided.
4. KNX Installation· installation-check· Medium
▸
Correct answer
B — All the realized functions, and that the installer's warranty expires with any change to the realized KNX installation.
Learning tip
Correct: With the signature the customer agrees to all realized functions and that the installer's warranty expires with any change to the installation.
Source: KNX Basic Course Documentation — 17.8 — p. 119
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Q20
In the sequence for checking a KNX installation, which check is carried out immediately after checking the polarity of all bus devices?
- A.Measuring the insulation resistance of the bus cables
- B.The visual check of the bus cable-end marking
- C.Measuring the bus voltage at each bus cable end
- D.Recording the test results
4. KNX Installation· installation-check· Medium
▸
Correct answer
C — Measuring the bus voltage at each bus cable end
Learning tip
Correct: The polarity check is followed by measuring the bus voltage (minimum 21 V) at each bus cable end.
Source: KNX Basic Course Documentation — 17 — p. 118
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Q21
In a common installation box with a partition, what clearance and creepage distance does the source require between mains and bus?
- A.2,5 mm.
- B.8 mm.
- C.5,5 mm.
- D.0,5 mm.
4. KNX Installation· connectors-and-mounting· Medium
▸
Correct answer
C — 5,5 mm.
Learning tip
Correct: the source requires 5,5 mm clearance and creepage distances.
Source: KNX Basic Course Documentation — 8 — p. 108
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Q22
How should flush-mounted bus devices be fixed in the wall box?
- A.By clamp mounting, which is the normal method for bus devices.
- B.Screw or clamp mounting; either works equally well.
- C.By gluing the device into any available box.
- D.In wall boxes suitable for screw mounting; clamp mounting is usually not possible.
4. KNX Installation· connectors-and-mounting· Easy
▸
Correct answer
D — In wall boxes suitable for screw mounting; clamp mounting is usually not possible.
Learning tip
Correct: only wall boxes suitable for screw mounting may be used.
Source: KNX Basic Course Documentation — 9 — p. 109
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Q23
On the standardized KNX TP bus connector, which statement about the two parts is correct?
- A.The plus part is red and the minus part is black.
- B.The plus part is red and the minus part is dark grey.
- C.The plus part is black and the minus part is red.
- D.Both parts are green, matching the bus cable sheath.
4. KNX Installation· connectors-and-mounting· Medium
▸
Correct answer
B — The plus part is red and the minus part is dark grey.
Learning tip
Correct: the connector consists of the plus part (red) and the minus part (dark grey).
Source: KNX Basic Course Documentation — 10 — p. 110
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Q24
Where may a KNX bus cable legitimately end?
- A.Only inside the power supply unit.
- B.Anywhere convenient, as bare stripped cores.
- C.Only at a bus device or at a bus connector.
- D.At any 230 V mains terminal block.
4. KNX Installation· connectors-and-mounting· Easy
▸
Correct answer
C — Only at a bus device or at a bus connector.
Learning tip
Correct: the bus cable shall only end either at the device itself or at a bus connector.
Source: KNX Basic Course Documentation — 10 — p. 110
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Q25
How many bus wires can be connected to each part of the standardized TP bus connector?
- A.Up to 8 wires.
- B.Up to 2 wires.
- C.Exactly 1 wire.
- D.Up to 4 wires (6 mm stripped).
4. KNX Installation· connectors-and-mounting· Medium
▸
Correct answer
D — Up to 4 wires (6 mm stripped).
Learning tip
Correct: up to 4 bus wires, stripped to 6 mm, fit each screwless part.
Source: KNX Basic Course Documentation — 10 — p. 110
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Q26
For which task is the standardized TP bus connector used?
- A.Branching or extending the bus cable and connecting/protecting its ends.
- B.Coupling two lines together (line-coupler function).
- C.Discharging surges to earth (overvoltage protection).
- D.Supplying the 30 V DC bus power.
4. KNX Installation· connectors-and-mounting· Easy
▸
Correct answer
A — Branching or extending the bus cable and connecting/protecting its ends.
