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In the world of electrical power it's important that all connections be made securely. It's gotta be tight (not so tight that you strip threads off bolts/screws) to prevent high resistance contacts which will create heat.

Soldering of power connections (where practical) helps to alleviate any future problems however simply having proper torque with all strands in a connection point will be satisfactory.

Here is an example of a 220volt air conditioning unit power plug. The unit worked flawlessly for 7 years until one day it stopped cooling. When the power plug was pulled away from the 220volt wall outlet, one blade remained in the receptacle.

Why did this happen? The wire connection to that plug blade was not properly done and resulted in a high resistance point. Over time with the AC compressor cycling, the heating and cooling of that improperly made connection point got the issue worse. The wire itself began to burn. This is an example of a potential fire hazard due to bad wiring connection!

How could have this been detected earlier? A simple tug test on each wire when the plug was made up would have revealed an insecure connection. Also a thermal camera would have picked up a hot spot issue had one been made available for predictive maintenance. Even voltage measurements (where practical) on the load side of a connection will reveal any problem.

Step 1: Fixing the Plug.

Even though the wire is burnt not all of it needs to be condemned. An easy way to find a good usable portion of the wire is to cut back a bit (in this case I cut back 6 inches) and make a knife cut around the insulation. If it slides out easily (not being fused to the strands) and it's flexible and not discolored, the wire can be used now.

Again proper torque on the blade screws and ensuring all strands are inside is a great way to have it done. Doing a tug test per wire is highly recommended.

Step 2: Replacing the Outlet and Faceplate.

Since the original outlet and faceplate received thermal stress from the fault, it was necessary to replace those. The wiring in the outlet box was not damaged and installation was straightforward.

Now the air conditioning unit is working fine and future predictive maintenance will be applied.
<p>Mj!</p><p>This is one of your BEST instructables due to its' content. I wish I had a $ for every instance discussed over my LONG EE career! The most worrying I have encountered was the Main Power Panel on a friends BRAND NEW manufactured home. One week after he moved in, due to problems, we found no less than FOUR burned wires in the CB box!</p><p>Keep up the good work</p><p>Mr B</p>
Thank Ed! Glad to see worthy comments from a fellow engineer! You can check out my other instructables. I try to document some of my work for others to see the possibilities.
<p>Thank you...first of all...I didn't know you could even fix cords ends but I have a dyson that has same issue...so hooray. Second... thank you for the thermal camera idea. I am having electrical issues and it makes me so nervous...but that is a great idea just to make sure none of the outlets are too hot.</p>
You really need to sort out those electrical issues asap!
<p>future &quot;periodic&quot; maintenance will be applied</p>
<p>These plugs are only for flexible conductors and not for solid copper.</p>
You mean stranded conductors? Use of stiffer strands is perfectly fine but terminating in crimped fork/ring lugs is highly recommended.
<p>Oh I see, my fault. You used stranded conductro... It looked like a single solid one.</p>
<p>hey thats ok. from the angle anyone can be mistaken. I myself dont like hard stranded wire but we gotta work with what is there right? Thanks for the comments!</p>
<p>IMHO, using the $15 plug instead of the $2.95 plug is a good idea, too.</p><p>The wiring on the old outlet didn't look so hot, either. Maybe the same person wired both the socket and the plug.</p>
<p>so very true! you are quite observant. Sadly the 15amp plug selection in my country is sadly lacking however thankfully the 18000 BTU unit does not reach as high as 15amp during normal compressor operation (not including motor inrush).</p>
I don't think anyone has a great selection. There are plenty of 15a plugs, but most aren't really sturdy. I can use a couple of large DIY centers, but even then I can't always find something I trust.<br><br>I'm glad you got that repair done and know how to repair any deficiencies you find. Take care!<br><br>
<p>thank you very much! You take care as well!</p>
<p>In Canada you can't have anything that draws more 80% of capacity continually. So 12A on a 15A circuit.</p><p>I'd estimate that AC unit draws around 8A.</p><p>In this case it's obvious the problem was with the plug, and the guy that originally installed it.</p><p>Another easy test for a bad connection that's already in service. Let it run for 20min or so then pull the plug and feel the pins, if they are hot then you know you have a problem. old school version of a thermal camera.</p>
<p>very well said! same restriction on loading ampacity with our country with respect to NFPA 70. I'm actually using a thermal camera to survey that very same plug! Lets not say &quot;old&quot; school. Makes me feel old with the grays all over my head and chin. Lets say ORIGINAL School for those without the priviledge of knowing basic troubleshooting skills.</p>
<p>Is this in the USA? That brass compression connector looks odd and what is the cable type running open above the suspended ceiling?</p>
<p>certainly not USA. That is not a compression connector but rather a brass gland on a steel wire armour (SWA) cable. The other cables are communications cables and not under my care. Yeah, looks messy I know.</p>

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