Switching Power Supply on North American 240v AC (split phase)

[IanB]

They are controllable via RF433 modules as well as across the internet, mobile, remote controls, google assistant etc

Me hatches evil plan to hack your house and take over your heating 

[Richard Crowley]

In any case, easy to go look it up in the code to be sure. No need to spread potential misinformation on a public forum.

I guess not easy enough for you to look it up?
I tried creating a login at nfpa.org to get a free peek at the National Electrical Code.
They sent me an instant spam email, but, alas not the required confirmation email.
If you know of some better access, please share it with us.

If someone is serious enough, they can look it up for themselves.
They don't need to take my (or your) interpretation of rules.

[ejeffrey]

Can I safely use a supply like this with both the L and N being at 120v with only the ground as a neutral?

No, NOT "with only the ground as a neutral".  With the ground as Ground!

To reiterate this point, and answer the actual question asked:

If you have a 3-wire 240VAC circuit (live, live, ground), you can connect an appropriately rated switch mode power supply by connecting the two hot wires to "Line" and "Neutral" on the power supply, and connecting the green/yellow safety ground wire to the "ground" terminal on the power supply.  The fact that your "neutral" is at 120 VAC relative to ground doesn't matter.

Do not connect the green safety earth to anything labeled neutral, doing so defeats the purpose of the ground wire.

In the past, it used to be allowed for high power appliances (electric dryers and ovens) to use the same wire for neutral and ground, using the "ground" wire to return a small amount of current to run 120 V control circuitry.  This hasn't been allowed in new installations for many years, but many examples of it still exist.  When done properly it wasn't the _worst_ thing ever -- the current was small, the wires were large (to handle the potential fault current form the high power circuity) which made them both low resistance and physically robust.  The nature of large appliances was that the cables were not usually exposed to much wear and damage and the wiring was a single run back to the breaker rather than stopping at multiple outlets with wire nuts that could get removed.  So a neutral fault that resulted in a live chassis was very rare but it is much better to use the dedicated safety earth as is now required.

[station240]

Most switch mode power supplies (SMPS) don't make assumptions as to one input being live and one neutral, both are feed to the AC inputs of a bridge rectifier, via a filter network.
The earth is connected to the metal work, and some capacitors in the input filter, the filter also treats both AC lines equally where capacitors are connect between AC and earth.

Another way to consider it, is a non earthed neutral (or two lives) is the same as connecting the power supply via an isolating transformer.
Which is a very common way to safely work on a SMPS.

[trevers]

Thank you all for your advice. Especially those who actually answered my question.

I have decided to use a 10w PCB mounted PS (Lets please not debate size of traces needed). Since this PS has no user replaceable fuse I will be adding fuses to both of the "hot" inputs.
Only ground will be connected to ground.
Sorry about the terminology confusion. Way back in the thread I stated that the connection to the mains had no ground, this is incorrect, in reality it had no neutral wire.

[cowasaki]

They are controllable via RF433 modules as well as across the internet, mobile, remote controls, google assistant etc

Me hatches evil plan to hack your house and take over your heating 

You are going to need one hell of an aerial......