Another DIY AC Glycol Chiller

[wootz001]

Hi All,

Picked up a used window AC today, which was directly opened up for cleaning and examination. This being an older unit, there are some spots of surface rust on both the evaporator and condenser coils (mainly the sheet metal supports). I am pretty sure a wire brush and some tin snips will take away most of it... But, it did get me thinking... With the whole evap coil going into the glycol bath: sheet metal, copper, aluminum and all... Is rust something that just happens with these projects over long term use? Is there anything I can do now to help prevent rust and prolong lifespan? I am thinking maybe a couple coats of Rustoleum to the supports at least might be some cheap insurance? Is there any detriment? If I am thinking about setting up a glycol loop, would a small sediment filter in the loop be a good idea? Hopefully you can see where I am going with this. I know I am not the first person to do this, and appreciate your words of wisdom and advice.

Thanks,
-Mike

 

[ryan_george]

I had quite a bit of corrosion of the steel parts and aluminum fins. I ended up cutting/removing everything and just leaving the copper coil/lines. Very labor intensive... and be careful not to damage the copper too much! It is fragile when it is not being supported and protected by the aluminum fins.

 

[Bobby_M]

They make a rust inhibitor for glycol and you can add it yourself or buy glycol that already has it in there.

 

[wootz001]

Thanks, @Bobby_M

I’ve already purchased 2 gallons of food grade (uninhibited) glycol to make 6-8 gallons of diluted solution. Any recommendations on product to treat it? I see now I probably should have gone down the RV antifreeze or Dowfrost route…

 

[wootz001]

Since I already had the uninhibited food grade glycol, here is what I picked up to treat it:

https://www.chemworld.com/Propylene-Glycol-Corrosion-Inhibitor-p/f811-64.htm
After doing some research, strongly recommend anyone else to go straight to a corrosion inhibited product whether that's RV antifreeze or food-grade inhibited glycol such as Dowfrost. The costs are fairly comparable, and, with all the mismatched metals in these systems, it seems like cheap insurance if it will help save from having to replace an A/C, pump, or solenoid valve down the road.