I feel a little bit silly in floating this out here, but I've change my boiler operating habits and I'm seeing something that causes me concern.
Back in December 2012, we installed a new Weil-Mclain 680 boiler. There was a very detailed post about that project on here at that time. The system is a 2-pipe Dunham and the venting is through a pair of Dunham Air Eliminators and both have air checks on them. After a steam cycle, the system goes into vacuum and it holds well. At 1 cycle per hour, there is not a discernable loss of vacuum. However, if there is not a call for heat, the vacuum will dissipate before 2 hours passes. So, the system is not 100% tight, but is pretty darned tight. There is no underground returning piping. All of the basement piping is visible with steam lines insulated. There are no leaking radiators, no leaking traps or inlet valves. There is no visible leaks in the boiler and there is no white smoke. So, this sounds like a very tight system, right?
A change in my LWCO blow-downs has caused me to question it. In the past, I have flushed the 2 MM LWCO devices and have also done a quick flush of the drain. The boiler has been treated with SteamMaster tablets from the beginning. I catch the blowdown water in a bucket and it is always very clean. When I flush the LWCOs, I always manually top the boiler off to the normal water lever, using the bypass on the autofill meter (VXT) Each fall, at the beginning of the heating system, I drain the boiler and wand out the bottom, refill, add Steammaster tablets, and bring it up to steaming for 15 minutes.
So, this year, rather flush out clean water and cause the treatment to be diluted, I cut back on the blowdown routine. I waited until Thanksgiving to for the first blowdown, and it was perfectly clean. So, I waited until February 1 for the next. What I noticed was that I was beginning to see water use on the VXT meter. I did one more blowdown at April 1, and again, the water was clear. However, now, at the end of the season, the VXT is showing 36 gallons used. The boiler holds around 50 gallons as I recall. The only place that I can identify that water is lost, is in the humid air that is expelled in the venting oz.
Your thoughts and insight would be greatly appreciated.
Dave in Quad Cities, America
Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.http://grandviewdavenport.com