Click here to Find a Contractor in your area.
In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Need to contact us? Visit

How Much Can You Downfire an IN5 ?


    Need some advice on an oversized boiler situation.

The total EDR of the system is 230.10 Sq.Ft

The boiler that should have been installed was an IN4 @ 271 sq. ft of steam (IBR Net)

The boiler that was installed was an IN5 @ 358 sq. ft of steam (IBR Net)

The result is that the present boiler is 128 sq. ft. oversized.

Now the question is: How much can you down fire an IN5 ?


Thanks for your help!

- Rod


  • Down-firing Burnham atmospheric

    This may be a question for the Burnham tech support. Possibly, the nozzles could be changed in the burner to reduce the fire evenly across the bottom.

    Situations like this make it even more important to have the venting and balance as good as possible, with massive main venting, and slow rad vents.--NBC
  • RodRod Posts: 2,067
    Oversized Boiler

    Hi Nick- Thanks  for the reply!  I'm going to suggest increasing the main venting.

    - Rod
  • BioBio Member Posts: 255
    edited November 2013
    Venting/two stage gas

    You can increase the radiator vent as well or add a two stage gas valve controlled by a vaporstat, and run on low to match EDR, here is a picture of one of Gerry Gill's installation
  • SWEISWEI Member Posts: 7,356
    Two stage retrofit on natural draft boiler

    very interesting.  Got a link, or more information?

  • BioBio Member Posts: 255
    edited November 2013

    I'm a H.O. and I did some research for my tenants oversized boiler but boiler broke a leak early this year and had to be change, but check these couple of links
  • Big-AlBig-Al Member Posts: 263
    edited November 2013
    I did it

    I had an oversized Burnham IN-6 in my house, which is basically the same as an IN-5, except with one more section.  I contacted Burnham and they told me that it could be downfired no more than 10%.

    For natural gas at normal elevations, these boilers come with #45 (pink) orifices, part number 822711.  #47 (white) orifices, part number 822710, will downfire the boiler about 10% compared to the #45.  I made that change on my boiler and it went a long way to quieting the nasty hissing radiator vent issue I was experiencing.  (Yes, I had already vented the snot out of the main.)  I clocked the gas meter before and after to confirm the reduction in gas use. I also did before and after flue gas analysis which confirmed that the boiler was still operating properly. 

    I ran it that way for only one heating season, and I didn't notice any fuel savings . . . just a quieter system with less short cycling.  I got a great deal on a smaller (IN-5) boiler the next summer and replaced the IN-6 . . . resulting in another 10% reduction in steam output.  This set-up seems to be the sweet spot for me . . . a nice quiet system that fills all the radiators evenly and almost never cycles off the pressuretrol.

  • SWEISWEI Member Posts: 7,356

    Still have some questions on the piping, but this looks quite promising.
  • RodRod Posts: 2,067
    How Much Can You Downfire an IN5 ?

    Thanks everyone for your input!

    - Rod
This discussion has been closed.


It looks like you're new here. If you want to get involved, click one of these buttons!