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Water chemistry for MC-80 boiler

PostPosted: Fri Aug 24, 2012 10:03 am
by tesla00
I recently purchased and had installed a new MC-80 high efficiency boiler for my home. The manual for the boiler mentions to have specific ranges for the water used inside the hydronic closed loop, otherwise I risk "heater failure due to improper water chemistry that is not covered by the warranty". The total volume in my closed loop is about 54 gallons of water. Based on performing a water quality test on my tap water, I'm considerably above the water hardness level. My water hardness is at 21 grains of hardness while the boiler manual mentions it should be less than 7 grains. I also have twice the sodium level that is mentioned in the manual. My first hunch is to dilute/titrate the tap water with distilled water until I'm within the adequate levels.

Is adding distilled water the correct approach? Should I be adding other additives to prevent any metal corrosion? Is it necessary to add propylene glycol to the system as mentioned in the manual even though there is no danger of the hydronic lines ever freezing?

Thanks in advance for any replies

Re: Water chemistry for MC-80 boiler

PostPosted: Wed Aug 29, 2012 3:46 pm
by BrentAldenn
Sir, water quality is of a concern in a closed loop hydronic system only if fresh water is introduced frequently (in cases of a leak), water in a closed loop system will be "heated and beated" and will become neutral very quick and will not cause any damage to the appliance, as far as initial filling of a system dilluting with distilled water would be the proper procedure , however in my opinion it is not necessary provided system has no leaks and piping has been properly flushed of contaminates, also no other addditives would be needed. Glycol is only necessary if the possibility for freezing exists, it is not mandatory.

Re: Water chemistry for MC-80 boiler

PostPosted: Thu Aug 30, 2012 3:02 pm
by tesla00
Hi Brent, thank you for your email. I'm performing a flush of the system now before its initial start this coming winter. Thanks to a garden hose bib tee on both the drain and supply lines, I'm able to flush out the sediment in the lines from over 80 years of use. I figured that the water in the closed system after much heating and circulating will reach some equilibrium that is likely neutral. My greatest worry is that the high water hardness from my city water make-up/fill line will create significant scaling in the boiler, drastically reducing the high efficiency of the boiler. I think all of these water requirements are likely to keep that +95% efficiency. I don't plan on doing the glycol treatment since there is no danger of freezing pipes.