Mildly Infuriating

My very first maintenance I went down to look at what I needed to do. It's a trane unit, so the evaporator coil and the condensate pan come out on a slide which is pretty fancy.

If it's the style I'm thinking of then you are flexing the refrigerant pipes whenever you do that. It's designed to do that but just be aware that copper work hardens so you can only flex it so many times before it gets brittle and snaps. With your system being new there isn't too much risk of snapping a line but it won't be new forever. If it is possible to clean the evap without bending those pipes then that is the best way to do it.

As far as coil cleaner goes the most we ever recommend one of our customers use is just plain water out of a gardenhose (definitely not a pressurewasher). For most people that should be enough. But you're not my customer so here's what I use depending on the coil.

For small evap coils like a residential central air system I often use Evap Foam No Rinse. That stuff is pretty gentle and probably fine for most people to use. If kills any growth on the coil and foams up to push dirt out of the coil. Once applied it doesn't need to be actively rinsed off because it's designed to be rinsed off just by the condensation that builds up on the coil as the system runs.

For larger evap coils like in commercial roof top units or more heavily soiled evaps I will use either Tri-Pow'r HD or Evap Pow'r-C. I've found both to be about equally as effective but the evap cleaner does foam up a bit more. Both are still fairly safe to use but if you mix them more concentrated then you do need to actively rinse off the coil well when you're done. I have a hard time imagining anyone breaking anything with either of these but technically they can do damage if left on the coil for too long.

When it comes to the new style microchannel condensers, heavily degraded older style fin and tube condensers, or lightly soiled older style condensers, I will also use Tri-Pow'r HD except I will mix it much stronger.

When it comes to heavily soiled older style fin and tube condensers which are otherwise in good physical shape I will use Nu-Brite. Nu-Brite is nasty shit. It will instantly burn skin, melt plastic, strip any oxidation off of metal, etch concrete, strip paint, strip the coating entirely off a coated coil, and, if left on a coil long enough, etch holes through the condenser pipes forcing you to buy a whole new condensing unit. It literally starts to smoke if it sits on the coil too long. It is aggressive as hell but man does it clean coils. I was working at a flour mill recently and made extensive use of this stuff to clean mouldering packed in flour mud out of condensers and it takes no time at all to do it's job even with the worst soils. This stuff is perfectly safe to use if you use it right but if you don't use it right then there is basically no fixing the damage it does. If you ever did decide to use it, just be sure to have a hose nearby ready to hose it off as quick and completely as possible. Once it starts foaming and smoking it has started doing damage.