Power User Conference


Results 1 to 18 of 18
  1. #1
    Andy Jarchow's Avatar
    Andy Jarchow Guest

    Default Boiler turns on and off often??? What will cause this?

    Is it normal for a boiler system to run for 3-5 minutes or so and then shut off for a minute or two and start back up again? The boiler I inspected yesterday kept turning on and off like this. The pressure was 27 psi and the water temp was only 100 degrees. The pressure didnít appear to go down at all before the unit came back onÖ

    Is this normal or is it because the limit switch is set at 27 psi?

    Could the pressure tank be water logged?
    What do you think could cause this?

    The boiler is a Weil-Mclain.

    Thank you for your advice!
    mk

    Similar Threads:
    Certified Master Inspector CMI

  2. #2
    Ron Bibler's Avatar
    Ron Bibler is offline Member
    Join Date
    Mar 2008
    Location
    Healdsburg Ca
    Posts
    2,499

    Default Re: Boiler turns on and off often??? What will cause this?

    That could be a lot of things. Its sounds like its cycling

    The boiler stat is faulty, Pump or motorized valve faulty. How dirty was it?

    Sound like it need some service or replacement time.

    How old is this thing.

    Best

    Ron


  3. #3
    Ken Rowe's Avatar
    Ken Rowe is online now Member
    Join Date
    Nov 2009
    Location
    St Paul, MN
    Posts
    1,496

    Default Re: Boiler turns on and off often??? What will cause this?

    Agreed with Ron.

    MinnesotaHomeInspectors.com
    Minnesota Home Inspectors LLC
    ASHI #242887 mnradontesting.com

  4. #4
    David Bell's Avatar
    David Bell is offline Member
    Join Date
    Oct 2009
    Location
    CT shoreline
    Posts
    657

    Default Re: Boiler turns on and off often??? What will cause this?

    The aquastat controls when it comes on. If it is a cold start boiler it should only fire on a call for heat. If you have a triple aquastat, it has 2 settings, a high limit and low limit which keeps domestic water hot. Normal settings are usually between 120 and 140 on the low side and 160 to 180 on the high side. If the boiler is just used for heating the aquastat should be 160 to 180, unless there is radiant floor heat, that is normally around 120 depending on design temp. The other possibility is a t-stat that has too close of a temp differential programmed into it. Most digital t-stats are easy to adjust.


  5. #5
    James Duffin's Avatar
    James Duffin Guest

    Default Re: Boiler turns on and off often??? What will cause this?

    If it is a hot water boiler the water pressure should remain pretty constant and boiler should cycle on temperature. There could be a aquastat controller that is set on a fixed temperature. On this controller there is normally a differential setting on that determines how much the water temperature has to drop before the boiler comes back on. Or there could be a reset controller that resets the water temperature depending on how cold it is outside. If it's 0 outside the water would be 180 degrees and if it's 60 outside the water would be 100 degrees. This setup had an outdoor temperature sensor somewhere in the system.

    It is is a steam boiler 27 lbs is mighty high for a residential system!


  6. #6
    David Bell's Avatar
    David Bell is offline Member
    Join Date
    Oct 2009
    Location
    CT shoreline
    Posts
    657

    Talking Re: Boiler turns on and off often??? What will cause this?

    Quote Originally Posted by James Duffin View Post
    .

    It is is a steam boiler 27 lbs is mighty high for a residential system!

    If it's a steam boiler it is now a large humidifier as the relief valves for steam are 15 lbs!


  7. #7
    Andy Jarchow's Avatar
    Andy Jarchow Guest

    Default Re: Boiler turns on and off often??? What will cause this?

    Yes it's a water boiler.

    I didnít know what the cp number was so I didnít record it. I guess you need this number to determine the age (the cp number is the serial # for Weil Mclain). I called the company and they said it is a 2000 to present.

    Thank you for your help all!


  8. #8
    Join Date
    Mar 2007
    Location
    Santa Fe, NM
    Posts
    73

    Default Re: Boiler turns on and off often??? What will cause this?

    Sounds like short cycling!

    Was it baseboard or infloor.

    I have seen short cylcling on both. Infloor zones need to be balanced more or less i.e same loop size.

    Most manufacturers recommend bypass piping / valve primarily for cold start up (short loops) to control condensation

    Some have bypass integrated such as some lochinvar models.

    Boiler size; pump(s) sized for install; temp settings on aquastat


    Bypass_Piping_Explaination

    Hydronics Piping Checks Can Be A Breeze

    Charles @ PreVue Property Inspections, Santa Fe, NM
    http://www.prevuepropertyinspections.com/
    "How can someone with glasses so thick be so stupid?"

  9. #9
    Andy Jarchow's Avatar
    Andy Jarchow Guest

    Default Re: Boiler turns on and off often??? What will cause this?

    Quote Originally Posted by Ron Bibler View Post
    That could be a lot of things. Its sounds like its cycling

    The boiler stat is faulty, Pump or motorized valve faulty. How dirty was it?

