Cooker circuit.

[holmslaw]

..

 

[DP]

That is why I am using a switch. Swich operates the contactor.

In fact the contactor will have bigger clearance between contacts when off compared to a manual switch.

Not only that, I have seen manual 45amp switches fail (on cooker and shower circuits) because of poor conductance. Contacts on a contactor are self cleaning resulting in enhanced operation. If a contactor could not be utilised, I can see a lot of equipment I service ending up in a deep well.

Last week I was working on an electrical boiler where the timer operated two contactors to give stepped operation. The main switch on that equipment only switches a small current (through the timer) but heavy load was carried by the contactor. Isolation also provided by the same mains switch. Cannot see that mains switch carrying 5amps let alone 45.

 

[holmslaw]

..

 

[ban-all-sheds]

A contactor is an automatic device, because when a voltage is applied to the coil it starts an automatic process. Voltage flows in the coil, the coil then causes a magnetic field to develop in the plunger, the plunger moves, compressing a spring, and the contacts close. A five stage automatic process, if any part of that process fails the contactor will not close.

A switch is an automatic device, because when a force is applied to the operating lever it starts an automatic process.

To quote you extract, a contactor has the "the capability of starting, operating, moving, etc., independently"

Independently of the operator initiating the closing of the switch in the supply to the contactor coil?

A manual switch (designed in accordance with the BS) has a lever that is directly mechanically connected to the switch contacts. If you move the lever you move the contacts.

I think you'll find that most (and by the time you get to high current ones, all) manual switches have a mechanism where the switch contacts are opened and closed at speed by springs. Once the lever or pull cord etc is moved beyond a certain point the contacts automatically move to the fully closed or fully open position.

A contactor can be used as a means of emergency isolation, but it cannot be used as a form of isolation in accordance with 640.

I don't think you'll get many takers for that.

 

[ban-all-sheds]

DP, Ive clearly explained why your proposal does not comply with the regs.

No you haven't.

You are creating a potentially and needlessly dangerous situation.

No he isn't.

 

[holmslaw]

..

 

[mdbalson]

Holmslaw, of late you are being a pendent, arguementative, s*d, who thinks that everyone but yourself is wrong when in fact it is you who is often wrong

 

[ban-all-sheds]

BAS you are talking nonsense.

I'm sorry you are unable to understand my words.

I'll try and think of a way to explain it more simply.

 

[holmslaw]

..

 

[holmslaw]

..

 

[ban-all-sheds]

EG, This post is solely about isolation of a cooker. Ive stated the reg that refers, Ive explained why a contactor is not suitable

But your explanation is not a fact.

Your explanation explains why your interpretation of the regulation means that a contactor does not comply.

which is followed up by BAS's copy and pasting but not actually addressing any of the issues raised.

I did address them.

You said that a contactor wasn't suitable because it operated automatically, unlike a mechanical switch.

I pointed out that firstly your description of the "automatic" process can also be said to apply to a manual switch because once enough force is applied to the actuating mechanism events then proceed automatically, just like they do when enough force has been applied to the switch in the contactor coil circuit.

Secondly I pointed out that a contactor would not act independently of the person operating the switch in the coil circuit.

I believe that your interpretation of 460-01-01 is incorrect, and that a contactor does provide a non-automatic means of isolation ans switching.

But if you are going to pretend that nothing I said in my posts addresses the issues you raised, and are just going to say that I'm talking nonsense then we will indeed have a mindless argument here.

But I won't be the one responsible for the lack of presence of a mind...

 

[bonebill]

Spose you could if you really want.

You would need a low current supply for the control circuit though.

Would an MK 1 gang 45A DP switch not be just as neat, and a lot less fuss?

A fine suggestion, and I for one wish that MK Electric made such a thing.

But according to the MK on-line catalogues, and every electrical reseller I have checked for such a thing, the largest current rating they do in a 1-gang switch is 32A.

As far as I can tell the product depicted is a K5105, a 32A DP switch.

 

[DP]

Holmslaw, Can you explain why an electrical boiler would utilise contactors for passage of heavy current under control of a low current carrying switch (timer or an on/ off switch), if what you say is dangerous

 

[Spark123]

For a 45A flavour you will need the bigger one:
http://www.tlc-direct.co.uk/Products/MKK5215.html

FWIW, I don't believe a contactor is suitable for use as an isolator too, it isn't really a secureable device. Probably me looking at it from a EAWR pov.
Are those 45A ones securable? Or I suppose if they are under the control of the person working on the piece of kit they may be OK.
FWIW, we do not rely on contactors when working on motors. If we are isolating to stop a function from happening we may just turn off and lock the isolator, if we are working on the motor itself we will remove the supply fuses as well as turning off the isolator.

 

[holmslaw]

..