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My Boiler Is Acting Up. Is 210 degrees normal!?

NTL1991 Member Posts: 103
Hello. This is only the 2nd time the heat  has kicked on this season; the furnace was just cleaned and serviced (It's done annually) but it seems like it's acting strange.

First off, the boiler I'm speaking of is in my 3 family home. The house was heated with one steam system. I removed all of the radiators and pipes and installed 3 separate hot water (baseboard) systems in it's place. The steam boiler was converted for hot water use and is now used for the 1st floor apartment. It's a Weil McLain "Gold" Oil-Fired Boiler.

I wanted to test the heat before the night set in, so I set the thermostat to 71 degrees. It was 68 inside. The boiler kicked on and began producing heat. The cold pressure for the 1st floor is roughly 12-15 PSI. I was in the basement observing the temp rising through 140* and then 150*. After running for about 30 minutes or so, the temp rose to 69 and then 70, and I could hear the boiler kick off. About 5 minutes later, I went back down to the basement and checked the temp/pressure gauge. It read 25PSI and 210 degrees Fahrenheit. I checked the pressure release valve and it was dripping. About a drop every 2 seconds or so. The circulator was running. With the boiler off, I could hear what sounded like water and air bubbles running through the lines (they're mostly PEX). I went back up and checked the thermostat and it was still calling for heat because it hadn't reached 71 degrees yet, but the furnace wasn't kicking on.

Should my pressure be that high? It seems abnormal. 170 or 180 sounds like a proper temperature, but I really have no clue. Do I need to adjust the temperature or pressure? If so, how. I know how to adjust the pressure, but I'm not sure how to adjust the aquastat.

Any help would be appreciated.

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Nick, Cranston, RI


  • Brad White
    Brad White Member Posts: 2,393
    Not normal but

    what is your high limit aquastat set to? There should be an operating high limit set maybe at 180F and another safety device or setting at about 200F.

    Is the piping entirely copper fin-tube/low volume or does any of it connect to old cast iron piping and/or radiators? If such is the case, your expansion tank may be too small. That is more common than you would think. (You did say you replaced it all, but I have to ask the extent, just to be sure.)

    Your expansion tank also might have a ruptured bladder. Not like Tycho Brahe, well, sort of. May need a replacement. Too bad Tycho did not have that option.

    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • NTL1991
    NTL1991 Member Posts: 103
    edited October 2010
    200 Degrees

    Hello. Every one of the cast iron radiators has been removed. The only remnants of the steam system are the holes in the floors, and the pipes in the walls. It is all copper finned baseboard now.

    Behind the gray cover of that Honeywell box, there's a silver dial. The point is lined up with 200. What's the little arm which is locked into the grooves of the dial to the left of the 200 degree setting?


    Nick, Cranston, RI
  • Robert_25
    Robert_25 Member Posts: 361
    edited October 2010
    A few thoughts

    It is not uncommon for the boiler temperature to creep up a little bit after a call for heat.  If the boiler is firing until it hits 200 degrees, 210 isn't out of the question after shutdown...especially with an oversized, high mass boiler.  I would start by changing the aquastat high limit on the Weil Mclain to 180 degrees. 

    Your expansion tank could be undersized, but I would bet that the air pressure in the tank is low.  Every expansion tank I get off-the-shelf has about 8-9 psi, and it should be 12 psi.  Depressurize the boiler and check the air pressure in the expansion tank, adjust as needed.

    Was the pressure relief valve recently opened?  It is common to check them during the boiler service, and the valve doesn't always seat correctly...especially if it is old and/or there was some crud around the valve seat.  You could try opening and closing the valve a few times, but I would be proactive and replace it.

    Something I don't see in the pictures is any type of air removal device.  Is there an air scoop directly above the expansion tank?  
  • NTL1991
    NTL1991 Member Posts: 103

    Hello. I set the aquastat down to 180. After checking the other two boilers, they were both set to 180.

    How do I check the expansion tank? It looks like a tire valve; would a tire pressure gauge work? Would I add air with a pump as I would a tire?

    Also, on top of all three expansion tanks are "Amtrol Air Purgers"

    These boilers (except the 3rd floor natural gas burner @ 84,000 BTU/Hr) are extremely over sized. The Weil McLain Oil Boiler is operating at 131,000 BTU/Hr and the LAARS Oil Boiler at 103,000 BTU/Hr.

    The 1st and 2nd floor apartments are identical in size and room arrangement. They are "stacked", basically. I've done a rough calculation of the heat loss for the 1st floor, which is about 57K BTU heat loss per hour.

    Are they as oversized as I think they are? The 1st floor boiler runs fine now and doesn't cycle on and off rapidly. The LAARS boiler does, however. In about an hour (with the t-stat set to 70, aquastat set to 180 high and 120 low, it will cycle on and off about 4 or 5 times. Is this normal?


    Nick, Cranston, RI
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