    Sound like it need some service or replacement time.

    How old is this thing.

    Best

    Ron
    It's only about 5 yrs. old and was pretty clean. The house was empty for about a year and a half though if this makes a differance.


  10. #10
    jason schatz's Avatar
    jason schatz Guest

    Default Re: Boiler turns on and off often??? What will cause this?

    Do you know if the whole system was drained and refilled since it was vacant for so long?

    Temp only gets to 100 before it shuts off? My first guess would have been the water logged tank like you mentioned.


  11. #11
    Andy Jarchow's Avatar
    Andy Jarchow Guest

    Default Re: Boiler turns on and off often??? What will cause this?

    Quote Originally Posted by Charles Smith View Post
    Sounds like short cycling!

    Was it baseboard or infloor.

    I have seen short cylcling on both. Infloor zones need to be balanced more or less i.e same loop size.

    Most manufacturers recommend bypass piping / valve primarily for cold start up (short loops) to control condensation

    Some have bypass integrated such as some lochinvar models.

    Boiler size; pump(s) sized for install; temp settings on aquastat


    Bypass_Piping_Explaination

    Hydronics Piping Checks Can Be A Breeze
    They have the big radiators Ė the house was built in 1920. The boiler is about 1 to 10 years old but the owner said it was new (not sure what new means). I found a lot of asbestos like insulation and corroded valves too.

    I need to do some reading. Iíve only ever had to inspect two water boilers and they were both this week. I think they both had issues too. The one I did yesterday seemed to work fine until the temp went all the way to 192. The boiler shut off for 5 to 10 minutes and then started back up again. Is this normal? Dave Bell mentioned (above) that 180 is on the high end.

    What temp do you suggest shutting things down at if it keeps climbing? I was going to shut this one off at 195. I had my finger on the service mans switch and it shut off on its own.

    Itís a Vaillant so I have no idea how old this one is. I checked all of the archived posts on this site and searched the web but no luck. I sent the company an email but I really donít expect an answer.

    Thank you for your help all!
    mk


  12. #12
    jason schatz's Avatar
    jason schatz Guest

    Default Re: Boiler turns on and off often??? What will cause this?

    I've wrestled a lot with boilers, not from the HI perspective but rather my own properties...they can be a pain to figure out, but 90% of the time it was the simplest answer.

    On a secondary note, I am new to this site (and enjoy all the conversation), but is it really the duty of you as the HI to figure this out? Shouldn't you just note the problem?


  13. #13
    Andy Jarchow's Avatar
    Andy Jarchow Guest

    Default Re: Boiler turns on and off often??? What will cause this?

    Quote Originally Posted by jason schatz View Post
    Do you know if the whole system was drained and refilled since it was vacant for so long?

    Temp only gets to 100 before it shuts off? My first guess would have been the water logged tank like you mentioned.
    My guess is that it wasn't drained. Will that gum things up?


  14. #14
    jason schatz's Avatar
    jason schatz Guest

    Default Re: Boiler turns on and off often??? What will cause this?

    I was thinking more along the lines of if it was refilled, maybe it was done so incorrectly.

    How many stories is the house? 27psi seems like a lot unless it's feeding baseboards on a third floor.


  15. #15
    Andy Jarchow's Avatar
    Andy Jarchow Guest

    Default Re: Boiler turns on and off often??? What will cause this?

    Quote Originally Posted by jason schatz View Post
    I was thinking more along the lines of if it was refilled, maybe it was done so incorrectly.

    How many stories is the house? 27psi seems like a lot unless it's feeding baseboards on a third floor.
    2 story house almost 3000 sq. ft.


  16. #16
    jason schatz's Avatar
    jason schatz Guest

    Default Re: Boiler turns on and off often??? What will cause this?

    Then 27 definitely seems high.... Had that issue before, although it wouldn't shut off quite that fast.

    Auto water fill wasn't working correctly so it was over filling the boiler tank.


  17. #17
    Andy Jarchow's Avatar
    Andy Jarchow Guest

    Default Re: Boiler turns on and off often??? What will cause this?

    Quote Originally Posted by jason schatz View Post
    I've wrestled a lot with boilers, not from the HI perspective but rather my own properties...they can be a pain to figure out, but 90% of the time it was the simplest answer.

    On a secondary note, I am new to this site (and enjoy all the conversation), but is it really the duty of you as the HI to figure this out? Shouldn't you just note the problem?
    Your right- we (HI) are required to call out that the unit isnít working right and recommend an evaluation by an HVAC person repair/replace as needed. However it is helpful to know how everything works to determine if it is working as intended. Iím always curious to find out why.

    If you ever had kids you will know what Iím referring to. Young children always ask why to everything. Well I never grew out of that.

    Have a great weekend all!


  18. #18
    jason schatz's Avatar
    jason schatz Guest

    Default Re: Boiler turns on and off often??? What will cause this?

    Haha no problem - I'm with you.... Being a science teach/HI is a result of my constant 'why's' as well!


Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •