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FAQ Pizzato

In this section you can find answers to the most frequently asked questions.

Contact our experts for more information. 

Which switches, and how many of them, do I need to install on my machine to comply with regulations?
The risk category of a machine is determined by the manufacturer based on several criteria: the severity of potential accidents (death, serious injury, abrasion, etc.), the likelihood of people being in the danger area (rare, frequent or permanent), the possibility of preventing the accident (machinery with slow movements allowing the operator to avoid danger, etc.). Consult the General Catalogue and standard EN1050.
Once the risk category has been determined, the manufacturer must design a safety circuit suitable for said category. Based on the category, this may include a single switch, two switches, or two switches connected to a safety control unit.
Is it true that safety switches must be red?
The regulations do not specify the colour of safety switches. Some manufacturers use red to distinguish them from other products, but they could choose any colour.
What is the MTTFD of a safety switch?
For electromechanical devices, it doesn’t make sense to talk about the MTTFD without knowing how frequently the device itself is used. While it can be assumed that electronic devices will experience linear deterioration with the passing of time, this is not true for electromechanical devices. To calculate the MTTFD, another parameter is needed: B10d, which indicates the number of operating cycles within which 10% of the samples tested experience dangerous failure. These two parameters are connected by the formula MTTFD=B10d/0.1*nop, where nop is the number of expected operations in one year.
What Performance Level (PL) can I achieve with a safety switch?
The PL of a safety circuit depends on the architecture of the circuit, the reliability of the devices in it and other parameters. Therefore, it doesn’t make sense to ask whether a safety switch is suitable, for example, for a PL e circuit, as the maximum PL that can be achieved depends not only on the device but on a series of other parameters. These include the circuit architecture, diagnostics coverage, causes of common fault, frequency of use etc. Essentially, a safety switch can be used in circuits up to PL e, but achievement of this PL depends on other parameters.
To calculate the Performance Level (PL) of a safety circuit, which parameters do I need to know and where can I find this information?
Four parameters are required:
  • safety category of the circuit (you need to know the architecture of the circuit, i.e. whether it is a single-channel circuit, a single-channel circuit with cycle testing or a dual-channel circuit)
  • the MTTFD of the various devices used (this parameter indicates device reliability)
  • diagnostic coverage (DC, this parameter indicates the system’s ability to self-detect any possible internal failures)
  • common cause failure (CCF - applies only to category 2, 3 and 4 circuits and analyses all common cause failures that can compromise system redundancy).
What is a switch with positive opening action?

Switches with positive opening action don’t have an elastic linkage between the moving contacts and the actuator to which the actuating force is applied. All positive-opening switches carry the positive-opening symbol on the cover. A switch with spring rod, for example, cannot have positive-opening contacts. If only one switch is used in a safety application, the switch must be actuated in positive mode.

For safety applications, the opening contact (normally closed) must be with “positive opening”: All switches with the symbol are provided with NC contacts with positive opening. In case of two or more switches, they should operate in opposite modes, for example:

  • the first with an NC contact (normally closed contact), actuated by the guard in positive mode;
  • The other with an NO contact (normally open contact), actuated by the guard in negative mode.

This is a common practice, though it does not exclude the possible use of two switches that are actuated in positive mode (see diversification).

What is a slow-action switch?
A slow-action switch has a contact carrier that moves at a rate proportional to the actuation speed (slow actuation means the contacts will separate slowly). These switches are suitable for applications requiring medium-to-low currents and rapid actuation movements (if actuation is too slow arcing may persist during opening).
What is a snap-action switch?

A snap-action switch has a contact carrier that moves independently from the actuation speed (even if actuation is slow, the contacts snap apart rapidly, producing a distinct “click”).
These switches are suitable for applications that involve high currents and/or slow actuation movements (the electric arc is interrupted by the snap action of the contact carrier).

I am looking for a switch that opens an NC contact when actuated to the right and a second NC contact when actuated to the left.
Pizzato Elettrica designs various types of switches with independent contacts, featuring B16 contact blocks and a swivelling-lever head. Those most frequently used are: FR1631, FR1654, FD1631, FP1635 etc.
Is it true that, since 2001, all limit switches have a metric thread for the cable gland?
No, that is not true. Standard EN50262 did come into force in 2001, establishing that all new designs must use equipment with metric threads. However,this did not affect the design of existing product ranges. Pizzato Elettrica continues to produce switches with PG threads and has also made versions with metric threads available.
Can I set up my swivel-lever switch so that the swivelling lever only operates if the lever is rotated to the right?
Yes, this is possible with all switches in series FD, FP, FL, FC, NA, NB, and NF, as they are equipped with a special plunger that can be used to make the switch unidirectional.
I need a switch for a safety application. Which switch should I use?