Learning tip
Correct: the connector is used for branching, extending, protecting the bus cable ends and connecting the cable to bus devices.
Source: KNX Basic Course Documentation — 10 — p. 110
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Q27
What does 'primary protection' mean in the KNX lightning-protection context?
- A.Fitting an overvoltage protector directly at each bus device.
- B.Connecting active conductors indirectly to the equipotential bonding bar via lightning current arresters.
- C.The basic 2 kV immunity built into every bus device.
- D.The reverse-polarity keying of the TP bus connector.
4. KNX Installation· protection· Medium
▸
Correct answer
B — Connecting active conductors indirectly to the equipotential bonding bar via lightning current arresters.
Learning tip
Correct: this indirect connection of active conductors through lightning current arresters is primary protection.
Source: KNX Basic Course Documentation — 11 — p. 111
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Q28
For primary protection of the 230/400 V AC mains, what minimum nominal discharge current (10/350 us) is required per conductor?
- A.2,5 kA.
- B.5 kA.
- C.12,5 kA.
- D.25 kA.
4. KNX Installation· protection· Medium
▸
Correct answer
C — 12,5 kA.
Learning tip
Correct: at least 12,5 kA (10/350 us) per conductor is required for the mains.
Source: KNX Basic Course Documentation — 11 — p. 112
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Q29
For primary protection of the KNX bus line, what minimum nominal discharge current (10/350 us) per conductor is required?
- A.5 kA.
- B.12,5 kA.
- C.0,25 kA.
- D.2,5 kA.
4. KNX Installation· protection· Medium
▸
Correct answer
D — 2,5 kA.
Learning tip
Correct: at least 2,5 kA (10/350 us) per conductor is required for the bus line.
Source: KNX Basic Course Documentation — 11 — p. 112
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Q30
How does loop area relate to lightning-induced surges in a KNX installation?
- A.The larger the loop area, the smaller the surge.
- B.Loop area has no effect on surge magnitude.
- C.Only loops smaller than 1 m2 generate surges.
- D.The larger the loop area, the larger the expected peak surge.
4. KNX Installation· protection· Medium
▸
Correct answer
D — The larger the loop area, the larger the expected peak surge.
Learning tip
Correct: the source states peak surge grows with loop area.
Source: KNX Basic Course Documentation — 13 — p. 114
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Q31
To what surge voltage (core to earth) is the basic immunity of bus devices tested (IEC 63044-3)?
- A.4 kV.
- B.2 kV.
- C.600 V.
- D.350 V.
4. KNX Installation· protection· Medium
▸
Correct answer
B — 2 kV.
Learning tip
Correct: basic immunity is tested with a 2 kV surge core to earth.
Source: KNX Basic Course Documentation — 14 — p. 115
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Q32
Which situation is NOT listed by the source as a cause of more significant interference on the bus?
- A.Installing bus devices in loops.
- B.Running bus and high-power mains in parallel over a long distance.
- C.Using a certified twisted-pair bus cable of the correct colour.
- D.Bus devices connected to metal walls or central-heating pipes.
4. KNX Installation· protection· Medium
▸
Correct answer
C — Using a certified twisted-pair bus cable of the correct colour.
Learning tip
Correct: cable certification/colour is not listed as a cause of interference.
Source: KNX Basic Course Documentation — 14 — p. 115
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Q33
What does the source recommend for bus devices installed on cable ends?
- A.No extra measures, because basic immunity is always sufficient.
- B.Primary protection only, via a lightning current arrester.
- C.Removal of the terminating bus connector.
- D.Additional secondary protection (an overvoltage protector).
4. KNX Installation· protection· Medium
▸
Correct answer
D — Additional secondary protection (an overvoltage protector).
Learning tip
Correct: additional secondary protection should be provided for bus devices on cable ends.
Source: KNX Basic Course Documentation — 15 — p. 115
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Q34
How is the overvoltage protector with KNX bus connector design classified, and how does it differ from primary protection?
