I own a commercial AC which according to the technician should never be unplugged while running. At the moment the device is plugged into one of these sockets shown below. These are old swiss sockets but the successor model is only marginally better to prevent accidental disconnection. Are there any plugs / mechanisms which could prevent accidental disconnection?

EDIT: Actually the technician said the correct procedure is to shutdown the device and then wait for at least 5min before unplugging. Thanks @Harper for priming my memory.

Old swiss electrical socket

  • 9
    Would check with a local electrician but should be. In north America there are plugs/outlets that need a twist to plug in/out instead of a simple pull.
    – crip659
    Commented Aug 22, 2021 at 10:19
  • 6
    No idea about Swiss codes, but unless there's a specific need for a plug, hardwiring the connection to a junction box (typically a service disconnect box, so that the function of a power disconnect in sight of the unit for service safety is fulfilled) is a typical approach for non-portable AC power connections. But if your plugs don't fall out of the sockets on their own, "accidental" disconnection of a plug is rarely a problem, unless you run the cord where it can be tripped over.
    – Ecnerwal
    Commented Aug 22, 2021 at 13:04
  • 4
    Why not just hardwire it? Presumably "commercial AC" means it is not portable.
    – J...
    Commented Aug 22, 2021 at 18:25
  • 10
    Do unplanned power distribution failures never occur in Switzerland? If so, providing a "non-removable" plug doesn't solve the problem.
    – alephzero
    Commented Aug 22, 2021 at 20:30
  • 8
    Roll of blue tape and a sharpie : "DO NOT UNPLUG"
    – Mazura
    Commented Aug 22, 2021 at 20:43

8 Answers 8


Replace the plug with a 90 degree one where the cable would run directly downwards and clamp the cable to the wall about 10cm away. This will prevent removal in any manner that I would consider "accidental".

90 degree swiss power plug enter image description herestick-on cable tie

  • 17
    Be sure you CAN unplug it in case something bad happens (smoke, sparks, flames, etc...). Otherwise, it is hardwired for all purposes.
    – fraxinus
    Commented Aug 22, 2021 at 21:39
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    @fraxinus agreed, but that should be doable by leaving the clamp a b it loose so you can slide slack in the cable up to be able to unplug it while still preventing bumping it loose and having a visual indicator that this outlet shouldn't be used for the cleaners vacum. Commented Aug 23, 2021 at 0:25
  • Combine this cable with one of the new sockets, where the connector is recessed. That should be enough to make it almost impossible to pull the cable out by accident
    – dube
    Commented Aug 23, 2021 at 5:58
  • 1
    This is no better than the standard UK style of plug, which can quite easily be pulled out by the cord. OK, not as easily pulled as a standard two-pin US or EU plug, but still easy enough to be frequent.
    – MikeB
    Commented Aug 23, 2021 at 9:21
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    @MikeBrockington "which can quite easily be pulled out by the cord" - I'm going to assume that's sarcasm because the UK plug was specifically designed so that pulling the cord won't cause the plug to come out of the socket. If it's a hand-wired (ew...) plug then the cord's contacts inside the plug will disconnect, live-first, neutral-last - if it's a moulded plug (as they should be) then I honestly have no idea what the failure-mode is there...
    – Dai
    Commented Aug 23, 2021 at 20:15

Consider why not to unplug it while running.

A "short cycle" is when a heat pump compressor is running, stops, and then then restarts too soon -- before system freon pressure has had time to equalize. That means the pump is doing a hard start against full back pressure, which it's not rated for (why would it need to be?)

Your heat pump has a protection circuit to prevent it from starting too soon after it shut off. However, when you unplug it, that circuit "forgets" and it can restart immediately, causing a short cycle.

Some people don't understand why short cycling is bad, and unplug and re-plug on purpose to get it to run immediately. So unplugging should not be done for that reason.

If people are unplugging it on purpose, they need to be scolded to stop.

Accidental unplugging is a simple matter. Wait 10 minutes before plugging it back in again (if it has been running). That lets the freon balance/settle in the system, and avoids a "short cycle".

However, the greater concern is why it's being unplugged frequently. If it is being unplugged by accident by people meaning to unplug something else, then perhaps a more suitable receptacle can be provided for those other users. However, if it's being struck, then it's in a bad location and the socket needs to be moved or the area provided with physical protection.

Don't defeat the ability to unplug it altogether. You might want to unplug it in a hurry if it catches on fire.

