Metal finishing Q&As since 1989

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Testing Brazes and locating very clean HVAC coils

March 10, 2020

Q. I have several questions about a coil I want to install as part of an HVAC system. This part would be in the ductwork. TRANE model # 4PXABU30BS3. The coil and fence are aluminum, and the brazing rod is also aluminum.

Because of an unusual immune system problem, I am hypersensitive to lots of substances including the kind of manufacturing residue often found on metals, so we have tried to clean the unit many ways before installing it.

We've tried soaking the whole unit (of course keeping the open ends of the tubes well above water) in diluted isopropyl alcohol, distilled white vinegar [in bulk on eBay or Amazon], detergent, sodium carbonate / washing soda [affil links], sodium bicarbonate, sodium percarbonate, and baking soda (separately). We've used warm water in a power washer. Finally, we've also combined baking soda and vinegar to make a volcano of scrubbing bubbles. There's no way to scrub the fins because they're so deep and close together.

1) Does anyone have any ideas about how to further clean a coil in as non-toxic a fashion as possible?
2) We're also worried that even though these cleaning materials were approved by expert sources, that we may have damaged the brazing. Can anyone comment on that?
3) Does anyone know a way to test the integrity of the brazing? Again, because of immune system problem, release of refrigerant into the whole HVAC system would be catastrophic.
4) Does anyone know of a source for an alternate coil that'd either be more pristine upon arrival or would be manufactured in a way that could withstand our cleaning attempts without being damaged? Trane does stream clean their units, and this one seemed to start from a pretty good point, but we couldn't get it where we needed it to go.
5) Can anyone recommend another source or consultant that may be able to help us with these questions?

Perhaps some industry requires particularly clean coils, and we could go down that path? Alternatively, we recently learned of custom stainless steel coils - maybe they would require welding that would better stand up to our cleaning? I assume there would still be some brazing required to provide copper outlet tubes that run to the compressor.

Thanks for any input you can offer!

Robin Pfaff
- Palo Alto, California

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Need Advice for Cleaning Aluminum Coil

Q. What type of cleaning would be best for removal of manufacturing residues such as oils, and solder resins from a copper coil heating/cooling coil?

Steam cleaning; pressure washing; ultrasound; CO2 dry ice/snow blasting? Or other?

For medical reasons the coil must be very clean.  Could expansions or contractions of very cold or hot damage the coil? If so are there procedures for gradually decreasing temperature when using CO2 cleaning that might help?

The coil is ADP model TG 326 36 D175 B16. It's an A-frame 3-ton aluminum coil (with some copper) with aluminum fins. It's not supposed to have any coatings. We haven't installed it yet.

Robin Pfaff
- Palo Alto, California
June 5, 2020