Announcement

Announcement Module
Collapse

How To Post Images

Want to know the how to upload images to your posts? Image Posting Tutorial
See more
See less

My boiler is short cycling

Page Title Module
Move Remove Collapse
X
Conversation Detail Module
Collapse
  • Filter
  • Time
  • Show
Clear All
new posts

  • My boiler is short cycling

    I have a Weil-McLain EG gas boiler that provides steam heat. I bought the house last August. Started to turn on the heat probably in late Oct or early Nov. I would leave the thermostat at 68 degree all day because my grandmom is in the house. I don't remember the boiler would ever short cycling like now. It would fire up for 3 minutes every 15-18 minutes but there is no heat to the radiators. If I push the thermostat up 69 or 70, then I can feel the heat is coming out from the radiators. Or if I let the room temperature drop to 66-67 and then set the thermostat to 68, then I can feel the heat coming out from the radiators.

    Over the weekend, I took the air vents out and rinse them and shake out any particles. Some of them seem very old. Also, I made sure all the valves in the radiators are fully open. I think it was back in mid-Nov or late-Nov where I drained the boiler. The water in the glass tube looked fine but the water coming out from the drain was close to dark brown. Not sure if the draining has anything to do with it.

    Also, last night, I changed the Honeywell thermostat from the default 6 cph to 3 cph. Do you think that will help?

    I need help. When I saw the last gas bill, it was quite expensive - $662.45 for 395 thermals from Keyspan. Almost double my previous bill.

  • #2
    Re: My boiler is short cycling

    Obviously there is something wrong. 3 minutes is not enough time to produce steam. You should have a professional have a look.

    Changing the CPH on the tstat might help but I believe something else is wrong. Steam boilers need to be blown down all the time. Once a week during a cold season not every few months. Replace the steam vents and blow down the boiler and see how it does.

    Comment


    • #3
      Re: My boiler is short cycling

      Can you shoot over a photo of the boiler and controls.?
      sigpic

      Comment


      • #4
        Re: My boiler is short cycling

        These are the possible causes of your problem. Some you can check, and others you may want to call a service tech for. The thermostat is out of calibration.If it is, the burner will be bouncing on and off. Make sure you use an ammeter when you're checking the calibration. Don't guess at that anticipator's setting.
        Check, too, to see if the thermostat has a mercury switch. If it does, make sure the thermostat hangs level on the wall. And check to see if the thermostat is in a cold draft, or if it's hanging on a poorly insulated, outside wall. Make the necessary corrections.


        The boiler is oversized.You're supposed to size the boiler and fire the burner to the connected piping-and-radiation load. In the boiler manufacturer's literature, they call this load the D.O.E. Heating Capacity. If your boiler is too big, its ability to produce steam will exceed the system's ability to condense steam. The burner will short-cycle.
        You may be able to solve the problem by down-firing the burner, but be careful when you try this. You may down-fire to a point where the flue gases begin to condense. Fire only to the connected load.


        The boiler is properly sized, but overfired.If there's too much fire, you'll get lots of steam in a hurry. That will quickly raise the boiler pressure and short-cycle the burner off the pressuretrol.
        Raising the pressuretrol setting isn't a good solution to this problem. Over-firing will also throw water up into the piping. This leads to water hammer, uneven heating and short-cycling.
        Check your gas pressure, or your nozzle size (on an oil-fired system).


        The boiler is making wet steam.Check the near-boiler piping against the manufacturer's specifications. If the piping can't separate the water from the steam, the water will cause the steam to condense, and the burner will short-cycle.
        Check the boiler water's pH and its cleanliness too. You may have to clean the boiler and the system and balance the pH with chemicals.


        The steam traps aren't working.Two-pipe steam is like a ladder. Each radiator is a rung on that "ladder," and at the end of each rung you'll find a steam trap. Part of the trap's job is to keep steam from entering the no-pressure side of the ladder. If even one trap fails in the open position, steam will jump across and pressurize the air on the other side of the system. As the pressure builds, the burner will short-cycle on the pressuretrol.
        Float & thermostatic and bucket traps serve the same purpose at the ends of the mains, and at the base of risers. If they fail in the open position, or, with bucket traps, if they lose their prime water, steam can move into dry return lines and cause burner short-cycling and water hammer.
        Trap maintenance is essential.


