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DHW pump relay

Hello all,

I have a lochinvar knight that can control the DHW recirc pump based on a sensor on the return line of the recirc line. 

I’d like to use a Caleffi zone relay since it’s already in the system but if I zone the recirc it will turn on the boiler pump via closing the TT terminals, correct? Is there anyway to use this relay for what I need besides getting a single zone switching relay just for the pump— I’d just like to use the zone relay to switch from 24v to 120v when it gets a call from the boiler without turning anything else on...

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,817
    Recirc pump should operate whenever the water in the HW line is below the desired temperature. I would not use a 24V relay that operates the boiler as does any multi-zone relay. Where is the temperature sensor for the HW pipe? That sensor (or most of those types of sensors) can usually be wired 120V direct to the pump without a relay. If the sensor is remote and the only wire is a low voltage thermostat wire then you should get a single zone switching relay as you originally indicated.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • Erin Holohan Haskell
    Erin Holohan Haskell Member, Moderator, Administrator Posts: 2,281
    @alangeoffrey, welcome! I've merged your duplicate posts into one post here.
    President
    HeatingHelp.com
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,817
    edited February 2021
    I reviewed the Lochinvar instruction manual for the Knight boiler and I cannot find any reference to the DHW re-circulator. There are 2 DHW terminals dedicated to DHW for an indirect water heater. One set is for a sensor supplied by Lochinvar that you would install in the indirect tank. this is a temperature sensor that gives real-time tank temperature readings to the boiler control. The other DHW terminals are to be used if the sensor is not compatible with the tank you selected to use. These sets of terminals are an either/or choice, NOT BOTH. They ultimately control the tank temperature based on the signal sent from the tank to the boiler. the boiler will operate the DHW circulator and the burner in order to send HOT boiler water into the indirect water tank heat exchanger to heat the potable water in the tank. once the tank temperature is at the setpoint (the thermostat is satisfied) the burner and DHW pump will stop.

    RE-circulation of hot water is where a pump circulated potable water from the tank into the hot water feeder pipe to all the faucets, showers, and taps in the home. This is done to conserve water. The pump and control system for this system should be separate from the boiler and have its own control system separate from zone valves, zone pumps, and boiler controls on the space heating system.

    I hope this helps with your project

    respectfully submitted,
    Mr.Ed
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • alangeoffrey
    alangeoffrey Member Posts: 9
    edited February 2021
    Thanks for the reply Ed, 

    I have the newest KHB model of the knight, I don’t think the older models had this feature:

    DHW recirculation sensor
    The Knight Wall Hung Fire Tube boiler is able to control a DHW recirculation pump. To operate this feature, a #100170581 temperature sensor must be installed in the circulation loop return. Connect this sensor to the DHW recirculation sensor terminals on the Low Voltage Connection Board.
    DHW recirculation pump
    When the DHW recirculation sensor (as described above) is connected, the Knight Wall Hung Fire Tube SMART SYSTEM control will output 24 VAC to control a DHW recirculation pump relay (field supplied). Connect the coil of the DHW recirculation pump relay to the 24 VAC recirculation pump relay coil terminals on the Low Voltage Connection Board.

    I want to run all my pumps from the boiler because I can take advantage of programming them a lot more sophisticated than a relay, I was just looking to get the 24v to 120v off the relay I use to power my smart thermostats but you’re saying my best bet it just a single zone? That’s what I suspected but I was hoping there was some way since the relay has this function 



  • hot_rod
    hot_rod Member Posts: 22,110
    Which Caleffi relay do you have the ZSR or the ZVR? Send a pic with the cover off the relay box.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • alangeoffrey
    alangeoffrey Member Posts: 9
    Hi Bob,

    Currently building it, Im using the ZVR with caleffi zone valves
  • alangeoffrey
    alangeoffrey Member Posts: 9


    Can anyone help me with this? I was hoping to use this Caleffi ZSR101 to control my DHW recirc pump from the boiler but I’m stuck. The boiler outputs 24v constantly on the red, I have a jumper wire on there to make the pump run continuously temporarily…will this relay work or will I have to buy something else? I can only connect to the TT connections not the coil
  • mattmia2
    mattmia2 Member Posts: 9,623
    What are you trying to do with the Caleffi control? The output of the boiler is designed to control just a relay directly, the boiler connects to the coil of the relay and the normally open contacts of the relay are connected in series with the hot to the pump to control the pump. You would use something like this:

    https://www.supplyhouse.com/Functional-Devices-RIBU1C-Enclosed-Pilot-Relay-10-Amp-SPDT-w-10-30-Vac-DC-120-Vac-Coil

    or this:

    https://www.supplyhouse.com/White-Rodgers-90-380-Fan-Relay-Type-184-24-VAC-Coil-50-60-Hz-SPNO-SPNC-Coil-Data-77-Ohms-DC-Resistance-125-mA
  • alangeoffrey
    alangeoffrey Member Posts: 9
    Yeah I was hoping to somehow control it with the caleffi because it looks cleaner but I guess it’s not possible…
  • mattmia2
    mattmia2 Member Posts: 9,623
    You'd need another relay just to close TT on the Caleffi relay control to do it that way. A 4" square box with the RIB relay in it and appropriate connectors and grommets would be neat. Or the plain relay screwed to the back of a 4" square box. There might be space to mount either in the boiler as well.
  • alangeoffrey
    alangeoffrey Member Posts: 9
    Would i remove the zsr101 and just use that relay in a junction box?
  • mattmia2
    mattmia2 Member Posts: 9,623
    Yes. Or even in a knockout in the boiler itself.
  • alangeoffrey
    alangeoffrey Member Posts: 9
    Thank you for your help, I really appreciate it!