I'm the operator of a 2-pipe steam system in a 60 (and 50) year old nursing home. For some reason neither I nor any of the techs who've come in to do work can figure out why my condensate is gaining a couple of hundred gallons a week, while the freshwater feed (that I've got a meter on) shows no new water being added to the system, since there's no demand given the main condensate tank is overflowing anyway.
I'm running a Hurst boiler at 3-5 pounds. It was enabled 4 months ago when the outside temp dropped low enough. For the first 3 months I had enough condensate loss to cause the system to add about 10-20 gallons of fresh feedwater a day. That's as expected, as I'm confident that there would be some condensate loss due to evaporation from the top of the condensate tank, and minor leaks in the network of pipes throughout the building.
For the past month, however, I'm ending up with more condensate than I started with. I know that it isn't fresh water being fed in by the automatic system, because I've ensured that by closing off that water valve (just long enough to test this). I've made sure that it isn't from water leaking into the steam pipes from a couple of heat exchangers used as supplemental potable hot water heaters (actually, it is on one, but I've isolated that both on the steam and return side). I've got two 300 gallon condensate tanks that I dumped nearly all of the water out of (enough was left to keep the system running). Even with no new fresh feedwater, both tanks fill up to overflowing in a little over a week.
Because the building is old and has been expanded twice, there is the original steam piping in half the building, and new piping in the other half (which also has a heat exchanger for a heating water system for part of the building). The old part is where all the extra condensate water comes from. The new part acts like I expect, and will lose a normal amount of condensate throughout the day. I've confirmed this by shutting down the pumps that move condensate from the old part of the building to the new. The new part has a steam line that runs to the old part in the opposite corner of the building, where the original boiler used to be. And there is a single pipe that runs from the old part to the new for pumping condensate collected in the old, original part of the building to the new boiler room. I get way too much condensate in the old part, and that gets pumped to the new boiler room and overfills the new condensate tank.
Has anyone else experienced anything like this, where you get more water coming back than going out? Especially in only half a building?
It's driving me nuts because it screws up my water chemistry. It acts like I'm getting lots of fresh tap water added to the system, because the conductivity and pH readings are close to straight tap water, and not what I had a little over a month ago. Apparently this system has had this same problem for the past 10 years, where for a few months in the middle of winter it will overflow its condensate tanks, and then go back to normal. In the summer I can empty the tanks and they stay empty until I start up the boiler in the fall. So it's not like a plumber connected a sink drain to the condensate return line, or I'd have this problem year around.
I'd love to hear if anyone else has even had this problem, and/or new ideas on what can be done to diagnose it and prevent it from happening in the future. And yes, I know that 3-5 pounds is high. I'd rather run at 2-3 but my boss is fixated on "higher pressure is better" as in she wants 7-10 pounds, and I can only argue so much.