contactor arrangement..

[Mr T]

Evening all what do you think of the following set up...Its not something I had come across on any jobs thats I have completed so far...

single phase wylex board and a three phase wylex board..

3 phase from the electric meter to the top of the contactor and then from the bottom of the contactor to feed the three phase board..

6 amp breaker in the small wylex board marked up contactor , t&e 1 mm red and cpc (black not connected into the Neutral bar) go into the contactor box the red is connector blocked and so is the CPC , another 1mm2 t&e runs out of the contactor box , the 2 reds are connector blocked as are the CPC , the black from the small db is taped up and the black that is outgoing is in A1 with red sleeving , there is a red link from L1 supply side to A2 ...the outgoing T&E runs to a 3 gang standard switch at the front door and is connected into the switch...

so to summarise the switch switches the contactor which then kills the power to the three phase board..What do you think about having 415 V at a standard switch...as it happens the contactor is welded shut and therefore the switch isnt switching the three phase board off...the 6amp breaker marked up contactor also has an a supply going out to the alarm so despite the MCB being switched off the alarm engineer still had 180 V at source...I know that removing the link from L1 to A2 will kill the voltage but is this a standard set up...

sorry to waffle

 

[Andy™]

definately wrong, A2 should be connected to neutral, and a 230v coil used

 

[Sidewinder]

Not always wrong Andy, struggled to understand the post, but 400V control is common.

 

[Mr T]

Which bit did you stuggle to understand ? I will try and explain it better ,I agree its a bit of a waffle.. been a long week..

 

[steptoe]

sounds like some one has tried to latch the 3phase board and failed badly.!

what do you want the contactor to actually do?

and how do you want it to do it?

 

[Evans Electric]

More information Mr T.

To recap , you have a 3ph board controlled by a 3ph contactor , the coil switched from a 3 gang switch .

a) If there is 415v at the 3gang switch it just needs a warning label on the plate or the grid.

B) If the contactor is welded closed its probably either too small or the wrong AC rating , What does the board do? General stuff ? inductive ? Resistive?

 

[ProDave]

I would say the BIG thing wrong is taking the supply from the single phase board.

If you are going to switch a 400V contactor coil phase to phase, then BOTH phases feeding it should come out of the 3 phase board, and NOT from the single phase board.

And in that case the switch should be rated 400V

Is it an on / off switch, or a stop / start circuit with a hold on contact?

All the same, with the switch OPEN there should be no voltage on the live coming out of the single phase board. Perhaps the switch has been arcing and is now carbonised and tracking?

Some serious rework needed.

If the contactor has welded, it needs replacing. So replace it with one with a 230V coil, then A2 goes to neutral in the SAME board that feeds it, and the switch will be okay being a 230v switch, but do check that it's okay (really is open circuit when turned off) Also check the switch rating. Some big contactors can have some pretty high inrush currents.

Oh and supply the alarm from a separate MCB to the contactor circuit, if nothing else to allow the alarm engineer to isolate without dropping out the whole 3 phase board.

 

[Evans Electric]

Dave , its no good feeding the control switch from the board thats being switched :C Has it been a long day

 

[ProDave]

Dave , its no good feeding the control switch from the board thats being switched :C Has it been a long day

Doh yes.Wet Fish

In which case the OP's description "there is a red link from L1 supply side to A2 " is wrong, it MUST be a 230V contactor. and A2 must connect to neutral, one would hope from the single phase board (but I guess not since the black is not terminated in the single phase board, so we have a borrowed neutral)

Still replace the stuck contactor, check the switch and separate the contactor and alarm circuits and sort out that borrowed neutral.

 

[Sidewinder]

Don't think you can Dave by the sound of it as the contactor kills the power to the complete 3ph board.

 

[kerching]

Surely......3 phase from the electric meter to the top of the contactor and then from the bottom of the contactor to feed the three phase board...is a tad incorrect? Should it not go via an isolator switch/fuse? Otherwise how do you isolate the contactor to work on it................... :coat

 

[Mr T]

you cant lol...

---------- Post Auto-Merged at 21:50 ---------- Previous post was made at 21:47 ----------

the three phase board does MOT ramps three phase ,sockets,lights, controlcircuit for the compressor....

 

[Evans Electric]

Why is the contactor needed ?

Is it just to ensure everthing is switched off when they go home or what . ?

 

[Mr T]

The black from the t&e from the single phase board is not connected in the board or in the contactor...the outgoing black sleeved red is connected to A1 which runs through to l1 at the switch...there is a link from A2 to L1

---------- Post Auto-Merged at 22:10 ---------- Previous post was made at 22:06 ----------

Why is the contactor needed ?Is it just to ensure everthing is switched off when they go home or what . ?

Yes.. however we are doing away with it as I have taken a supply from the 3 phase board to a new single phase board which has computer equipment , a new alarm and a fire alarm..

 

[steptoe]

L to switch,

sw to contactor

N from contactor to the corresponding N in the board the L is taken from

thats it,

this is assuming the coil is 230V of course

 

[ProDave]

...there is a link from A2 to L1

Please expand on that.

What are you meaning by L1?

For this to work, A2 must go to NEUTRAL and it should be the neutral from the single phase board.

So exactly what and where is this "L1" you are talking about?

 

[Mr T]

L1 the supply side of the contactor (T1) to A2 , no neutrals ( not connected in the single phase board and taped up in the back of the contactor box) A2 is a permanent live and A1 is a switched live.. reds connector blocked feeing Common on the switch

---------- Post Auto-Merged at 22:23 ---------- Previous post was made at 22:18 ----------

thats it , coil is 415 v though

 

[ProDave]

L1 the supply side of the contactor (T1) to A2 , no neutrals ( not connected in the single phase board and taped up in the back of the contactor box) A2 is a permanent live and A1 is a switched live.. reds connector blocked feeing Common on the switch---------- Post Auto-Merged at 22:23 ---------- Previous post was made at 22:18 ----------

thats it , coil is 415 v though

So as quite rightly pointed out following my earier faux pas HOW does it work.

you are getting a live (which phase we don't know) so I'll call it L? from the single phase board via a switch.

You are now telling us it's a 400V coil and it gets's it L1 from the 3 phase board.

But as was pointed out, the 3 phase board is dead until the contactor energises, so L1 is at 0V

Is it "luck" that lets the contactor pull in on only 230V?

It still all needs a complete re design as wired like that it shouldn't work.

 

[steptoe]

FFS,

so, you have a mash up and of a 3ph install and need us to sort it for you?

do you realise what will happen if you get it wrong?

---------- Post Auto-Merged at 22:29 ---------- Previous post was made at 22:28 ----------

So as quite rightly pointed out following my earier faux pas HOW does it work.you are getting a live (which phase we don't know) so I'll call it L? from the single phase board via a switch.

You are now telling us it's a 400V coil and it gets's it L1 from the 3 phase board.

But as was pointed out, the 3 phase board is dead until the contactor energises, so L1 is at 0V

Is it "luck" that lets the contactor pull in on only 230V?

It still all needs a complete re design as wired like that it shouldn't work.

thats why its welded Dave.!

 

[Mr T]

I havent installed it steptoe !!!! its how it is now.....