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Annual Cast iron baseboard explosion

I have a two story with half cast iron baseboard and half fin and tube; the two on different zones (pre-existing).
When I moved in four years ago, the kitchen radiators (12 sections) were cut off at the basement and left ww an open pipe because one along the interior wall was cracked. I replaced that section and reattached the length to the system.
Each year for the last four years, at least one section of the two-foot radiator peices has busted open. Each time I drain the system, take the full length apart, rent the connection tool and replace the section. Afterwards I bleed what I can access and await the next burst. Usually the breaks occur in the kitchen and are only hairline cracks along 9-inch rust-ridden iron. The one last winter was an obvious sign of expansion and along an exterior wall (assumed from a freezing draft). This was already the fourth section in that room; two along an interior wall and another along the exterior. So during the summer we had the house fully insulated with foam and blown-in cellulose. We also had the Weil-McLain Gold boiler professionally converted from oil to natural gas.
Then during this fall at the start of the heating season, one broke in the bathroom along an interior wall. I replaced all of the 6 shorter sections with two 9 inch against the exterior wall only because the shorter ones are no longer available.
Last night during dinner another kitchen section exploded, splashing us all at the table and hitting the ceiling (no injury).
The house psi is 30. The boiler is set at 120L - 140H. Boiler gauges read 142 F, 50 psi and 110 feet H2O. There is a relief valve rated at 150 psi which allows water flow when manually opened. There is an expansion tank attached above the boiler.
What In the world is happening?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 17,033
    Well, for one thing your pressure in the system is WAY too high. The system should be set somewhere around 15 psi running pressure. The expansion tank should be set to that, too, If there is an automatic refill pressure reducing valve, that should be set to that.

    And the pressure relief valve should be a 30 psi valve, not a 150.

    Get these changes done as soon as possible, preferably yesterday evening. You are sitting on a bomb.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    1MatthiasSTEVEusaPArick in AlaskaJUGHNE
  • SoImJesse
    SoImJesse Member Posts: 2
    Literally. I'm off to replace that valve and find ways to reduce the pressure. Any instruction would be appreciated. But your advice suggests that I should change the whole house pressure as well? Or can I isolate the boiler pressure from the rest of the water system?
  • pecmsg
    pecmsg Member Posts: 2,317
    SoImJesse said:

    Literally. I'm off to replace that valve and find ways to reduce the pressure. Any instruction would be appreciated. But your advice suggests that I should change the whole house pressure as well? Or can I isolate the boiler pressure from the rest of the water system?

    Now I have to ask should you really be doing the work with a question such as that!

    Maybe get a qualified tech on site to inspect the unit for any other issues!
  • Jamie Hall
    Jamie Hall Member Posts: 17,033
    No, your house pressure is fine -- but the boiler has to be isolated from it somehow. As @pecmsg said, maybe it's time to get a qualified heating person on site to look at it -- because I'll bet there are other problems as well.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England