Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit https://heatinghelp.com/contact-us/.

Need help wiring aquastat

My plumber just finished setting up a hot water loop today off my Weil McLain steam boiler (with a heat exchanger and 2 circulators) and all seemed to be working OK until a few hours after the plumber left and we noticed that even though the hot water zone reached the set point in the hot water loop thermostat and the steam thermostat the boiler was still firing. So basically even though both thermostats are set to 68 the house is now 75 degrees because the boiler keeps firing. I suspect this is because the aquastat (a strap on aquastat strapped to the supply line feeding into the circulator feeding the heat exchanger) is checking for water temp and in turn firing the burner even though the hot water zone thermostat isn’t calling for heat. I suspect the aquastat isn’t wired properly in the Taco Sr 501 relay the plumber installed. Any ideas? If I can just move a wire in the relay and fix this that would be great. We are roasting here.

Comments

  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 6,053
    Just turn the aqustat down for now.

    I can't tell you how to wire the system without a lot more information. Apparently you plumber needs to call in someone that knows controls
  • LongIslandSteamerLongIslandSteamer Member Posts: 11
    > @EBEBRATT-Ed said:
    > Just turn the aqustat down for now.
    >
    > I can't tell you how to wire the system without a lot more information. Apparently you plumber needs to call in someone that knows controls

    Thanks, Ed. Good idea. I will do that. This guy it totally clueless. I will try and get a photo of how it’s wired now to see if that helps.
  • LongIslandSteamerLongIslandSteamer Member Posts: 11
    > @EBEBRATT-Ed said:
    > Just turn the aqustat down for now.
    >
    > I can't tell you how to wire the system without a lot more information. Apparently you plumber needs to call in someone that knows controls

    Ed - just to be clear, the aquastat shouldn’t be checking to see if the boiler is at temp unless the hot water loop is calling for heat, right? Just need a sanity check.
  • Jamie HallJamie Hall Member Posts: 11,227

    > @EBEBRATT-Ed said:

    > Just turn the aqustat down for now.

    >

    > I can't tell you how to wire the system without a lot more information. Apparently you plumber needs to call in someone that knows controls



    Ed - just to be clear, the aquastat shouldn’t be checking to see if the boiler is at temp unless the hot water loop is calling for heat, right? Just need a sanity check.

    That's correct. The problem may be in the actual placement o the aquastat -- as well as its wiring. If it is in the hot water loop or heat exchanger loop with the pump off, it won't be able to sense the boiler water temperature. It has to be located to sense the boiler water temperature, not the loop temperatures.
    Jamie

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • LongIslandSteamerLongIslandSteamer Member Posts: 11

    > @EBEBRATT-Ed said:

    > Just turn the aqustat down for now.

    >

    > I can't tell you how to wire the system without a lot more information. Apparently you plumber needs to call in someone that knows controls



    Ed - just to be clear, the aquastat shouldn’t be checking to see if the boiler is at temp unless the hot water loop is calling for heat, right? Just need a sanity check.

    That's correct. The problem may be in the actual placement o the aquastat -- as well as its wiring. If it is in the hot water loop or heat exchanger loop with the pump off, it won't be able to sense the boiler water temperature. It has to be located to sense the boiler water temperature, not the loop temperatures.
    Thanks Jamie. I am not home to take a picture but the aquastat is a strap on type and it's strapped to the pipe going to the circulator which goes to the heat exchanger. I noticed that the piece of pipe it's strapped to is a small length of iron pipe as opposed to the copper pipe between the circulator and the heat exchanger. Do you think it makes sense to move the aquastat to the length of copper pipe between the circulator and the heat exchanger? I would think copper would be a better medium for conductivity than black iron pipe.
  • Jamie HallJamie Hall Member Posts: 11,227
    Problem is that that pipe won't be at boiler temperature unless that circulator is running.
    Jamie

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • LongIslandSteamerLongIslandSteamer Member Posts: 11
    Good point. So i guess the black iron pipe is where it will stay for now. I seemed like it was seated properly when i last looked at it but I wouldnt be surprised if it needs adjustment. Ideally the plumber shouldve installed an aquastat in a well. Having said all that, i think the wiring is the main issue right now.
  • LongIslandSteamerLongIslandSteamer Member Posts: 11
    Jamie - actually now that I thought about it again, the circulator will always be running when the hot water loop zone is calling for heat. that's what should then trigger the aquastat to check the temp on the copper pipe - so i'm thinking the copper is a better place, no?
  • STEAM DOCTORSTEAM DOCTOR Member Posts: 924
    Somewhat common to use strap on aquastat in such a setup. The kicker is that they are almost never accurate. Might take some trial and error. Turn down to the point where boiler won't produce steam but there will be hot water in the loop. Obviously, there may be other factors at play
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 6,053
    @LongIslandSteamer

    not knowing what you have for controls makes it a guessing game.

    I would use a two pole relay with NO contacts.

    When the thermostat calls for heat (hot water zone) 1 pole starts the HW circulating pump, the other pole goes in series with the aquastat and starts the boiler.

    When the stat is satisfied the boiler and pump shut off. When the stat calls the pump and boiler run. The aqustat shuts off the boiler if it gets too hot but will allow the pummp to run to disipate heat as long as the stat is calling

    You would be much better off with an imersion aqustat in the boiler and skip the strap on. You don't need an aqustat on the hx or zone piping
  • LongIslandSteamerLongIslandSteamer Member Posts: 11
    Finally got home from work and was able to take a look at my plumber's handiwork. As expected, the aquastat is definitely not wired up correctly. As you can see in the photos, the aquastat is only wired directly to the boiler and has ZERO wires going into the relay.

    Is this a simple wiring fix?







  • HVACNUTHVACNUT Member Posts: 2,569
    edited November 6
    Why is there a jumper between R and W on the SR501?

    Edit: disregard. I'm the meatball.
  • Jamie HallJamie Hall Member Posts: 11,227
    Ah. You do have a relay. @EBEBRATT-Ed 's wiring description is how you want it to go.
    Jamie

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • LongIslandSteamerLongIslandSteamer Member Posts: 11
    HVACNUT said:

    Why is there a jumper between R and W on the SR501? If you didn't put it there to test something temporarily, then remove it ya meatball.

    I didn't put anything there. I'll tell my plumber to remove it.
  • LongIslandSteamerLongIslandSteamer Member Posts: 11
    HVACNUT said:

    Why is there a jumper between R and W on the SR501? If you didn't put it there to test something temporarily, then remove it ya meatball.

    I just zoomed in and i dont see a jumper. I think it's just the way the wire is laying in the photo.
  • HVACNUTHVACNUT Member Posts: 2,569
    > @LongIslandSteamer said:
    > (Quote)
    > I just zoomed in and i dont see a jumper. I think it's just the way the wire is laying in the photo.

    You're right. Apologies. Maybe it's time to see the optometrist.
  • HVACNUTHVACNUT Member Posts: 2,569
    edited November 6
    @LongIslandSteamer
    Discuss with your plumber but this should be acceptable. The L4006A aquastat is a Hi Limit only with an adjustable differential. It will basically act as a cold start.
Sign In or Register to comment.

Welcome

It looks like you're new here. If you want to get involved, click one of these buttons!