For the installation of switches with safety functions:

  • only use switches with positive-opening contacts,
  • connect the safety circuit to the normally closed contacts (11-22, 21-22, 31-32),
  • actuate the switch at least up to the positive-opening travel indicated in the travel diagrams,
  • install the switch so that the switch completes the positive-opening travel upon opening of the guard.
What is the differential travel of a contact block?

The differential travel is the difference (only for snap-action contact blocks) between the switching point on forward travel and the switching point on return travel. Essentially, the contact block does not snap at the same point. For example, for contact block B5, the forward operating travel distance is 2 mm, while on return travel it is 1 mm. The differential travel is therefore 1 mm.

N.B. for slow-action contact blocks, there is no differential travel.

Is it possible to replace the actuator of a position switch?
No, this is not possible. For safety reasons, we do not supply replacement actuators for position switches.
Is it possible to replace the actuator of a pre-wired switch (series NA, NB, and NF)?
Yes, pre-wired switches (series NA, NB, and NF) are modular switches for which the actuator, lever, actuator head, housing (including contact block within) and connector can be purchased separately.
How do you correctly adjust a rope safety switch?
In order to function correctly, rope switches must be correctly adjusted by tensioning the rope. This ensures that the rope is not cut or slack, guaranteeing correct functioning of the switch. All switches are provided with a green ring that shows the area of the correct tightening of the rope. The installer has only to tighten the rope until the black indicator will be in the middle of the green area. If the tension indicator is in the correct tension zone, the electrical safety contacts can be closed by pulling the blue reset knob into its armed position. Under the reset knob there is a second green indicator ring to check the status at a glance.
Why are the contacts of the rope safety switch that I purchased in the opposite state to that indicated?

First of all, it should be noted that the state of the contacts should be checked with the rope correctly tensioned and the reset knob in the armed position. The rope switch may be incorrectly adjusted or the rope may be slack or broken. We recommend checking the tensioning of the device rope following the instructions in the relevant section of the catalogue and operating manual (section 4.3 Rope installation) for rope safety switches.

Why am I unable to arm the reset device (where present)?

First of all, it should be noted that the state of the contacts should be checked with the rope correctly tensioned and the reset knob in the armed position. The rope switch may be incorrectly adjusted or the rope may be slack or broken. We recommend checking the tensioning of the device rope following the instructions in the relevant section of the catalogue and operating manual (section 4.3 Rope installation) for rope safety switches.

What are the maximum spans for rope safety switches?

The operating manual (and catalogue) contains examples of installation in paragraph 4.4 Installation examples. These include examples for switches with longitudinal and transversal heads, along with indication of the maximum spans and rope lengths for rope safety switches based on usage.
Paragraph 4.5 Rope tightening contains tables indicating how the maximum lengths recommended vary for different installations. These depend on the temperature fluctuations (temperature difference) it is expected that the switch will be exposed to in the work environment.

Do you supply interlocking devices with lock for ATEX environments?
The interlocking devices for ATEX environments we currently offer are electromechanical devices without actuator locking, and therefore without electromagnets.
How many devices can I connect to the P‑Connect connection gateway and how many guards can I control independently?
Up to six devices in total (interlocks, control device units, handles, etc.), including a maximum of two RFID safety switches, if managed independently. In addition, with a special configuration, it is possible to establish series connections with “Y” connectors, creating two independent sections (with two or three switches from series NG, NS, NX or ST). In this case, the unlocking command can independently control the two series of interlocks, but not a single device.
Can P-Connect gateways be connected in series?
Yes, these connection gateways have two connectors. One supplies power to the device and the other is used for the connection to the fieldbus network. This enables series connection of multiple P-Connect gateways simply by connecting the corresponding input and output connectors. For their correct identification, it is necessary to set a unique IP address, following the method described in the catalogue.
Which field buses/industrial communication protocols are supported by the different versions of the P‑Connect gateway?
Different versions of the P‑Connect gateway are available, each dedicated to a specific field bus. Safety information is exchanged via PROFIsafe, CIP Safety or Safety over EtherCAT extensions. It is not a multibus gateway that can be configured via software: the bus depends on the model.
Do P‑Connect and the BC series (passive distribution box) have the same function?
The main difference is that P‑Connect is an active safety device, while the BC series passive distribution box makes it possible to group the various input and output signals in a single box. P‑Connect integrates electronics, safety functions and field-bus communication (PROFINET/PROFIsafe, EtherNet IP/CIP Safety or EtherCAT/FSoE), making it possible to connect safety devices directly in the field and transmit safety and diagnostics signals to the safety PLC.
The BC series, on the other hand, does not perform any safety or communication function. It serves exclusively to make wiring quicker and better organised, distributing device signals to I/O modules or external safety relays.
I have connected the outputs of a PLC to the IS1 and IS2 inputs of the NS series switch, but it doesn’t work. Why not?
For the switch to work correctly, inputs IS1 and IS2 must be connected at a voltage of 24Vdc.
What is the procedure for reprogramming a new NS series actuator?

