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Dunham Bush Metro?

jumperjumper Member Posts: 977
Does anybody know what that was? I think it was a method for one pipe in multi-storey.


  • Dave in QCADave in QCA Member Posts: 1,660
    Vari-vac Metro

    The metro system was a particular type of the Dunham Bush Vari-vac, which is a two pipe system. I have not been able to find any specific details about this system, but in a snippet view in Google Books, I could see reference to a "single riser" system installed in a college in 1960, So, I would suspect that it might be an overhead down-feed system that utilizes an express riser to above the top floor of a building, then down feed through the building. Maybe someone can find some more information.

    One thing for sure, it is not a one-pipe system, as Dunham systems were always 2-pipe, being the first company to introduce the steam trap.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
  • jumperjumper Member Posts: 977
    single riser two pipe?

    Interesting. I got into the business in the seventies. Then old timers said that Dunham-Bush was trying to hold on to its share of the market. So I wonder if Dunham didn't come up with some less expensive system to compete with hot water.
  • Dan HolohanDan Holohan Moderator Posts: 11,877
    A lot of these are in Philadelphia.

    Yes, it was a way for them to compete with hot water. The steam went to the top of the building and then worked its way down through the building's baseboard radiators from floor to floor without benefit of steam traps or valves. The upper floors get steam; the middle floors get a mix of steam and condensate; the lower floors get hot water. It's like lacing a sneaker. At the bottom of each downfeed riser there's an F&T trap, and beyond the taps there's a D&B vacuum pump that fed the condensate back to the boiler.
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  • jumperjumper Member Posts: 977
    multi-storey one pipe

    Isn't condensate interference always a problem with multi-storey one pipe? Condensate drips down the inside wall of the riser to mess with steam route to radiator? Were there fittings with an eyebrow to route condensate out of steam's way?
  • Dan HolohanDan Holohan Moderator Posts: 11,877
    It's one, long, parallel-flow circuit

    Starts at the top. Goes horizontal one way across a room and then drops to the room below and goes horizontal in the opposite direction. And so on until it reaches the trap in the basement. Quite unusual.
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