Boiler Heat System shuts off....

Discussion in 'HVAC Heating & Cooling' started by mudslider, Dec 14, 2009.

  1. mudslider

    mudslider New Member

    Messages:
    21
    Location:
    wa
    We had the same problem last year, system calls for heat..everything comes on and after 3to 5 minutes it shuts itself down. Last year the old Tech came out replaced the pressure switch and we were good. Same symptoms this year, old Tech no longer in business. I call a local reputable company and he comes out, not the pressure switch, not the aquastat, not the pump....He thinks the pipes are plugged and water isn't moving enough to cool down , so system shuts down. I pay the bill, I have no heat because he can't fix it.

    My question is:

    How can I tell if the pump is working? Manual says that the pump will continue after the blower and burner shuts down. How do I know this is happening?

    It is a Crown Boiler, thanks
  2. Doherty Plumbing

    Doherty Plumbing Journeyman & Gas Fitter

    Messages:
    810
    Location:
    Penticton, BC
    Sounds to me like the boiler is tripping on it's high limit. Which is *usually* caused by a lack of flow through the boiler assuming its a low-mass boiler.

    This can be caused by either a blockage in the line (VERY UNLIKELY), or a failing pump. Sometimes a pumps impeller will get plugged up with gunk and it will not push as much water through the system and thus your boiler over heats.

    You may also want to clock the appliance to make sure it's not putting out more heat then it should.

    You can tell if your pump is working by putting a screw driver to the pump and then to your ear. You should hear the motor humming away. Have someone kill power to the pump and start it back up again. You should hear it start and stop. You can also pull the pump and check the impeller for debris like I described above.

    This may be a stupid question but are you sure all the valves are open in the system and it's not just something silly like that? Also check to make sure your zone valves are actually opening all the way.


    I am no mod but you might want to post this in the boiler forum.
  3. mudslider

    mudslider New Member

    Messages:
    21
    Location:
    wa
    thanks

    I will share this info with my husband..He is a Drywall contractor..not a plumber or heat guy. And as for the switcheson the radiators..I really do not know which is open, which is closed.....


    I will try the Boiler forum as well, thanks...
  4. mudslider

    mudslider New Member

    Messages:
    21
    Location:
    wa
    good advice

    So, we did some trouble shooting and have determined this.

    The expansion tank is not waterlogged and has the right air pressure

    We have figured out that the Taco pump is not pumping when a call for heat is issued. It only runs when the blower and burners are running.

    SO, the aquastat is supposed to control all that..is it bad?:eek:
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,183
    Location:
    New England
    Some systems have multiple pumps. While the boiler is on, at least one of them should be running, or it's like water on the stove, eventually, it will overheat. A boiler (unless it is designed to produce steam - kind of a misnomer here) should only get the water hot. If it gets to the upper limit, the boiler will shut off.

    Often, the circulator is controlled by the house thermostat. It the house needs heat, it turns the pump on and sends a signal to the boiler that heat is required. IF the boiler temp is low, then it will fire; if it is in between the high and low limits, it normally doesn't until the water gets too cold.

    When the boiler turns off, there is some residual heat in it, and it can continue to get the water in it hotter, so most systems decouple the circulator and let it keep going.

    Not knowing how yours was hooked up, can't say why it is doing what it is...if it shuts off before the house reaches the thermostat setting, something's wrong. If it does, it is just doing what it is supposed to.

    If the boiler has more than one circulator, it may either be using one for each zone, or be using a primary/secondary loop system. The primary loop often runs any time the secondary loop calls for heat, and for some time after.

    To diagnose your system, would require more details.

    Is the house eventually getting to the temp you want? Do you have a central thermostat? Do you have zone valves? Do you have more than one pump? Are all of the boiler controls internal to the boiler, or is there an external box(es)? If more, do you have any idea what they do? Maybe a picture of the setup would help, but is not a guarantee. Sometimes, you just have to be there...

    As asked earlier, are you sure all of the required valves are open?

