Water Treatment Related to HVAC

• Chilled Water: Industrial/commercial Glycol solution used for chilled water already has its built in corrosion inhibitor. Make up solution of the same concentration should be able to maintain the correct chemistry. Periodic chilled water analysis done usually during plant maintenance would give good indication what and how to adjust bleed and make-up necessary to maintain chemical quality/integrity of the chilled water.
• Condenser Water: Chemicals to adjust pH is a function of water concentration to avoid calcium precipitation in heat transfer surfaces. If the condenser water is cooled through a cooling tower, evaporation loss is made up, along with the blowdown, with a make-up water. The no of concentration ratio (Circulating condenser water TDS Concentration to TDS to make-up water TDS concentration) should have good balance with your chemical addition (cost) and blowdown. The index to watch is called LSI (Langelier's Saturation Index). From the internet, there's a good reading material on LSI and how to calculate it, once you have a good grasp of your circulating and make-up water analyses, operating temperatures and pH. (http://www.water-services.info/pdf/CALCIUM_CARBONATE.pdf) What LSI mean to your water is: How close is your water condition to incur Calcium Carbonate precipitation (Scale formation). When calcium carbonate precipitates on hot surfaces, it becomes scale, and scale reduces the heat transfer capability of the heat transfer surface, increases friction loss and therefore costs more money to operate, and to maintain. If you stay away from scaling condition, you won't even have to worry about acid cleaning. When you eventually need it, a 5% acid solution is usually sufficient. Check with your chemical supplier for procedure for safety's sake. The good part of circulating water being on the higher pH (8-8.3) side is that it is not corrosive to most piping materials typically used on water, such as steel pipe, there's a good chance that it gives a better LSI. It just depends on your make up water quality. Then, the last of the equation would be to calculate your blowdown. Again, balance of chemical cost and waste, which also costs money, is at stake here. Your water treatment chemical supply representative can run your water analyses (ON THE CIRCULATING WATER & MAKE-UP WATER) and typically gives a report on the LSI. This is where their sales pitch comes in. However, understanding the LSI concept, you are better prepared to readily comprehend what they are offering.

I hope this helps.

rpocamp2

Most HVAC chilled water loops do not use glycol. Glycol is expensive, decreases heat transfer slightly, and at the low temperature of chilled water is more viscous which increases pumping cost, perhaps requiring larger pipe and bigger pumps. Also while ethylene glycol works better, because of its toxic nature, non-toxic propylene glycol is often used, which, with its higher viscosity, takes a little more pumping energy than ethylene.

The chilled water loop still needs corrosion and biological inhibitors. Also in some applications, the same chilled water loop is also used for heating in winter. In that case the treatment needs to be compatible with the higher temperature of heating hot water.

for something a little different, take a look at the Zeta Rod. www.zetarod.com We installed several at a large airport for scale issues and cured that and more. It is designed to reduce the need for chemicals.

Zeta Corporation, the company that manufactures the Zeta Rod has just launched a blog open for discussions and information (this is besides their website). It is worth checking out: www.zetablog.typepad.com

Consider non-chemical water treatment - Clearwater Systems pulsed power Dolphin Water Treatment System has been proven in over 3000 cooling tower and boiler applications to date. It addresses scale formation, biofouling and corrosion without using any chemicals. Go to www.dolphinwatercare.com for more information.

There is a long history to non-chemical devices being used for water treatment dating back to 1865. Most of the history is not good. For an overview of that history, I recommend that you visit this web page before investing large sums of money into a non-chemical device. Here is the link: http://www.richardhouriganinc.com/non-chemical_devices.html

Regarding the Dolphin, I suggest you visit The ProChemTech web Page: http://www.prochemtech.com/Literature/literature.html and download the three reports that de-bunk that device. Similiarly, there is a case history on the Zetarod on this same web page.