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  1. #1
    I woke up last night at 3:30am freezing and found that the zone-valve (1 of 3) was OPEN but the circulator pump would not operate for that zone only.

    I verified that the circulator pump was OK and responding correctly to the other 2 zones by turning up those thermostats. I also found that the zone-valve was functioning properly because this zonevalve happens to make ticking sounds constantly when opened (very easy to hear).

    Now if the thermostat is OK, (zone-valve opened) and the circ pump is OK, and the burner and everythign else is OK, what would cause the circulator pump to not activate on that one zone only?

    As a temporary fix, I turned up the thermostat on another zone just to get the circ pump running and we did have heat for the rest of the morning (which proves everything else is working).

    Could the Honeywaell L8124A Aquastat Relay be bad? I dont think so because it cannot tell the difference between zones, right?

    Thanks in advance, I really don't know what it could be.


  2. #2
    Join Date
    Mar 2001

    End Switch

    You have a bad end switch on the zone valve. Change the power head or the complete zone valve if out dated......

  3. #3
    Join Date
    Mar 2003
    Typically a zone valve will have an end switch which
    closes when the valve is fully open, allowing power to
    the relay which starts the pump. Also, most valves have
    a lever that will manually open the valve. Ticking
    sound isn't normal. Maybe gears have been damaged
    for a while and finally failed completely. Since you get heat to that zone with others calling the valve must be
    partially open but maybe not enough to close the end
    switch and start the pump.

  4. #4
    WOW, thanks for the quick reply guys!

    So the opening of the valve is what triggers the circulating pump ...that explains it perfectly. Yes, the valve is very noisy; it probably finally failed last night.

    It's a Taco zone valve and was probably installed in 1980 when the house was built. I wonder if I have to replace the whole valve assembly or just twist off the top and replce the top?

    I ask because it's gonna be real tough to do the soldering there.

    Thanks again!

    [Edited by tony17112acst on 02-06-2005 at 01:59 PM]

  5. #5
    Join Date
    Jan 2005
    If its a Taco you turn down the thermostat and twist it off. Quick question is the thermostat new? Is the heat anticipator set to .9 on the thermostat?

  6. #6
    The thermostat is about 1 year old and has been working fine. I also have it set at .9.

    I found out from documentation that I can just twist off the power head and water shouldn't start shooting out all over me (180 degree water no less).

    It looks like I'll hafta pay $80 for a new assembly and hope that I can just switch out the power head, but as a previous poster said, I may also have to replace the whole valve (booo!).

    I think I will switch the powerhead with another zone that I rarely use just to get by until I fix everything.


  7. #7
    Join Date
    Sep 2004
    Geez, all you need to do is the standard replacement procedure for a Taco zone valve head. Be sure the power is off to the unit (or just remove the 24 volt #1 terminal and wait a minute) then then twist the head. If it's green in color, it's definately no good. Those green colored heads are terrible, the new and much improved design is gold colored. Change any others that are green too while you're there. I got a few extra heads laying around too, let me know if you're interested.

  8. #8
    Yes, Plz email me with your price. I will switch the powerhead tomorrow with one of the good ones to be sure that all I need is the head.


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