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Would this be the correct orientation for replacing an old Trane relay with a new Trane contactor?

It looks like the 4 flathead screw/lugs on either end match up with the 4 screw terminals on the original relay, and the tab connectors on either side match up, as well. Red and black wires on one end, brown wires on the other end... blue and yellow wires on opposing side tabs. The old relay is a Trane RLY03346.

enter image description here

TheBigCat
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1 Answers1

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Per their spec sheets they should be like for like terminal wise. The old contactor was rated at 50 amps, the new one is 40 amps. I couldn't believe the difference in price. The original OEM replacement is almost $200. It may not last as long but for that price you can buy a few.

JD74
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  • Yeah, so this Trane Executive BTD736A100B0 is rated at 3 ton, and apparently a 24V 40A contactor can work with this unit. This thing is from the mid-1980s, but still blows cold really cold air. The only thing is the contactor/relay is pitted and has been sticking intermittently. I'll give it a test with the new contactor tomorrow. Mild temps here for the next 2 weeks, so I got plenty of time for trouble shooting, haha. – TheBigCat May 21 '23 at 01:27
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    @TheBigCat 40 amps will be fine, even a 5 ton would only pull 25 amps. – JD74 May 21 '23 at 01:41
  • Oh, btw... what is the purpose of that brown 'loop' wire connecting the 2 terminals at the back [bottom of photo] of that old relay/contactor? – TheBigCat May 25 '23 at 12:32
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    @TheBigCat I'm guessing that it goes to the starting capacitor. It looks like they didn't use both poles of the contactor when they wired it. Which leaves the motor windings always energized even when the contactor is open. – JD74 May 25 '23 at 17:20
  • Yeah, I'm wondering if it was even necessary. It's only like 5 inches long and it just 'bridges' across the back left and right terminals. But those terminals already have a purple wire for one side and a brown wire for the other... and then black and reds on the front two terminals. Odd. – TheBigCat May 25 '23 at 18:16