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was this job sized correctly?

Joseph_4 Member Posts: 278
hello out there,
I had a job where the old boiler was large and the new one wouldnt fit through basement stairwell so we decided to do 2 boilers to replace the old large one. for one zone the heatloss calculation for the rooms equaled 53k output. However believe it or not in the basement there were about 85 feet of 2 1/2" iron pipe upfeeding and downfeeding to these radiators.. There was another 100 feet of 2" steel pipe doing the same thing.. same zone all located in basement.. I called manufacturer of boiler what pickup factor to use.. i expected much higher than the normal forced water pickup factor of 1.15. Manufacturer said keep the 105k input boiler that is sufficient for the 53k load of rooms and make a 1" bypass going right back into return so doesnt condensate.. I followed the instructions.. The house gets hot. but I sat in the boiler room for 3 hours straight and never saw boiler hit 180.. it never got past 170.. im afraid he is going to get huge gas bills.. was i given the correct advice?
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  • Ironman
    Ironman Member Posts: 7,379
    From your description, this is a converted gravity system with cast iron rad's?
    That type of system has a lot of mass and a "natural reset" built into it. It will probably seldom see SWT's above 160*. It's gonna have the flywheel effect (takes a while to get up to speed, and a while to slow down). So, using a somewhat larger boiler won't cause short cycling or less efficiency.

    If the pipes are in an unconditioned area, they should be insulated.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Gordy
    Gordy Member Posts: 9,546
    The water content of those big gravity flow pipes act as a built in buffer also.

    The question is did the rooms reach setpoint in sufficient time?

    Was this 3 hours you watched continuous with out the burner cycling?

    Did you do an emitter survey to see how many btus the emitters are capable of putting out? Gives a nice picture of what is going on. Chances are they have more output capability than the boiler does.
    EBEBRATT-Ed Member Posts: 15,635
    Check that all radiators are heating and that nothing is air bound