Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

return temp on RFH system

I have a Resolute 90 / System 2000 oil fired boiler and an in floor Radiant Heat system. I am curious as to what I should expect the return temperature to be on the loop. The boiler cycles between 120 and 140. Hot water is supplied to the zone at 140 down to 120 then it shuts off the zone and reheats. The return temp never seems to remotely approach the inlet temp with the zone valve open. Also the return line and the supply line at the boiler seem to be the same temperature even though I can see the temp dropping on the temperature gauge. The flow path is confusing me....

Comments

  • hot_rod
    hot_rod Member Posts: 18,190
    some piping pics would help. Generally radiant designs around a 10- 15 degree temperature drop, but it will vary from a cold start to a shut off condition
    temperature differential would be wide in start up, closing up as the load satisfies

     
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • cjjeeper
    cjjeeper Member Posts: 5



  • hot_rod
    hot_rod Member Posts: 18,190
    Odd looking piping with two zone valves and two bypasses in the near boiler piping?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • heatdoc1
    heatdoc1 Member Posts: 14
    Thank you for your post about radiant in floor temperatures, @cjjeeper .
    The Resolute boiler’s Digital Energy Manager controls the burner using the boiler return temperature. If the return temperature drops below 120°F on an oilheat system, the zone valves will close to prevent condensing, then open back up when the return reaches 140°F. Note that the supply temperature will likely be 140°F to 180°F at those times. I mention this because in your post you mention supply temperatures, and I believe you are referencing return temperatures.
    It is a bit difficult to tell from your photos, but it looks like your Honeywell zone controllers operate the zone circulators and likely give a heat demand to the boiler. The Honeywell control will likely be the control that targets/sets the radiant supply temperature in your system. As @hot_rod mentioned, you will have a large temperature drop in your radiant zones when they first start heating, and the radiant return temperatures will get closer to the supply temperature the longer the system runs.
    Overall, your radiant return temperature will be dictated by the run time, the design and flow of the system, and the radiant supply temperature, among other factors. The other issue may be that the zone that is 4th from the left is piped with closely spaced tees that could drop your supply temperature to the other zones when it is running. If you are having operational problems, you can always contact our tech support team at 1-800-323-2066
    John Ringel
    Technical Support Specialist
    Energy kinetics
    John Ringel
    Senior Technical Support Specialist
    Energy Kinetics
    szwedj
  • hot_rod
    hot_rod Member Posts: 18,190
    looks like zone valves near the boiler and the green one near the bypass?  One for the indirect possibly, which is the protection valve?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • pedmec
    pedmec Member Posts: 711
    trying not to judge but kinda of a mess. multiple expansion tanks, too many zone valves.

    educated guess:

    close zone valve on primary loop and open zone valve for indirect hot water tank. priority zoning?

    open zone valve on primary loop close zone valve for indirect hot water heater. heat loop operational. second circulator taking off of primary loop for high temperature zone. low temperature zone valve close on 4 zone manifold close.

    zone valve on low temperature manifold opens on demand for low temperature manifold. has manual bypass acting as manual mixing valve. me thinks this zone valve could have been eliminated.

    never worked on a system 2000 so i dont know if this is there piping plan. cant imagine they would be asking for two expansion tanks


  • heatdoc1
    heatdoc1 Member Posts: 14
    Pedmec no this not a system 2000 piping plan but we do make ourselves available to help with systems that are attached to our boilers.
    John Ringel
    Senior Technical Support Specialist
    Energy Kinetics
    szwedj
  • cjjeeper
    cjjeeper Member Posts: 5
    Thanks for all the replies...my issue are the bypasses also. I'm not really certain of the flow path of the return based on the two bypasses.

  • cjjeeper
    cjjeeper Member Posts: 5
    cjjeeper said:

    Thanks for all the replies...my issue are the bypasses also. I'm not really certain of the flow path of the return based on the two bypasses.

    John, if you think this can be improved I would interested in discussing. It works okay, just not sure it works well.
  • cjjeeper
    cjjeeper Member Posts: 5
    heatdoc1 said:

    Pedmec no this not a system 2000 piping plan but we do make ourselves available to help with systems that are attached to our boilers.

    John, if you think this can be improved I would interested in discussing. It works okay, just not sure it works well.
  • heatdoc1
    heatdoc1 Member Posts: 14
    cjjeeper if you send your contact information to [email protected] I will reach out to you so I can get more detailed information and we discuss your system.
    John Ringel
    Senior Technical Support Specialist
    Energy Kinetics