Via input I3 it is possible to replace the coded actuator with a second actuator at any time (refer to paragraph 5.6 Actuator replacement in the operating manual).

What are OSSD outputs?

OSSD (output signal switching device) outputs are solid-state commutation devices used in industrial safety circuits (photoelectric barriers, sensors and laser scanners).
They constantly monitor the signal, ensuring reliability, advanced diagnostics for short circuits and immediate blocking of the machine in the event of failure.
Redundancy: They typically operate in pairs (dual channel) for reciprocal monitoring of signal integrity.
Auto-test: They issue brief test impulses to detect short circuits to the supply voltage (+24Vdc) or to earth (0V).
Active safety: If a failure or interruption is detected (e.g. person crosses the barrier), the output changes immediately from ON (+24Vdc) to OFF (0V), stopping the machine.
Low voltage: Supplied with direct current (+24Vdc), they usually manage safety relays or controllers.

What is the difference between manual and monitored reset for series CS AR?

With manual reset, the module is activated on the rising edge of the reset signal. With monitored reset, activation is on the falling edge of the reset signal. In the case of monitored start, any sticking or breakage of the button in contact-closed state is detected. With monitored start, such a failure changes the start from manual to automatic.

How does the CS AT safety module function? And how does it differ from the CS FS safety module?
The modules in the CS AT series are single-function modules that can be used for emergency-stop purposes and end-position monitoring for movable guards with contacts delayed upon opening of the inputs.
In fact, CS AT modules manage single or dual-channel inputs, safety outputs with instantaneous contacts and safety outputs with contacts delayed upon de-energizing.
Essentially, they perform an “off delay” function. Opening of at least one of the input channels will trigger immediate deactivation of the instantaneous outputs and, after a fixed or settable delay, deactivation of the delayed contacts.
CS FS modules, on the other hand, are safety timer modules that enable timing of the safety output. The main difference between a CS AT module and a CS FS module is that the safety timers of the CS FS series are only equipped with delayed contacts (they do not have instantaneous contacts).
There are various types of CS FS timer modules:
  • With CS FS 1 and 2, the safety function is set up so that from the moment the supply voltage is applied to the module, a time delay is applied, after which the outputs, with switch-on delay contacts, are activated.
  • With CS FS 3, the safety function is set up so that from the moment the supply voltage is applied to the module, a time delay is applied, after which the contacts delayed on energization are deactivated.
  • With CS FS 5, the safety function is set up so that on opening of at least one of the input channels, a time delay is applied, after which the outputs, with switch-off delay contacts, are deactivated.
Can module CS ME be used on its own?
No, CS ME modules are contact expansion modules that must be connected to a safety base model.
Is it possible to order a configuration of the BN series that is not in the catalogue?
The catalog lists only a few BN versions; on the website, you can view all versions that have already been coded and are available. For new versions, a technical and commercial analysis must be conducted, and you should contact the technical support department.
Is it possible to replace a device in a BN series control device unit?
Yes, that is possible. The catalogue lists the part numbers of the individual devices available.
Is it possible to replace a contact block in a BN series control device unit?

No, that is not possible. The contacts on BN push-button panels are fitted directly onto the circuit board and therefore cannot be replaced by the customer.

Is it possible to use a 4-position selector switch with standard contacts?

No, that is not possible. The 4-position selector switch is only compatible with dedicated contacts mounted on a 3-slot mounting base (E2 1BAC1*). To avoid ordering errors, 4-position selector switches are not available as a separate device, but only as the E2 AC-DXBC**** assembly (selector switch + base + contacts).

Is it possible to use the joystick with a 3-contact mounting adapter?
No, this is not possible. Due to the arrangement of its cams, the joystick is only compatible with the 4-contact mounting adapter. This applies to 2-position and 4-position versions.
Is it possible to order a version of a connector that is not included in the catalogue?
Yes, it is possible to order connectors with different cable lengths, “L” connectors and different sheath coatings. Minimum order quantities apply (as stated in the catalogue).
Is it possible to order screw-cover seals for fixing safety devices and actuators?
In the event of loss of the seals supplied with the devices, it is possible to order seals with unique marking. This enables customers to use the seals and identify which have been used as spares in order to avoid bypass.

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