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Taco SR502-4

Hi
  I’m installing a Rianni combi boiler with a Taco SR 502.  It has a 2 zone switching relay.
  Everything seems to be wired correctly, the thermostat calls for heat and the boiler fires.
  The problem is that the zone led’s are not coming on and neither are the pumps.
  I removed all the thermostat wiring and jumped across RW and still no change.
  I have currently tied the pumps together with the power to keep the pumps flowing.
  Any help would be appreciated.
  Thank you 

Comments

  • SteveSan
    SteveSan Member Posts: 156
    If you are in front of the control please give Taco Technical Services a call during normal business hours Mon-Fri 8am-5pm EST 401-942-8000 and just ask for Technical Services. Are you getting voltage out of the transformers and are the fuses good? Be sure that the factory jumper between ZC/ZR is tight.
  • JMC_Services
    JMC_Services Member Posts: 4
    Fuses are good.  No voltage out of relays.  Voltage out of the transformer.  ZC/ZR are tight
  • pecmsg
    pecmsg Member Posts: 3,540
    edited November 2022
    Did you measure voltage across the fuse?

    Why are all the Hots wired together?
  • Why are all the Hots wired together?
    "I have currently tied the pumps together with the power to keep the pumps flowing."
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
  • JMC_Services
    JMC_Services Member Posts: 4
    pecmsg said:
    Did you measure voltage across the fuse? Why are all the Hots wired together?

    pecmsg said:
    Did you measure voltage across the fuse? Why are all the Hots wired together?

    pecmsg said:
    Did you measure voltage across the fuse? Why are all the Hots wired together?

    Did you measure voltage across the fuse?
      I have 120volts on both sides of the fuse, but when the thermostat calls for heat and the relay clicks I loose power to the relay 
  • Joe Mattiello
    Joe Mattiello Member Posts: 651
    Place a jumper across R/W for a validated demand, see if you have voltage at ZR terminal
    let me know 
    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
  • JMC_Services
    JMC_Services Member Posts: 4
    Yes, voltage at ZR.
      I spoke with Taco tech he thinks it might be stuck relays (bad)