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89fx
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Join Date: Sep 2009
Location: Cocoa, Florida
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Stainless Steel as a Conductor

05/23/2011 3:26 PM

I have an HVAC unit that has stainless steel spade lugs coming off the contactors, they are all highly corroded and some have heated up and melted the insulation off of them. They are the right gage/type wire for this app. I am suspecting the lugs. Any ideas?
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lyn
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#1

Re: Stainless steel as a conductor.

05/23/2011 3:33 PM

Steel is a relatively poor conductor, compared to copper and aluminum.

CONDUCTIVITY OF METALS SORTED BY RESISTIVITY
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kramarat
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#2

Re: Stainless steel as a conductor.

05/23/2011 4:29 PM

Are you sure they're stainless and not aluminum?

Regardless, the corrosion is probably due to the salt in the air where you live...........it's relentless by the ocean. If you could find copper lugs, they would work better.

Replace the lugs and buy some battery terminal protector from the local auto parts store. Or better yet some of this..............it works well, I've used it. You just want to clean them well with some acetone or alcohol beforehand.

Living by the ocean, I would apply some sort of protection to all connections that are exposed to the outside air.

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JRaef
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#3

Re: Stainless steel as a conductor.

05/23/2011 5:48 PM

Not likely SS; besides being a poor conductor it also doesn't stick to copper very well. What makes you think it's SS? Much more likely is that it's copper or brass plated with silver, tin or maybe nickel.

Over heated lugs can be the result of several factors, almost never the actual lug design itself. But spade lugs in general are notorious for this problem and the only reason they are there is because the OEM HVAC industry insists on it as a cost cutting measure in the mass production assembly process. Contactor mfrs hate the idea but have to comply if they want the business.

Sometimes people change the field wiring and put on cheap female connectors that make poor connection to the male stabs. Sometimes corrosion builds up and the connections become more resistive, heating them up. Sometimes people retrofit VFDs in the circuits and the harmonics cause extra heating in the connectors. Sometimes there is a problem in the control circuit and whatever the contactor is controlling is being turned on-and-off too rapidly (called "short cycling"). Don't just jump to the least likely cause, look at the entire system for more probably issues.

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Fredski
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#4

Re: Stainless Steel as a Conductor

05/24/2011 9:04 AM

I've worked on thousands of HVAC contacters...never saw SS used.

I've been to Cocoa Beach, it's a pretty harsh environment on all types of metals. You also have bugs that just love to make a home around electrical fields generated by small coils. When they get smashed in the contacts they cause all sorts of arcing as they BBQ.

Sounds like $15 and 15 minutes and you've solved your problem with a new 2 pole contacter.
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kramarat
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#5
In reply to #4

Re: Stainless Steel as a Conductor

05/24/2011 11:40 AM

I had never realized the bug thing until I saw it. My air compressor stopped working, so I tore apart the little contact/relay box................it was packed with little brown ants. Yep, they had fried everything inside. I ordered up a new box and sealed the entire thing up with Goop to keep the little buggers out.

So far, so good.

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dj95401
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#8
In reply to #5

Re: Stainless Steel as a Conductor

05/25/2011 3:21 AM

Hey Mark, I seen those same brown ants in a buddy's water well pressure switch, he have the nerve to call me at 4:30am, because he didn't have any water!

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lyn
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#6
In reply to #4

Re: Stainless Steel as a Conductor

05/24/2011 12:19 PM

Happens in AZ too. We have two units at work. One quit are that's all it was BBQBUG. We have service contract, so tech came out. He showed me. Next time I'll check before I call the man.
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JRaef
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#7

Re: Stainless Steel as a Conductor

05/24/2011 1:25 PM

Bugs (and varmints) in contactors are a real problem. When I did a lot more field work here in California, Black Widow spiders seemed to like electrical equipment. Warm, dry and it attracted other bugs, their food source. I had one crawl out of a contactor I had disassembled and was holding in my hand once, went up my sleeve and scared the bejeebus out of me. After that I got into a habit of tapping a contactor with the back of my screwdriver before taking it apart just to scare the little she-devils out of there.

Lately every place I have visited with outdoor electrical equipment has rattlesnakes. All the heavy rains in California this winter meant more grasses, which means more mice, which means more rattlers. Fricken things are EVERYWHERE this year...

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