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Dirty water causing short cycling

Here's a crazy problem I didn't know I could have. 
First off, the customer was having an issue with the vapor-stat not cutting in after it cut out. He would have to tap the control to get it to close. It was the 0-16 oz model that I've see this problem before, so I got the 0-4 psi model and that worked. But when testing, after a few minutes the boiler was short cycling before the mains were hot. 
Plenty of venting here. I have 4 gorton #2 on the mains, all the radiator vents were replaced and this is the 2 second year of operation. 
The water was visibly dirty in the gauge glass and the water line was going up and down. So I flushed it, skimmed it and put some steam clean in. After that it ran a full cycle without building even 6 ounces. 
I thought the only way the boiler would build pressure is if the boiler was filling the system faster then it could vent or all the vents are closed and the boiler is still making steam. 
Has anyone else seen rapid short cycling caused by dirty water? 


  • KC_Jones
    KC_Jones Member Posts: 5,707
    If it was surging due to oils or high PH from excessive water treatment it can definitely build pressure.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
    EBEBRATT-Ed Member Posts: 15,346
    If it wasn't cycling on low water, my guess is that the connection to the vaporstat was "panting" like a one pipe radiator vent with water in the run out.

    Probably some water splashing in and out of the pipe manifold for the pressure controls.

    Could always tap a hole and put the controls on the header.....if there are no valves

    Was this on a cold start? or was the system hot?
  • AMservices
    AMservices Member Posts: 610
    The boiler was hot, the piping was not. 
    I could watch the low pressure gauge and see it steadily rase and drop. Wasn't like a chattering from a sudden burst.  Never shut off from low water. 
    After cleaning it ran like a champ. 
  • clammy
    clammy Member Posts: 3,094
    I have been bottom cleaning the boiler lately by wanding out after a good steaming ,I ve found it drastically cuts down skimming timeand return visit I have also over the years discovered that when a replacement boiler is installed to replace a poorly piped system that after the boiler is totally clean that with in a month that new dry steam will slowly clean the main out leaving you to return yet again to clean the boiler and possibly wet returns .i always include extra time for cleaning other wise your doing it for free and nobody wants that .i did one the other day most likely never cleaned from day one 20 year ago still had some oil and ran like garbage after words performed like a different boiler even heated radiators that never got hot for first time amazing for 20 years no body knew peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating