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Current state: enter image description here

Original: enter image description here

I am repairing a cordless kettle's base plate whose the power cord was cut. The new wires need to be connected to the contact pins in the base. Originally, quick disconnect terminals were used with two crimped sections, one on the wires and another on the insulation, all covered with heat shrink.

Is there any safety concern with soldering wires directly instead of using crimp terminals?

I don't have the same type of quick disconnect terminals or the required crimp tool. The options I can think of are:

  1. Buy general purpose quick disconnect terminals which can be crimped with a regular crimp tool. The insulation is probably not rated for 105C like the power cord, though I don't think the base of the kettle should be reaching such temperatures.

enter image description here

  1. Try to reuse the old quick disconnect terminals by uncrimping the wires and then soldering the new wires into the terminals, and using heat shrink over the whole thing to approximate the original assembly.

  2. Solder the new wires directly onto the terminals and cover with heat shrink.

The power cord is 16 AWG and rated for 105C and 300V.

Option 3 would be the easiest for me and require no new purchases. Option 2 would take the most effort and time, but require no shopping trip. Option 1 would look the best, but I don't know if the insulation used is suitable in this case. I would think it should be passable, but... what are your thoughts?

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  • In the first, current state, photo, Why are there 5 wires and 3 terminals?
    – Alaska Man
    Commented Oct 30, 2020 at 19:32
  • 1
    Go to a decent supplier and get the sleeves and crimp terminals - they are available. Used to use them and still have the crimping tool. Just remember sleeve first :)
    – Solar Mike
    Commented Oct 30, 2020 at 19:36
  • @AlaskaMan Sorry for the confusion, the third wire on the power cord on the left side is out of the image. The loose terminal was cut off of it. The left and right power cords are from the same 3 wire cord; it was just cut.
    – adatum
    Commented Oct 30, 2020 at 19:36
  • If you do not have new disconnects, or want to buy them, then perhaps it would have been best to have left the original connects, cut the cord and spliced/soldered the new cord on to the old one and heat shrink-ed that all up. Is the ground wire on the new plug clearly labeled or can make sure you get it right?
    – Alaska Man
    Commented Oct 30, 2020 at 19:39
  • In hindsight, keeping the original connectors and soldering to the wires would have been best, but it's too late. I don't know where I would find the same time of disconnect terminals, and I don't have the right crimp tool for it anyway and don't think it's worth buying for a single job. Also, none of this addresses my original question.
    – adatum
    Commented Oct 30, 2020 at 19:43

1 Answer 1

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Soldering this connection is illegal and unsafe; it's prohibited in AC mains wiring by NEC, and in appliances by the UL White Book; both proscribe conditions in which soldering is OK, and this is definitely not one of them.

Feel free to do exactly what they did: use uninsulated crimp terminals and then shrink-wrap over the works once it is crimped.

I get uninsulated crimp terminals by removing the insulation from insulated terminals. There goes the temperature limit!

After you crimp it for a complete and secure physical and electrical connection, feel free to solder it also if you really want to. This is how NEC tells you to use solder. You can't just hork-a-dork solder like you do on hobby electronics projects; this is a high-current connection. Solder has a low melting point, so voltage drop across the solder is something that matters quite a lot. And that makes the resistivity of solder matter a lot. In this application it combines rather adversely with the high temperature operating conditions and high current.

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  • Good point, removing the basic insulation plastic avoids worries about it melting. The heat shrink I have (CFP-1/8-4-BLK) is rated for "continuous operating temperature from 55C to 135C" so that's ok. Since the kettle is rated up to 1500W, the connection should not fail with high currents; that's certainly a concern. I could verify the resistance after soldering (if soldering) as a sanity check. With solder's melting point at a bit under 200C depending on the alloy, that should not be a problem though, right?
    – adatum
    Commented Oct 31, 2020 at 2:59
  • The problem is, once you solder to those spade connectors, they will be ruined for any other use, and you will need to buy a new kettle (assuming you can't obtain that assembly as a repair component). Soldering is illegal and unsafe. Just because product safety is "new to you" does not mean it is the wild west. UL wrote the book on how things like this must be done; it's called the UL White Book. I would say "read it" but UL keeps it paywalled. The upshot is, appliance repair is OK; deviating from approved design is not OK.
    – Harper - Reinstate Monica
    Commented Oct 31, 2020 at 15:24
  • OK, thanks. I don't want safety risks so I'll just get some crimp terminals and use them without their insulation and add my heat shrink, as suggested. Should the insulation be removed before or after crimping? Before might be easier and won't risk damaging wires, but I don't know if the insulation's thickness is required for proper crimping. As for the UL White Book, I wish I knew the standards and the reasoning behind them. Since I don't, I asked here.
    – adatum
    Commented Nov 1, 2020 at 5:59
  • @adatum yes, I wish the White Book wasn't so opaque. My strategy is to remove insulation first (comes off easily) then use the positions on the crimper intended for uninsulated crimps.
    – Harper - Reinstate Monica
    Commented Nov 1, 2020 at 19:01
  • "positions on the crimper intended for uninsulated crimps" --> I don't have this. Just a basic stripper/crimper combo tool that has three positions labelled by insulation color (red, blue, yellow).
    – adatum
    Commented Nov 1, 2020 at 20:08

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