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could loss of air (pneumatic) cause boiler flooding?

ratio Member Posts: 3,626
Had a thaw-out this weekend at my church. As I turned off the feed to the water loop, I noticed that the steam boiler was flooded to the point where the pressure in the pigtail was over the cutout point (we heat four classrooms via hot water from a heat exchanger). After I dealt with that, I noticed that the air compressor pressure switch had failed open. I replaced the switch, patched three fancoils, & everything seems to be back to "normal" (as in, doesn't appear to be worse than before), but is the loss of pneumatic control likely to be the cause of the flooding? As I see it, we ran out of air sometime overnight, everything went wide open about the same time, we start condensing like mad, the water level drops, we start feeding quickly, the condensate all starts to return at once, the pump does it's thing, the water level rises over the pigtail, & we're done steaming 'til I get there that afternoon. Possible? Likely? Do I need to keep looking for more obscure problems? It all makes sense to me, but I'm just a washed-up electrician.


  • nicholas bonham-carter
    The pigtail may be plugged, or the pressuretrol itself. When the steam pressure gets out of control, it can blow the water up into the returns, causing as you say a low water situation, and an unneeded feed.
    I presume the pneumatic system is controlling the valves for a steam zone or two?--NBC
  • ratio
    ratio Member Posts: 3,626
    The pigtail probably isn't plugged - I had it apart last week or so, installed a Vaporstat Alternative as seen in a previous thread, and the pressure on the 60 oz/in gauge dropped as I let water out. It's a larger boiler (1100k DOE output IIRC) with two 4" risers going up roughly 4-5 feet (yah, feet) to a 6" header that's equalized & dripped more-or-less correctly. The pneumatics runs the stats in about 8-10 classrooms, plus the valve on the heat exchanger. No audible water hammer, but the needle does flutter wildly from time to time during a burn.
    All these issues are ongoing however, but this is the first freezup I've had, and it happened to occur at the same time the compressor went south. I don't believe in coincidence, but I don't know enough to be sure that my reasoning is sound and that I've fixed the underlying problem.
    I know I just blew off the existing problems as the primary cause of the flooding, but there is one thing that I believe is in play: a(nother) leak in one of the underground returns that might be delaying condensate return and exacerbating the problem.