230v Estop

[Steve Crotty]

Im not an electrician, but im wiring up a panel. The panel im being asked to wire has 3 phase coming to it, with 120V each phase, and no neutral. We normally have 120V estop circuits, but on this machine, we dont not want to go through the expense of buying a step down transformer just to create the 120V.

So what my boss wants me to do is have a ESTOP circuit running off of 230V. Is this alright to do? I personally would like to switch to 24V, but then we would need to buy new contactors ect..

regards,

Steve

 

[rsdoran]

You can use the 230v for an estop ckt, there are several ways to do this. You dont necessarily have to stop the incoming power in an estop ckt but if you feel that is necessary then use a 3 pole contractor/relay, capable of carrying the cabinet current, and use a 230v coil in it. This can be as simple as using the ESTOP button(s) with a Normally closed contact to hold in the contactor/relay.

Depending on situtaion you can use the control voltage, which in this case would be 2 legs of the incoming power, to create the estop control circuit. This can use a Master Control Relay to shutdown just the control circuit.

ALL of this is application specific...ie it DEPENDS on the application, situation etc.

I can not believe I do not have drawings for something as simple as this readily available, I will real soon though.

 

[Tom Jenkins]

"3 phase coming to it, with 120V each phase"

Is this correct, or did you mean 230 VAC each phase? In this case the voltage is 230 VAC phase to phase. I am expecting that you have one leg grounded, which gives you about 132 AC to ground.

If you get a switch with NEMA A600 contacts which are rated up to 600 Volts you should be OK but check the coil current draw data against the switch contact ratings.

 

[rsdoran]

Have to agree with Tom on that one, without a neutral the voltage is measured line to line, in this case will give you the 230vac.

I said I would offer a drawing soon of a basic stop start circuit, in this case it shows a motor but you could change M to be an MCR to control the 3 phases. There are other options but this should portray one of those.

 

[Orn Jonsson]

EPO lamps and PBs

Some of my clientd request that all devices mounted in the panel door of a control panel be low voltage <60V.

Therefore, I build everything with no greater than 24V in the Panel door. If an idiot screws the lense cover off a indicator lamp and the he sticks his finger in the socket he'll get a MILD reminder.
Nobody gets hurt

 

[rogerhollingsworth]

Measure your incoming voltage phase to phase and phase to ground.
post your readings. I would like to know exactly what you have before giving a fix.
Roger

 

[Eric Nelson]

The question here seems to be "Can I use 230V for my control circuit?"

Can you?... Yes. Actually, I don't see restrictions that say you can't use 480V!...

Should you?... Again, it depends...

Personally, I'd stick a control transformer in. Even though they may be rated for it, I just don't like 230V running through my pushbuttons. I don't even like 120V... All mine are 24VDC.

C'mon, you only need a few dozen VA to pull in the coil. Stick a little 50VA transformer in the panel. For under US$50, you'll have piece of mind.

If you DO use 230V, be sure to fuse the control circuit seperately.

beerchug

-Eric

 

[TimeFluxCap]

Steve, isnt it illegal in Canada to do electrical work without holding an electrical license?

 

[DRThorne]

I've been wiring skids in Canada for about 5 years for industrial use and no body has asked me if I was a licensed electrcian (I'm just an electrical technologist), but I do get my control panels built by a CSA approved panel shop.

 

[Tom Jenkins]

I don't know about Canada, but in the US a distinction is made between site work, which in most jurisdictions requires the presence of a licensed electrician, and panel building, which does not. Panel building is looked on as being more like the people on an appliance assembly line or such, where the system is pre-designed and only assembly is taking place. On a construction site judgement and experience have to come into play to make decisions about materials and methods.

 

[seppoalanen]

Steve, isnt it illegal in Canada to do electrical work without holding an electrical license?

I have experience in Canada, I tryed make sure motor was mis-winding and I connect it to free Motorstarter (only 575V) for Current measuring.
Canadian electricians soo it and advised me what I can do there and what not. They sent some US guy back to US for same reason, but they gave mercy for me. In here I have permission to do what (legal) I like with electricity but it is not legal in Canada ?

 

[rogerhollingsworth]

The question here seems to be "Can I use 230V for my control
circuit?"
The question here seems to be "Can I use 230V for my control
circuit?"

I too haven't found anything to say you can't use 230v or 480v as a control circuit but it sure is a bad idea. I worked with a water treatment (WQC) system that had all 480vac control, got zapped a couple of times off the aux contacts, very painful. It sure made me think twice about safety when working on that system. The price to pay will be much greater if someone gets electrocuted or burned. You probably have the stuff laying around somewhere.
Remember that unsuspecting workers will be handling push buttons and other control devices.

Play it safe
Roger

 

[kellian]

Have found with 240v control induction can cause problems for fault finding.
Had a wire disconnect in a loom out to switches mounted on door of panel. had 70v to ground.
Could have given a nasty fright. Was located on a hot metal furnace deck. A jump the wrong way and ??
Rewired to 48vDC.
In Oz coal mining control cct 110v (55 to ground)

 

[rsdoran]

In an earlier post I answered YES its possible but I will have to agree that I also prefer 24vdc. I am redoing a machine now that was all 240vac but I am changing the control to 24vdc. The added cost of a transformer/rectifier or power supply factored against the possibility of harm from shock makes it a "cheap" safety solution.

I am not saying this will make the machine safe but that it will lessen the "shock" threat imposed by using 120/240/380/480 AC with control wiring.

 

[seppoalanen]

I have done some 'NEMA' projects to US and Canada. Striking common philosophy difference is control voltages between US and EU. Here we commonly use 24V= control even for small motor staters and pneumatic valves where power needs are small. Othervise we use interface relays.

In Finland we also have MCCs with cell type motor starters for process industries, but usually control voltage 230VAC for contactors is common from one of the tree phase directly witout control voltage transformer(s) when main voltage is 400VAC.

For field device as EMS, proximity switches etc. control voltage is 24V=. I have not done enything else since 1978 when PLCs have come.

I think 24V= is "safety 1'st" for electricians as rsdoran sed.

230VAC is good for lighting etc. but in control circuits it is zero
100 times/second with 50Hz. In field cabeling, capacitance between wires is some kind bleeder current problem with long cables.