Emergency stops for LAB sockets

[infinity]

I have been tasked with installing emergency stop buttons at the doorways to a few labs, so in an emergency they can hit the stop button and it will kill the power to all the sockets in the room.

Now the problem is they are all rings with the DB's some distance away. Had they been radials t would be easy, simply break the circuit as it comes in and wire through the EMG Stop, job done, has anyone had a scenario like this and overcome it?

Would the only way be by mounting something at the DB Like a 4 pole relay, wire the ring from the MCB straight into it, and control that by an EMG Stop button sited in the circuits room, wired from the DB where the sockets are?

Or possibly catch the ring as it enters the room and mount the relay there if the legs close together, as some rooms are Dado trunking on walls.

Any advice/ help?

 

[Pete999]

Bloomin hades put a contactor in circuit before the distribution board, simples

 

[infinity]

Not simple! ha Circuits are some distance away with awkward runs to the rooms, as a cable would then be required from the board to the room where the sockets are :/

 

[Tiny Spark]

4 pole 32A contactor is the way forward here me thinks.

 

[MDJ]

Stick a contactor in where the ring enters the room, and wire the stop button to the coil, I would recommend a stop button with a key facility, that way a competant person will have to use a key to open it and would do so only if it is safe to do so.

 

[Guest55]

split the rings into 20a radials

or tell the client ( truthfully ) that his requirements are going to be expensive to achieve with extensive alterations.

 

[infinity]

Yes, i was thinking installing it where it enters the room and use stop button to coil on N/C contractor but its highly unlikely the two legs of a ring will be next to one another will probably go to either end of the socket runs which are quite large areas.

I also suppose for the purpose a 2 pole N/C contractor would suffice just cutting the two live cables?

 

[plugsandsparks]

Yep agree with above, need to think about how to reset the contactor after EM trip. Not really acceptable to just twist the e/s back to the normal position as this would energise the ccts again with un-predictable consequences.

 

[Pete999]

Agreed

 

[Billythekid]

I'd make sure that anything you agree is documented with your client, is there a requirement for under voltage protection, etc.?

Regards

Billy

 

[Lucien Nunes]

I would not use separate poles of a contactor to break two legs of a ring separately, and certainly not break only the line in that way. If the contact resistance rises it could interfere with the current sharing, and if one contact went high resistance you would not know about it because the sockets would carry on working. I would prefer to see the control cable run back to contactor adjacent to the DB and the ring moved from the DB into it.

If the cables run to the rooms together, with suitable checks and precautions you could possibly parallel them and create a lollipop circuit so that the contactor could go in the room.

As far as re-energising method etc, this needs to follow from their risk assessment which should show what specific risks they are trying to minimise, and how the E-stop is intended to minimise them.

 

[infinity]

Yes a key option would be installed, this makes no difference to the install side just a couple quid extra for the switch.

 

[Pete999]

Jeeze in aint rocket science control the DB with a contactor

 

[Lucien Nunes]

What if the lights are on the same DB? And the contactor coil circuit?
Also surely he wants a separate stop for each room?

 

[Pete999]

I thought the original post said ALL THE SOCKETS are fed from the same DB if they are not the fit a new DB just for the sockets and control that one via a contactor

 

[tazz]

Run all emergency points back to the db, you know where all the rings are then, either N/C 230v or N/C low voltage, to control contactors at the db. Reason for N/C is to fail safe the system

 

[MDJ]

Obviously I can't see the set up there, when we used to wire labs we built panels for individual rooms, very simple types as well, a serel enclosure with some mcbs and dim rail plus some little plastic trunking under them and a contactor or 2 inside as well, we used to wire the ring or rings to the serel enclosure and have a start stop station with a green and red indicator lights connected to the enclosure via auxillary contacts, you could do something similar if you could find the rings going into the rooms and use then to supply the enclosure, without actually surveying the site it is all guess work, but you could make a decent job of it without switching the DB or indeed running cables that distance.

 

[Guest55]

I thought the original post said ALL THE SOCKETS are fed from the same DB if they are not the fit a new DB just for the sockets and control that one via a contactor

which is fine if the client doesnt mind every socket going dead in every lab when someone presses any 1 stop button.....................

and also assumes that all the lab circuits originate from the same db.


quite frankly , its going to be easier to convert the rings into radials so each lab only has 1 supply point to interupt.

