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TMB - Plumbing Engineer - Columns: January 2009: Modern Hydronics

Hard to remain neutral

By Paul Rohrs, Radiant Expert

Biggerstaff Radiant Solutions, Lincoln, Neb.

Modcon boilers are getting mighty efficient these days. Where does the efficiency come from? Boiler manufacturers are gaining this extra efficiency by extracting heat from the exhaust gases. The exhaust temperature is lowered until it reaches its dewpoint and condenses. This condensate flows back down the exhaust pipe, where more heat is extracted through a heat exchanger. It is then piped to a trap and down the nearest drain.

We are going to look at the process a little more in depth, talk about why it's important to neutralize the condensate and give some examples of various neutralizers available on the market today.

Condensate from modcon exhaust gases has a low ph level, which is how the fluid's alkalinity or acidity is measured. It is normal for this condensate to have a ph ranging from the mid 4.0's to the mid 5.0's. Ph levels below 7 are considered acidic. If we don't neutralize the condensate to a neutral 7 or 8 range, it can slowly eat away at a drainage system. This lower ph condensate will attack cast iron soil pipe, ABS pipe and septic tanks, to name a few. A ph level of 4 is 10 times more acidic than a ph of 5, so it is important to note that we are dealing with a mild acid with effects that will manifest themselves over time.

The modcon at our shop had been running for only three months and was close to a drain but was not piped completely to the drain. We noticed that it was etching the limestone and cutting a groove in the concrete. See photo below. We corrected this "open flow to drain" by piping it all the way to the drain. After looking a little more closely, you might notice that it was actually eating away at the bronze strainer of the floor drain. Bronze floor drain strainers are not safe from the effects of untreated condensate.

I do have a small control test started, because I wanted to see the long term effects of condensate on cast iron. Why? Imagine all of the equipment out there producing condensate that is being funneled into the floor drain of a house with cast iron pipes for its drainage system. If this condensate eats away at the cast iron, it will only be a matter of time until it eats through the pipe and starts to wreak havoc below the house. I took a small piece of brand new cast iron no-hub pipe, dated it with a Sharpie and placed in the flow path of our condensate. I will report back on the actual life span of the cast iron pipe when the results are conclusive.

This process does not only occur with high efficiency boilers. Think about all of the standard atmospheric forced air furnaces that have been changed out to high efficiency units. High efficiency furnaces also produce condensate and all of that condensate, left untreated, has a head start at eating away at the drainage system. On your next service call or scheduled maintenance, inform the homeowner of the need for a condensate neutralizer.

Several models of condensate neutralizers are available on the market today, or you can make your own. Dave Stroman is a hydronic contractor in Denver. I noticed him building his own, very effective neutralizer out of commonly stocked PVC fittings. Photo 2  below shows the model we cloned from his idea. The condensate is collected in the standpipe where it enters the bottom tee's branch inlet. The condensate is afforded quite a bit of contact time with the neutralizing agent before it rises up to the branch of the higher tee, where it then gets piped down to the nearest drain.

Photo 3 below shows a sample of a pre-manufactured neutralizer available from JJM Boiler Works. Stock models are available from several boiler manufacturers, such as Lochinvar and Viessman. JJM Boiler Works offers several stock models but can also custom design a neutralizer to meet your specifications.

On scheduled maintenance visits, we have found that the interior of our neutralizers, as well as the marble, has turned an orange color. This is a natural chemical reaction and should not alarm you. It is, however, a reminder that you should test the ph of the fluid exiting the neutralizer so that you can ensure that the useable lifespan of the neutralizing medium (marble or limestone) isn't over. Am I suggesting that you carry small amounts of crushed marble or limestone along with ph test strips on your service trucks? Yes! These neutralizing mediums have a life expectancy, and you should be ready to service them as well. This is yet another value-added service that you can add to your service arsenal and charge for.

The future of condensing boilers and furnaces is bright. Condensate is here to stay, so contractors should stay on the cutting edge of this technology by offering the appropriate neutralizer as part of their standard proposal package. To counter the negative effects of untreated condensate, contractors can order pre-made units or build them themselves. Standard service contracts or routine maintenance can be used to maintain the units' effectiveness.

Responsibly designed radiant systems that feature condensing appliances can be enhanced with the addition of condensate neutralizers. It isn't just for show, and you'll be confident that your customers and the litmus paper will be able to tell the difference.

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