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oversized? Undersized? Just right?

ChrisJ Member Posts: 15,686
Yesterday we woke up to a cold house because someone hit the boiler switch at the top of my basement stairs on Sunday. 

After I realized what happened I turned the system back on and watched to see just what would happen.

House was 61F and it was 30F outside, set temperature was 69F.  System ran for a total of 1 hour 20 minutes and started building pressure at around 1 hour or so when all of my vents finally closed on the radiators.  After around 1 hour 15 minutes it cut out on pressure @ 1.5PSI.  Cut in was at 0.5PSI but with the damper opening and all didn't kick back on and start climbing again until 0.25PSI which I assume is still perfectly acceptable.  During this my water level was 3 inches or so in the gauge glass so some how my low water issue no loner exists so I'm happy about that.

after 1 hour 20 minutes the system shut off and created a pretty good vacuum, my 3psi Wika gauge ended up pointing straight down which is when I decided to close the valve to it to protect it as the vacuum was still increasing.  After maybe 10 seconds I heard the Gorton 1s open 30 feet from me and suck in air pretty hard.

<strong>Does this behavior suggest I sized my boiler well,   or is it a little on the large side being it hit 1.5psi after 1 hour 15 minutes?  I have to assume being able to do a 8 degree recovery and only going off on pressure once is pretty good?  Should I consider having someone come in and reduce my fire a little or leave it alone?</strong>
Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment


  • Dave in QCA
    Dave in QCA Member Posts: 1,785

    You operating observations indicate the boiler is about as perfectly sized as it can be.  Remember, the pickup part of the piping and pickup allowance cause the boiler to be oversized compared to the actual radiation of the system.  Withouth that most systems will have problems with even distribution and you don't want to invite that.
    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.
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