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I feel embarrassed asking this question but here goes. I recently installed my Taco SR501 single zone switching relay with my Nest thermostat and everything is working great. I was browsing this site and was looking at other Taco installations and noticed some leave this rigid white piece of paper inside the Taco box. I remembered that my Taco came with a rigid white piece of paper inside it and removed it before I installed it. I took a picture of it, it has the numbers 9300-2944 printed in the side of it. What's the purpose of it and why do some leave it inside their Taco box and others don't? What's the point of it?
Thanks in advance.
Here's a picture of mine and another picture of one I found on the site.
Long Island, NY