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Sudden Temperature Rise and Drop

astoria Member Posts: 8
I have a 5-family building with a single pipe steam heating system. The boiler was replaced 4 years ago and the heating bills were always very high. (before the boiler change and after) The same exact building immediately next door has consistently used 1/2 the gas.

I recently installed a temperature monitoring system so that I could monitor the temperatures of each apartment. This helped me to better regulate the heat control but I noticed that all the apartment temperatures quickly rose once the boiler got hot enough but then drop even faster after the boiler shut down. 

According to the temperature data, it looks like something is sucking the heat out of the building. The other 5 family building with the same temperature monitoring system holds its temperature much better. The rise and drop of the apartment temperatures are much more gradual.  Both buildings were built at the same time about 60 years ago and are almost in the same condition with similar windows.

The near boiler piping on my boiler was not done to the manufactures recommendations, copper was used and the pipes are not insulated. Can this be the cause of my sudden temperature changes?


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,449
    identical buildings--dissimilar fuel bills

    i assume the same type of steam system is in each of the 2 buildings, so why not heat each building to the same temp, at the same time; and then cut off the boilers for a couple of hours. this will enable you to monitor true comparative heat loss.

    this test can also be performed in reverse by cooling each building down to say 55 deg, and then seeing how quickly each regains the identical set temp. this will tell you how effective each system is.

    if you have greater heat-loss in one than the other, perhaps there is a difference in attic insulation, or in thermostat anticipation/placement.

    most likely, you will need to make sure the piping of the new boiler is corrected in layout especially, and check the main venting, and pressure. the steam should arrive at all radiators, simultaneously.--nbc
  • FJL
    FJL Member Posts: 354
    Internal Ventilation

    Another factor to look at is ventilation systems.  One building might have stronger ventilation and be sucking out heat at a faster rate.  Wind also can effect heat loss.  On a windy day, my boiler runs much more than it does on a day with little or no wind.  
  • Mike Kusiak_2
    Mike Kusiak_2 Member Posts: 604
    Solar gain?

    Does the neighboring building get a lot more sun? The solar heating effect can make a surprising difference in fuel consumption.
  • astoria
    astoria Member Posts: 8
    Ventilation & Solar effect

    The neighboring building by all accounts should consume more fuel to heat itself. It has similar exposure to the sun, but it is approximately 1.5 feet wider in width and it is located on the corner of the block with much more exposure to the north wind. The layout of both buildings are almost identical.

     Another fact that I forgot to mention is that the neighboring building is using a 350MBTU boiler and I have a 260MBTU boiler. According to my estimations based on the neighboring building I should have a 300MBTU boiler.

    The data for both buildings are available online at and (cold one). You could see how the temperatures of 2905 rise and fall much faster by scrolling down to the temperature graphs of each apartment.

    I have a feeling that the near boiler piping has something to do with my problem but I'm not sure. There are no indications of water hammer and the heat takes a while to start climbing but once it does its very fast. As soon as the call for heat is satisfied the temperature begins to drop very quickly and depending on how cold it is out side the boiler will turn on again.

    I've been monitoring and tinkering with this since January 4th. and I've only been able to make some minor improvements thanks to the control system I'm using.

    Any suggestion would be greatly appreciated

  • Jamie Hall
    Jamie Hall Member Posts: 15,719
    Somewhere, somehow...

    the one building is losing a lot more heat (or, just possibly, gaining a lot less -- but I'd bet on losing a lot more) than the other -- so although the floor plans may be exactly the same, or almost exactly the same, something is significantly different in terms of heat loss.  It could be infiltration -- that's very commonly the biggy.  Windows?  Storm windows?  Doors?  Roof scuttle?  Is there an elevator and if there is, is there a machine room on the roof which is leaking air?  Then there is insulation?  What are the differences there?

    Do you have a tenant or two in the one building who is a fresh air freak?

    Lots of things to look at.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • astoria
    astoria Member Posts: 8
    Air Infiltration not the problem

    We spent the last 2 months chasing every air infiltration issue. We found several problems and we were able to minimize or eliminate all of them. At the start of this project the heating bill difference was almost 3X and we got it to just under 2X but we are still scratching our heads with this.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,665
    Could this be a sociological problem?

    I have a friend who absolutely insists on opening windows at night for "health reasons." Yet she complains her place is cold. She got over this habit when she got a condo where she has to pay for her own heat.

    Her daughter insists on opening windows during the day (when she is away at work) to "let the germs out."

