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I installed an Ultra 105 with DHW and 2 heating zones. I used a Taco 502 relay connecting my 2 heat zones. The DHW is tied into the U control on the Ultra and the 2 circs for my heat on the 502. I connected one heat zone to zone 2 on the 502 and the other heat zone to zone 3 on the 502. Only zone 2 is juiced I cannot get juice through zone 3 for the life of me.

I tried jumping the t stat I checked the circ (which is good) I cheched all wiring for a reason I don't know about I cannot get power to the other heat zone using the 502. I wonder if I need to use a 503 relay? When the Ultra fired up everything is fine DHW and the other heating zone.

Anyone who has installed a system with 2 heat zones and DHW let me know what you did for controlling the circs. > Thanks



  • Alan (California Radiant) Forbes
    Sounds fine

    When you jumpered the t-stat on zone 3, did you check for voltage at the pump 3 contacts?

    If you are wiring the DHW through the Ultra, try using the zone 1 contacts for your thermostat and pump of zone 3 doesn't work. 

    Also, if zone 3 isn't powering your pump when you close the t-stat contacts, get a new SR502.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • gennady
    gennady Member Posts: 839
    edited November 2011
    ultra wiring

    There is no zone 3 wiring on ultra. Boiler controls 3 pumps: DHW pump, boiler pump and system pump.  if you want to have 2 zone system, please use 2 zone controller, wire boiler switch on zone controller into  heating thermostat contacts, red on left  1 and 2.  and do not wire any system pumps into boiler panel. And please, take time to read the manual
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    How my ultra 3 80 is wired.

    I have two zones and an Indirect Domestic hot water heater.

    Priority Input 1 runs the Indirect. It activates the circulator for the indirect; circulator #1. The aquastat in the indirect is connected to the Priority Input 1. The plumbing for this is directly across the supply and return of the boiler. The supply and return also go to closely spaced Ts and the rest of the stuff for primary-secondary piping.

    Priority Input 2 runs a radiant slab zone. It activates the boiler circulator (#2) and the circulator(#3) for the radiant slab zone. The thermostat in the slab zone activates the Priority Input 2.

    Priority Input 3 runs a baseboard zone. It activates only the boiler circulator (#2). The thermostat in the baseboard zone activates a Honeywell RA832A relay with two sets of contacts. One set activates the circulator (#4) for the baseboard zone. The other set activates the Priority Input 3. I need the 832A because the U-control has no #4 output.

    Have you programmed the U-control correctly? It is important to read that part of the Installation Manual very closely. You will probably not like the defaults. I am not sure how you are wiring the Taco 502 to your U-control. It seems to me that if you use the 502 to operate the zone circulators, either of them will activate the U-control Priority Input 2 (or Priority 3), and nothing to the other priority.  Ideally you and I would both like an additional circulator output from the U-control so we would not need the auxiliary relay box.

    So, thinking out loud here, I suggest.

    1.) Have the 502 control the heatiing circulators directly.

    2.) Take the X-X output from the 502 and connect it to the Priority 2 T-T input of the U-control.

    3.)  Program the U-control to run only the boiler circulator when Priority 2 has control. This assumes you will be satisfied with the same reset curve for both zones. I wanted different reset curves, so I did it my way.

    You may want to turn off the priority switch on the 502, unless you understand it and want it on.

    I see I am assuming you have your heating zones piped primary-secondary and your indirect is across the supply and return of the boiler before the closely-spaced Ts (or hydraulic separator).

    Since I am not a professional, you may want to be sure you understand what I am saying and check to be sure I have not overlooked something.
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