RE: Triple evac
So… there is a discussion on an HVAC fb page concerning triple evac. There are several saying that it’s not imperative to pull a triple, for various reasons. I was taught the nitro helps remove moisture and have always pulled a triple evac. I know this is a much better forum for answers so…
Do you triple evac? Why or why not???
Having done a lot of testing and experimenting, I came to the conclusion (on the resi side) that a triple evacuation is only necessary when the pipes aren’t new/clean since the rest is.
If the copper is clean and the install done properly, I find no benefit whatsoever to pull a tripe evacuation. So what is a proper install for me ?
Flush the copper if it absolutely needs to be reused. Keep it plugged till the last minute, free of any debris.
Flow nitrogen when brazing and cores out. A must! Always try to keep a positive pressure of nitrogen.
Once brazing is done, and keeping the cores out, I pressurize for leak test with the intent of pulling an evac just after without introducing contaminates. For that, I install 2 Appion vacuum rated core removers right away on pressure test. Once I’m happy with my test, I install 2-1/2” vacuum rated hoses directly on the core removers, using them as a manifold and connect them to the vacuum pump. I also use 2 vacuum gauges that I install on the core removers (it’s a bit overkill but I have them from all the testing I’ve done).
Once the system is in place and ready to pull, I let the nitrogen go through the top port of my pump (TEZ-8) and as soon as there’s nothing but a shallow breath of N, I start the pump and my gauges.
If everything goes well, I can have a standing vacuum below 500 microns in 5 to 15mn max.
It always takes me longer to finish the wiring and clean up then pulling a vacuum.
Removing the cores, using large vacuum rated hoses and eliminating the manifold makes the process MUCH faster and reliable.
Once I’m ready, I crack open the liquid line to bring the system to a positive pressure. It’s easy to see since the vacuum gauges are still on. Once under positive pressure, I close the liquid line, take the hoses off and reinstall the cores without any risk of introducing contaminates into the system. I fully open the valves, connect my gauges, flush the hoses and start up the system.
I bought brass plugs for the vacuum hoses to keep them clean. Cheap trick with great results.
This might seems like a long process, but it is actually much much faster then anything else I’ve tried and see anyone do.
I’ve never had an issue once I started doing this as long as the pipes were clean.
Remember that your regular hoses are made for pressure and not vacuum, and that the inside diameter is quite smaller than the 1/2” hoses. It does make a big difference because air expands a lot under vacuum and a greater volume in the hoses means a faster evac.
Thanks for reading this till the end. I hope it’ll be useful to you.