Fourth pole on isolator

[bsr]

Hi, what's the fourth pole in this rotary isolator for?

Is it to give the option of a switched neutral on three phase? It already has an unswitched neutral block near the earth block.

Or could it be for some auxiliary control circuit for a machine?

PS yes I know the insulation is knackered on the black. First time I've opened the switch, I will repair with some tape.

Thanks

 

[EFLImpudence]

The 4th pole would be for the Neutral if used with 3 Phase and Neutral.

It's just a 4 pole switch though and the four switches could be used for whatever you wanted.

 

[Risteard]

The 4th pole would be for the Neutral if used with 3 Phase and Neutral.

It's just a 4 pole switch though and the four switches could be used for whatever you wanted.

The neutral pole is early make/late break. It is for the neutral - not any random purpose.

 

[JohnW2]

The neutral pole is early make/late break. It is for the neutral - not any random purpose.

It could be used for a 'random purpose' if that purpose was adequately served by its making/breaking behaviour.

 

[bsr]

Would you say that symbol is make early / break late then? To me it looks like a normal switch:


Whereas a make early / break late looks like this:

 

[JohnW2]

Would you say that symbol is make early / break late then? To me it looks like a normal switch:
View attachment 284060
Whereas a make early / break late looks like this: .....

To be honest, the symbol on the illustrated isolator is not one with which I'm familiar,so I would probably have to ask Mr Google for advice/education ...

Kind Regards, John

 

[JohnW2]

It could be used for a 'random purpose' if that purpose was adequately served by its making/breaking behaviour.

I could have added that I have, in my time, used a 4-pole isolator for switching the L & N of two different single-phase circuits - in which case at least one of the neutrals is then obviously switched by something 'intended' (certainly labelled) as 'phase'.

 

[Why Not Indeed]

Google says it's a "disconnector". It also suggests it's a game of hangman in progress.

 

[JohnW2]

Google says it's a "disconnector". It also suggests it's a game of hangman in progress.

If you're talking about the symbol, then thanks for sparing me the need to ask Mr Google myself. However, I'm not sure it really helps me - what exactly is a "disconnector" which distinguishes it from any other sort of switch?

Kind Regards, John

 

[333rocky333]

When I looked on kraus and muller website they do 3 pole and N as well as 4 pole ones, the dedicated N ones are marked N
In my view,
The one pictured is designed for a 3 phase machine and to isolate a single phase control circuit, the Neutral is connected to the solid link and therefore not isolated.
I personally always use the 3 pole and switched N ones.
Using a 4 pole as pictured could possibly cause 415 across any internal 240 volt equipment, if only for a fraction of a second

 

[JohnW2]

When I looked on kraus and muller website they do 3 pole and N as well as 4 pole ones, the dedicated N ones are marked N

OK

In my view, .... The one pictured is designed for a 3 phase machine and to isolate a single phase control circuit, the Neutral is connected to the solid link and therefore not isolated. ....

When you say "the one pictured", do you mean the one in the OP. If so, if you're right that the N terminals are a solid link, then what on earth is that symbol on it (which definitely looks like some sort of switch)?

I personally always use the 3 pole and switched N ones. Using a 4 pole as pictured ...

The terminology is starting to confuse me! Are you saying that a "4-pole switch/isolator does not switch/isolate one of the four poles?

could possibly cause 415 across any internal 240 volt equipment, if only for a fraction of a second

Can you explain the thinking behind that?

Kind Regards, John

 

[Risteard]

OK

When you say "the one pictured", do you mean the one in the OP. If so, if you're right that the N terminals are a solid link, then what on earth is that symbol on it (which definitely looks like some sort of switch)?

The terminology is starting to confuse me! Are you saying that a "4-pole switch/isolator does not switch/isolate one of the four poles?

Can you explain the thinking behind that?

Kind Regards, John

A four pole will open & close all four poles, but without early make/late break. This can cause voltages approaching 400V to appear on equipment. Basically if the neutral is lost then you could potentially have a fireworks display.

 

[333rocky333]

Don't know what the symbol is tried years ago, as you say it is a switch, but I'm sure it's meant for a control circuit.
The solid N link on the Ops one is to the left side of the poles it's just a flat bit of metal same as the earth.
The ones I buy don't have that symbol, and are Marked N with a different symbol.
I think the op's one evolved from old days when you linked 1 phase to the 4th pole when feeding a contacter, so then you isolated the 3 phase and the single phase control circuit, to work safely on the contactor or whatever.
As for the 415 I mention, we do fryers with 3 x 240 v elements and 240v electronic controls,, when all 4 poles try to switch together, I feel if the 4th pole in the isolater shown was a bit slow and used as N, loss of neutral can cause two phases to oppose each other via the elements causing up to maybe 415 volt between phase and N
Though isolaters when I was taught were not designed to use as switches, to switch under load.
All irrelevent to the OP really as he is switching Single phase.

 

[RandomGrinch]

I would probably have to ask Mr Google for advice/education ...

Mr Google got me here (which seems an interesting resource):

Switch Disconnector 3P | Single Line Symbols

Switch Disconnector 3P - Single Line Symbols

symbols.radicasoftware.com

- a 3P switch disconnector.

...and with the aid of Mr. Wiki:

Disconnector - Wikipedia

en.m.wikipedia.org

I would suggest that the symbol refers to the entire isloator and not just the neutral switching.
The switch is also for off-load isolation of the appliance, with normal operation and shutdown switching, provided elsewhere (which would also make early make/late break on the neutral unnecessary?)

 

[Why Not Indeed]

what exactly is a "disconnector" which distinguishes it from any other sort of switch?

What RandomGrinch says - not intended for use under load.