Wiring NVR Switch

[James BerrymanParticipant @jamesberryman81033]

Hi All,

I am replacing the switch on an old Fobco bench drill and have bought the following switch:

http://www.axminster.co.uk/kedu-nvr-switch-230v-1ph-e-stop-200093

The wiring for the live and neutral appears straight forward, but Im less clear on what to do with the earth. There doesn't appear to be any points to link the the earth from the mains and from the motor. The diagram provided shows them connected, but Im not sire where.

The found the below diagram for a similar switch:

https://d27ewrs9ow50op.cloudfront.net/manuals/h8240_m.pdf

Again showing the earth linked, but no details on where.

Currently the switch is straight forward three wires in and out.

Any help would be greatly appreciated

Thanks, James

[James BerrymanParticipant @jamesberryman81033]

[Ian ParkinParticipant @ianparkin39383]

Just add an earth point on the machine  body and connect to the earth wire from the plug and link the earth to the wire going to the motor and also a wire from body to the motor frame as well if its a resiliant mount

That switch you have bought does not need an earth connection anywhere ( to the switch mech )

Edited By Ian Parkin on 30/12/2016 12:35:46

Edited By Ian Parkin on 30/12/2016 12:37:44

[Les Jones 1Participant @lesjones1]

Hi James,
I would only expect 3 wires in and three wires out. The link to the technical data page from your first link shows shows the incoming earth linked to the earth in the cable which goes to the motor. The terminal used for this link will also connect to the NVR box if it is metal. If it is not metal then you could also link the earth to the machine metalwork. You may be able to do this via one of the fixing screws for the NVR box.

Les.

[James BerrymanParticipant @jamesberryman81033]

Thanks all for the reponses, seems pretty straight forward.

That said on removing the original switch from within the body (aide from being slight gummed up with grease…and so I took it apart and cleaned) it appears to be functional, but the old cables coming into it have four wires, red, blue and white with the green linked to the drill case?

I wanted to to give it a try with the motor and see if ts any good and why it had been replaced by an external switch but the external switch only has the standard three cables coming in/out – not the white.

The original switch has 240v 16a written on it so I assume it should be suitible for single phase? I did read somewhere that the switches used for three phase machines (motors) could be used for 240v. Thats Said Im a little stumped by the extra wire.

It would be nice to get the original switch going again.

Thanks

James

[James BerrymanParticipant @jamesberryman81033]

I meant to add I dont think the motor is original and it could have been at this point that the switch was replaced/changes to an external one for simplicity, the new motor is 230v.

[Les Jones 1Participant @lesjones1]

Hi James,
It could be that the drill was wired with 4 core cable (Which would be required for three phase.) so that either a single or three phase motor could be used. If it has a single phase motor then one core will be unused. I have no idea what the original switch was like on your drill. I don't know how you have confirmed that is functional with your limited electrical knowledge. If it is not an NVR switch it may have been replaced to meet safety regulations.

Les.

Edited By Les Jones 1 on 01/01/2017 08:18:00

Edited By Les Jones 1 on 01/01/2017 08:27:08

[James BerrymanParticipant @jamesberryman81033]

Thanks Les,

I thought some pics would help:

Original switch

Replacement switch (which I was going to replace with a NVR switch

Could the original switch be used, despite only having three wires now?

Thanks

[AjohnwParticipant @ajohnw51620]

You just need a piece of barrier strip with a rating that is suitable for the motor. Use one way to link the earths.

The small size is aimed at lighting – 5amp. The larger one power which I think is 25amp. There may also be a middle sized one. You'll probably find them in DIY stores. Screwifix and Toolstation are bound to stock them also electricians suppliers. RS, Ebay etc.

They are shrouded so can just dangle about. If you want to fix in place break off 2 and fix with a screw.

Interesting problem. If that box had anything to do with general electrical wiring in houses, factories or what ever it's illegal to not provide an earth terminal.

John

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[Ian ParkinParticipant @ianparkin39383]

Both of your switches pictured above (old and replacement) are designed for 3 phase use so disregard the colours used.

Is ok to just use 2 of the connections for live and neutral but you Must have a permanent continuity for the earth from the plug to the machine body and any load connected ( motor ,light etc). I.e. Don't switch the earth connection

[James BerrymanParticipant @jamesberryman81033]

Thanks for the replies!

With the original switch (you might be able to make this out in the picture) the ear terminals are joined into a a single wire ring terminal which is bolted to the machine body with the the bolts that hold the switch in.

I could easily replicate this with the earth wires if I were to wire in the old switch. Can you just leave out the white wire.

Or more fundamentally, should I give up on the old switch and go back to the original idea of fitting the NVR switch? Is this advisible from a safety perspective?

[AjohnwParticipant @ajohnw51620]

You should fit an NVR switch. The main idea is to prevent some one switching on being unaware that the machine will start. That might include you.

My answer to that in the past when there could have been prying fingers about was to put a main switch well out of reach but I could always have forgot to switch things off. Actually if some one has that problem, kids really I'm not convinced that the usual position for a combined NVR and stop button is ideal. What that does is prevents an operator from having a surprise when a switch some where else is used 'cause they forgot to turn the machine off.

The NVR also takes care of when the mains fails – it does at times.

I don't see your problem really. Just go get some barrier strip. As some one mentioned don't have a switch on the earth leads.

John

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[Les Jones 1Participant @lesjones1]

You would be better off using the NVR switch for safety reasons. I suspect that the original rotary switch was replaced by the other 3 pole switch because it was faulty. If it is a 3 position switch (Forward off reverse) then it may have been replaced to prevent it being used in reverse. If at least 2 of the 3 contact sets test OK (Resistance less than an ohm when the switch is on and greater than 20 Meg ohms when in the off position) then it could be used.

Edit. I should have also said that the insulation resistance between the contact sets should be at least 20 Meg ohms.

Les.

Edited By Les Jones 1 on 01/01/2017 11:49:54

[AjohnwParticipant @ajohnw51620]

Some links for you.

**LINK**

**LINK**

And probably the right size for you and a far more sensible price.

**LINK**

Some call it connector strip. Others chocolate blocks but that tends to be electronics people.

John

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[Bodgit Fixit and RunParticipant @bodgitfixitandrun]

I would use a 30 amp strip in order to protect the wiring. A Domestic power ring is usually protected by a 30 amp breaker so your wiring needs to be at least this rating in order not to melt before it can trip. Yes there should be a smaller fuse in the plug but you would be amazed at what some people try to get away with.

[AjohnwParticipant @ajohnw51620]

He appears to be using a mains lead not a ring main so a 16amp one would be fine. Even at that size the bare wire ends may need doubling over to get a nice fit.

The only problem with using them really is making sure that the wire is under the screw.

If it came to a race between a 5amp one and a ring main fuse I'd back the barrier strip and wire used against the ring main fuse.

John

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Edited By Ajohnw on 01/01/2017 15:37:58

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ajohnw on 01/01/2017 15:36:46:

… the bare wire ends may need doubling over to get a nice fit.

The only problem with using them really is making sure that the wire is under the screw.

.

Alternatively; the better quality strips have leaf-spring blades …

MichaelG.

[AjohnwParticipant @ajohnw51620]

I'd probably use a 5amp one due to the wire size. Daren't say that on here.

I suspect the actual physical sizes come from how many cable ends an electrician can stuff down each hole not the actual current rating.

John

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