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Very short cycles

Thanks Timmie,....Again.



  • John G. Merritt
    John G. Merritt Member Posts: 140
    Very short cycles

    Hi Fellas!
    I have had several service calls where a Boiler with 2 or 3 Taco zone valves, suddenly starts and shuts off in a matter of seconds. The problem is that the controls and thermostats seem to be OK.
    Anybody know what causes this to happen?

  • kevin
    kevin Member Posts: 420
    I have....

    seen his happen with Tacos....Bad heads...Just another reason I don't usethe 271's.Other than changing the heads in adition a taco zone valve control MIGHT help..kpc
  • John G. Merritt
    John G. Merritt Member Posts: 140
    How would you check?

    > seen his happen with Tacos....Bad heads...Just

    > another reason I don't usethe 271's.

  • John@Reliable
    John@Reliable Member Posts: 379
    Short cycles

    Thermostat set @ 1.2 ? Is thermostat level ? What is aquastat is at, I find 180* 190* on high and 160* 170* on low if using 8124 w/dif @ 20 works for me. Hope this helps John@Reliable
  • John G. Merritt
    John G. Merritt Member Posts: 140
    Everything seems to be set

    Thermostats are level and Amps are correct. Settings on R8184 are 160-180 Degrees.
    Could be bad head. Hard to check out which one.
    can't figure what is causing this problem exactly, but have heard other Techs complain about this same thing.

  • Glenn Harrison
    Glenn Harrison Member Posts: 405
    Bad Taco powerhead

    Have seen it a few times where one powerhead won't depress the piston all the way or the end switch will go bad and cause the short cycle. The trick is to figure out which powerhead it is, since frequently it is an intermitent problem.

    Glenn Harrison, Residential Service Techician

    Althoff Industries, Crystal Lake, Illinois

    Althoff Industies Link
  • John G. Merritt
    John G. Merritt Member Posts: 140
    Something else to drive me nuts.

    I think you fellas have it . Bad power head.
    Just something else to drive me nuts!
    Ever hear of Easton Zone Valves?

  • Which heads?

    If it is the green heads then the end switch on the zone that is calling is bad. Change the head. Do this by process of elimination.

    If it is a gold head that is unusual because they use a micro switch instead of open contacts.

    Another way to tell is to hook up an ampmeter(in series from t'stat to #1 termianl) to the head and make sure the amperage on start is over .9 usually around 1 to 1.2 amps. When the #1 and #2 contacts open the amperage will drop. If that does not happen change the head.
  • John Abbott
    John Abbott Member Posts: 356
    Zone valve cycle

    Usually setting the thermostat heat anticipator to 1.1 to 1.2 will correct most short cycle problems if they are ocurring frequently.Some short cycling is unavoidable and the more zones the more chance you have of this occuring.If your water temp drops to to the high limit setting less differential 3 seconds before the end switch opens you have a short cycle with the more common aquastats.Perhaps there are controls out there with a minimum cycle length but the more common aquastats I work with don't have that feature.

  • antman
    antman Member Posts: 182
    Hydrotherm flue condensation

    I do not come across these boilers to often, but when i do they never seem to be in good shape, I am not slamming them, i'm just curious about this particular situation.

    Today i had a situation where i had to go on a no-heat call, pilot out, ok go to change the thermocouple, HELLO, thermocouple literally melted and fused to pilot assembly, NEVER seen this before. So ofcourse i don't have a pilot assembly (#@*&^n' helper) run to the supply house pick one up, fine, fire up the boiler, nothin, go through the procedures, find a loose connection on blocked vent switch, damper opens, nothin, bypass flame roll out switch, bingo, boiler fires, ok, now i need a new vent switch because the terminal is broken loose, and a new flame roll out switch, I remove the flame rollout switch and sure enough someone had wrapped a wire around the twom leads bypassing the fusable link,Ok, go get the parts come back, good to go boiler fires, after 5 minutes I see, droplettes coming out from under damper onto draft hood, then i hear drip, fizz, drip, fizz flames are freakin out, bam boiler shuts off, flame roll out switch goes again, so i by pass it let run to get customer heat while i hang out, Explain to them that there is a flue gas condensation problem,

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  • John G. Merritt
    John G. Merritt Member Posts: 140
    Makes sense

    John Abbott:

    Thanks. Makes sense. I'll check it out.

This discussion has been closed.