PT1000 Locaton Question

[AKJammer]

Hello All, Hopefully this is an easy answer after a long explanation.
I put a new metal roof on my house last year. The roofing company removed my solar hot water collector, then replaced it after the roof was on. What I didn't realize was that they only hooked up the plumbing, not the T1 Sensor wire that goes with the SunEarth TR 0301 U Controller. I discovered that the wire was just cut and sitting in the attic yesterday. I have a new PT1000 on order and will be here tomorrow.
My Solar collector panel is sitting above the garage area. The attic is unconditioned and there is no insulation above the garage ceiling. We live in the Florida Panhandle where we don't often freeze, but we do get freezing temps a couple times a year. This past year it got down to 19F several days running.
The T1 sensor goes on the outlet side of the piping where it will be hottest coming out of the collector. There is about 3ft of copper piping on the outside before it dives back into the attic to return to the hot water tank.
So to the question. I'd rather not poke another hole through my metal roof to feed the sensor wire, or I can dig through the silicone where they punched through the water line, but I'd rather just strap the sensor to the pipe just below the roof in the attic space. Is that acceptable? i realize I'd probably lose a degree or two of accuracy, but it's only hot water, so I'm not too concerned with that. I think the attic will get cold enough to kick on the anti freezing pump during the winter (Controller manual says it kicks on at 41 degrees F.). So can I do that?

Thanks,
Jim

[Liam]

Hey, I get why you don’t want to poke another hole in your new metal roof. But honestly, strapping the sensor to the pipe in the attic isn’t a good bet – it’ll mess with the freeze protection more than you’d think.

Here’s the straight answer: go through the existing plumbing penetration.

That hole where the copper pipes come through already has silicone around it. You can usually sneak the T1 sensor wire right next to the pipe without ripping the seal apart. Use a stiff wire or a fish tape from inside the attic, push it out gently, tape the sensor wire to it, and pull it back. Then mount the PT1000 on the outside copper, right on the collector outlet side where it belongs. Patch the hole with a dab of outdoor silicone – done.

It’s a 10-minute job, and it’ll save you from waking up to a burst pipe the next time it drops to 19°F. The attic trick just isn’t reliable for anti-freeze, especially in the Florida Panhandle where you do get those cold snaps.

So yeah, don’t overthink it. Use the hole you already have.