I was reading the install manual for my Harman Hydroflex 60 Boiler and came across something interesting.
It states the following:
Anti-freeze and / or boiler water treatment:
There is no restriction on the type of commercial antifreeze used. When filling the boiler water system, it is
recommended that some form of boiler water treatment be used.
Has anyone done this? What are the pros and cons of not adding it?
And, how would you do it if it wasn't done during installation (a year ago)?
Any input would be greatly appreciated. Thank you.
CYA statement from the manufacturer.
If you wanted your system to be winterized such that you didn't have to worry about it freezing if there were no power or heat, then the antifreeze would be recommended. However, it is very expensive and should be bought pre-mixed with De-ionized water for purity. It also must be made with inhibitors formulated for HVAC systems. Automotive antifreeze can damage parts of an HVAC system. It is best bought in 55 gallon barrels. I bought a barrell two years ago at $6 per gallon premixed to 40% (wholesale cost) or $330 per barrell plus tax. I used it in my workshop system, so I didn't have to keep the heat on in the workshop all of the time.
Note that antifreeze will "clean" the system and any leak will show up. It is a pain to keep the stuff from leaking from valve packings.
If your system is already filled, don't worry about water treatment. Once sealed, the oxygen reacts and is used up. Adding water treatment in a residential size system after the fact is a waste of time and money.