International Thermal Research CO105D, Руководство оператора

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6.10 PROTECTING HYDRONIC HEATING SYSTEMS
The advantage of closed hydronic heating systems is that as long as there are no leaks, (i.e., no need for
constant make-up water), the fill neutralizes (that is, it reaches equilibrium). The long term result is
minimal scale build-up and insignificant corrosion since after operating for a period of time, most
oxygen has been "starved" out of the boiler fill water. While boiler fill water treatments have their
place, leak prevention is the single most important preventative maintenance item.
Regular maintenance and prompt repair of leaks, combined with a one time application of appropriate
inhibitors, can help you enjoy problem-free heating. Since it is difficult to guarantee that a hydronic
heating system will never leak, corrosion inhibitors and scale inhibitors added to "fresh" boiler fill
water can act as low cost "insurance" for hydronic systems.
Causes of Scale
Tap water is the most typical source selected for boiler fill water. Water contains dissolved solids such
as magnesium and calcium which when heated becomes much less soluble and forms scale. Scale
comes out of solution in the largest amounts where the temperature is highest in the system (i.e., the
boiler heat exchanger). As the scale builds up, noise and cold spots develop since scales plug up water
channels and acts as an insulator that impedes proper heater transfer.
Acidity and Corrosion
Corrosion is the result of metal oxidizing (that is, metals reacting with oxygen-rich boiler fill water).
The acidity of any liquid (including water) is a good indicator of how much corrosion will actually take
place. As a rule of thumb, boiler fill water should have a pH greater than 7 and less than 10.5. The key
to preventing corrosion is to make sure that the heating system is free of leaks and there is no need to
replace it with fresh, oxygen rich boiler fill water. Corrosion inside a hydronic heating system stops
quite quickly as the fill water stabilizes and becomes oxygen-starved. The pH should be measured at
least annually.
Since most hydronic heating systems are comprised of different metals (e.g., iron, copper, etc.), and
since boiler fill water is an electrolyte (that is, it will conduct electrical current), electro-chemical
reactions ("galvanic" reactions) can take place. As the fill water stabilizes, however, it becomes a very
weak electrolyte, so galvanic corrosion rarely becomes a problem - as long as the system remains leak-
free.
Preventative Treatments
Corrosion and scale inhibitors are relatively inexpensive. Ideally, they should be applied, once only, at
the time of a new installation or whenever a system has been completely drained. Boiler water
treatment specialists almost unanimously agree that the prevention of leaks and the elimination of the
need for frequent boiler water make-up are top priorities for hydronic systems.