NVR Switch - What is this terminal?

diyer56 · 20 Oct 2014

Hi,

I recently purchased a no voltage release switch to operate a small lathe. There is a wiring diagram on the side of the casing and I am wondering if someone can help me by explaining what the terminal marked "A1" is for please?

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I intend to connect the line/neutral feeds to 13 and 23 retrospectively. I will then connect the line/neutral lathe supply to 14 and 24. Terminal A1 is smaller in size and is connected to 14 via a symbol marked "U<". Is this for a signal wire or maybe a indicator light?

Thanks in advance for your help.

greasedmonkey · 20 Oct 2014

Possibly the electromagnet to hold the switch on.

I think if you don't connect a1 to 24, you will need to hold the switch for it to operate.

bernardgreen · 20 Oct 2014

There are two possibilities.

Most likely it is the supply for the coil ( the U< ) that holds the contacts closed when the green button is pressed and released. If it is then it needs to be connected to the 23 terminal. This will energise the coil when contact 13~14 is closed by pressing the green button and the energised coil holds the contac closed after the green button is pressed. Having a separate terminal for the coil means an external OFF switch can be wired as a normally closed switch between A1 and 23. If the supply fails the coil de-energises and the switch releases to be OFF

Possible but un-likely it is a release coil and connecting A1 to 23 will energise the coil if the switch is ON and the energised coil unlatches the switch.

diyer56 · 20 Oct 2014

Thanks for your replies greasedmonkey/bernard.

I also found this while searching:

http://www.instructables.com/community/Need-help-with-wiring-a-KJD17-switch-for-homemade-/

So when the supply to the coil is released this releases the switch - and therefore the "no voltage release".

Does it matter if it is connected to the neutral before or after the switch (23 or 24)? I presume not as the coil just wants to ensure the power is not interrupted.

bernardgreen · 20 Oct 2014

Connecting A1 to 24 ( output ) is the better option as it leaves the coil and motor completely isolated when the switch is open ( OFF )

diyer56 · 20 Oct 2014

Makes perfect sense.

Thanks again both.

davelx · 21 Oct 2014

bernardgreen said:
Connecting A1 to 24 ( output ) is the better option as it leaves the coil and motor completely isolated when the switch is open ( OFF )

I think the reason that a separate terminal is provided is so that you can make that connection via a series of NC emergency stop buttons located at suitable places in the workshop.

Rowan S-Bradley · 15 Aug 2020

The next question is HOW best to connect A1 to 24. I have a crimp that will fit the terminal A1, but crimping two wires into the terminal that attaches to 24 seems a very inelegant solution. It seems to me that the designers of this switch did not think very carefully about how it would be wired. Does anyone have a better solution for this wiring?

Thanks - Rowan

333rocky333 · 15 Aug 2020

Sureitsoff? · 16 Aug 2020

might just be me, but those piggyback connectors always look like a bodge to me

Simon35 · 16 Aug 2020

Rowan S-Bradley said:
The next question is HOW best to connect A1 to 24. I have a crimp that will fit the terminal A1, but crimping two wires into the terminal that attaches to 24 seems a very inelegant solution. It seems to me that the designers of this switch did not think very carefully about how it would be wired. Does anyone have a better solution for this wiring?

Thanks - Rowan

You've resurrected a 6 year old thread....

If anyone is using the information in this thread, please ignore the uninformed and dangerous advice about connecting estops in series to the release coil. That isnt what its function is, and it cannot carry out that function reliably.

SUNRAY · 16 Aug 2020

Simon35 said:
You've resurrected a 6 year old thread....

If anyone is using the information in this thread, please ignore the uninformed and dangerous advice about connecting estops in series to the release coil. That isnt what its function is, and it cannot carry out that function reliably.

What makes it dangerous? or unreliable?
I don't know that exact product but in principle that's what has been done for years.

How should this device connected?

Simon35 · 17 Aug 2020

SUNRAY said:
What makes it dangerous? or unreliable?
I don't know that exact product but in principle that's what has been done for years.

How should this device connected?

If you were carrying out the required design and calculations for the functional safety of this woodworking machine, in order to meet your obligations under the Machinery Directive or PUWER, how would this device meet those requirements? I've had a look at the data sheet, no reliability data, no mention of any European harmonised standards.

yacompo · 22 Aug 2020

I have been struggling for a couple weeks now with a table saw refurbishment i've been working on, after much googling and replacing the wrong spare parts I have realised that the replacement switch I have ordered had the dreaded A1 terminal whereas the original did not. I desperately want to wire this thing up and get it working.

@Simon35 / anyone who knows, what is the best way to wire the switch up?

Black5f · 6 May 2021

Hi. There is no point wiring an Estop to do the same thing as the red off button which is internally wired between A1 and the coil. The EStop should completely cut off the mains supply to the KJD17 and not allow a restart until it is reset. In the above diagram even if the estop is triggered, the green button will still operate the machine while pressed (a kind of jog mode). KJD17's fail, springs break, contacts weld, this method of Estop will not stop the machine in event of a switch failure. A1 is provided for interlock switches, like guards, machine compartment doors, even "off" foot switches etc. If there are none of these, connect it to pin 24 and it becomes a 4 pin switch. But please fit a proper EStop which actually renders the machine and KJD17 dead, ideally between 13 and the mains, preferably 23 and L as well. Sorry, new here, but this is dangerous. Thanks. Tom

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NVR Switch - What is this terminal?

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