- A.It is secondary protection at the devices; primary protection uses lightning current arresters on active conductors.
- B.It is just the bus device's own 2 kV basic immunity.
- C.It is primary protection; secondary protection is the equipotential bonding bar.
- D.It is the same thing as a lightning current arrester.
4. KNX Installation· protection· Medium
▸
Correct answer
A — It is secondary protection at the devices; primary protection uses lightning current arresters on active conductors.
Learning tip
Correct: the overvoltage protector is secondary protection, distinct from the primary lightning current arresters.
Source: KNX Basic Course Documentation — 16 — p. 116
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Q35
What minimum nominal discharge current (and impulse shape) must the secondary overvoltage protector provide?
- A.At least 2,5 kA (10/350 us).
- B.At least 5 kA (8/20 us).
- C.At least 12,5 kA (10/350 us).
- D.At least 350 A (8/20 us).
4. KNX Installation· protection· Medium
▸
Correct answer
B — At least 5 kA (8/20 us).
Learning tip
Correct: the overvoltage protector must provide at least 5 kA (8/20 us).
Source: KNX Basic Course Documentation — 16 — p. 116
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Q36
How is the overvoltage protector connected, and can it branch the bus cable?
- A.Only by cutting the bus cable and hard-soldering it in line.
- B.It is the normal way to branch the bus cable into three directions.
- C.Via a conventional bus connector or directly to a bus device; it cannot branch the bus cable.
- D.Only through the 230 V mains terminals.
4. KNX Installation· protection· Medium
▸
Correct answer
C — Via a conventional bus connector or directly to a bus device; it cannot branch the bus cable.
Learning tip
Correct: it connects with a bus connector or directly to a device, and cannot be used to branch the bus.
Source: KNX Basic Course Documentation — 16 — p. 116
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Q37
What nominal system voltage does a KNX TP power supply unit produce and monitor?
- A.30 V DC
- B.30 V AC
- C.230 V AC
- D.21 V DC
4. KNX Installation· power-supply· Easy
▸
Correct answer
A — 30 V DC
Learning tip
Correct: The PSU produces and monitors the 30 V DC system voltage needed for a KNX TP installation.
Source: KNX Basic Course Documentation — 5.1 — p. 102
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Q38
What is the minimum voltage a KNX TP bus device needs for safe operation?
- A.12 V DC
- B.21 V DC
- C.30 V DC
- D.24 V DC
4. KNX Installation· power-supply· Easy
▸
Correct answer
B — 21 V DC
Learning tip
Correct: Bus devices require a minimum of 21 V DC for safe operation.
Source: KNX Basic Course Documentation — 5.1 — p. 102
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Q39
For at least how long can a KNX power supply unit bridge a short interruption of the mains?
- A.1 s
- B.10 ms
- C.100 ms
- D.100 microseconds
4. KNX Installation· power-supply· Medium
▸
Correct answer
C — 100 ms
Learning tip
Correct: The PSU can bridge short power gaps of a minimum of 100 ms.
Source: KNX Basic Course Documentation — 5.1 — p. 102
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Q40
How is a KNX TP line supplied with bus voltage?
- A.One PSU in the installation supplies every line through the couplers
- B.Bus devices are powered directly from the 230 V mains
- C.No PSU is needed if fewer than 21 devices are used
- D.Each line needs its own power supply unit
4. KNX Installation· power-supply· Easy
▸
Correct answer
D — Each line needs its own power supply unit
Learning tip
Correct: The source states each line needs its own PSU to supply its bus devices.
Source: KNX Basic Course Documentation — 5.1 — p. 102
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Q41
Why is a KNX TP power supply unit resistant to short circuits?
- A.Because it has integrated voltage and current control
- B.Because each bus device has its own fuse
- C.Because the bus is a SELV network
- D.Because it operates from the 230 V mains
4. KNX Installation· power-supply· Medium
▸
Correct answer
A — Because it has integrated voltage and current control
Learning tip
Correct: The integrated voltage and current control makes the PSU resistant to short circuits.
