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#144946 - 02/05/06 07:10 AM D.O.L. Remote Stop  
Uppeydog  Offline
Member
Joined: Jul 2004
Posts: 68
Loch Lomond
3 Phase & Neutral Supply, 3phase Motor.

240v Contactor Coil.

I've only ever connected a Remote Stop between the unit's Stop & the Overload.

Is there a ruling on this. Because I've come across a couple of Motors with the Remote Stops on the Neutral Side of the circuit.

Cheers!


All I Wanted Was A Cup Of Tea!!

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#144947 - 02/06/06 01:14 AM Re: D.O.L. Remote Stop  
renosteinke  Offline
Cat Servant
Member
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
I have not the slightest clue as to your local rules....but would not switching the neutral be in vain, should there be a short between the motor and the switch? A short there would result in a motor you couldn't turn off.


#144948 - 02/06/06 02:04 PM Re: D.O.L. Remote Stop  
Uppeydog  Offline
Member
Joined: Jul 2004
Posts: 68
Loch Lomond
Quite Right renosteinke, unless you hit the Stop on the DOL box itself.

Plus if the overload was siezed in the closed position as well as the short to Earth after the coil & someone was jammed in the machine, the remotes would do nothing.

Thats why I want to know if there is a regulation I can state to my workshop manager, because his attitude is,"They wired it up, so put it back the same way as they had it!" If there is no regulation. I'm going to have to go to the Director & tell him to Phone the Factory concerned to tell their Electrical Foreman my concerns.

Thanks Reno. Another shouting match Tomorrow, I'll let you know the outcome.

As I mentioned if anyone knows of a site I can copy a written regulation from; it'll save a big barny & possibly someones life!

Thanks.


All I Wanted Was A Cup Of Tea!!

#144949 - 02/07/06 09:09 AM Re: D.O.L. Remote Stop  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Couldn't you argue on the general rule about single-pole switching in a circuit with one earthed conductor (neutral) having to be in the live side?

The concerns over an earth fault preventing the contactor from releasing are noted here:
http://www.tlc-direct.co.uk/Book/3.2.2.htm



[This message has been edited by pauluk (edited 02-07-2006).]


#144950 - 02/07/06 01:25 PM Re: D.O.L. Remote Stop  
Uppeydog  Offline
Member
Joined: Jul 2004
Posts: 68
Loch Lomond
Thanks Paul,
I went in this morning,the machine in question had gone, so I went into the office & asked if he had notified the customer that I had noticed their wiring wasn't right for the remote Stops. I was expecting an explosion of abuse, but he mumbled something & said that, he was just about to ring them...(aye Rite!!) So I stood there & the manager the other end said,"no problem I'll checkit out right away as we are just about to reinstall it"

No shouting... but a strange silence all day....Looks like I've lost my weekend OT!!


All I Wanted Was A Cup Of Tea!!

#144951 - 02/07/06 01:42 PM Re: D.O.L. Remote Stop  
PaulCornwall  Offline
Member
Joined: Jun 2003
Posts: 112
England
Can you change the coil to a 415v coil??

wouldnt switch the neutral..


#144952 - 02/07/06 06:29 PM Re: D.O.L. Remote Stop  
Uppeydog  Offline
Member
Joined: Jul 2004
Posts: 68
Loch Lomond
Aye that would work, but even on 415V I've only ever added a remote stop in series with the fixed stop & O/L.
The Mach. came in, was over-hauled, wiring tidied (conduit etc). Thisis where I noticed the240V set up, with the remotes. But I was told not touch it as the other company's sparkies had wired it that way.
If we would have built it, it would be ok to do it right. But in this case I suppose the Gaffer's attitude was "They're not paying us to do that!"... At least I've got him to notify them to correct it!


All I Wanted Was A Cup Of Tea!!

#144953 - 02/10/06 03:15 AM Re: D.O.L. Remote Stop  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,223
SI,New Zealand
Let's look for a second at what a E-stop or Stop switch is in a circuit.
All the contact does is opens the energising circuit of the Main Contactor.
IE: It drops out the coil, which releases the hold-in contact and de-energises the circuit.
Any Remote Stop will be in Series with the original and as long as things like Voltage Drop are taken into account, you should be OK.
The Neutral really doesn't come into it.


#144954 - 02/10/06 05:24 AM Re: D.O.L. Remote Stop  
kiwi  Offline
Member
Joined: Dec 2004
Posts: 354
christchurch new zealand
Uppeydog I've seen D.O.L.s that switch the neutral too ! Remote stops should always be wired in series with the overload and emergency stops should always be wired in series with the main contactor coil so as to cut power and control voltage in the system.


#144955 - 02/10/06 09:28 AM Re: D.O.L. Remote Stop  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Quote
The Neutral really doesn't come into it.


The potential is there for a ground fault to render the emergency stop non-functional though.

Assume the control wiring is as follows:

Phase -> Start -> Overload -> Local stop -> Coil -> Emergency stop -> Neutral.

Now imagine a ground fault develops on the line between the coil and the E-stop switch. You would never notice it until you came to use the E-stop, because the local stop would still function just fine.
Of course, you could say that putting the E-stop on the "hot" side of the coil also leaves room for a short to phase to do the same thing, but I would have thought that a ground fault would be the more likely.


[This message has been edited by pauluk (edited 02-10-2006).]


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