Thoughtful Termination (Of Wires)

When you are checking a unit of any kind, you should be keeping your eyes open for signs of arcing and melting at all of your wire connections and contact points. We find issues with melting terminals on contactors and in disconnects regularly. Still, We rarely think about the relationship between circuit ampacity, wire size, and the connections to our equipment.

First, consider that a #10 wire doesn't always have an ampacity of 30 amps; it has an ampacity of 30 amps with a 60° Celsius rated assembly at 30° Celsius ambient.


Now, look carefully at the wire and the contactor at the start of the article.

The wire (conductor) is rated at 90°, and the contactor is rated at 75° when torqued down to 22 in/lbs on screw-type terminals and 40 in/lbs on lug-type.

So, the entire assembly is only as good as the weakest link, and the weakest link is the terminals, and the terminals are only as good as the contact they are making.

Conclusion: The termination (connection) points are usually the weakest point of the circuit.

When sizing conductors, don't forget ANY of the termination points. From the breaker to the disconnect to the unit, every termination point should be properly connected. Check the rating if you intend to use any ampacity other than 60° Celsius.

Check those connections. Make sure they are snug and properly suited for the ampacity of the circuit.

For more great info on this, go HERE.

—Bryan

Related Tech Tips

Defrost Termination & Fail-Safe
As an A/C tech, I can sometimes get the terms “defrost termination” and “defrost fail-safe” mixed up because they sound pretty similar. Before we cover these terms, let's set the basic defrost groundwork for refrigeration (coolers and freezers). Defrost is accomplished in one of a few ways; these first two only apply to “coolers” where […]
Read more
How I Failed to Re-diagnose: The Lesson I Learned
This is the tale of how I found myself stuck on a service call for over 12 hours on a weekend due to my failure to re-diagnose an issue. I was working for a service company that had many accounts with local gas stations. These were large customers, and we did everything we could to […]
Read more
What Willis Understood 
I've been reading a book called Cool: How Air Conditioning Changed Everything, and it got me interested once again in the history of air conditioning and refrigeration. Like many things, the people who are credited with “inventing” are the ones dogged enough to make an idea commercially successful, not the idealists forever tucked away in the […]
Read more

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

loading

To continue you need to agree to our terms.

The HVAC School site, podcast and daily tech tips
Made possible by Generous support from