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We have an a/c window unit in our basement, vented to outside. A carpenter snipped the cord when he was moving it. Can that cord be replaced (and by whom), thus saving the (fairly new) a/c unit or should we buy a new a/c window unit?

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    ...the carpenter, or the carpenter's insurance company should be buying the new unit, or replacement cord and installation, not you. Many newer window AC units have cords far more complex than a typical or generic appliance. They require the same for replacement.
    – Ecnerwal
    Commented Nov 30, 2022 at 18:16
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    i would re-use the cut cord (since you know it's good enough for the load). Just strip the ends off of all three wires, and re-connect them with level-type wago connectors, one piece per wire color. Wrap with 3m electrical tape or heatshrink when done to keep levers from popping open.
    – dandavis
    Commented Nov 30, 2022 at 23:42
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    Can you please clarify - is this a free-floating power cable like a vaccuum cleaner, or is it permanent in-wall cabling? Secondly, if its appliance cabling, how much wire is still attached to the unit ? A photo might help.
    – Criggie
    Commented Dec 1, 2022 at 8:58
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    Just an observation: If a "curb find" ac or fridge has had its power cord cut, this damage is sometimes a token signal meaning "I'm not giving this away, I really want it taken out of service and its coolant carefully drained before it can leak and cause environmental damage". It's a requirement for some of the programs that pay a small amount to encourage that decision. I can't speak for anyone else, but when I've done this I would really prefer that someone not invalidate that promise. (Then again, I usually do more than that to junkify a fridge.)
    – keshlam
    Commented Dec 1, 2022 at 9:22
  • Side note: this is why using a licensed, bonded, and insured repair professionals is so important. This will ensure that anything the professional does is fixed by the professional or someone the professional pays to fix at no extra cost to the customer. Commented Dec 1, 2022 at 20:17

4 Answers 4

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If you are in the US, you should not cut the plug or splice the cord. You should replace the entire cordset with a compatible one. You would do this by opening up the AC unit and disconnecting the cord there.

The best would be to order a replacement cord from the manufacturer.

This is because US regulations require portable air conditioners have a protective device on the cord to prevent fires, most typically a leakage current detection interrupter. (NEC 440.65) Replacing the plug or a splice repair would defeat this protection and increase the risk of fire.

(A LCDI works by surrounding the current-carrying live and neutral wires in the cable with a conductive mesh. Current flowing on the mesh indicates physical damage to the conductors and insulation that could lead to overheating and a fire.)

The plug should have a small box on the end with test/reset buttons, you should ensure whoever repairs it does not replace it with a generic plug.

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    Replacement cords with leakage current detection interrupter are available at Home Depot and presumably other hardware stores, etc. Commented Dec 1, 2022 at 4:01
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    1) The LCDI is there because it has been observed that window A/C cords tend to become damaged and caused fires in certain ways unique to window A/Cs. 2) It's easy to buy a whole replacement LCDI cord set. So I would not splice the cable or replace the plug. Buy a new proper cord, open the unit and replace it. Anything else you do will seem to work at first. You might sell the thing in 10 years and the next person might experience a fire. You won't know. For the sake of a $25 new cord you may as well do it right.
    – jay613
    Commented Dec 1, 2022 at 14:08
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    @Tetsujin I would say it absolutely precludes joining. As jay613 has just explained, it is not a shield. It has a very specific, very different function — which also happens to be a rather new and exotic function, unknown to many/most DIY'ers. (This is certainly the first time I've heard of it.) How do we know that when an average DIY'er splices this thing that looks like a shield, using splicing techniques that might be appropriate for a shield, that the actual leakage detection function will be safely preserved? Commented Dec 1, 2022 at 16:49
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    @Tetsujin I join shielded cables all the time, too. If I came across one of these LCDI A/C cables, and didn't know it wasn't a shielded cable, I might do the same — and create an unsafe condition. It looks like a shielded cable, but it is not a shielded cable. Casually splicing it might preserve its function — or it might subtly not preserve its function, or it might create a dangerous situation, or it might cause the LCDI to nuisance-trip all the time. It's a bad idea. Commented Dec 1, 2022 at 17:01
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    It's an LCDI's job to say "This cable is damaged and should be replaced." Here we have a cable where we don't even need an LCDI to tell us: the cable is damaged and should be replaced. Commented Dec 1, 2022 at 17:04
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On a large appliance, the cord will typically be connected to screw terminals inside the appliance, in which case the best thing to do is to replace the entire cord/plug.

However, on small appliances often the cord is not designed to be replaced. If that is the case, if the cut is near the plug end then you can usually replace just the plug. If the cut is closer to the appliance then it can be a problem as splicing a cord is a little harder to do correctly and a cord that is too short lends itself to use of extension cords, which is not a good idea on a large load and/or an essentially permanently installed appliance (and this is both a large load and an essentially permanently installed appliance).

