Warning
Water quality has a significant impact on the lifetime and performance of a boiler's heat
exchanger.
Improperly prepared water in a heating circuit may cause damage to the heat exchanger
through fouling or corrosion. Repeated or uncontrolled water fills will increase the
potential for damage.
High levels of dissolved solids or minerals may precipitate out of the fluid onto the hottest
part of the heat exchanger, impairing heat transfer and resulting in overheating and
premature failure. The amount of solids that may form on the heat exchanger will depend
on the degree of hardness and the total water volume in the system. A high water volume
system with a low hardness count may cause as much damage as a system with less
volume and higher hardness, so it is recommended to treat water so as to reduce
dissolved solids to 30 ppm. Other water chemistry allowable limits are as follows:
Acidity pH is to be between 6.6 and 8.5
Chloride is to be less than 125 mg/l
Iron is to be less than 0.3 mg/l
Cu less than 0.1 mg/l
Conductivity is to be less than 400μS/cm at 77°F (25°C)
7 grains/ gal (120 ppm)
Important: Ensure that these limits are acceptable for the other water-side components
in the system.
BOILER HEAD LOSS SL 26-260 G3
Flow rate (gpm) 6 10 15 20 25
Head @ flow (ft wc) 2 3.5 5.5 8 13
Table 8 SL26-260 G3 Boiler Head Loss
BOILER HEAD LOSS SL 40-399 G3
Flow rate (gpm) 20 25 30 35 40 45
Head @ flow (ft wc) 1 1.5 2 3 4 6
Table 9 SL40-399 G3 Boiler Head Loss
Ensure that the pump is rated for the design circulating water temperatures; some pumps have a
minimum water temperature rating above the low temperature potential of the boiler. Following
installation, confirm the actual performance by measuring Δ°T (under high and low flow conditions)
after establishing the correct firing rate.
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