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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

CuriousIndeed
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    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 Aug 22 '21 at 10:19
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    Have you checked what sockets are available in Switzerland that meet their code? That would be the obvious course of action... Stores like Jumbo, Coop, Hornbach all have websites where you could find out the range of sockets... – Solar Mike Aug 22 '21 at 10:27
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    Yes. Plenty. Is there space for a large plug? If so IEC 60309 plugs are probably approved in Switzerland, and certainly not something that will be unplugged accidentially. – vidarlo Aug 22 '21 at 10:52
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    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 Aug 22 '21 at 13:04
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    Why not just hardwire it? Presumably "commercial AC" means it is not portable. – J... Aug 22 '21 at 18:25
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    @J... Because in Switzerland everything hardwired will be looked at by the safety inspector. And this is an old building so if I hardwire it into the junction box the safety inspector will need to look at it and will probably find other non-conformities within the junction box (we have very strict rules) – CuriousIndeed Aug 22 '21 at 19:56
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    Do unplanned power distribution failures never occur in Switzerland? If so, providing a "non-removable" plug doesn't solve the problem. – alephzero Aug 22 '21 at 20:30
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    Roll of blue tape and a sharpie : "DO NOT UNPLUG" – Mazura Aug 22 '21 at 20:43
  • @Rubus So, presumably the same would apply if you were to change the outlet to a different type? It would need to be inspected also? Meaning you would not entertain solutions which involved changing the outlet to a different type? – J... Aug 22 '21 at 22:03
  • @J...Yes every socket needs inspection so this is why I'm trying to avoid installing a new socket – CuriousIndeed Aug 23 '21 at 08:07
  • @alephzero I can't remember being affected by an unplanned power distribution failure, ever, and I have lived in Switzerland my whole life. I'm sure it happens, but it's very much an exceptional thing. And the machine here is only harmed if it happens repeatedly, I think. – Nobody Aug 23 '21 at 09:57
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    What's the reason for the "accidental disconnections"? People tripping in the cable? People wanting to disconnect something else? People finding it easier than using the controls of the AC? Or are you just proactively trying to prevent something you don't even know will happen? Where is this? Your home? Offices? A place you rent out for short periods? – jcaron Aug 23 '21 at 10:16
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    The original question was about "accidental removal" and my answer presumed the intent was to avoid the nuisance of that. NOT to avoid harming the equipment. I think in fact the equipment is harmed by reconnection in under 5 minutes, not by removal. But if in fact removal can damage the equipment, I think the original question and my answer both miss the mark and a much more robust solution would be appropriate, most probably hard wiring even if it means getting into full local standards compliance. – jay613 Aug 23 '21 at 12:31
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    It seems contradictory that a country with such a highly reliable grid would also have unreliable air conditioners. Before going to any significant lengths to prevent unplugging, I would challenge the technician's assertion. I think jay613 is on the right track about reconnection too early. – donjuedo Aug 23 '21 at 13:57
  • A lot of fridges (so, same components in a different box) warn about powering up within some period of moving the device to ensure all the fluids in the thing have time to settle, I wonder if this is a (mis-quoted) reference to something similar? – John U Aug 23 '21 at 15:39
  • Based on @jay613 's comment above, and the OP's change to the question apparently inspired by https://diy.stackexchange.com/a/232434/59207 , the correct Question should be "How to avoid turning a device back on less than (3-, 5-, 10-) minutes after it was turned off?" And the answer is to build a circuit like this: https://electronicsarea.com/surge-protection-circuit-voltage-delay-circuit/ or a product containing such a circuit, typically something like this (but it's for Spain): https://www.amazon.com/BSEED-Appliance-Protector-Voltage-Brownout/dp/B07R3GK6DM/ (note yellow DELAY light) – user6297 Aug 24 '21 at 15:50
  • @jay613 Indeed. Besides, the grid can lose power at any moment. HVAC equipment, and especially commercial HVAC equipment should generally be very robust against loss-of-power events. – J... Aug 24 '21 at 15:54
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    Re, "...technician said the correct procedure is...wait for at least 5min before unplugging." You may have mis-remembered that. The usual caution for air conditioners and other heat pumps is, to wait five (or ten) minutes after powering the unit off before you power it back on. The reason is, to allow time for the pressure between the "hot" side and the "cold" side of the refrigerant loop to equalize. The compressor motor in some units is not strong enough to start the compressor turning when there already is a significant pressure difference. – Solomon Slow Aug 24 '21 at 16:02

8 Answers8

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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

jay613
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    Be sure you CAN unplug it in case something bad happens (smoke, sparks, flames, etc...). Otherwise, it is hardwired for all purposes. – fraxinus Aug 22 '21 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. – Dan Is Fiddling By Firelight Aug 23 '21 at 00:25
  • 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 Aug 23 '21 at 05:58
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    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 Aug 23 '21 at 09:21
  • Indeed, if the question was "how can I make this much more robust even than a UK plug" the answer would have been different. Can you demonstrate a UK plug being removed both "quite easily" and accidentally? – jay613 Aug 23 '21 at 12:49
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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 Aug 23 '21 at 20:15
  • @Dai No, I wasn't being sarcastic. I agree that they are designed to do pull out as easily as continental plugs do, but they still do - a straight continuous pull generally won't. but a pulse of just the right type (usually from someone tripping over a taut cable) will often flick them out. Depends what level of certainty you need, what the risks are. – MikeB Aug 24 '21 at 08:52
  • @Dai - must chime in here. If you mean the old UK plugs (not moulded) I've always thought what a bad design they had, as occasionally I found that when pulled by the wire, the earth was more likely to come adrift before the others. That created a potentially fatal situation which did claim the lives of several guitarists. As H&S in schools in the 60s/ 70s, I was forever finding earth wires loose. – Tim Aug 25 '21 at 08:26
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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.

Harper - Reinstate Monica
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    Thanks that made me remember that he actually said not to unplug the AC after it had been shutdown for at least 5min.. – CuriousIndeed Aug 22 '21 at 19:51
  • @Rubus That makes no sense. You mean that unless you unplug it within 5 minutes of shutdown, you need to leave it plugged in *for ever"? – alephzero Aug 22 '21 at 20:33
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    @alephzero I meant that you could unplug it after it had been shutdown for at least 5 minutes.. – CuriousIndeed Aug 22 '21 at 21:08
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    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 Aug 23 '21 at 05:13
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    @davidbak From what I've seen, often no. – End Anti-Semitic Hate Aug 23 '21 at 07:26
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    According to the technician the devices could be damaged. But it's not that every power failure leads to damage, it just something that should be avoided – CuriousIndeed Aug 23 '21 at 08:04
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    ^ 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 Aug 23 '21 at 15:36
  • @JohnU because of the short-cycle issue I mentioned. – Harper - Reinstate Monica Aug 23 '21 at 19:41
  • @Harper-ReinstateMonica - you mentioned it, you didn't actually say why it's a problem / what damage it might do. Also, while some devices may "forget" when unplugged it's not impossible to imagine a protection circuit or device (EG pressure based) that doesn't forget or that doesn't need to remember. – John U Aug 24 '21 at 07:46
  • @JohnU Edited. Sure, I imagine they could make a freon compressor that is immune to short cycling. How much extra would you be willing to pay for that? – Harper - Reinstate Monica Aug 25 '21 at 04:59
  • @Harper-ReinstateMonica - I thought freon was outlawed years ago. – Tim Aug 25 '21 at 08:29
  • @Tim they just switched to other R- gases that don't shred the ozone layer. There are dozens of them. I guess Freon is technically a brand name. – Harper - Reinstate Monica Aug 25 '21 at 18:32
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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..

Mołot
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Peter Green
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    +1 These are also commonly known as "commando" sockets - a keyword that's helpful when shopping. – J... Aug 22 '21 at 18:24
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    And also known as "CEEform" if you want another term to search for. – Simon B Aug 22 '21 at 19:37
  • I have seen them in Switzerland, although only the 400V version, didn't know they also had 230V versions. – Nobody Aug 22 '21 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 Aug 23 '21 at 08:17
  • @Mołot And 110v are yellow – MikeB Aug 23 '21 at 09:23
  • @Mołot My dad's house in Switzerland has a couple of them for large 400V machines (and now that you describe the color coding, it's possible some of them are blue and actually just 230V), so it's not just construction. – Nobody Aug 23 '21 at 09:50
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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 Aug 23 '21 at 09:53
  • @Mołot Ah, that makes sense. – Nobody Aug 23 '21 at 09:56
  • You also see lots of yellow plugs/sockets in the UK, where people are using transformers to power 110v power tools: https://www.screwfix.com/p/defender-3000va-intermittent-transformer-distribution-kit-240v-110v/230kp – Mark Booth Aug 25 '21 at 08:49
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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

Journeyman Geek
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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.

https://www.screwfix.com/p/mk-logic-plus-13a-switched-fused-spur-flex-outlet-white/13479

CSM
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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.

MonkeyZeus
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  • 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 Aug 23 '21 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 Aug 23 '21 at 12:51
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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

RedGrittyBrick
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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

Crine
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