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Slow Radiators

ddog777
ddog777 Member Posts: 18
in Strictly Steam

Is there a logical explanation for the 2 radiators closest to the boiler to be the slowest to heat. Both are equipped with #5 vent valves, The boiler fires well and makes good , quiet steam for the most part. Any thoughts?

Comments

  • dabrakeman
    dabrakeman Member Posts: 653

    What vents are on all the other radiators?

  • ddog777
    ddog777 Member Posts: 18

    c's and d's on second floor radiators ( 4 total), #6 on remaining first floor radiators

  • PCapNJ
    PCapNJ Member Posts: 17

    C's and D's may be too big for the 2nd floor and could be pulling the steam to them instead of sharing the steam in a balanced way. There are many other variables at play (main pipe venting, boiler sizing, EDR calcs, pressuretrol settings) but I'm assuming all that is "correct" before answering your question directly.

    Dan's books are an amazing resource if you are interested in learning the "Art of Steam Heating".

    For reference, after learning from the various books and this forum, I landed on improving my main vents and then have my 2nd floor radiators #6, dropped a couple fast ones to #5s, and all my first for radiators are #4s. Not applicable to everyone as I have a boiler that performs under very low pressure.

    delcrossvethicalpaul
  • ddog777
    ddog777 Member Posts: 18

    Boiler performed fine for fifteen years until first fire this season, pressuretrol set at .5 plus 1, main venting seems good, radiators are slightly pitched. I'll try reducing the second floor vents to see if that changes things.

    Thanks all

  • dabrakeman
    dabrakeman Member Posts: 653

    How is the comfort room to room in the house? If a room seems slow to warm up relative to others from a comfort standpoint given your existing radiator vent sizing I would start by slowing down some of the vents in the other rooms. A "D" is too big for any radiator.

  • ddog777
    ddog777 Member Posts: 18

    I'll switch to 5 or 6 on the second floor. The 2 radiators I initially referred to are A:, the 2 largest and B: get steam to the first couple of sections quickly , but slow down and don't get blazing until the end of cycle. Just seems like the steam gets stuck for awhile

  • dabrakeman
    dabrakeman Member Posts: 653

    The first radiators off the main will start getting steam progressing into their takeoffs before the other radiators further away unless the steam travel through the main to the main vents is virtually instantaneous. As steam start down the main it will be at some pressure say two or three ounces. Once it reaches that first takeoff you can pretty much calculate the steam progression through the takeoff toward that radiator just by knowing the vent rate of the vent on the radiator and the volume per foot of the takeoff pipe heading toward the radiator.

    Say it takes 60 seconds for steam to get through the main from the point of that radiator takeoff to the end of the main. Say you had a 1.5" inlet pipe going to that near radiator and pressure was a 3oz and you had a #6 vent on that radiator that would vent 0.3ft3 per minute. If it took a minute for steam to pass that takeoff and get to the end of the mains then during that time the 1.5" takeoff that has a volume of .0141 ft3/ft could fill (.3/.0141)=21ft worth. Doubt the takeoff to that "near" radiator is that long so the radiator will be filling early in the cycle before others further down the line. This can be minimized by venting the mains faster or slowing that near radiator down more. Once the mains close the steam travel is for the most part going to be in accordance to the ratios of all the radiator venting and the volumes needed to be filled.

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