Source: KNX Basic Course Documentation — 5.1 — p. 102
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Q42
Which set of output currents corresponds to available centralized KNX TP power supply units?
- A.100, 200 and 400 mA
- B.160, 320, 640 and 1280 mA
- C.1, 2 and 4 A
- D.25, 40 and 80 mA
4. KNX Installation· power-supply· Medium
▸
Correct answer
B — 160, 320, 640 and 1280 mA
Learning tip
Correct: The source lists these as available centralized PSU output currents.
Source: KNX Basic Course Documentation — 5.2 — p. 103
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Q43
Which statement about the choke in KNX TP power supplies is correct?
- A.Every PSU always requires a separate external choke
- B.A choke is only needed on the 230 V mains side
- C.Some PSU types have an integrated choke; others need an additional external choke
- D.Chokes are never used in KNX TP installations
4. KNX Installation· power-supply· Medium
▸
Correct answer
C — Some PSU types have an integrated choke; others need an additional external choke
Learning tip
Correct: The source states exactly this.
Source: KNX Basic Course Documentation — 5.2 — p. 103
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Q44
What determines how many devices can be installed in a KNX TP line?
- A.The type of PSU used and the individual power consumption of the devices
- B.Exactly 64 devices, regardless of the PSU
- C.The colour of the bus connector
- D.Only the physical length of the bus cable
4. KNX Installation· power-supply· Medium
▸
Correct answer
A — The type of PSU used and the individual power consumption of the devices
Learning tip
Correct: The source states the device count depends on the PSU type and each device's consumption.
Source: KNX Basic Course Documentation — 5.2 — p. 103
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Q45
On a KNX power supply unit, what does a YELLOW LED indicate?
- A.The unit is overloaded, possibly due to a short circuit
- B.The 230 V mains supply has failed
- C.The power supply is active and within its normal operating range
- D.An external voltage higher than 30 V has been applied to the bus side
4. KNX Installation· power-supply· Medium
▸
Correct answer
D — An external voltage higher than 30 V has been applied to the bus side
Learning tip
Correct: Yellow indicates an external voltage above 30 V on the bus side.
Source: KNX Basic Course Documentation — 5.2 — p. 104
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Q46
Under what condition can a single power supply unit feed two lines?
- A.When additional current is needed, depending on the load
- B.Always – every PSU feeds exactly two lines
- C.Only if both lines together have fewer than 21 devices
- D.Never – one PSU can only ever feed one line
4. KNX Installation· power-supply· Medium
▸
Correct answer
A — When additional current is needed, depending on the load
Learning tip
Correct: The source allows one PSU to feed two lines if extra current is needed and the load permits.
Source: KNX Basic Course Documentation — 6 — p. 105
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Q47
What is the maximum number of centralized power supply units allowed in one line?
- A.One
- B.Two
- C.Three
- D.Unlimited, as long as spacing is kept
4. KNX Installation· power-supply· Easy
▸
Correct answer
B — Two
Learning tip
Correct: It is not allowed to have more than two centralized PSUs in one line.
Source: KNX Basic Course Documentation — 6.1 — p. 106
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Q48
In a distributed power supply, how is the bus powered?
- A.By connecting the 230 V mains directly to the bus
- B.By batteries fitted inside every bus device
- C.By several devices on the line, each containing a Decentralized Power Supply Unit (DPSU) with an integrated choke module
- D.By a single large centralized PSU only
4. KNX Installation· power-supply· Medium
▸
Correct answer
C — By several devices on the line, each containing a Decentralized Power Supply Unit (DPSU) with an integrated choke module
Learning tip
Correct: The source describes the bus being powered by devices each containing a DPSU with an integrated choke module.
Source: KNX Basic Course Documentation — 7 — p. 107
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Q49
How many DPSUs may be mounted in one single bus line (even if it consists of segments)?
