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Thread: Pump ony runs when burner/blower are on

  1. #1
    DIY Junior Member mudslider's Avatar
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    Default Pump ony runs when burner/blower are on

    So, after alot of reading and troubleshooting we have determined that the Taco pump only runs when the blower /burners are on. It is my impression that is is supposed to run off the inital call for heat, then the water temp determines the blower/burner coming on. So, is this a bad aquastat? What is happening is that the water does not circulate enough 2-5 minutes and the system shuts down because its hot. Can I just rewire so the pump will operate all the time?


    Cristan

  2. #2
    Plumbing Contractor for 49 years johnjh2o1's Avatar
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    If you are not getting your domestic hot water from the boiler there is no reason for it to maintain temperature when not calling for heat.

    John

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    DIY Junior Member mudslider's Avatar
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    Default heat only boiler

    This is a single pump heat, boiler to pipes to baseboard radiators. Manual says the pump should run thorughout the full call for heat,not just when the burner/blower is on. Because it is only circulating a few minutes, system never cools and shuts right down. The aquastat controls this, can I bypass it? everything else it controls seems to work fine. If I can bypass it ( aquastat) I can better know if it is working ( the pump)

    thanks

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    Take the cover off the aquastat and take a picture of it, close up if possible so I can see the wiring, or if you can not do that tell me what you have for an aquastat and what make the boiler is.

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    DIY Junior Member mudslider's Avatar
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    Default a whole new problem.

    ok, its a Crown Boiler CXE4..The aquastat is a honeywell L8148A..I have been online, have both Manuals, schematics...everything. Not bad for a laid of Mortgage Banker. So, you have been talking to me on another thread because I put this in the worng place to start. But we took the cover off the Aquastat and found that the tech had contected the pump directly to L1 and L3 instead to C1 and C2. We raised the high stop limit to 200 as Boiler Manual directed....It had been on around 170. So this time during the call for heat I noticed the return pipe into the pump is hot...but only about 3 feet back, so the heat is backing up out of the boiler. Makes me wonder if the Pump is working. We have 120V on the C1,C2 relay. We bleed the air out of all the radiators (convection style)...not alot of air. Still no heat to units.
    what now?..all that is left is the pump isn't working (TacoOO7) or???? Expansion tank is very old, no fitting to check air pressure, but does ot seem waterlogged....so today I decided to check the pressure switch..manual said pull the tube and it will shut off the burners and after that reattach the tube and they will fire...that all happened the way it should then return pipes started screeching and shaking and making bad nosies, so I turned it off until my husband got home.....of course it hasn't happened since, but i swear that was the first time I heard the water moving inthe pipes.

    So I feel good aquastat is fine..how do we check pump? and thank you so much!

  6. #6
    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Default

    Quote Originally Posted by mudslider View Post
    So, after alot of reading and troubleshooting we have determined that the Taco pump only runs when the blower /burners are on. It is my impression that is is supposed to run off the inital call for heat, then the water temp determines the blower/burner coming on. So, is this a bad aquastat? What is happening is that the water does not circulate enough 2-5 minutes and the system shuts down because its hot. Can I just rewire so the pump will operate all the time?


    Cristan
    This would depend entirely on how your system is wired and what controls/switches it uses to bring on the pump.

    In some piping systems the pump will start on a call for heat because the boiler used to heat the system is a low mass boiler and it must have flow going through it before it can fire. A flow switch is used to determine if there is flow there or not. The pump should run and stay on as long as their is a call for heat (or if the boiler over heats).

    If you have an aqua-stat controlling the call for heat it's entirely possible that its the culprit. But if that was the case the call for heat should go away and the boiler should stop firing.

    I need more info on your system before I can help you. How exactly is it set up? What is it's sequence of operation?

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    The pump wiring is WRONG. Move the pump wires to C1 & C2. L1 is Line in or power to the control.

  8. #8
    DIY Junior Member mudslider's Avatar
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    Default rewired

    I rewired the pump. Is there a way to check the pump? c1/c2 has 120V.
    I am starting to think it got vapor locked or air, it quit working and then it froze here. Now it is
    50 out and yesterday the return was screaming and I noticed last night that the unit came on alot more frequently and there was knocking in 2 units.
    I am going to try to bleed them again and see if I have more air. Its been 3 weeks,,it would be nice to have it fixed by Christmas and if i have to order a pump....The tech said the pump worked, but then he wired it to L1, so who knows? How do i know for sure if it is the pump...or a combo of things?

  9. #9
    Retired Defense Industry Engineer jadnashua's Avatar
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    While not the nicest thing, keep in mind that the pipes knocking might just be an indication that they are getting some heat and expanding. If it is running more normally, rather than just starting, the temperature difference and therefore the expansion/contraction may not be as great and it might be quiet.

    Also, if the 'banging' is coming from the boiler, it could be flashing into steam because the water is not moving, so finding where it is making noise becomes a good diagnostic item. When the boiler is on, generally, the pump must be moving water through the boiler, or it can make some nasty noises before the overheat or limit switch shuts it down. But, if it is pipes further out in the structure banging because they are getting hot, see what happens after awhile. Best not to stress the safety circuits too often!
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  10. #10
    Network Engineer rmelo99's Avatar
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    Ok, sounds like you fixed your initial problem of the pump being wired wrong. With it on the C terminals you know it will run when the aquastat is getting a call for heat. You can short out the LowVoltage (thermostat terminals) at the boiler to make sure you have a call for heat. This will make it easier, or u can just crank the thermostat while working on the boiler.

    Now bc u said it froze...here is what you might have to deal with.

    1.) Frozen pipe somewhere? I had this happen on on of my properties once. Was going crazy trying to figure out the prob with the boiler and it turns out one of the pipes froze. Pics would help us walk you through confirming you are good. I would try and confirm the path of the water through the loop at the basement/boiler. Make sure it is making it full circle from supply back to the return without any obstructions.

    2.) Circulator was connected to line power...meaning it could have died. Not because of voltage but running too long. Usually they are water or oil cooled, but your pump could be shot now.

    I would start there and see if u can some back with drawings/pics so we have a better understanding of your setup. There are a million ways the thing can be piped.

  11. #11
    DIY Junior Member mudslider's Avatar
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    Default Problem solved

    I finally had enough, pulled out the rotozip..made a bigger access to the unit and got ready to pull the pump..found out the auto fill valve did not work and the supply line was shut off. Filled it to high end of suggested psi, bled the rads again....and it works. After 5 weeks, so stupid. dont you think the tech might have checked it when i paid for the service call....good thing my husband is a sheetrocker, cuz i took out a big old hole! but we have heat!b

    THanks to all of you for the help,as I now this sytem inside and out...not bad for a laid off mortgbage banker......

    Cristan

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