        The air vents aren't working.If they're not, the system will trap air and pressurize it. Remember, steam and air are both gases, but steam is lighter than air, so the two won't mix.
        When the steam heads down a pipe, it pushes air ahead of itself. If the air can't get out at the end of the pipe (through a vent), the steam will just compress it. The pressure builds, and the burner shuts off on the pressuretrol. The burner short-cycles, but that's not your only problem. The building also remains cold because the radiators and mains are filled with air instead of steam. Usually, someone comes along and raises the pressure. They mean well; they're trying to solve the short-cycling and give the folks some heat. But the higher steam pressure just compresses the air a bit more. It usually doesn't help the lack-of-heat problem. It just raises the fuel bill.
        Check the air vents, and clean or replace them where necessary.


        The pressuretrol or the pigtail is clogged.If there's sludge in the pressuretrol or the pigtail that connects the pressuretrol to the boiler, the burner will short-cycle. The pigtail's job is to fill with water and keep the steam temperature from reaching into the pressuretrol. A pigtail is a natural collector of sludge. If you can't clean the pigtail (a tough job), replace it.


        The pressuretrol has a mercury switch and it isn't level.Some pressuretrols have mercury switches. If the pressuretrol isn't plumb and level, the mercury might trip too soon. That can cause the burner to short-cycle.
        If the pressuretrol sits on a pigtail, make sure the curved part of the pigtail faces front to back (when you're looking straight at the pressuretrol). If you have the curved part turned from side to side (so you can see through the circle when you're looking straight at the pressuretrol), the burner might short-cycle. This is because the curved part of the pigtail straightens a bit when heated. As it straightens, the pigtail tips the mercury and stops the burner. When you turn the pigtail so that it faces front to back, it tips the pressuretrol from front to back, but not from side to side. This doesn't affect the mercury switch.
        sigpic

        Comment


        • #5
          Re: My boiler is short cycling

          These are old photos. Let me know if you need more shots.

          http://mysite.verizon.net/zuffy/boiler.jpg
          http://mysite.verizon.net/zuffy/control.jpg
          http://mysite.verizon.net/zuffy/gauge.jpg
          http://mysite.verizon.net/zuffy/lowwater.jpg
          http://mysite.verizon.net/zuffy/psi.jpg
          http://mysite.verizon.net/zuffy/feeder.jpg

          Comment


          • #6
            Re: My boiler is short cycling

            Originally posted by plumberscrack View Post
            Obviously there is something wrong. 3 minutes is not enough time to produce steam. You should have a professional have a look.

            Changing the CPH on the tstat might help but I believe something else is wrong. Steam boilers need to be blown down all the time. Once a week during a cold season not every few months. Replace the steam vents and blow down the boiler and see how it does.
            I have 3 bedrooms and a bath in the second floor. The master room and the second room has a single pipe fined radiator about 3.5' wide. They look like using a fairly large vent hole. The third bedroom radiator is about 2.5' with a tiny air vent. Can I put in an air vent with a larger hole?

            Second question, how do I tell what size are the existing air vents?

            Comment


            • #7
              Re: My boiler is short cycling

              As to the model of the boiler, it's either the Weil-McLain EG 40 or 45 gas boiler. The thermostat is a Honeywell T8600D.

              Comment


              • #8
                Re: My boiler is short cycling

                1 is the water at the right level and there is a re set on the low water cut off try this

                2 if you jump out the t stat does the boiler stay running

                3 is the damper on the flue pipe opening

                4 does the flame look the same as it did last time it was running good

                5 check the pressure switch

                some thing is telling it to shut down and it is not even running long enough for the water to get hot

                and you need to run a pipe off the relief valve down to the floor ,if it goes off and you are standing close you will get a face full of hot steam

                let us know if you checked this stuff
                Charlie

                My seek the peek fundraiser page
                http://observatory.mountwashington.o...nal&fr_id=1040


                http://www.mountwashington.org/weather/conditions.php

                new work pictures 12/09
                http://public.fotki.com/hvachawk/

                Comment


                • #9
                  Re: My boiler is short cycling

                  1 is the water at the right level and there is a re set on the low water cut off try this

                  Yes, the water is at the right level. It's at least half fill.