- A.Up to 8
- B.Up to 2
- C.Up to 16
- D.Up to 64
4. KNX Installation· power-supply· Medium
▸
Correct answer
A — Up to 8
Learning tip
Correct: Up to 8 DPSUs may be used; more than eight can negatively affect communication.
Source: KNX Basic Course Documentation — 7 — p. 107
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Q50
Which voltage is used for the KNX TP bus?
- A.30 V DC
- B.24 V DC
- C.30 V AC
- D.230 V AC
4. KNX Installation· selv-and-insulation· Easy
▸
Correct answer
A — 30 V DC
Learning tip
Correct: The documentation states the voltage used for the KNX TP bus is 30 V DC.
Source: KNX Basic Course Documentation — 1.1 — p. 97
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Q51
What does the abbreviation SELV mean, and what is its key property?
- A.Standard Electrical Low Voltage: a circuit that must be bonded to protective earth
- B.Safety Extra Low Voltage: a low-voltage circuit electrically separated from higher voltages and isolated from earth
- C.Secure Ethernet Line Voltage: a data-only supply
- D.Single Ended Low Voltage: a voltage referenced to one mains phase
4. KNX Installation· selv-and-insulation· Easy
▸
Correct answer
B — Safety Extra Low Voltage: a low-voltage circuit electrically separated from higher voltages and isolated from earth
Learning tip
Correct: This matches the definition given for SELV.
Source: KNX Basic Course Documentation — 1 — p. 96
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Q52
What is the permitted voltage range in a SELV network?
- A.120 V for AC and 50 V for DC
- B.25 V for AC and 60 V for DC
- C.50 V for AC and 120 V for DC
- D.30 V for AC and 30 V for DC
4. KNX Installation· selv-and-insulation· Medium
▸
Correct answer
C — 50 V for AC and 120 V for DC
Learning tip
Correct: The text lists 50 V for alternating current and 120 V for direct current.
Source: KNX Basic Course Documentation — 1 — p. 96
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Q53
Below which voltages is NO special protection against direct contact required?
- A.50 V AC or 120 V DC
- B.60 V AC or 25 V DC
- C.30 V AC or 30 V DC
- D.25 V AC or 60 V DC
4. KNX Installation· selv-and-insulation· Medium
▸
Correct answer
D — 25 V AC or 60 V DC
Learning tip
Correct: These are the limits stated for omitting direct-contact protection.
Source: KNX Basic Course Documentation — 1 — p. 96
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Q54
How must a SELV network be treated with respect to earth?
- A.It may not be earthed and is isolated from earth and protective earth conductors
- B.It must be solidly earthed at the power supply
- C.It must be connected to the protective earth of the mains
- D.It must be earthed only in wet rooms
4. KNX Installation· selv-and-insulation· Medium
▸
Correct answer
A — It may not be earthed and is isolated from earth and protective earth conductors
Learning tip
Correct: SELV must not be earthed and stays isolated from earth and PE conductors.
Source: KNX Basic Course Documentation — 1.1 — p. 97
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Q55
May a cable intended for mains installation be used to wire the KNX TP network?
- A.Yes, any cable rated for 230 V is suitable for the bus
- B.No, cables intended for mains networks may not be used for TP networks
- C.Yes, provided the cable is green
- D.Yes, but only in dry rooms
4. KNX Installation· selv-and-insulation· Easy
▸
Correct answer
B — No, cables intended for mains networks may not be used for TP networks
Learning tip
Correct: The documentation prohibits reusing mains cable for TP installation.
Source: KNX Basic Course Documentation — 1.1 — p. 97
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Q56
What generates the SELV voltage for the KNX TP bus?
- A.A direct tap off one mains phase
- B.The earthing system of the building
- C.A power supply with secure mains separation
- D.A battery inside each bus device
4. KNX Installation· selv-and-insulation· Medium
▸
Correct answer
C — A power supply with secure mains separation
Learning tip
Correct: The documentation states a power supply with secure mains separation generates the SELV voltage.
Source: KNX Basic Course Documentation — 1.1 — p. 97
View the full question page →

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