    Could the cold one of these buildings have tenants like my friend and her daughter?
  • astoria
    astoria Member Posts: 8
    No Open windows

    The building is immediately next door to my office and I check on it periodically. The windows are not open. We had a tenant with an air conditioner in the window and we took care of that quickly.
  • seabee570
    seabee570 Member Posts: 89

    the near boiler piping should be corrected as it may contribute to the problem. insulation will also help. what I see is that 0n 7:43am,all areas,apartments(zones) are calling for heat at the same time at 29-05 address.with an undersized boiler,and a newer modern steam boiler,you do not have a larger steam space in the boiler,thus causing the sudden call for heat,with no cushion,to cause the boiler to work to make up for 29-01 there is no such call for heat at the same time,from multiple zones,and you have a larger boiler.back to 29-05,how does this system call for the boiler to run? can you put a runtime meter/sensor on the boilers? can you adjust the differential on the system to allow 29-05 to come on a little sooner? need lots more info on how the system is configured. maybe you can use an averaging temp at 29-05 to get better control.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,449
    unexplained difference

    your charts and graphs remind me of my old Audi-so many switches to play with, and lights to look at, i can hardly find time to look out the front.

    if you do the cool-down and heat up tests, you will either see that the cooler building is not getting the heat performance it should, or that it is cooling too quickly. time is running out for testing due to the arrival of spring, so that any needed reworking can be done during the summer when you are not under the gun for heat.

    things to check now [for both systems] would be:

    1. pressure-is it below 1.5 psi [for functionality], or 8 ounces [for economy/comfort]?

    2.main line venting-how does the air get out so the steam can get into the radiators? you may be paying your fuel company to squeeeeze the air out through constipated little openings. your burner clean and adjusted?

    this is just a start, but all of the points, if neglected, can add up to inefficiency, and we wouldn't want that would we?--nbc
  • astoria
    astoria Member Posts: 8

    The system call for heat is based on the average temperature of all the

    apartments. It has a day and night time setting. The day time setting

    is between 6AM and 11PM and it is set for 70Deg F. The night time is

    set for 65Deg F.The weather has been very mild so it is difficult to see exactly what has been going on.

    You can see when the boiler comes on and off from the chart on the web link  The column is the boiler status, yes means on and no means off. Each row represents approximately 20 minutes.
  • astoria
    astoria Member Posts: 8
    unexplained difference

    The pressure was set to cut out at 4PSi and cut in at 2 psi. We lowered to cut out at 3 PSI. We tried to go lower but the spring in Pressuretrole has lost its bounce. I realize its should be lower and we are in the process of getting a new one but I don't think it would be cause of our sudden temperature rises and drops.

    The boiler has 2 main steam pipes which rise from the header. The shorter one (about 10 feet) does not have a main air vent, the longer one( about 20 feet) does. All of the other vents on all the radiators in the building have been replaced with different size vent holes based on distance and size of radiator. Every apartment has heat but the temperature rise and drop is very abrupt when compared to the neighboring building or any other building that I have worked on. 
  • seabee570
    seabee570 Member Posts: 89

    in the colder apartment building,you may have to adjust setpoints for day and night to a closer differential. ie-66 degrees night,and 69 day. you may also have to change times.maybe 12 midnight night setting and 530am for can see on the day i mentioned,that it takes a long time to satisfy all sensors,this is telling you that the boiler has to worker longer and harder to satisfy the zones.what about sensor placement?
  • seabee570
    seabee570 Member Posts: 89

    even though the boiler is fairly new,you probalbly need to have it cleaned,and checked,with a combustion efficiency test. if the boiler efficiency test is good,then you have system problems.
  • astoria
    astoria Member Posts: 8
    next steps

    We found the plumber that installed the boiler and he agreed to come and make the necessary changes based on the manufactures recommended near boiler piping.

    The copper pipe will be replaced with steel, 2 boiler feeds will be used instead of 1 and the piping will match the manual exactly. Gas valve will also be adjusted and pressuretrole replaced and set to 1.5 PSI cut out with 1/2 psi cut in .

    We are also planning on insulating everything. I know all this will help but I'm not sure how much. Hopefully it will be enough

  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,449
    reworking the boiler

    as you are correcting the installer's mistakes, why not get a vaporstat, and a good low pressure gauge [ 0-15 ounces]. you will want one later, so why not install it now? also check your main line venting, so that can be done along with the rest of the work.--nbc
  • astoria
    astoria Member Posts: 8
    boiler reworking

    Good idea

  • Alan Welch
    Alan Welch Member Posts: 249
    water leak?

    Is a water leak in buried return piping, or boiling away out the flue a possibility ?
This discussion has been closed.


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