High Temperature Limit

Discussion in 'Boiler Forum' started by Kiko, Feb 5, 2013.

  1. Kiko

    Kiko New Member

    Messages:
    175
    Location:
    Royal Oak, Michigan
    The boiler for my apartment building is located in the laundry room, and occasionally a tenant will try to raise the high temperature limit. Normally the temp. fluctuates from between 140-160, but the last time I glanced at it, it was 190. The pressure is still at 20 psi.

    I hate to notify the manager, since this is the first time I've had real heat in my apartment, but I don't want the thing to explode while someone's doing their laundry. Is 190 a safe operating temperature?
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,024
    Location:
    New England
    Most boilers can safely operate at that or possibly even higher temperatures. That is one reason for maintaining them under pressure just like your car's radiator...raising the pressure, raises the boiling point. The taller the building, the higher the pressure that may be 'normal'.

    It's possible that the boiler has something called an outdoor reset, which monitors the outside temperature, and adjusts the boiler's setpoint so it can still produce heat economically.
  3. Kiko

    Kiko New Member

    Messages:
    175
    Location:
    Royal Oak, Michigan
    The "building" is a row of ranch-style apartments, so it is not high at all. The end units tend to be very cold when the boiler is set to the "normal" temperature. On cold days, it is hard-pressed to reach 60 degrees in my apartment.

    I won't complain if it is safe, though, because my unit got up to 70 today. But I'm sure the cheap-skate owner will come around and lower it again.

    Edit: I noticed the temperature was creeping up over 200 degrees, so I decided to mention it to the manager. It turns out that he was the one who raised the temp. Apparently, a cute girl moved into one of the end units and was complaining about the heat. And voilà, he cranks it up to 200! I've been complaining for years and was told to go out and buy a space heater. :mad:
    Last edited: Feb 5, 2013
  4. Dana

    Dana In the trades

    Messages:
    2,849
    Location:
    01609
    Even a cheapskate landlord should be willing to spring for installing a smart economizer control like an Intellicon 3250 or Intellicon LCH, or Beckett Heat Manager, which auto-adjusts the high temp based "learned" responses from burn cycles to anticipate the end of a call for heat. They also heat-purge the boiler down to the (user programmed) low temp before firing the burner on a new call for heat. The net result is that the average temp of the boiler drops, which means the standby losses to the boiler room plummet. The average distribution plumbing temp & losses drop too, but during peak-cold periods everybody still gets to stay warm.

    The heat-purge-before firing aspect means that when the loads are low it will "exercise" the thermal mass of the boiler over some delta-T to keep it from short-cycling (something that outdoor reset strategies are prone to doing), but the average temp of the system still remains low for low-loss.

    The net fuel savings will be far more than chiseling away hand-tweaking the high temp until the tenants complain. During cooler weather it auto-adjusts up, during warmer weather it backs off, but even during cooler weather the standby losses go way down even if the peak temps are banging on 220F, since it "parks" the system at the end of a call for heat at a temp below the peak temp it reached when firing.

    The programmed low-temp limit can be set as low as 130F for most gas fired boilers, but holding the line at 140F is prudent for oil fired systems to avoid damaging condensation in the flues or the boiler's heat exchanger.

    20psi is on the high side for a 1-story application- most run at 12-15psi. There is no advantage to running it any higher than necessary.
  5. Kiko

    Kiko New Member

    Messages:
    175
    Location:
    Royal Oak, Michigan
    Good information, but this particular slumlord wouldn't listen.
    I think he enjoys going around to his various properties and turning down the boiler temp. I don't think this manager will last long once the owner sees what he's done.

    To give you an idea of how cheap the owner is, we have very old dumpsters, and every year he hires a welder to weld the holes in the bottoms and repair the wheels that keep falling off. The trash removal company has refused to empty them on many occasions. He could rent the dumpsters like everyone else and have clean grounds, but he says it is cheaper to keep repairing the old broken ones.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,024
    Location:
    New England
    Maintaining a reasonable temperature in an apartment is a requirement...the local housing authority would make him fix it if alerted.
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