                  2 if you jump out the t stat does the boiler stay running

                  It will stay running but once it gets up to the set temperature, it will do it's short cycling from what I can remember

                  3 is the damper on the flue pipe opening

                  Yes, it open each time the boiler comes on. I can hear it.

                  4 does the flame look the same as it did last time it was running good

                  I have no idea

                  5 check the pressure switch

                  some thing is telling it to shut down and it is not even running long enough for the water to get hot

                  Which one is the pressure switch or where is it?

                  and you need to run a pipe off the relief valve down to the floor ,if it goes off and you are standing close you will get a face full of hot steam

                  Someone pointed that out to me when I got the house. All taken care of.

                  let us know if you checked this stuff

                  Thanks for the help

                  Comment


                  • #10
                    Re: My boiler is short cycling

                    If all that stuff checks out, go to the part in my post about cleaning the pig tail.
                    sigpic

                    Comment


                    • #11
                      Re: My boiler is short cycling

                      Which one is the pig tail? Is that the big pipe in the boiler? I remember I open that valve when I was draining the boiler. I think like 2lb of black crap came out.

                      Comment


                      • #12
                        Re: My boiler is short cycling

                        the pig tail is the small brass pipe that does a loop

                        the picture that you have marked control is your pressure setting and the small pipe is a pig tail
                        Last edited by HVAC HAWK; 03-11-2008, 08:34 PM.
                        Charlie

                        My seek the peek fundraiser page
                        http://observatory.mountwashington.o...nal&fr_id=1040


                        http://www.mountwashington.org/weather/conditions.php

                        new work pictures 12/09
                        http://public.fotki.com/hvachawk/

                        Comment


                        • #13
                          Re: My boiler is short cycling

                          after it heats up the first time is it making steam before it shuts down

                          the valve with the yellow handle next to the glass tube ,put a bucket under it and open it if nothing comes out wait untill the boiler heats up then open it . this is a skimmer valve and if the water gets oil or a lot of stuff in it it will not make steam , so you need to skim this stuff off .
                          Last edited by HVAC HAWK; 03-11-2008, 08:38 PM.
                          Charlie

                          My seek the peek fundraiser page
                          http://observatory.mountwashington.o...nal&fr_id=1040


                          http://www.mountwashington.org/weather/conditions.php

                          new work pictures 12/09
                          http://public.fotki.com/hvachawk/

                          Comment


                          • #14
                            Re: My boiler is short cycling

                            Steam systems run best at a max of 2psi.
                            I noticed in the pics that the guage was at or near zero, was it operating at the time?
                            Also I noticed the pressuretrol was all the way down to .5, maybe a little increase might slow the frequency it cycles..don't go more than 2 psi, in fact only a small amount per try until it either stops short cycling or you're @ 2psi on the boiler guage when it shuts off.

                            My #1 guess is whats already been mentioned, the pigtail feed to the pressuretrol might be clogged, thats very common.
                            Usually it's good measure to replace both pigtail and presuretrol at the same time while you're at it.

                            IF any of this sounds confusing, please consider getting a pro to look at it, if you mistake one thing for another and accidently alter/damage a safety, you could create a hazardous situation.

                            Comment


                            • #15
                              Re: My boiler is short cycling

                              When you said clean the pig tail, you meant inside the tube right?

                              OK, I turn the thermostat up 1 degree to 69 to get the boiler firing. I have left the thermostat to 68 since last night. When I got home at 7pm, I have not seen the boiler coming on and it's 9pm. Also, the radiators were cold too when I got home.

                              The boiler has been running for the last 15 minutes since I set it to 69 degree. Steam are coming up at the radiators and boiler is still firing.

                              Comment

                              Working...
                              X