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Wet base gas steam boiler sizing and suggestions

steve_173steve_173 Member Posts: 140
When looking at the spec sheets of wet base oil boilers and

planning to use a gas gun, is the I=B=R sq. ft. steam the same with a gas gun

or does the boiler need to be up-sized to produce the same output?

Which gas gun is best to use with the Slant/Fin Intrepid series? I tried in a

past year to get a G-8, but it was difficult and didn't happen.

I'm uncertain of the convector EDR numbers for my exact convectors. How should

I error on the boiler sizing? I'm at about 756 sq. ft. of steam. How much

efficiency do I lose when up-sizing or can I adjust some with the gas gun?

In comparing atmospheric to wet base it seems to be only a ~2 (EI)-4(no EI)% difference. Here, I read 6-7%. I'm trying to make sure wet base is worth the trouble and expense.

Anyone know of a good person to do this job in the NYC area. This is residential, single pipe steam. The current boiler is original from about 1920.


  • SteamheadSteamhead Member Posts: 13,863
    edited October 2011
    The Intrepid

    is approved for either the Carlin EZ-Gas or Midco EC-200 gas burners. You should not need to upsize it. Once you know your EDR, post it here.

    The 6-7% is the difference in thermal efficiency- DOE output as a percentage of Input. Atmospherics typically show a thermal efficiency of 80-81%, while wet-base units are about 86%.

    AFUE ratings are misleading, since they assume the heat lost from the base of an atmospheric is useful inside the house. But you want the heat to go to your radiators rather than leaking into the boiler room, where the draft will carry it up the chimney.

    Dan's book "E.D.R." has ratings for many different convectors- it should have at least some that are close to yours.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • steve_173steve_173 Member Posts: 140
    Burner and convectors

    Which burner is better if both have the right size? Is that sized to match the BTU input per the manufacturer as if using oil?

    I've had trouble getting my hands on that book. I could take pictures and dimensions and upload them somehow. I have the convector height and width and cabinet height, width, and depth. There are two types of varying sizes in the home. It would have been clever to stamp/cast the EDR into the radiator sections and convectors in some manner. My calculations based on using convector tables as I could find online came to an EDR of 756. The convector EDR is 333 of that 756 so there is plenty of room for error. How widely do convectors vary from type to type?

    The installer has to add a header that then branches in two directions and a Hartford loop. Any particular tips?
  • SteamheadSteamhead Member Posts: 13,863
    Have you tried

    ordering the book from Dan? Go here:

    333 and 756 are quite different- we need to know what size boiler you will be using. I'll tell you what I think once we have that nailed down.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • steve_173steve_173 Member Posts: 140
    edited November 2011

  • steve_173steve_173 Member Posts: 140
    edited November 2011

    I double checked everything only to find out my old numbers were accurate to within 5 sq. ft. steam. I now have 761 sq. ft. steam. That includes an allowance of 18 for a radiator removed from a bathroom, but that needs to go back eventually. So the current load is 743 + a possible 18 for this radiator. I estimated 18 based upon the other baths of similar size being 18. Do I need to consider that the EDR may not equal square feet of steam for convectors as per the discussion here: ? Am I oversizing the boiler using only EDR due the significant percentage of the EDR that is from convectors?

    What wet base do you suggest using?

    - The Intrepid comes 746 and 796.

    - Series 8 is 775 at the high rating (I vaguely recall something about using low rating with a gas gun, is that correct?).

    For atmospheric comparison:

    - The Galaxy comes in 750 and 758.

    - The gas company special comes as IN9 at 725 and IN10 at 812.

    Is the best bet the Intrepid TR-50 and adjust the gun to get close to the exact sq ft of steam? Slant Fin says the TR-50H and TR-50 are the same other than the burner. The H was introduced at some point to qualify for tax incentives. Can those be

    adjusted by using different orifice sizes on the gas gun? Would it be worthwhile to run one orifice accounting for the missing radiator now and then change the orifice if and when the radiator is added? Which gas gun is most suitable for this setup? It looks like the Carlin isn't a great option as it tops out at 275 MBtu in. The Midco EC300 offers a little more at the top end. Is one product better than the other in any  significant way? Is one fan noisier?

    I can't get a straight answer on whether I need a larger gas line. Some plumbers say yes and others say no.

    There is a reasonable amount of piping so that 0.33 pickup factor might get mostly used. The basement pipes are currently not insulated. I’m debating insulating paint versus cheap fiberglass versus a proper pipe fitter covering the elbows. Anyone tried the paints?

    I’m still undecided on indirect versus a standard water heater.

    Much thanks in advance.
  • kcoppkcopp Member Posts: 3,510
    Don't overthink this...

    Do the math and trust the numbers. Remember the EDR numbers were there when the house was built and they probably did not use much if any insulation or good windows.... If it were me I would do the Smith 8 series and use the Carlin EZ gas. I like it a bit better than the Midco.... sets up easier. The pick up factor is built in to the ratings... No need to add anything more. Insulate your piping w/ Fiberglass, preferably 1"thick... insulating paint amounts to snake oil,  it does not work. as to the water heater.... its your money as to how much you want to spend. I suggested the booster tank.
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