Like the title says, I would like to know if it is possible to connect the 0V reference output of any switching power supply to the neutral conductor. Here is an image of what the connection should look like:

0V output of power supply connected to neutral

What would happen if I place this connection? Is it safe? If that isn't such a good idea, is there another way to reference de 0V output to the neutral?



marked as duplicate by brhans, Daniel Grillo, Dave Tweed Oct 14 '16 at 11:34

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  • \$\begingroup\$ Why do you want to do that? What are you ultimately trying to accomplish? What's the big picture? \$\endgroup\$ – Nick Alexeev Oct 11 '16 at 19:16
  • \$\begingroup\$ The goal is to make the neutral conductor that run through a house to be at the same potential of the common signal of a LED dimmer. I really can't tell more about this project, sorry. \$\endgroup\$ – Gui W. Eckert Oct 11 '16 at 19:27
  • \$\begingroup\$ Neutral is, at all times, to be considered as dangerous as a live conductor. So, most definitely not. \$\endgroup\$ – marcelm Oct 11 '16 at 20:12
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    \$\begingroup\$ Also, "I really can't tell more about this project, sorry." is unlikely to entice visitors to actually help you... Context is important. Besides that, people are curious, and you being secretive might simply dissuade people from trying to help. \$\endgroup\$ – marcelm Oct 11 '16 at 20:13
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    \$\begingroup\$ "I really can't tell more about this project, sorry." In that case, hire an electric safety consultant, have him sign an NDA. \$\endgroup\$ – Nick Alexeev Oct 11 '16 at 20:33

Don't do that

Depending which country you live in and what type of plugs and sockets you use, touching the DC output side becomes "less safe than it should be", "outright dangerous", or "just as bad as touching mains".

If you have a separate earth pin on your mains plugs, and all sockets in your jurisdiction have an earth connection, you could consider connecting to that instead of neutral. Alternatively, if you're trying to get rid of high frequency noise, you could connect a capacitor across there. Use a capacitor which is designed for it - look into Y rated parts.

The only time it would be acceptable to do what you're proposing is if the DC side is treated like mains from a safety point of view. With e.g. double insulation. If this is what you are doing, you may be better off with a transformerless AC to DC power supply.

  • \$\begingroup\$ In this case the DC side would be treated like mains. And also there is an earth conductor, but in this case the 0V output wouldn't refer to the neutral but to the earth potential. \$\endgroup\$ – Gui W. Eckert Oct 11 '16 at 19:22
  • \$\begingroup\$ OK. I don't think I understand what you are trying to accomplish. Why do you want your "DC" referenced to neutral? Would it matter if it accidentally became referenced to live instead (which could happen if there is a fault in the mains wiring)? If the DC output is treated like mains with respect to enclosures/insulation/double insulation/protective bonding/protective impedance/etc then it could be safe, but we can't tell without seeing the whole system. \$\endgroup\$ – Jack B Oct 11 '16 at 19:34
  • \$\begingroup\$ It really wouldn't matter if it became referenced to live, because the system will be placed inside the distribution board of a house. \$\endgroup\$ – Gui W. Eckert Oct 11 '16 at 19:40
  • \$\begingroup\$ Sounds like the safety (or lack thereof) is going to depend on lots of things you haven't shown in your question. But yes, in principle it is possible to do this safely. You might find you can get the same result cheaper with a transformerless AC to DC power supply. \$\endgroup\$ – Jack B Oct 11 '16 at 20:13
  • \$\begingroup\$ Also, if it's going inside a distribution board there are likely some extra safety regulations to meet. A fire in a distribution board, for example, is worse than a fire in a regular appliance because it is harder to isolate the supply. I don't know much about the applicable regs though, and they probably vary from country to country. \$\endgroup\$ – Jack B Oct 11 '16 at 20:16

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