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Rinnai RE180iN

ColdHeater Member Posts: 1
edited November 2023 in Domestic Hot Water
Newly installed unit keeps shutting off flashing code12 (gas issue) after several hours of being installed by certified Rinnai contractor. Installer checked static gas pressure at WC8" opened the PRV to check hot water flow. WC dropped to WC5". Rinnai tech says that is a big issue and thats why heater keeps shutting down. I turn it off and on as alarm kicks on and then after 5-6 cycles it stays on through out entire shower time. Gas company has checked gas flow and says all OK plus my other gas appliances are working normal. This water heater replaced a 18yr old tankless but different brand which has the same gas requirements. What could be my issue. Regards


  • GGross
    GGross Member Posts: 1,105
    A 3" pressure drop indicates that the gas supply is not sufficient. Sized correctly you should see no more than a 1/2"-1" wc pressure drop. I would start out by mapping out the gas line including pipe sizes, lengths, and fittings, as well as the input BTU rating of each gas appliance attached to the gas supply
  • Slimpickins
    Slimpickins Member Posts: 341
    Yes, work on that press drop, I've seen them work with big drops but not idea. Other things to check is the concentric venting. Make sure the inner exhaust pipe is fully engaged and the gasket isn't rolled. If you don't have the lube, soapy water will work, Check your outside termination and make sure you have good clearances and not sucking exhaust gases. Also, make sure you have a solid electrical ground.