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Easy fix for Mod Con upgrade to 2 zone baseboard convector heating system that's struggling?

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Digital
Digital Member Posts: 4
edited February 1 in Radiant Heating

I'm a long term lurker that is NO professional when it comes to HVAC but I know enough to be dangerous. My home is heated with a Triangle Tube Challenger combi that's still limping along 14 years later and that upgrade will be a different discussion.

A lady at church complained this morning that her heat went out and "they replaced the boiler but it's not working- it's only 68F in my house". She said they've made many visits since they first upgraded the boiler but the heat still isn't keeping up. The HVAC installers told her at the next visit they will be cleaning all of the baseboard convectors because that might be the problem.

I found what looks like a fairly-well installed Rheem Thermaforce 199KBTU Mod Con trying its best but just not keeping up. Both zones were calling for heat and the display read 136F and when I pressed the radiator symbol it showed the target temp was 185F.

Both circulators (grundfos) were set to speed III. There is a taco zone board managing the 2 zones of brand new thermostats that were installed at the time of the upgrade.

Convectors that I spot checked by hand were warm.

I told her to ask her HVAC contractors "if the boiler knows it needs to make 185F water why isn't it doing better than 136F?"

I think we all know that if the boiler was successful in making 185F water she wouldn't be complaining that it's too cold in her house.

Knowing that her old boiler worked fine to heat her poorly insulated house with dusty convection radiators before its death at 35 years old - is it crazy to think the HVAC installers missed something simple in the setup of the boiler? Or did they just plain pick the incorrect boiler for the application?

2 story house from 1910, less than 2000 sq ft, natural gas. Outdoor temp today is in the high teens/low 20s and this has been a rough week of 0F at night.

Thanks for any advice!

-Dylan

Comments

  • Digital
    Digital Member Posts: 4

    Probably should have taken more photos.. but here are the 2 I have.

    IMG_6939.jpeg IMG_6940.jpeg
  • kcopp
    kcopp Member Posts: 4,646

    68F at 136F is pretty great.

    Im pretty sure the boiler needs some setting arranged.

    They will need to go into the menu and up a couple values.

    I have a similar boiler in my home.

    Digital
  • GGross
    GGross Member Posts: 1,797

    If its set to 185 and not able to get there, being that it is 199, my money is on a flow issue. are you sure the call for heat never goes away? the boiler just keeps puttering along, never reaches setpoint or fixed high limit? I'm assuming it will not go to high fire, or at least for very long. 199,000 btu/hr is a lot, much more than that house needs.

    Digital
  • GroundUp
    GroundUp Member Posts: 2,487

    Either the boiler is not hitting high fire, or it's simply undersized. VERY hard to believe that a 199k couldn't heat a 2000SF home, but stranger things have happened. Do we know how many BTU the previous boiler was? I'm not familiar with that Rheem in particular but most combi units have a function where space heating firing rate can be limited, and have seen more than once that somebody accidentally changed those parameters to limit the rate.

    GGross
  • Digital
    Digital Member Posts: 4

    Thanks Kcopp, GGross and GroundUp-

    I agree with your input, it's hard to believe that this is the wrong boiler, it's more likely the setup is wrong.

    I don't know what boiler was removed.

    If there is a flow issue, the only plumbing changes from what I see are near-boiler piping.

    I'm 99% certain that the tstat is always calling for heat because she had it set to 78F in an innocent attempt to warm the house. I left it alone. The weather hasn't changed much, it's still below freezing.

    I'll check in with her and see if there's any news. Appreciate your input!

  • GGross
    GGross Member Posts: 1,797
    edited February 3

    Can you find this value? what does it tell you? that should show what your current setpoint temperature is

    (edit ignore this first bit I re-read your original and see you pressed the radiator icon to see 185, leaving it for reference)

    setpoint.JPG

    If the boiler is not using outdoor reset you can adjust the setpoint like this. I haven't found the instructions in the book to adjust the outdoor reset curve(edit found it). If there is an outdoor sensor installed and a curve is used you would need to adjust that value if the setpoint is too low. There is a note that if an outdoor sensor is used to "See separate controller manual for parameter information" There is a separate manual for the controller, its rather in depth hopefully you have that on site. I will link the manuals I was looking through below. If you look through the installer parameters, and advanced parameters it goes over minimum supply temps, outdoor curve, and the advanced has limiter options for the max output for space heating. that should be all the relevant parameters!

    space heating temp.JPG

    install manual

    https://files.rheem.com/blobazrheem/wp-content/uploads/sites/2/CombiInstallationandOperatingInst_84156404w.pdf

    Controller menu (has outdoor reset control parameters and how to change)

    https://files.rheem.com/blobazrheem/wp-content/uploads/sites/2/BoilerCombiControllerManual_84159404w-1.pdf

    I think we should confirm first without a doubt what temp the boiler is trying to make

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