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Rheem/ruud combi help

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bradybunch319
bradybunch319 Member Posts: 5
in Radiant Heating

installed a rheem/ruud combi boiler 180k LP. PVC venting 2”. Full propane tank, auto feeder installed with incoming pressure gauge. External pump, hydro smart radiant WiFi t stat. Single zone control/relay box. Air eliminators expansion tank. 8 radiant loops. Outdoor temp sensor. Condensate with a neutralizer. Whole nine yards.
But can’t get it to fire, can hear the igniter sparking/humming/buzzing but won’t fire. Checked incoming gas pressure it was 12.45 in W.C. On the inlet of the gas valve but when trying to fire it would drop to .61 in W.C. Check on the port under the unit where gas ties to get same incoming pressure but when firing would go up to almost 15. Making me think the gas valve is bad or not opening for some reason. Checked power to valve it was gettin 117v being a 120VAC valve thought that was fine but still won’t open the valve to allow fire. Second stage regulator off of tank is rated for 950k btu and set to 13 in WC. Had someone look at it they thought it was bad control board. So rheem sent a new one. Installed it and it’s still doing the sam thing as before won’t fire

Comments

  • GroundUp
    GroundUp Member Posts: 2,467

    I would suggest taking it back to Menards and buying a quality boiler. These things are nothing but trouble, I replace about 10 a year that are less than 3 years old. There is a reason they are half the price of any other combi

  • HVACNUT
    HVACNUT Member Posts: 7,235

    120 volt gas valve?

  • bradybunch319
    bradybunch319 Member Posts: 5

    yes 120 volt gas valve. Getting about 117 volts when I checked it.

  • hot_rod
    hot_rod Member Posts: 26,607

    The boiler should work properly, did you use a combustion analyzer to check when it does fire?

    Could be an LP supply issue if inlet LP pressure drops when it fires. What size LP line at the unit?

    I think that is an Intergas product, plenty of them installed around the world.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • bradybunch319
    bradybunch319 Member Posts: 5

    no combustion analyzer used.

    3/4 black iron at the unit

    second stage regulator off of the lp tank is rate for 950k btu and is set at roughly 12.5 inches. When checking gas pressure at the port under the unit where the gas ties in, when static it checks at 12.45 and when trying to fire it jumps up a little bit to like 14. But if checking inlet at the gas valve it checks 12.45 but the outlet drops to the .6 when trying to fire

  • Big Ed_4
    Big Ed_4 Member Posts: 3,364

    Bad gas regulator , starving for fuel ?

    There was an error rendering this rich post.

  • hot_rod
    hot_rod Member Posts: 26,607

    Is it this model? The L series? If not go to the Rheem website and download the correct manual.

    https://files.myrheem.com/webpartners/ProductDocuments/D77746D9-DA6F-4990-996D-9E9CA68D3C43.pdf

    The manual tells you the required LP pressure. If you are dropping to .6" WC I doubt it will run? Readings will depend on which port of the gas valve you are connecting the manometer to?

    Screenshot 2025-12-20 at 1.56.54 PM.png Screenshot 2025-12-20 at 1.57.43 PM.png Screenshot 2025-12-20 at 1.58.30 PM.png
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    GGross
  • kcopp
    kcopp Member Posts: 4,630

    Model #? The BTU input makes me think it is Not the Thermoforce (Intergas) model.

  • GroundUp
    GroundUp Member Posts: 2,467
    edited December 21

    He told us that it's a Ruud 180k. Obviously not one of those.

  • bradybunch319
    bradybunch319 Member Posts: 5

    RUCBH180DVLP is the model number

  • kcopp
    kcopp Member Posts: 4,630

    This looks more like a rebadged HTP unit.

    High Efficiency Combination Boiler | Ruud Combi Boilers

  • bradybunch319
    bradybunch319 Member Posts: 5

    i checked static and dynamic pressure at two different places on the unit. First on the gas valve itself there is two ports one labeled for inlet and one for outlet, checking static and when firing. And then under the unit where the gas ties in same thing static and when firing and took the readings with the manometer.

    im not a tech of any sorts, I am a licensed plumber though… so some of my questions might seem off to some of you.

    both the intake and exhaust are borderline on minimum/maximum lengths could that be an issue with some sort of saftey for the gas valve not opening?

  • kcopp
    kcopp Member Posts: 4,630

    You have an incoming gas pressure issue if the incoming pressure goes from 12" wc to 0.61"

    GGross
  • Big Ed_4
    Big Ed_4 Member Posts: 3,364
    edited December 21

    Take the pressure reading at the discharge of the regulator on the tank .. Static and when unit is trying to fire . The 12" drop indicates a lack of gas coming down the pipe . A gas cock can leak enough to reach static pressure but not enough volume to run unit …

    There was an error rendering this rich post.

  • Big Ed_4
    Big Ed_4 Member Posts: 3,364

    This is when you find the meter locked out :)

    There was an error rendering this rich post.

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