How to wire mains power to an SPDT (maintained) switch

[meketrex]

I currently have a Single Pole Double Throw switch with 5 pins (as shown below) which I want to wire up to UK mains:

         ┌─────┐
         │ NC  │
         └─────┘
┌─────┐  ┌─────┐  ┌─────┐
│  -  │  │ NO  │  │  +  │
└─────┘  └─────┘  └─────┘
         ┌─────┐
         │ COM │
         └─────┘

So I'll have a typical 3 core mains cable with LIVE, NEUTRAL, EARTH going in and a LIVE, NEUTRAL, EARTH coming out:


I've searched for how to do this and found conflicting information:

Suggestion 1:

• LIVE IN connected to "NO" & "+"
• LIVE OUT connected to "COM"
• GROUND connected to "-"

Suggestion 2:

• LIVE IN connected to "COM"
• LIVE OUT connected to "NO"
• GROUND connected to ???

I am a novice with this so if possible could you explain in very simple terms like:

• LIVE IN = COM
• NEUTRAL IN = ?
• EARTH IN = ?
• LIVE OUT = NO
• NEUTRAL OUT = ?
• EARTH OUT = ?

Really appreciate some assistance with this

 

[meketrex]

Is this accurate?

---

 

[SparkyChick]

Firstly, if you wire the LED to the mains, it will explode... the LED in that switch is designed to run on 24v DC.

Second, without more information about the application it's a little tricky to provide a definitive answer.

 

[meketrex]

Firstly, if you wire the LED to the mains, it will explode... the LED in that switch is designed to run on 24v DC.

Second, without more information about the application it's a little tricky to provide a definitive answer.

Thanks for coming back!

I have a 4 gang plug wired into an arcade cabinet. It's connected to a IEC panel mounted at the back. This means the on/off switch is at the back of the cabinet.

I want to install an on/off switch at the front. My plan is to cut the wire from the gang to the IEC panel and extend it to this switch:


The switch does have an LED and is metal.

Does that help?

PS. This image I supplied in my second post was something I found while googling.

 

[SparkyChick]

I'm going to make an educated statement... I'm guessing that all the kit you're putting in the cabinet will be powered by switched mode power supplies... SMPs are great, BUT, they can have huge in-rush currents when first switched on. The contacts on that switch are rated at 3A... once powered up, that's probably ample but it is insufficient to cope with the inrush current and this will lead to premature failure, most likely due to the contacts welding themselves together.

For your use case, I would always select something like this:-

C6053ALNAE | Arcolectric (Bulgin) Ltd Illuminated DPST, On-Off Rocker Switch Panel Mount | RS

uk.rs-online.com

It's not as stylish by any means, but it is more suitably rated for dealing with the inrush current and as such, should last.

 

[meketrex]

I'm going to make an educated statement... I'm guessing that all the kit you're putting in the cabinet will be powered by switched mode power supplies... SMPs are great, BUT, they can have huge in-rush currents when first switched on. The contacts on that switch are rated at 3A... once powered up, that's probably ample but it is insufficient to cope with the inrush current and this will lead to premature failure, most likely due to the contacts welding themselves together.

For your use case, I would always select something like this:-

C6053ALNAE | Arcolectric (Bulgin) Ltd Illuminated DPST, On-Off Rocker Switch Panel Mount | RS

uk.rs-online.com

It's not as stylish by any means, but it is more suitably rated for dealing with the inrush current and as such, should last.

Thank you very much!

I would have 3 devices that would be connected to the gang:

• DE10 Nano (using a 5 Volt 4 Amp power supply)
• 27" 1080P Monitor
• Soundbar

Does that match your assumption about power usage?

 

[SparkyChick]

The problem with power figures as provided by equipment manufacturers is that they are for steady state... i.e. the device is already running. So if you consider the monitor, lets say 100W... it's a little more complicated because it's an electronic device but if you use the simple formula Power = Voltage x Amps you can get that the steady state will run at around 0.5A. However, the in rush current could be much greater than that... and whilst it may only last a fraction of a second, it can still be long enough to do damage to the switch.

To give you some context, I had a four way extension lead with individually switched outputs. Into one of those outputs (via a couple of 4 way extension leads) I had a small collection of audio equipment... a mixer, a couple of rack mounted synth modules, a small rack mount mixer, a MIDI interface, an audio interface and the wall wart for another synth module. None of them being high powered devices (total power rating would be around the 500-600w mark). The switch itself was rated for 13A (as it was for a 13A socket outlet) and it failed and welded itself closed so I was unable to switch it off.

