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I have a cable with 3 X 10 AWG stranded conductors, L1, L2 and Earth. This cable will need to pass 32 amps of continuous current for 24+ hours at a time. I have this contactor: enter image description here

As you can see, the contactor has box screws (is that what they are called?) and I intend to use them as the UL standard for "faston" (quick connect) crimp terminals won't allow for more than 25A continuous through a yellow terminal. Actually, maybe someone could confirm this for me?

I feel a bit cheap shoving the AWG 10 stranded wire into the hole and clamping it down with the screw. I realize this may actually be the best method, but I am wondering if there is a cleaner, safer alternative.

I thought of using something like this but for the life of me, I can't find a current rating. I can't even find a confirmation that it will handle as much as the conductor it's crimped to. Also, I'm not sure that this would create a better contact in the contactor than just bare wire...

I would appreciate any insight! Thanks!

Matthew Goulart
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    google `high current ferrules` – jsotola Sep 13 '20 at 01:57
  • Why wouldn't quick connect terminals work? They're just bare metal metal if you choose to use uninsualted terminals. If they really can't accept more than 25A then neither can the tabs on your contactor which were designed for quick connect terminals. Maybe that's why there are multiples of them in parallel on your contactor (or at least that's what it looks like to me from the photo). In which case, break out your 10AWG wire with a butt splice to multiple quick connect terminals. Or use quick connect terminals that attach mid-wire at 90 deg and have a row of them on the same wire. – DKNguyen Sep 13 '20 at 02:03
  • @DKNguyen I assume the 4 tabs are there because the manufacturer *also* makes relays for 30, 20, 15 and 10 amps, none of which have the "box screw". Probably just to save on manufacturing costs. I did think of using multiple quick connects, but I can't think of a clean and space-conscious way of doing it. – Matthew Goulart Sep 13 '20 at 02:08
  • [These 10AWG ferrules](https://nl.farnell.com/multicomp/e6012-green/ferrule-10awg-20mm-nylon-green/dp/9972269) are rated for 50A. Whatever you do, don’t clamp the screw directly on the wire. – StarCat Sep 13 '20 at 06:27
  • @StarCat would you elaborate on why it's so bad to clamp the wires directly? – Matthew Goulart Sep 14 '20 at 12:17
  • By screwing directly on the wire, you'll damage the strands and/or drive them apart which will create higher contact resistances and possible failure (especially in environments with movement or vibration). For high current applications you need to keep the strands tightly together and undamaged. – StarCat Sep 14 '20 at 12:52
  • @StarCat roger that, just bought a ferrule crimper and a boatload of ferrules. Thanks for the info! – Matthew Goulart Sep 16 '20 at 01:02

1 Answers1

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Two solutions exist:

Use multiple 90 degree angled quick connect terminals and put them in a row onto the same wire.

https://media.digikey.com/photos/Tyco%20Photos/60851-2.JPG

From TE Connectivity

Use a crimp terminal that looks like a long narrow flat bar with or without a short 90 degree bend at the tip and screw that into the screw terminal. I'll try and find their formal name. They are called "flat blade" terminals or "PIDG tabs".

enter image description here

From TE Connectivity enter image description here

From TE Connectivity

Personally, I wouldn't be too worried going from 25A to 32A as long as it was made of copper (and not steel), especially if you used a non-insulated crimp terminal without any plastic to melt. But if it is running 24 hours, I understand since no one will be around to see anything go wrong.

I tend not to worry about current ratings of a connector too much if it is all metal (no plastic to melt), is all copper, and looks to have the same cross sectional area and contact area of the copper wire it is connecting to.

DKNguyen
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