 

[tazz]

All depends on setup.....is there an mcb for each room..?.....if there is then wire back to db....if not ring finding time

 

[MDJ]

You may find it is not that simple, the reason we used to make control panels for labs is down to rules about H&S regarding the children or staff using the room, a team leader needs to have control of the circuit locally and thats why not only a stop button installed but also control regarding a start station as well. If it were me I Would speak again to the customer regarding specific requirments. Mike

 

[infinity]

There are various rooms, some rooms have one circuit, some rooms have 2 rings, all fed from various different DB's. Switching Db's is obviously not an option as offices etc are also supplied.

If i can find the rings coming into the rooms it will be a lot easier. It does look like a tidy install not too old, all labelled up so i would expect to see a tidy install above the ceiling as well, which will also help.

 

[HandySparks]

.... and use stop button to coil on N/C contractor ...

Do you really mean this "N/C"?

If so, I suggest that the job goes elsewhere.

 

[tazz]

With offices a various dbs now in equation ....this sounds like new circuits are required
Infinity ment N/C circuit Handy sparks

 

[infinity]

N/C circuit with switch opening the circuit what's wrong with this handyspark?

The circuits in the rooms do not supply figures just the DB's do hence no switching of DB.

 

[i=p/u]

Or as biff says change to radials....

 

[ahtyrrell]

You may also want certain sockets in the room to stay on even if the E stop is pressed E.g. computers around the room or a computer and projector on the front desk

 

[HandySparks]

N/C circuit with switch opening the circuit what's wrong with this handyspark?

Nothing.

But what you said was N/C contactor, ie closed when the coil is de-energised, which for an em-stop circuit is not what's required.

 

[netblindpaul]

Work to the relevant & recognised Code Of Practice as published by the BSI, that is BS4163 and all will become clear, the requirements are spelt out in that standard, easy.

 

[not clever]

28 posts and only 2 give a descent reply
Mdj with the e stop and separate single key reset switch and blind Paul with the code of practice to go by.

 

[tazz]

28 posts and only 2 give a descent reply
Mdj with the e stop and separate single key reset switch and blind Paul with the code of practice to go by.

And your answer to multiply rooms with radials & rings mixed with offices, with numerous dbs located in different areas .....IS...?

Always one to make big comment.....without a solution.....!!!!

 

[Hawkmoon]

If I were faced with this (as described) I would:

1) Install submain DB to each lab incorporating contactor etc on din rail.
2) Get above ceilings and rewire/reroute all cabling as necessary to separate the labs/offices accordingly.
3) End result - each lab with own ring fed from new sub DB
4) E-Stop with keyswitch wherever.

A lot of work/cost etc but I don't see an alternative - just get stuck in!

 

[tazz]

good constructive input

 

[Engineer54]

If I were faced with this (as described) I would:

1) Install submain DB to each lab incorporating contactor etc on din rail.
2) Get above ceilings and rewire/reroute all cabling as necessary to separate the labs/offices accordingly.
3) End result - each lab with own ring fed from new sub DB
4) E-Stop with keyswitch wherever.

A lot of work/cost etc but I don't see an alternative - just get stuck in!

Very similar to the requirements within our Medical Labs Building, except ours are a bit more involved, many being monitored by safety isolation supply units (similar to that found in many school lab classrooms), and a hazardous gas detection alarm system....

 

[Hawkmoon]

Very similar to the requirements within our Medical Labs Building, except ours are a bit more involved, many being monitored by safety isolation supply units (similar to that found in many school lab classrooms), and a hazardous gas detection alarm system....

Not worked on that kind of setup - sounds interesting.

Strangest emergency stop install I've come across was in a number of MOD establishments where the stop button, when pushed, shorted neutral & earth on an RCD protected server installation (N+E picked up at nearest socket then wired to n/o on stop). I wasn't testing the install so thankfully did not have to code it lol.

 

[i=p/u]

What he means monitored is by rcd .

 

[Engineer54]

What he means monitored is by rcd .

If you're talking about my post, you would be making the wrong assumption here!!