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Arco Model K eruption! Help!

tmw Member Posts: 56

Please help this layman until I can get a steam pro to come out here (steamhead, I'm in NW Jersey-will contact you later in the week).

I've got an old Arco model k vapor orifice system.  Have been unable to lower pressurtrol below 2 lbs without burner kicking off. Gauge reads about 4-5 lbs when the system is generating steam.

Over the weekend I had the asbestos removed (by a pro) and reinsulated the near pipes with 1" fiberglass. I still have to insulate the T's and elbows but at this point there is more insulation on the near piping than before the asbestos was removed (it was only on about 50% of the near pipi9ng)I also replaced the water feed and LWCO valves.

Last night I took a look at the only trap I can find in the system. "Arco #915 multiport air eliminator"..   It had a ball bearing stuck to a small pipe (see pics) . When I took the ball bearing off of the pipe, a mild vacuum was noted at the pipe inlet. Probably lasted 10-15 seconds.

This morning I noted that my ignition had tripped off so I reset it and the system began to run. Within a minute, the small ball bearing had popped off the vent pipe. There was now "breathing" at the vent pipe.

The boiler was now running at a pressure of about 8 oz. instead of the usual 4-5lbs. Also, it was no longer rapid-cycling, but seemed to stay on a good 30-40 minutes, before shut down.  All of the radiators that normally heat (all of the 2nd and 3rd floor) were heating well. Those that do not get hot (basement-boiler level) stayed the same. i.e. cold.

Scary part:  the vent pipe is now blowing steam (in the picture, the fiberglass above the vent was just stuck there by me to protect some old bx, it is not piping).  I've got the system off now.

Do I need to replace that vent (of course I do-it's a dumb question but I needed to ask anyway)



  • Jamie Hall
    Jamie Hall Member Posts: 23,287

    you do need to replace the vent.  Since you say you intend to contact Steamhead, and since he's forgotten more about steam than I could ever learn, I'll leave it at that!

    Except that you might be able to get a new vent (if you can, a Gorton #2) and screw it in before he gets there...

    And if you can get the pressure even lower with that pressuretrol, you may not get that much steam out of it anyway.  If you could get it down to 6 oz. or so, that might just do it -- but I doubt that you can with a p'trol.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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