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Weil McLain indirect hot water heater, short cycling?..

john p_2
john p_2 Member Posts: 367
Not sure short cycling is the correct term for what happens but let me explain. My Taco zone control panel indicates a call for heat to the indirect zone and the boiler goes into its firing sequence but never fires just stops short of lighting. There is however no shortage of hot water when needed. Seems like it is increasing in frequency also.


  • Snowmelt
    Snowmelt Member Posts: 1,414

    Need more info like piping picture, pipe size, water heater size, boiler size, is there a perge going into the water heater.

    Here's an idea also, turn the boiler off, run the hot water till the tank is cold not Luke warm but cold, then turn the boiler on and tell us how long it takes to heT up from a cold tank.
  • Condoman
    Condoman Member Posts: 90
    Same Issue

    I had the same problem with my indirect also.  Since I work at my desk & shop in the basement I could hear it happen.  I was concerned as I had installed this myself, but nothing was wrong in the end.

    What I was able to do was hook up a 110V analog clock to the burner wires & view the ZVC404, clock & boiler temp with an interval camera taking a picture every 10 seconds.

    After analyzing hundreds of pictures I caught a short cycle.  It was nothing more than a confluence of triggers that had boiler temp just at a cutoff toward the end of a call for heat.  The clock showed under 5 second burner run.
  • heatpro02920
    heatpro02920 Member Posts: 991
    what are your temps

    what are the boiler controls temps or temp and what is the tanks temp set at?

    is this a new problem?

    does the circ run and then the boiler pulls in? Im trying imagine if your boiler is 200 degrees and your tank is set to 140 and falls to a low enough temp to call for heat, it starts the circ and the hot boiler water satisfies the tank before it gets a chance to start the burner...

    I would have to see how its wired... I have heard of the above problem, it happens with small efficient water heaters and large boilers... I had this issue in a building, it had a small indirect I think it was 28gallons, and a huge boiler that heated the building and all the offices, the boiler would start to fire {first stage} and then never go onto the second stage {this starts to cause issues after a while in some boilers} before the tank was already hot... opening up the boiler limits helped this and slowing down the flow to the hot water tank.. But it still wasnt perfect...

    Was your boiler previously a tankless
  • heatpro02920
    heatpro02920 Member Posts: 991
    you have too much free time, lol

    good for you.... I always thought about a boiler watching camera and data loger to help with intermittent problems..
  • john p_2
    john p_2 Member Posts: 367
    Weil McLain indirect hot water heater

    Yes a fairly new problem. The boiler is a Utica UB90 - 150. The aquastat in the boiler is set to 170 and the indirect has a temperature dial on the top that is set to about midrange but not sure what that temperature is.
  • john p_2
    john p_2 Member Posts: 367
    some more photos

    not sure these will help but here they are.
  • Snowmelt
    Snowmelt Member Posts: 1,414
    Looks nice

    What I would do is shut the boiler off, run the hot water till it gets cold, then see how long it takes to warm up?

    In mean time

    What size pump and what size piping is going to the indirect tank?

    In there a check valve making that it's own loop. .

    IS hot water from any zone going into that zone?
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    can you

    Post some pics of the piping on the side of the tank and hopefully the pump?
  • Zman
    Zman Member Posts: 7,569

    I am assuming that the indirect is a zone that is being prioritized by the Taco?

    The first thing I would do is be sure it is not a control issue. Does the zone valve open?

    If you manually open the zone valve and jumper the TT to the boiler does the problem go away? A flaky contact in the indirects aquastat, zone valve end switch or taco relay could be causing this.

    If the control side checks out, I would then check for proper circulation then start trouble shooting the boiler.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • john p_2
    john p_2 Member Posts: 367
    My thoughts...

    No, it is not set to priority. And correct me if I am wrong but we are never w/o hot water and there are 3 women, (2 of which are teenagers!), myself and an 8yr old son taking showers everyday .So, for that reason alone I think I can safely say the zone valve works. The S/R headers are 1-1/4" and the indirect S/R lines are 1", all other zones are 3/4". Is the aquastat in the indirect replaceable? I have  a sketch of how the system was wired, once I find it later I will upload.
  • icesailor
    icesailor Member Posts: 7,265

    I've had numerous problems with the thermostats on those indirects. They make a ton of water but you turn the knob down just a tad and it won't come on. The thermostat is at the end of a long wire. You may have a bad one and it will drive you nuts.

