ASHRAE pH Suggestion For Closed Loops

[fourgs]

I am looking for recommendations on the pH range that should be maintained in the following commercial building closed loops: chilled water, heating loop and heating loop with 30% glycol. I am not an ASHRAE member so I do not have access to their yearly handbooks. Are there any good sources for this information besides ASHRAE?

Thank you for your help!

[RichardL]

Sodium sulfite-caustic soda programs have been used successfully in many closed systems. The sulfite residual should be maintained between 30 to 60 ppm with sufficient caustic soda added to adjust the pH to within 9.3 to 9.5. This is an effective approach when properly applied. It is less expensive than other options, and presents few disposal problems. This treatment method is compatible with glycol.

If the closed system has leaks allowing air inside, the sulfite will be consumed at a rapid rate. Continued addition of more sulfite will cause an increase in the total dissolved solids.For more infomation go here:

http://www.watertechonline.com/article.asp?IndexID=5230109

[fourgs]

Thanks for your response.

[Russ57]

The desired PH for the reheat would depend on the chemical treatment program. Chemicals used are somewhat dependent on water temperatures and the metals in the system.

For standard comfort heating with water temps under 250 and steel piping Molybdate-Nitrite-Azole based systems are common. Desired PH would be in the 8.5 to 9.5 range. This product could be used in the chill water loop as well. However I caution that there are different products used that require different PH levels (systems with aluminum come to mind).

If you can afford it consider a water meter on your makeup water and softner if hardness is over 250 ppm of calcium carbonate.

BTW, your government puts out a great resource book that will answer all your questioons about water treatment. Search for document UFC 3-240-13FN.

[fourgs]

Thanks for your reply.