In addition, with either cord or cord/plug replacement you need to make sure everything matches the appliance requirements:

  • 14 AWG minimum wire size for use with a 15A circuit
  • 12 AWG minimum wire size for use with a 20A circuit (i.e., if the device came with a plug that would only fit in a 20A receptacle)
  • Plug type (pin configuration, which is based on current and voltage requirements) must match the original.
  • If the original plug incorporate GFCI or other special protection then the new plug should include the same protection.

All of these are important because with typical US 120V appliances anything will work for a little while. A 2-wire, no ground, no GFCI, 18 AWG "lamp cord" will connect to an air conditioner and seem to run OK. But over time the cord may overheat (but without tripping the circuit breaker because the in-wall wiring will be just fine and the circuit breaker is rated based on that), you will be vulnerable to ground-fault issues (which can happen with an air conditioner if condensate goes in the wrong place and there is an electrical fault somewhere), etc.

If you are not sure what you need, list the model # of the air conditioner and we can usually figure it out from the specifications.

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    Ecnerwal's comment - that the carpenter('s insurance company) should be taking care of this fix - is very important. No reason for the OP to be paying for someone else's mistake.
    – FreeMan
    Commented Nov 30, 2022 at 18:33
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    @FreeMan Agreed. However, (almost) nobody will go to insurance for this (deductible might be higher than an entire new air conditioner) so the issue is whether this was an honest mistake (which can happen) by an otherwise competent carpenter, or whether this is an incompetent carpenter who shouldn't be trusted to properly fix the air conditioner, including using (if that's the case) a proper $30 replacement instead of a "works but not as safe as the original" $10 replacement. Commented Nov 30, 2022 at 18:36
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    @FreeMan I suppose that OP might be doing the fix even if the carpenter is paying for it. Commented Dec 1, 2022 at 16:23
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    @manassehkatz-Moving2Codidact the right course of action, IMO, should be more or less this: 1. OP calls a qualified HVAC technician to do replacement, 2. the carpenter pays for the technician work, 3. the carpenter get the money back from his insurance (if it is something he finds convenient). Commented Dec 1, 2022 at 17:25
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    BTW, it should be pointed out that the cable splicing could well have a worst IP protection than the original. This might be a problem if the splice is located in a place where humidity or water infiltration could happen. Commented Dec 1, 2022 at 17:28
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You can repair the cut with a simple inline junction box, such as this

enter image description here

Example from large British electrical wholesaler/trade store - https://www.screwfix.com/p/debox-24a-in-line-junction-box-white/8692h

Standard practise in the UK, though it may depend on where you live.

Late edit
I have just discovered US portable* AC has a 'special' breaker structure with a shielded cable. It is still possible [& permitted certainly in the UK] to joint this cable type too - it's just slightly harder to find the correct boxes. Most you find in the UK are exterior-grade, designed for armoured cable; we don't tend to use shielded cables for domestic purposes. Your search may be easier in the US because of the increased usage.
*I don't know whether a window unit is considered 'portable'.

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  • Pretty much anything not nailed/screwed down is considered "portable" in the US. Then again, it's not really consistent, either. I've seen things that were considered portable that were nailed down, and things that weren't considered portable were easily carried and usually used as "portable". Commented Dec 1, 2022 at 20:28
  • This does not look like anything I'd expect to see in the UK. That junction box looks way too easy to accidentally yank apart. Commented Dec 2, 2022 at 16:20
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    Picture & link straight from Screwfix. It was just the first one Google came up with. Simple in-line box. Take your pick, though - screwfix.com/c/electrical-lighting/junction-boxes/…
    – Tetsujin
    Commented Dec 2, 2022 at 16:25
  • It comes with a locking pin that is supposed to prevent re-opening it without a tool. How well it works I don't know. For better or worse we brits (and I belive Europeans more generally) seem content to let manufacturers self-certify electrical stuff. Commented Dec 3, 2022 at 0:08
  • Ultimately, it's the installers responsibility to choose products that are fit for a given purpose. There are purposes I would consider that junction box fit for and purposes I would not, Commented Dec 3, 2022 at 0:22
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Yes, any Electrician can replace that or also look up Appliance Repair companies in your area. The inside ends of the cord just screw-on to terminals there. You may even ask for a longer cord to be the end result, if desired.

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    Ecnerwal's comment - that the carpenter('s insurance company) should be taking care of this fix - is very important. No reason for the OP to be paying for someone else's mistake.
    – FreeMan
    Commented Nov 30, 2022 at 18:33
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    Well, that depends if they have insurance or if their phone suddenly doesn't work anymore. It seems they've skipped on the responsibility side of things already.
    – Iggy
    Commented Nov 30, 2022 at 18:43
  • Valid point, Iggy. However, it's something the OP should be thinking about.
    – FreeMan
    Commented Dec 1, 2022 at 13:32

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