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Gravity Furnace

Gooz Member Posts: 7
I just saw my first gravity furnace!  I could not find any tags on it but one of the metal plates had the names Penn Aire and Union Mfg. Co.  Does anyone know where I can find more info on this boiler like its efficiency or sizing info?  Thanks guys!


  • Tim McElwain
    Tim McElwain Member Posts: 4,506
    Is it oil or gas?

    If it is gas all you have to do is measure the size of the orifice and go from there and you will have the input. The efficiency if it is a powerpile system is about 60 to 65% combustion efficiency.

    Are you looking to replace the furnace? If so I would do a heat loss on the house.
  • Gooz
    Gooz Member Posts: 7
    Its Gas

    Hi Tim,

    This system is running on natural gas.  I was getting an efficiency of about 71% with my combustion analyzer, but I've been told that it is probably inaccurate.  I would like to replace it.  Do you have any suggestions on any high efficiency, perhaps condensing furnaces, that I could look into.  I will do a heat loss calc and base my final decision on that. 

    Thanks again for the help!
  • Tim McElwain
    Tim McElwain Member Posts: 4,506
    There are many

    good Modulating Condensing furnaces on the market. I do not recommend any one particular brand over another. With the old gravity systems you will also have to look at the duct system to make sure it is compatible with a new furnace. One of the most important things is to insure that there is plenty of return air.

    Keep in mind also the venting will have to typically go out the side wall versus using the existing chimney.
  • Unknown
    edited September 2010

    I have not saw one of those since the mid 70`s!

    They used to fill the top "concave" with sand to hold the outside jacket together(cats loved it) & help keep the heat going to the ducts. Last one I saw had a blower attachment which was available way back then.

    The cold air return tied-in at the bottom,, but I see none on this.

    You`ll learn when you rip this "old lad" out!!
  • Tim McElwain
    Tim McElwain Member Posts: 4,506
    It looks like

    an old atmospheric upshot conversion burner on this unit perhaps a Roberts Gordon. Many of those old units did not have returns but simply used registers in the floor for air circulation.
  • Gooz
    Gooz Member Posts: 7
    I think you are right

    The ducts went up into registers on the floor and also a couple that shot into 2 separate mantles that looked like they were fireplaces.  On a completely different note, this house also had an old stove that looked pretty antique and is no longer in use.  Anyway, thought it might be interesting.
  • Thanks for sharing,

    Brings back memories!
  • John Mills_5
    John Mills_5 Member Posts: 935
    edited September 2010
    combustion & AFUE

    Combustion of 71% says burning at that rate once all heated up. AFUE or

    annual efficiency is probably 40-50% meaning that over the course of the

    winter, 1/2 of the heat paid for goes up the flue. That old boy would

    take forever to get up to 71% combustion efficiency so you lose a lot of

    heat then, as it cools down and during the off cycle she's pouring more

    heat up the flue 24/7 etc. So ought to be a big savings going to high


    In the original post it was called a boiler & a furnace. Which is it?
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,216
    Its a furnace

    I know of one other that dwarves this one but thankfully it is only a relic of the days gone by. Steam now warms that side of the home and the old furnace simply takes up space in the basement.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
This discussion has been closed.