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Water going through the lines not getting hot

Bronk
Bronk Member Posts: 3
Hi all,

My radiant heat unit is pushing water out at 140 degrees, but what is getting pulled through each of the circulator pumps to the 2 radiant floor heating zones is maxing out at 100 degrees per the temp gauges at each zone. The result is my main floor will not warm up past 66 or 68 degrees.

I’ve had a plumber come out who also talked with the manufacturer - they descaled and flushed the unit and the plumbing is all setup and piped correctly. We even tried replacing one of the pumps with a stronger pump, but no change.  They can’t figure out what the problem is and I’m running out of money to pay someone to troubleshoot it with no answers!

the unit is an HTP P-920C

Any ideas?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 16,532
    Without knowing how the thing is piped... haven't a clue. However, if it is primary/secondary (it should be) and if there is a thermotatic mixing valve allowing some of the return from the floor to recirculate (there should be)...

    So. How is it piped? A diagram or a very clear photo or two might help...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Bronk
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 9,630
    What you have to do is check and see if you get flow and how much flow through the radiant tubing. When they disconnected and flushed it they should have an idea if they are getting flow. Maybe the circulator is air bound
    Bronk
  • Bronk
    Bronk Member Posts: 3


    Here are a few pictures of the setup if that helps. I appreciate the feedback. 
  • Jamie Hall
    Jamie Hall Member Posts: 16,532
    I see no mixing valve? So... as @EBEBRATT-Ed suggested, first check and see that you are, in fact, getting flow through the manifolds and the piping. Then the next question I would ask is what are the relative flow rates of the circulating pumps and the primary (boiler) pump?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Bronk
  • mattmia2
    mattmia2 Member Posts: 3,598
    What di the supply and return temps on the boiler loop look like? Measure it with a thermometer as well as looking at the temp sensors in the boiler.

    Without looking at the manual, there are probably some 3 way valves and a pump in the boiler to switch between dh and dhw and there may be something wrong wit that, especially the 3 way valve. May also bee a strainer built in to the boiler. I suspect the boiler isn't getting enough circulation.
    Bronk
  • mattmia2
    mattmia2 Member Posts: 3,598
    If it is the same as a uft, somewhere in the information menu it will show you the firing rate. if the swt is 140 and the rwt is much lower and the firing rate is low, it is some sort of circulation problem with the boiler. if both are about 140 and the firing rate is low, the system isn't circulating for some reason. If it is firing at a high rate and there is a decent delta t between the supply and return it could be the mass of the system, but it sounds like you have run it for a while without the tubing heating adequately.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,215
    edited May 10
    EDIT BELOW
    From what I have been able to find on the WEB, the P-920C is a controller for a tankless water heater. The model number of the actual appliance (the controller is connected to) will be on a label (usually on the side of the appliance) with additional information like a serial number, BTU capacity, and electrical ratings. From the photos you have provided, it appears that you may have a combination unit that does both heat and hot water. It is hard to tell. Can you provide some photos from farther away and a model number? This will help with a better understanding of the problem.

    The part number you provided has directed me only to water heaters and not combi units.

    EDIT:
    Further research has provided a Combi unit with the model number EFTC-140F Hot Water Combination Boiler and an ELU-150 - 199K BTU Combi/Boiler. Can you verify the model of your unit?
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,215
    I believe I found your system (or one very close) and have adjusted the manufacturer-suggested piping design to match what you have "As-Built". It appears that you have only radiant floor heating (no other heating emitters) and DHW. this diagram illustrates that design.


    I have indicated A B and C for the locations @mattmia2 is looking for temperature readings.
    Here are the places on your picture to check the temperature.

    To check the temperature you can use a meat thermometer placed on the pipe and then wrapped with insulation (like maybe a potholder or a cut-up beer koozie). Check the temperatures after the system has been operating for at least 5 minutes. This will help determine where the heat is going and which circulator may not be operating at full capacity.

    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
    Bronk
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,215
    edited May 10
    So, If you are getting a temperature of 140° at location A and you are only getting 100° at location C then there are 2 possibilities:
    1. The pumps for the zones are not circulating enough water to the floor tubing. You may have air in the loops, you may have a blockage in the loops or the circulators may not be operating to capacity.
    2. The boiler pump is not providing enough GPM of 140° water to increase the temperature in the zone loops. There is a Return Strainer on this system that may be blocked. That strainer is indicated by #10 on this diagram.
    I hope this info is helpful.

    Mr.Ed

    BTW item #21 in the diagram is the P-920C control you referred to in your original post.
    If I picked the correct system your complete I/O manual is here https://www.afsupply.com/pub/media/catalog/product/matridtech/htp/install/UFTC-199W.pdf
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
    Bronk
  • JDHW
    JDHW Member Posts: 18
    Looks like the manifolds to the floor loops have flow gauges on them - little red tubes above top ones. What do they record when the system is running?
  • Bronk
    Bronk Member Posts: 3
    Thank you everyone - Ed, yes I believe you have the correct system. I’ll do some temp checks this week and see what I can find.  One zone actually got up to 140 degrees this weekend, per the temp gauge by the outflow tunes. That was the zone where we replaced the circulator pump with the stronger model. It was installed a week ago, but never got that hot until Saturday. 

    I’m going to check those temps this week and see what I come up with. I appreciate everyone sharing their knowledge and willingness to help!
  • mattmia2
    mattmia2 Member Posts: 3,598
    If there is not enough flow through the boiler and only one zone was calling, you may have transferred enough heat to heat that zone to the designed temp.
    Bronk