You can choose to try that switch, but personally I wouldn't waste my money. I'd always overrate the switch. And please don't forget my comment about the LED in the switch unit being rated at 24V only (that's taken from the data sheet available on the RS page you linked to).

 

[meketrex]

The problem with power figures as provided by equipment manufacturers is that they are for steady state... i.e. the device is already running. So if you consider the monitor, lets say 100W... it's a little more complicated because it's an electronic device but if you use the simple formula Power = Voltage x Amps you can get that the steady state will run at around 0.5A. However, the in rush current could be much greater than that... and whilst it may only last a fraction of a second, it can still be long enough to do damage to the switch.

To give you some context, I had a four way extension lead with individually switched outputs. Into one of those outputs (via a couple of 4 way extension leads) I had a small collection of audio equipment... a mixer, a couple of rack mounted synth modules, a small rack mount mixer, a MIDI interface, an audio interface and the wall wart for another synth module. None of them being high powered devices (total power rating would be around the 500-600w mark). The switch itself was rated for 13A (as it was for a 13A socket outlet) and it failed and welded itself closed so I was unable to switch it off.

You can choose to try that switch, but personally I wouldn't waste my money. I'd always overrate the switch. And please don't forget my comment about the LED in the switch unit being rated at 24V only (that's taken from the data sheet available on the RS page you linked to).

Thanks again for your detail and assistance. And I have taken note of your instruction about the LED

 

[Lucien Nunes]

Agree with the above, the switch might wear out rapidly or weld shut. OTOH your load isn't huge, it might work for many years, there's not enough data on the datasheet to know.

Your first posts contain a mix of references to automotive 12 / 24V DC and 230V AC mains wiring. What is correct on 24V might be lethal on 230V. The terminology can be confusing. For automotive 12/24V DC the terms 'earth' and 'ground' are synonymous with neutral, which is normally negative. There is no safety earth. For 230V AC mains, 'earth' and 'ground' mean safety earth, not neutral.

For 230V AC, in general:

• Earth must be unbroken, never switched, not connected to any part of switch except metal body if that requires earthing.
• For douple-pole switch, L & N pass through two poles of switch. For single-pole switch, only L passes through switch, neutral unbroken.
• With 230V illumination the lamp needs a connection to N, otherwise no connection from switch to N
• For single-throw switch with 230V illumination, line connects to either Com or N/O according to whether illumination is to be on all the time or only when switch on. For double-throw switch with 230V illumination, terminals are usually separate, you need to connect lamp to switched L and N. Does not matter which of Com and N/O is feed L and switched L.
• On any switch with ELV illumination e.g. 24V LED, that you want to use to switch 230V AC, you need to ensure electrical separation is maintained between the 230V and 24V circuits. Both by the switch and your wiring. Extra insulation might be needed to ensure the two can't come into contact e.g. if a lead pulls loose.

 

[meketrex]

Agree with the above, the switch might wear out rapidly or weld shut. OTOH your load isn't huge, it might work for many years, there's not enough data on the datasheet to know.

Your first posts contain a mix of references to automotive 12 / 24V DC and 230V AC mains wiring. What is correct on 24V might be lethal on 230V. The terminology can be confusing. For automotive 12/24V DC the terms 'earth' and 'ground' are synonymous with neutral, which is normally negative. There is no safety earth. For 230V AC mains, 'earth' and 'ground' mean safety earth, not neutral.

For 230V AC, in general:

• Earth must be unbroken, never switched, not connected to any part of switch except metal body if that requires earthing.
• For douple-pole switch, L & N pass through two poles of switch. For single-pole switch, only L passes through switch, neutral unbroken.
• With 230V illumination the lamp needs a connection to N, otherwise no connection from switch to N
• For single-throw switch with 230V illumination, line connects to either Com or N/O according to whether illumination is to be on all the time or only when switch on. For double-throw switch with 230V illumination, terminals are usually separate, you need to connect lamp to switched L and N. Does not matter which of Com and N/O is feed L and switched L.
• On any switch with ELV illumination e.g. 24V LED, that you want to use to switch 230V AC, you need to ensure electrical separation is maintained between the 230V and 24V circuits. Both by the switch and your wiring. Extra insulation might be needed to ensure the two can't come into contact e.g. if a lead pulls loose.

Excellent information. Thank you!