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Testing a Zone Relay

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JK_3
JK_3 Member Posts: 240
IS this a one circ system with 2 zone valves or a 2 circ ststem?


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  • DaveD_3
    DaveD_3 Member Posts: 9
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    Testing a Zone Relay

    I have a two-zone forced hot water system and one of the zone won't heat. The system hasn't been touched (or serviced) in years and it was working perfectly last season. I've tested the thermostat and it apears to be working properly. Opened the honeywell R845A relay box and the internal relay switch clicks on/off when the tstat is turned to on/off positions. But, with the relay switch on, the boiler doesn't fire and the circulator pump doesn't open the line for this zone. There are no problems with the primary zone.

    Q: how can I verify that the problem is in the relay switch? Is there a test or some way to bypass the relay?
  • DaveD_3
    DaveD_3 Member Posts: 9
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    Testing a Zone Relay

    I believe it's a one-circ w/ 2 valves. There's a single hot-water feed coming out from the boiler that branches into the two zones. Each branch has it's own circulator.
  • DaveD_3
    DaveD_3 Member Posts: 9
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    Solving zone problem

    I need to rephrase the question -- this zone has the honeywell R845 relay and a Taco circulator. I need to determine which of these is the cause of the problem. Any recommendation on a test that would eliminate one or the other?

    Thank you
  • JK_3
    JK_3 Member Posts: 240
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    Test for 110 volts at the terminals in the 845 that are marked circulator while there is a call for heat. 110 volt = bad circulator no volts = bad relay. hope that helps an Happy Thanksgiving to you and yours.

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  • bill nye_3
    bill nye_3 Member Posts: 307
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    845

    Dave, one would have to know if the 845 was wired correctly. Many times they are not.

    A voltage meter would determine if power is available for the circulator. A real simple test would be to disconnect the wire to the circulator and plug it into an extension cord but this is absolutely a "kids don't try this at home" unless you are real sure of what you are doing.

    There are three or four possible wiring combinations that could technically work. You need to check the 8182 or 8124 it is hooked up to , to see if ZC and ZR terminals are used.
  • JK_3
    JK_3 Member Posts: 240
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    I would tend to think that if the system has not been touched or serviced in years and this problem has just developed that the most likly problem(considering he cas see the relay clicking) is the 845 or the circulator and would start there first.

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  • bill nye_3
    bill nye_3 Member Posts: 307
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    JK

    JK, you could be right, but if the power to 3&5 comes from the ZC terminal , there will be no power to the circulator but the relay could pull in if L1 is hooked to the #1 terminal. I have seen any combination of problems with circuit boards and relays, we could speculate all night here. With out seeing it first hand I don't know, over and out.

    Or the pump could just be bad or "stuck".
  • JK_3
    JK_3 Member Posts: 240
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    Just thinking

    Before I even looked there i would look at the temp of the water. if the temp is up there (180-200) then i would look at the relay or circ. but if the temp is low i would look at the aquastat next.

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  • JK_3
    JK_3 Member Posts: 240
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    Your right about it could be any of the problems that you mentioned. but the first things i would not at are the most common and the easiest to have some one test with out being there myself(although i have walked many of my techs through phone diagnosis)

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  • DaveD_3
    DaveD_3 Member Posts: 9
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    Solving zone problem

    Thanks Guys.

    The temp on the line into the circilator is low. The line from circulator into boiler is pretty warm right now.

    I'll check the voltage coming off of the relay tonight.

    If it is the circulator pump, is there any component in the pump that I can try to replace before I replace the whole thing? Theres a cylindrical solenoid or resistor in there. Is that something that goes bad and can be replaced independent from replacing the whole circulator?

    Thanks for your help !
  • JK_3
    JK_3 Member Posts: 240
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    more testing

    you said the temp of the line is low but what is the boiler temp? also where does the circ get power from? is it wired into the 845? does the system have a min circ temp? as bill said above it could be any combination of circut problems depending on how it was originally wired and set up.

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  • DaveD_3
    DaveD_3 Member Posts: 9
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    Solving zone problem

    The circ is wired directly into the 845. The 845 has a power line coming directly from the main switch box for the whole system. There's a low-voltage line coming from the t-stat into the top of the 845. There's a 2nd low-voltage line going out from the 845 into the boiler -- that line is spliced together with the line from the other t-stat for the other zone.
  • JK_3
    JK_3 Member Posts: 240
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    temp and voltage

    what is the boiler temp and is there voltage at the circ terminals in the 845?


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  • DaveD is this a gas or

    oil system? If it gas then your thermostat for that zone is probably wired direct to the R845 for that zone. Then when it calls burner and circulator come on together. If you push in on the relay clapper bar does it work? If not and you have power to the relay then the relay is bad.

    How to prove it:

    Lets say the burner circuit is wired to terminal #5 and #6, then jump out 5 & 6 (24 volts) if the burner comes on the relay is bad.
  • DaveD_3
    DaveD_3 Member Posts: 9
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    Solving zone problem

    Thanks Tim,

    It's gas. The clapper is opening/closing (flipping up/down) in response to the thermostat being turned on/off. I think this confirms that the tstat is okay and the relay at least has power. I tried cleaning the contacts inside the clapper (very fine file) and that had no effect.

    A neighbor suggested that if the circulator is burnt-out or seized, it would prevent the relay from activating. But this didn't make sense given the configuration of Tstat -> Relay --> out to circ & burner.
  • martin
    martin Member Posts: 144
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    Zone problem

    Get a volt meter and test those output terminals that will solve all the what ifs. Ive had honeywell aquastat/relays that have failed after 4or5 years service. When mfged some terms were not cleaned properly and finally coroded enough to lose contact, just cleaned and resoldered.
  • Take a jumper

    (a short piece of 12 or 14 gauge wire stipped on both ends) jump out terminal #5 and #6 does the burner come on? If yes then those contacts are bad. Now jump #3 and #4 watch out those are 120 volts usually. Does the circulator come on? If yes then those contacts are bad. If you so desire try cleaning the contacts or get a new relay.
  • DaveD_3
    DaveD_3 Member Posts: 9
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    Solving zone problem

    Got 115v on contacts to circ. Boiler was at 220 when before it fired up.

    I also tried Tim M's suggestion and ran jumper tests. Nothing happened when contacts 1&2 were connected, but when I connected the 3&4 the zone turned on. I guess this means the relay is the issue.
  • DaveD_3
    DaveD_3 Member Posts: 9
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    Zone problem

    Correct that. It was the 5&6 (low-voltage) and 3&4.
  • DaveD_3
    DaveD_3 Member Posts: 9
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    Zone problem

    Jumped the 5&6 & nothing happened. Then did 3-4 and both the burner and circulator went on. Looks like the relay is the issue.
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