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Undersized Boiler? EDR

Silkey Member Posts: 18
Crown Boiler JSEi103S. 103MBH Input, 84MBH Capacity. IBR NET 263sq ft, 63MBH
80% efficiency rating

Calculated EDR 332

332 > 263

332 x 240 = 79.7

332 x 240 x 1.33 =106MBH

Does this mean the current Crown Boiler is undersized?

Gurney early 1920s Buffalo, NY
37" high, 2 Column, 7 1/2" Deep (4) * 8 section = 32
37", 2 Column, 7 1/2, (4) * 10 = 40
39", 3 Column, 9 1/2", (5) * 8 section = 40
38", 3 Column, 10" (5) * 6 sections = 30
38", 3 Column, 10" (5) * 6 sections = 30
10", 3 column, 9 1/2", (3.2) * 10 sections = 32
10", 3 column, 9 1/2", (3.2) * 10 sections = 32
other brand radiators
16", 5 tube, 12" (4) * 15 Sections = 60
13", 6 tube, 10" (3) * 12 = 36


  • ChrisJ
    ChrisJ Member Posts: 15,700
    You have 80K worth of radiation and 84K worth of boiler output.

    That gives you 4K for piping losses.

    In my opinion it should be able to be made to work quite well.
    Is all of the piping insulated? Has this system been in use, if so for how long and how does it seem to work?

    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
  • AdmiralYoda
    AdmiralYoda Member Posts: 629
    If your calculations are correct it would appear so, but this may not be the end of the world. Your 332 EDR was adequate to heat the house at its design day a century ago with zero insulation and poorly sealed windows.

    Does your house have better insulation and windows then when it was new? If so...you require less EDR than you have installed. This may mean that all of your radiators will never heat 100% all the way across but that will likely be okay since you may not need it.

    Also the square feet of steam of your boiler has includes a 33% pickup factor to heat up uninsulated pipes and other losses. You have an actual capacity of 342 square feet (zero pickup factor) which gives you about a 3% pickup factor.

    If your steam mains, header and risers are all well insulated I think you may have a good system especially if the near boiler piping was installed correctly. The usual problem with undersized boilers is getting everything balanced. If that can be done You'll have a pretty efficient setup.

    How well does the boiler heat the house? Does it have trouble keeping up? Post some pictures of the piping at the boiler.
  • KC_Jones
    KC_Jones Member Posts: 5,739
    Is this the same system that you posted about a few years ago? If so it was identified as an orifice system at that time. Many of those are to be sized to 80% of the total radiation to ensure no steam gets past the radiator.

    Not sure if you have that or not, just suggesting.

    I agree with @ChrisJ I doubt you have any problem with boiler sizing no matter which system it is.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
    Alan (California Radiant) Forbesmattmia2
  • Silkey
    Silkey Member Posts: 18
    Thanks for the reply!

    Yes, same system. All the supply lines have R6 fiberglass now and some pvc jacket.
    Risers are most likely not insulated, since the plaster gets warm where they are.
    The walls have blown in cellulose and the rim joist and attic (not heated) were spray foamed. 
    Second floor windows replaced.

    All valves were replaced.
    All Safety Vapor orifices were replaced (leaks, blockages, didn't know better) except one where there was not enough space for a 17C.

    Removed all of the individuals radiator air vents.

    Had some great help from Dave cleaning the inside of the boiler, skimming, adjusting the Gas valve pressure down to 3psi from 5, and installing a VaporStat. At least two other "Boiler speacialists" that came for clean and tune missed all of this. They just cleaned the heat exchanger, burner tubes and replaced thermocouplers.

    Return Vents were upgraded from Dole 5 to Gorton 1. No main vents, I have the parts, but the 100 year old iron pipes don't want to unscrew. Wires and house framing make using the torch difficult.

    The System works much better than it did.  Just got around to calculating EDR. Even though the boiler is 20+ years old, I've read it's better to keep a working balanced one than a new Combination higher efficiency unit. I was interested in the NY State Energy Assistance Program Grant's and low interest loans, but the gas bills don't show a need (and I would only trust Dave to install it locally)

    Thank you for all the help. Little would have been possible without reading Greening Steam and this website.
  • mattmia2
    mattmia2 Member Posts: 9,662
    if it is a vapor system the vaporstat should be set around 1/2 psi but if your calculations are correct it should really never produce more steam than the system consumes anyhow. It needs whatever the meetering devices are on the inlets of the radiators to keep steam out of the returns which will keep other radiators from venting properly.
  • ChrisJ
    ChrisJ Member Posts: 15,700
    edited April 3
    You have a control that was letting the boiler reach 5 PSI and now it's set to 3 PSI and you're concerned the boiler is undersized? 3 PSI is absurd, even for a normal single pipe system.

    What are you trying to heat a 100 story building?
    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