High limit switch installation direction/flow/orientation?

Old 04-15-19, 02:12 PM
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High limit switch installation direction/flow/orientation?

Hi all!

What a great forum!

I've got a Nordyne L1RA 072N-12B furnace. It was diag'd with a tripped limit switch. Technician claimed to have cleaned it and reinstalled. It worked for a few days then tripped again. I had time myself finally and removed it. It's old and heat stressed (actually cracked). I don't understand why the tech didn't replace it. Anyway, I ordered a new switch and plan to replace it this week. Image is below.

The problem I'm met with is I don't know the correct orientation of the switch into the air flow. It can go in one of two ways...the metal surface of the switch against air flow direction, or the back of the switch (plastic) against air flow direction. When I removed it, the plastic side of the switch was against the direction of air flow. I'm not sure this is correct. I contacted Nordyne and they emailed me the installation manual and wiring diagram. Neither of which show the direction of the switch. I search youtube and the www to no avail. It makes sense to me that the metal side of the switch should face (against) air flow. Am I correct?

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Old 04-15-19, 03:07 PM
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If you killed the fan and timed both ways I don't think it would make much difference.
Old 04-15-19, 04:47 PM
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Since this is a limit switch which sensors temp and not air velocity an educated guess is it could go either way but I would try facing the metal up and out of the direct path of the airflow to better sense just the temp.

Below is a sight with a number you can call for info. They are very customer friendly.


Hope this helps a little.
Old 04-15-19, 06:18 PM
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I think you'll find the mounting screw notches and holes to be slightly off-set. This helps to index it properly. You should be able to see it on the old switch. Looking at the furnace's manual you can also see it on the face diagram.
Old 04-15-19, 09:47 PM
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Welcome to the forums.

Fastback is correct. In this instance.... that switch is set up to mount in one direction. You are showing it correct in your picture. The metal part of the switch points up.

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As a rule..... I don't think the direction is all that critical.
Old 04-16-19, 07:28 AM
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guyold, spott, fastback, PJmax,

Thank you all!

I now see the slight offset holes on the switch mounting plate. The metal part of the switch does indeed point away from the air flow.

Old 04-18-19, 10:52 AM
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Also, Id bet, when installed correctly, the printing would be right side up.

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