    I don't completely understand your hot water problem but look into that thermostat. I never installed that heater, but every one I worked on had some kind of a problem with the thermostat.
  • john p_2
    john p_2 Member Posts: 367
    Not the thermostat...

    Well, it's not the thermostat inside the Weil McLain indirect. I replaced it today and still getting the phantom calls for heat when the boiler begins it's cycle and stops short of firing. Was talking to a contractor and remembered that during Super Storm Sandy I had lost a refrigerator due to the electrical surges during the storm and I believe that this is when this started and the frequency has just gotten worse - a lot worse and when it happens and I look at the Taco zone control panel it can be any zone now - I thought it was only the DHW zone. I'm leaning towards a bad zone control panel?!
  • icesailor
    icesailor Member Posts: 7,265
    Zone Controller:

    It may be the zone controller. It sounds like it might be.

    If any zone valves don't properly close all the way, or appear to be closed but don't completely break the end switch,  they can do what you are talking about. But, a yellow light will be on, or come on, But the red light never comes on. When it does this short cycling, do any of the controller lights come on?

    With Taco 57* valves, they can get rusty on the metal hold down plate and the piston from the actuator can get stuck not coming back all the way and the spring isn't strong enough to push the motor plunger all the way back. Leaving 2 & 3 still closed, almost. The yellow light will stay on. If the red light never comes on, the plunger is stuck. Take #1 wire off to kill the power for at least 2 minutes and remove the power head. If the metal top has rust around the hole, spray it with Kroil. Take a big pair of water pump pliers and put one end on the underside of the valve, the other side on the top if the plunger. Operate the plunger manually with the pliers until it works easily. Spray the inside of the power head with WD-40 or 556. The manual lever should then easily move up and down. Then, work the valve. If you need to replace the actuator/piston, this plier trick is a very good way to replace it. I buy a whole new valve but don't replace the body. Its cheaper than buying the parts alone and the time draining and refilling the system.

    You may indeed need a new control panel. Did you check the output of the transformer? There really isn't much else to go wrong with the ZC zone valve controllers. If it was a SR, another story. Those ice cube relays get lunched often.
  • john p_2
    john p_2 Member Posts: 367
    leaning towards the Taco Zone Control Panel...

    Sailor thanks for all your help...Still not understanding how all my zones are working w/o a problem, in that the house has no cold rooms and no cold showers. When I zones need heat, they are getting it. It's just these phantom calls for heat where the boiler never lights that's got me going crazy.
  • john p_2
    john p_2 Member Posts: 367
    forgot to mention...

    Also forgot to mention that I have Honeywell zone valves not Tacos
  • icesailor
    icesailor Member Posts: 7,265
    Honeywell Zones:

    I thought you probably had Honeywell's like in the photos. I was commenting on things which I have found with Taco's that might be of interest.

    Whenever I have found a Zone "Ghosting" for no apparent reason, it's always been either crud in the seat or something keeping the ball or paddle from seating properly.

    Because I have always considered Zone Valves to just being motorized flow checks, I always installed a standard flow check on any zone valve system. It stops any of that gravity flow or "ghost flow" that might happen. I'm probably not telling you anything, but, when the system is cold, turn up a zone that is NOT one of the Ghost zones. Feel a supply pipe to the ghost zone. If its getting hot or warming while another valve is calling, its a bad valve. Or crud under the seat. If there are isolation valves between the boiler and the system, shut off the supply and let the boiler get hot without the zones calling. Once hot, shut off the boiler. See if the ghost zones start warming. If any do, the seat is leaking bye. Its easiest if the valves are on the supply. Of they are on the return, its more complicated.
  • john p_2
    john p_2 Member Posts: 367
    Sailor, In an earlier post above you mentioned the ice cube relays in the zone control panels get "lunched" are they replaceable?
  • unclejohn
    unclejohn Member Posts: 1,833
    Have you checked the boiler water temp. when the DHW calls? Is it below 170*F. If its not on priority then the boiler may be up to temp.