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?
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.
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.
You can repair the cut with a simple inline junction box, such as this
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.
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'.