    When the house is calling for heat, is the pipe temperature on either side of the circulator about the same? How about further up?
  6. mudslider

    mudslider New Member

    Messages:
    21
    Location:
    wa
    reply

    It is a one pump system. The aquastat must be bad....it is not turning the pump on at the right time, so yes..it is overheating and shutting down...all the outgoing pipes are hot, return is cooler.....we have have no heat per say. Thermostate says 50-55, but I have been burning a wood stove and heaters. It was down to 10 degrees outside, now it is in the 50s.

    Frustration is the Tech who came out didn't have a clue....
    I paid a service charge and labor to have him tell me that he thinks the "channels" pipes were plugged.....tried to sell us an electric furnace.

    Cristan
  7. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    One pump system, the aquastat does not turn the pump on. There may be a relay in the aquastat that turns the pump on.

    If you have a dual aquastat ( high and low settings) the low setting runs the burner to maintain whatever the set point is and the high shuts the burner off. The circulator relay will energize when the thermostat calls depending on where the temp in the boiler is at the time. If the temp is below the low setting then the circulator will not run untill the boiler is at or above that temperature.

    Crank the low down as far as possible and do a volt check across C1 and C2 with the thermostat calling. If you have voltage (110) then your circulator is probably bad or the wiring is f'd up. If you get no voltage across C1 & C2 then the aquastat is bad and needs replacing.
  8. mudslider

    mudslider New Member

    Messages:
    21
    Location:
    wa
    volt check

    ok, volt check on c1 to c2 was 124.5v and we found that the pump is wired directly into L1 and L2...and it was 124.8v..So if the tech hooked me up direct? why does the pump not run?
  9. mudslider

    mudslider New Member

    Messages:
    21
    Location:
    wa
    rewire

    ok, we put the wires where they need to be, and it sounds like the pump is working, even when the burner/blower is not.. man this is a mess...the tech really screwed us up. So I am back to the begining, everything seem to be ok, except no heat to the radiators....
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,183
    Location:
    New England
    If the pump is now running, the boiler fires, but there's no heat, you either have a valve closed or there is air in the system preventing flow. Well, the impeller on the pump could be gone. Don't think that happens all that often.
  11. mudslider

    mudslider New Member

    Messages:
    21
    Location:
    wa
    maybe pump not runnin

    So, it seems that maybe the taco 007 is not running, or if it is it isn't very much. After all the trouble shooting and adjusting and bleeding everyone of those raditors, still no heat. The thing is, it was working, then it just quit.


    So, I think that the pump is not working becasue the return line was cold, now it is hot when the burners are on, but hot backwards....from the pump up the return line.....3 feet back it is cold again....pump?
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,183
    Location:
    New England
    Take a screwdriver, place one end on the pump and the other to your ear...you can normally hear if the pump is working - a poor man's stethescope. If the pump is getting really hot, it may be stalled. The Taco pumps use a cartridge, and you can replace that without having to break the end seals. Depending on where you are, sometimes you can buy a pump for less. Wouldn't hurt to have one on hand anyway.

    It doesn't take much air trapped in the system to block the flow.

    You'll get some hot water around the thing just from conduction, but if the inlet and outlet get about the same temp, the pump is probably working, but doesnt' have enough head to overcome an air lock, or the pump is bad.
  13. mudslider

    mudslider New Member

    Messages:
    21
    Location:
    wa
    Thanks

    Thanks for you input, it took alot of figuring what it was NOT..now it could only be a few things....

    Mudslider..more then just a drink,
  14. mudslider

    mudslider New Member

    Messages:
    21
    Location:
    wa
    ok, back to the start. before it got real cold it was working fine. The day it quit the kids had it cranked up high all day. It just quit heating. Boiler would fire and shut off after a few minutes.....a few days later it froze.....Now it has thawed and I wonder what that has to do with it, as I am getting something moving in the pipes since I bleed the air out......I am going to try to bleed more, I have 2 units now clanking. This sucks..thanks guys for all the help, I know more about this boiler and aquastat then I care too:D
  15. mudslider

    mudslider New Member

    Messages:
    21
    Location:
    wa
    problem solved

    We got it fixed. I pulled out the rotozip and took out the sheetrock and got ready to pull the pump..then We found the autofill valve did not work and the supply valve was off...so, filled it to top of manufactorers suggested psi. and it is fixed......thanks so much for all your help. after 5 weeks, we have heat.\
    \

    Cristanb
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