  • 2
    Thanks that made me remember that he actually said not to unplug the AC after it had been shutdown for at least 5min.. Commented Aug 22, 2021 at 19:51
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    @alephzero I meant that you could unplug it after it had been shutdown for at least 5 minutes.. Commented Aug 22, 2021 at 21:08
  • 5
    What happens in case of a power failure where the power is off for only 30 seconds or perhaps 1 minute? The devices have no protection for this?
    – davidbak
    Commented Aug 23, 2021 at 5:13
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    @davidbak From what I've seen, often no. Commented Aug 23, 2021 at 7:26
  • 2
    ^ asking the real questions, I'd be amazed if occasional unplugging / power failure could really hurt any modern device (and if so, I'd question the design/quality). Technicians are not always as knowledgeable as you might hope and sometimes just parrot things they've heard from other techs or mis-understood from a manual, which may once upon a time have been done to disauade customers from bad behaviours but are now irrelevant or not applicable. Unless the cord is being tripped over several times a day I would not worry about it.
    – John U
    Commented Aug 23, 2021 at 15:36

A 'simple' solution would be a lockable cover over the socket. It'll work with existing plugs (So you don't need to rewire anything), and could work in conjunction with other measures

A quick google search (for "lockable socket cover") suggests that there's a few different styles of this

enter image description here

Even if you don't use a lock, something like a cable tie (removable or otherwise) would make accidental unplugging impossible. You could also stick a label on it reminding you, or others to wait 5 minutes before unplugging.

I guess its a variation on the good old molly guard


If you have the space then likely your best option is an IEC60309 style socket. My understanding is these are acceptable across Europe though you should check with a local electrician.

The standard IP44 versions have a sprung cap which grips the plug and must be lifted before unplugging. The IP67 versions have a ring on the plug which screws to the socket. Neither type is likely to become disconnected accidentally and not being "standard domestic sockets" the chance of someone unplugging it to plug something else in is also reduced..

  • 5
    +1 These are also commonly known as "commando" sockets - a keyword that's helpful when shopping.
    – J...
    Commented Aug 22, 2021 at 18:24
  • 4
    And also known as "CEEform" if you want another term to search for.
    – Simon B
    Commented Aug 22, 2021 at 19:37
  • I have seen them in Switzerland, although only the 400V version, didn't know they also had 230V versions.
    – Nobody
    Commented Aug 22, 2021 at 20:15
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    @Nobody Genrally red ones are 400V and blue ones are 230V. I've only seen them at construction sites, but they do exist.
    – Mołot
    Commented Aug 23, 2021 at 8:17
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    @Nobody I meant I've seen 400V at workshops etc, but 230V ones only at construction sites, because everywhere else I've seen just regular 230V sockets, even in workshops. Of course they can be used, and in workshop conditions probably even should, I just haven't seen it happen.
    – Mołot
    Commented Aug 23, 2021 at 9:53

Are switched-outlets code-legal where you are? They are the standard way to have loads that must be isolatable, but rarely so.

These either have a hole at the front for the flex to come out of, or (as in this example) the flex is attached to the back. These are sized for a standard UK single socket or light switch.



What's the threat-model? People consciously unplugging it or somebody tripping on it?

If someone trips on it then it's preferable for it to unplug instead of fully tripping the person. I've walked through a cord before while carrying something heavy and I really appreciate that I ripped the plug out of the socket instead of me falling down.

A piece of tape wrapped around the cord with a prominent "NEVER unplug" would likely suffice especially in a residential setting.

  • When I wrote my (simple) answer I figured someone would suggest that it's inadequate if OP has an indoor soccer court or is raising rhinoceroses etc etc .... bring it on :)
    – jay613
    Commented Aug 23, 2021 at 12:47
  • @jay613 Hah, if the A/C is corded in your soccer court or rhinoceros habitat then I'm sure there are some much more egregious violations just waiting to be discovered =)
    – MonkeyZeus
    Commented Aug 23, 2021 at 12:51

In the UK I'd look for a "flex outlet plate"

flex outlet plate

There are switched and unswitched variations. You can get them with fish switches (simple key-operated switch).

There are also modular plates that might let you combine a flex outlet with a conventional dual-pole (DP) keyed isolator switch - a local electrician could advise whether that is possible.

Maybe there's something similar in your part of the world

  • OP wouldn't want a switched version - the problem would only still be there.
    – Tim
    Commented Aug 25, 2021 at 8:32
  • @Tim: a "key operated switch" or "keyed isolator switch" cannot be turned off by anyone who does not possess a key. Commented Aug 25, 2021 at 8:46
  • Comment was solely about the first suggestion.
    – Tim
    Commented Aug 25, 2021 at 9:10

Use a twist lock plug and socket. Here you first plug in and then twist it clockwise to lock it in place, and then you have to twist it anticlockwise before you can take it out.

enter image description here

  • 2
    The OP is in Europe, using a different outlet system Commented Aug 25, 2021 at 11:38
  • 1
    In the US, though, this is an excellent idea.
    – FreeMan
    Commented Aug 25, 2021 at 11:42

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