Excessive(?) boiler make up water
Excessive(?) boiler make up water
(OP)
Our condo building is heated by a Weil-MacLain LGB-11 steam boiler (31 HP, 1050MBH) supplying about 250 radiators in a two-pipe system with thermostatic traps. Steam pressure is less than 1psi at radiator inlets. The building is heated adequately and silently. But I am surprised that our seasonal (7,000HDD) make up water volume is about 130 cubic meters. A few liters are blown down weekly. Residents have not reported escaping water or steam nor are any losses seen in the boiler room. The condensate tank is vented outdoors and on very cold days wisps of condensate may be visible. The main condensate returns are hidden in concrete trenches. Our contractors are not surprised by the make up water volume. Is this volume typical? Can anyone suggest where to look for the losses?





RE: Excessive(?) boiler make up water
The make-up required for these systems should be VERY low. With the volume you describe, you're no doubt getting oxygen corrosion & scaling in your boiler, plus paying a for a lot of extra fuel, as you're heating dead-cold make-up water to steam temperature, instead of the nice running-start you get with hot condensate.
RE: Excessive(?) boiler make up water
RE: Excessive(?) boiler make up water
The fact that your contractor thinks your systems's make-up water volume is "normal" suggests to me that you have some guys who aren't all that familiar with steam.
You may wish to get hold of a copy of "The Lost Art Of Steam Heating" by Dan Holohan. It covers the whole range of low-pressure steam systems, and yours will be in there somewhere. His website is heatinghelp.com, and there a lots of very knowledgeable contractors who post on that site. There's very likely somebody local who can help you.
RE: Excessive(?) boiler make up water
There is some loss of steam through the thermostatic air vents at the radiators. Assuming that there are air vents on the radiators, consider the following.
"Steam pressure is less than 1 psi at radiator inlets." would result in partial vacuum in radiator during cycle 'off' when thermostats shut flow of steam. After the vacuum draws air into radiator, the air needs to be expelled at start of steam 'on' cycle. The thermostatic air vent at each radiator lets out the air with some steam, until steam temperature closes the air vent.
You might estimate the steam loss thru the air vents by a cycle rate of say 2 per hour, x 1 ft3 steam per cycle, x 24 hr/day x number of heating days x 250 condo units. If the estimated steam loss volume is 2,400,000 ft3, convert the vapor to liquid by dividing by 100. The 24,000 ft3 of water is almost 5x the 130 m3 of makeup water.
RE: Excessive(?) boiler make up water
One-pipe steam systems, however, MUST have air vents on the individual radiators, as they do not use steam traps.
RE: Excessive(?) boiler make up water
book to see what I'm missing.
Condensate leaves our radiator traps at a peak 170F but it reaches the condensate tank at about 85F. We time-modulate the main steam feed according to ambient and exterior and anticipated exterior temperatures and that is reflected in the average temperature being less than 170F. Also, the two main condensate returns are below grade for 100ft and 200ft and a lot of cooling must take place during that journey.
RE: Excessive(?) boiler make up water
everytime you startup (daily I suppose in most cases)
when you start up you evaporate into an empty space and depends on the volume of the system, the boiler will call for water... but what do you do with the water sent to the system... it will comeback to the return cond. tank eventually overflowing to the sewer.
there is your answer.
I manage to set the water level in the boiler so it will be a little high at start and lower when running, you can only do this if you are experience with controls. and on some boilers will be difficult to do so, in my case the boiler uses probes/sensors and easy to manage levels.
I built the boiler so was authorized to play with it.
genblr
RE: Excessive(?) boiler make up water
These old systems are beautiful in their simplicity.
RE: Excessive(?) boiler make up water
Condensate as he puts it is the same if a simple one pipe or 2pipe system. the start up will always have lots of return, the thing is: what to do with it, return it to the boiler if enough storage capacity or dump it to the sewer, in this case they are overflowing it to the sewer.
What is your advise for the post?
beautiful will not fix the posted problem.
RE: Excessive(?) boiler make up water
I see where YOU say the condensate tank is overflowing...
RE: Excessive(?) boiler make up water
RE: Excessive(?) boiler make up water
Holohan describes windows used this way as "double-hung zone valves". :)
RE: Excessive(?) boiler make up water
also
Please try the steamforum, a lot of low pressure posts out there. Murphy is a expert...
RE: Excessive(?) boiler make up water
Our problem is definitely leaking condensate returns that are virtually inaccessible. Holohan has a solution for that.
Thanks to all who shared their experience and offered ideas.