Ideally, it should range between seven (neutral) and nine (mildly alkaline). When the condensate returns from the system, the boiler will flood.Ĭorrect the pH with chemicals. The automatic water feeder will respond by adding water to the boiler. Foaming water will leave the boiler with the steam, and that will lower the boiler's water line. A pH of 11 or higher will make the boiler water foam. Also, make sure the boiler is as clean as possible. But don't underfire to a point where you'll only be simmering the water. Underfiring produces fewer steam bubbles, giving each more room. You can sometimes cure it by underfiring the boiler. This type of problem is built into the boiler design, and it's tremendously aggravated by dirt. If you have an automatic water feeder, it will open and eventually flood the boiler. The water in the gauge glass offsets this by falling into the boiler. When the steam bubbles condense, the water in the boiler will fall to a point lower than the water in the gauge glass. The two columns of water (in the boiler and in the gauge glass) ride at different levels until the burner shuts off on high pressure. This happens because there isn't any steam in the water in the gauge glass. If the sections are too narrow, the rising steam bubbles will lift the boiler water level to a point higher than the level in the gauge glass. This is a problem you'll sometimes run into with residential steam boilers. If you use motorized zone valves with a gravity-return system you also must use a boiler-feed pump and end-of-main steam traps. The next time the motorized valve opens, the condensate will flow into the boiler and flood it. If there's an automatic water feeder, it will open and add water to the boiler. The static weight of the returning condensate alone usually isn't enough to overcome the pressure in the boiler, so the water backs out of the boiler. When motorized valves close, you lose that "leftover" pressure at the ends of the mains. These two forces overcome the pressure inside the boiler and allow the condensate to enter. The "leftover" steam pressure at the end of the main combines with the static weight of the condensate that stacks in the vertical space between the boiler water line and the lowest, horizontal steam-carrying pipe (the "A" or "B" Dimension - see The Lost Art of Steam Heating). To get the water back into the boiler, a gravity-return system has to balance itself like a scale. The gravity-return system has motorized valves. Isolate the coil and watch the gauge glass for an hour or so. Before long, you'll have a flooded boiler.ĭon't blame the automatic water feeder solve the surging problem by cleaning the boiler, adjusting the firing rate or correcting the improper near-boiler piping.Įven a tiny pinhole in a tankless coil will flood a boiler because the pressure inside the coil is so much greater than the pressure in the boiler. If there's an automatic water feeder on the boiler, it will open and close each time the water line rocks. Dirty water, a too-high pH, overfiring and improper near-boiler piping can all cause the boiler's water line to surge up and down.
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