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EZ-Gas Orifice

BobCBobC Member Posts: 5,172
I am about to sign a contract for a Smith G8w3steam boiler with the Ez-Gas burner. While reviewing the details on the combo I found something odd.

That boiler is rated at 105,000 BTU. The Carlin Ez Gas burner spec sheet (1/09) has a table that tells one to drill the orifice to 0.228" for 100,000 BTU while the Smith G8 / EZ Gas sheet (no date) indicates you should use a 9/32 drill (0.281") to size the orifice.

0.228 does not equal 0.281", what am i missing?

I did the math on the EZ Gas orifice sizes on the Carlin web site and it seems that doubling the orifice size doubles the BTU's, which makes sense.

Also my steam system has about 200 sq ft of EDR attached and the Smith G8s3 is rated for 283 sq ft, can they drill a smaller size orifice to more closely match my needs without unduly impacting the efficiency?

I'm going to use a contractor to install this but I just want to understand why the differences in the tables exist.


Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
Vaporstat with a 12oz cut-out and 4oz cut-in
3PSI gauge


  • SteamheadSteamhead Member Posts: 14,192
    I've always used the chart that came with the burner

    and verified the firing rate by clocking the meter and making sure the manifold pressure is within spec. Then a combustion test to make sure everything is as it should be.

    In this case, the Carlin chart specs a smaller orifice than the one Smith uses. It's easier to enlarge an orifice if needed, so that's another vote in favor of Carlin's spec.
    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.
  • Tim McElwainTim McElwain Member Posts: 4,436
    Have your contractor

    contact Carlin and give them your specs and they will if they are not to busy set up a burner for you ready to go as far as sizing. Then it is a matter of fine tuning using a combustion analyzer test.
  • BobCBobC Member Posts: 5,172
    It's coming from Smith, not carlin

    This boiler is being supplied straight from Smith with the Carlin EZ Gas in place; I just want things to go as planned - no waves as Sgt King said in the old  "No Time for Sergeant's" movie with Andy Griffith.

    Can i down fire the nozzle by 10-15% to more closely match my load of 200 sq ft vs the boilers 273 sq ft of steam? I'll make sure I clock the meter so i know what the draw off the gas supply is.

    thanks for the help,

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Tim McElwainTim McElwain Member Posts: 4,436
    Sorry I misunderstood

    it is too bad you have to downfire as I am not a big fan of doing that. You trade off efficiency when you do that as boilers prefer being fired at maximum design firing rate. It can be done just make sure they send you the smaller orifice as EZ's are not really good at being drilled or changed.
  • BobCBobC Member Posts: 5,172
    I'll let Smith decide

    I'll tell the contractor to ask Smith to do whatever they think is best; ie if it is advisable to down fire the burner. I'm sure they know more about the way the EZ Gas works on the G8 then anybody else.

    thanks for the guidance,

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Tim McElwainTim McElwain Member Posts: 4,436
    Not necessarily

    do they know more than anyone else. The final outcome of your burner lies with the installer who many times is much more adept than anyone else in these matters.

    By the way the difference in sizes on orifices depends on what they are using for outlet gas pressure on the gas VALVE THAT IS WHY YOU SEE DIFFERENT SIZES LISTED.

    Some of those who post here have put in hundreds of conversions and some others even thousands so you will get good advice here.
  • JStarJStar Member Posts: 2,752

    Start small. Clock the meter. You can always make a small hole bigger later. I really wish the Carlins came with an extra orifice, or an easier way to remove it.

    Is it okay to install a union between the gas valve and orifice nipple?
This discussion has been closed.


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