heat exch loop Ph and galvanic prevention? 2

[evofxdwg]

I have a water source heat pump in my home. It has an auxilary (desuperheat) heat exchanger made of copper. I am adding a closed loop to this desuperheat exchanger with a titanium heat exchanger at the pool filter system, dumping heat to the pool during the cooling season. All piping is plastic (CPVC and PEX). The working fluid will probably be well water as I dont need freeze protection. But i would consider other non-toxic fluid mix (proplyene glycol?) if there is a reason for it. I assume straight well water at 5.5 Ph is NOT good for the copper (since i have just finished replacing ALL the cu plumbing in my home due to pinhole leaks). The CU exchanger in the heat pump unit is probably at chassis ground potential. There is a small 230V circulation pump with brass body, I assume local saftey codes require grounding it. The TI heat exchanger has a plastic outer body, but i can ground the TI loop at a fitting if needed or leave it isolated.

1. What is the ideal Ph to run the working fluid?
2. Is it OK to use sodium bicarb or borax (same stuff i use in pool) to raise Ph to the desired level?
3. Is there a reason to use other than treated water?
4. Are there any galvanic corrosion issues? If so, what should i do to prevent?
5. Should TI exchanger connection be grounded?

 

[EdStainless]

pH should be near neutral.
In any mixed metallurgy system a corrosion inhibitor is a good idea. Maybe some non-toxic auto antifreeze. You only really need the inhibitor, not the glycol. It wouldn't take much.

I don't like grounding each piece seperate, there is too great of a chance for offset voltages.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[deposition]

pH 5.5 is corrosive to copper. Ideal pH for copper is between 7.5 and 9.3. If you should use antifreeze, don't use automotive grade antifreeze because it contains silicate. Silicate is unstable in low pH. It forms gels and fouls your heat exchanger. If you use water, you can buy corrosion inhibitors, buffered with borate to neutralize low pH and inhibited with yellow metal inhibitor, azoles. The formulation usually takes care of multimetal piping. I prefer non-nitrite formulations in your case.