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Bad waterBoiler Chemistry


Boiler Chemistry is the fourth most important aspect of any hydronic heating system, after proper application, sizing and installation.
In a recent professional HVAC forum the question of high efficiency boiler longevity came up.


This was my measured response:


pH stripsThe “New Breed of Boiler? You mean the condensing boilers manufactured since 2000? Or the 20 year old HydroPulse we serviced last week?

I installed my first condensing boiler in 1987 (Glowcore). It replaced electric baseboard system and water heater and paid for itself in 5 years. The “payback” or ROI, is determined by the current cost of operation vs. the new cost of operation including; installation, fuel usage and required maintenance, period. 

It is now, as it was then; if you read, understand and follow the manufacturers' installation manual you will have success. The same is true for annual maintenance (mandated by all manufacturers of gas-fired equipment including cast iron boilers). 

I just looked at a 38 year old HydroTherm boiler that never was serviced (even though the local gas company and many others claimed it was). The cost of this kind of "reliability" is roughly 40% of the fuel bill. Given that the pump was on the wrong side of the waterlogged old-school expansion tank and no proper air eliminator was installed, the homeowner thought it was "normal" to hear the "water" rushing through the pipes for the last 25 years she has been in the house. 

As for chemistry. Get some. 

In the old days you could run anything through the cast iron boiler, pumps and 3/4" copper pipe and no one was the wiser. Sometimes it will give you a problem but most of the time no serious symptoms were detected. 

Fast forward to low-mass , sealed-combustion, condensing boilers driving low temperature radiation and you find yourself have to learn something about hydronics that you didn't know, you didn't know. 

For instance. All hydronic heating systems should be power-flushed. . . once. Then the heat transfer fluid should be specified as hard water only. Never softened, distilled and never, ever, RO. Filll the boiler from the cold water source be it meter or well and a system cleaner especially if you have used a torch an flux to fit the pipe to boiler. Flush, fill and dose the system tested for the proper level of inhibitor, pH and total dissolved solids (TDS) to make sure the system is within 10% of the tap water. 

Never flush and refill a closed hydronic system on a regular basis, as this introduces oxygen and TDS that will react with the metal components in the hydronic system, and the burner will precipitate new hard water components onto the waterside of the boiler, diminishing heat transfer, making noise and shortening the life of the heat exchanger. 

For aluminum heat exchangers like those found in the Crown Bimini, WM Ultra, Bosch and Buderus the pH is critical and must be kept in the specified range or serious errosion can occur filling the system full of the aluminum you wish were still on the heat exchanger. 

A "Y" strainer will certainly keep the debris in a hydronic system from racing through the system physically eroding the components therein, but is just another item to service when you go messing about the boiler when you should be filling out the annual maintenance report including chemistry, combustion analysis, etc. 

We too are seeing many neglected modulating/condensing (modcon) boilers in the field. We just replaced a Buderus GB142 that was so severely neglected it had to be replaced. This can and should be blamed on the original contractor who did not emphasize the importance of annual maintenance for this high performance boiler and the homeowner for not reading the owner's manual and following the clear advice to have a qualified technician service the unit. In contrast I have the same model heating a 2000 sq.ft. addition with a fan coil, 1000 sq.ft. garage, 80 gallon indirect and 250 sq.ft. of snow melting for 8 seasons this year, still operating in factory specs. 

Some installers here in Minneapolis are telling people that condensing boilers do not need service! I ask them if they have their cars oil changed? Most say yes. And would you take your BMW to Jiffy Lube? Most say no. 

I can make any one of the 12 different condensing boilers we have installed since 2000 last 20 years in a normal residential application.

All modern boilers are direct-vent, sealed-combustion, eliminating the need, and the waste caused by atmospheric venting; have the highest conversion rate at 96%+ thermal have outdoor reset improving comfort and lowering fuel usage and take up less space than any Cast Iron antique boiler.

We have invested time and money in training and equipment to PowerFlush and properly treat ever hydronic heating system we install or service, as we know this in the only way to assure long term efficiency, reliability and extend the serviceable life of any hydronic heating system.