Three phase sockets, isolators, interlocks

[wills-mill]

Evening all. I'm looking into supplies and costs for wiring up a new three phase system.

Previously setup had wall mounted isolators, followed by a separate wall mounted socket that the machines plugged into.

Looking around, there are units available which comprise a box fitted with a socket and 'interlock' (lots of them made by Gewiss which seem remarkably cheap).

Is anyone able to tell me whether these fulfil the function of an isolator and the requirements regarding legislation, I am confused by the different terms.

Thanks, W

 

[RobinBHM]

I dont know the answer, but they look like a neat solution.

 

[Chrispy]

Are you sure that that's three phase? If so then it hasn't got an earth as far as I can see.
Also some new machines need a neutral wire as well so in which case you need a plug/socket with five pins in all.

 

[wizard]

That is NOT 3 phase it should have 4 or 5 prongs

 

[n0legs]

They provide isolation for the socket outlet that is attached.
Isolation of a piece of equipment plugged into said socket will be achieved by operation of the switch, isolation of a piece of equipment plugged into the socket could ( I say should ) be further enhanced by unplugging the equipment.
The issue is connecting plugs and sockets whilst under load conditions, therefore an isolator is required.

The one pictured is a 2 phase and earth socket, used for a piece of equipment that only requires 380+ volts not full 3 phase.

For a new installation I would go for a 5 wire installation, 3 phase+N+E. All sockets would be 5 pin, if a piece of equipment doesn't need the earth or neutral then you have lost nothing whereas the other way round could be a pain and lead to bodging.

 

[Myfordman]

That looks like a photoshopped image. Could be correct in yellow or blue but not in red.

A supplier that can put up that picture possible has little idea about what they are selling. I would not necessarily trust any reply they might give to technical questions.

look for BS 4343:1968 or IEC 60309 with either 4 pins or preferably 5 pins and integrated isolator at the correct current rating for your application and proposed wiring gauge.

 

[n0legs]

That looks like a photoshopped image. Could be correct in yellow or blue but not in red.

A supplier that can put up that picture possible has little idea about what they are selling. I would not necessarily trust any reply they might give to technical questions.

.

As said it's a 2Ph+E socket, they are available and have been for a long time.
Check here:-http://www.csedistributors.com/acatalog/Gewiss-Sockets.html
First one of the third row down.

 

[wills-mill]

Apologies, it was quite late, so I grabbed an image of the first red one I saw.

I will be using 5 pin/ 3 phase N + E plugs and sockets, I've seen people get caught out only using 4 pins and no neutral. I'm really happy to over spec cabling as you never know how hungry the next machine may be....

Even looking at MK Commando interlocked sockets (which are approaching £100) I wonder whether there aren't savings when you look at sparky time?

 

[Bradshaw Joinery]

Ive just bought 14 of these from city electrical, about £25 each iirc, no problem buying four pin, if you get a 5 pin machine just run a new wire from the board and change the box? The if of potentially owning a five pin machine when you have all four pin plugs etc already is more of a cost than changing it when necessary, so dont get too caught up on overspeccing.

Safer than a seperate isolator/plug as you cannot acces the socket with it turned on....

 

[DennisCA]

None of my 3-phase machines use the neutral because the combination of the 3 phases = 0. They all do use earth however.

 

[n0legs]

On a properly balanced 3 phase load no neutral is required, however as some equipment/machinery is fitted out with single phase accessories such digital readouts, work/task lighting etc, a neutral connection is needed.
Wiring up to provide 3 phases, neutral and earth is good practice. Granted slightly more expensive but not so much as to cause serious out of pocket problems .
My old instructor would say " do it right, do it once ".

 

[DennisCA]

I do use the cables and connectors that have all of them included, the neutral is just not hooked up, unless needed. For the machinery I use there is nowhere for the neutral to be hooked up, it's just simple motors with a breaker switch.

 

[n0legs]

I do use the cables and connectors that have all of them included, the neutral is just not hooked up, unless needed. For the machinery I use there is nowhere for the neutral to be hooked up, it's just simple motors with a breaker switch.

Then you have done right.
If the manufacturer of the machine, in it's standard form without any additions/modifications, does not deem it necessary for a neutral connection then there is no more you can do.

I suppose my attitude is swayed somewhat by the amount of things (see bodges) I have come across over the years. My opinion is that if you offer all that someone could need now or in the future, then the likelihood of someone "modifying" (see bodge once again) a piece of equipment is reduced.
Many people, and again this is in my own opinion, are just happy something works as they expect it to do. They often have little concern for if it working safely.

I'll give you an example.
Someone with a little knowledge in a local upvc window factory decided he could connect a new 3 phase machine to try it out.
Three 3 core flexes were wired to three 3 pin plugs. The three flex/plug combinations were wired into the 3 phase terminations of the machine. His intention was to plug each plug into different sockets in the factory as he knew the sockets around the building were wired to different phases (the initial purpose of which was for load balancing). Apparently he was stopped before he got to plugging it in.
Someone dodged a bullet that day that's for sure.

 

[mindthatwhatouch]

PM sent

 

[furnman]

Hi William, unless you are going to move machines around as I think you are not there does not seem much point in using these plug & sockets. In my workshop I have just used "mem" isolater boxes hard wired into the machines with armoured cable. You can pick up the isolater switches on ebay second hand for about £25 each and are all metal, rolls royce quality and will stand up to a pounding. as mentioned above it is unlikly that you will need a neutral .