I've worked with a few different TPO welders over the years, and you're right—same wattage doesn't always mean same performance. I found Leister models, especially the Varimat V2, pretty consistent once you get familiar with their quirks. They're not cheap, but the digital controls and airflow adjustments make dialing in temperatures much easier.
That said, even with a reliable welder, ambient conditions like wind or colder weather can throw things off. I've had days where the same settings from yesterday just didn't cut it today... frustrating, but that's roofing for you. Usually, I start around 1000°F (540°C) and adjust slightly depending on how the seam looks after a test weld. If you're seeing smoke or discoloration, you're definitely too hot.
One thing I've learned: always do a quick test weld on scrap material first. Saves headaches later on.
I've definitely had those days where yesterday's perfect settings suddenly seem way off today—roofing can be weirdly temperamental. I remember one job where it was chilly and breezy, and even at around 950°F, the seams were scorching and discoloring. Had to dial it way back and slow down my pace. You're spot on about test welds though... learned that lesson the hard way after wasting half a morning redoing seams.
Yeah, I've run into similar issues myself. I don't weld TPO every day, but when I did my garage roof, it surprised me how quickly things got overheated. I was around 900°F at first and thought that'd be fine, but nope—ended up dialing down closer to 800°F and slowing way down.
"roofing can be weirdly temperamental."
Exactly this. Weather, wind, even humidity seems to mess with things. Test welds saved me a ton of headache after the first few mistakes... now I always do a quick test strip before committing.
I've found that sometimes it's less about the exact temperature and more about technique. When I did my shed roof last summer, I started around 850°F and thought I'd nailed it after a few test strips. But halfway through, things started getting messy again. Turned out it wasn't just the heat—I was moving too slowly and lingering in spots, causing overheating even at lower temps. Once I picked up the pace slightly and kept a steady rhythm, things smoothed out nicely.
Not saying temperature doesn't matter—it definitely does—but sometimes tweaking your speed or angle can make just as big a difference. Roofing really is finicky though... seems like every project has its own quirks.
Yeah, totally agree with you on technique being just as important as temp. I remember doing a small TPO job a couple years back—thought I had it dialed in around 800°F, but ended up with some ugly seams halfway through. Turns out I was holding the gun at a weird angle and lingering too long in spots, causing overheating even though the temp wasn't crazy high.
Once I adjusted my angle and kept things moving steadily, it was night and day. Roofing really is one of those "feel" things... you can read all the specs you want, but until you're actually up there sweating bullets and cursing quietly to yourself, you don't really get it, haha.
I'd say anything consistently over 900°F is probably pushing your luck with TPO, but like you said, every project has its quirks. Just gotta find that sweet spot between temp, speed, and angle—and maybe sacrifice a few test strips to the roofing gods first.
