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new Rennai?

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beezer
beezer Member Posts: 40
in THE MAIN WALL

My Lochinvar WBN80 is dying. its over temping and over pressuring. plus there wispd of steam coming from the burner door…. I think its the heat exchanger, so thinking about a new replacement like a Rennai I series 90,000btu. The boiler only model (not tankless). the WB is running a sidearm, I'm fine with that system and would prefer to stay with it. the current system has 3 pumps. one for the boiler loop, one for the sidearm, and one for the baseboards. the sidearm pump does all the work for the domestic hot water, the other two both run at the same time for the baseboards, I have 2 zones. does the Rennai sound like a reasonable replacement? parts for Lochinvar are harder to get here, and more $$. this one is 18 years old too, so thats a big consideration.

also, the sidearm tank. its a Squire 40Gal. its 18…. any thoughts.

Comments

  • JasonHogan
    JasonHogan Member Posts: 2

    Replacing an 18-year-old Lochinvar WBN80 that is leaking steam, over-pressurizing, and over-temping with a Rinnai I-Series (i090S or IP090S Solo, 90,000 BTU) is a very solid, practical choice.

    1. The Boiler Choice: Rinnai i090S / IP090S Solo

    • Great Match for Size & Reliability: Replacing an 80k BTU Lochinvar with a 90k BTU Rinnai solo model will comfortably handle your 2 baseboard zones plus domestic hot water (DHW). Rinnai’s stainless steel heat exchangers are reliable, and their parts availability and tech support in North America are generally much better and less expensive than Lochinvar’s specialized components.
    • Smart Controls: The I-Series controller handles DHW priority built-in. When the sidearm calls for heat, the boiler will shift away from space heating, step up its water supply temperature (e.g., to $180^\circ\text{F}$), and power the indirect pump to recover the hot water tank as fast as possible.
    • Fuel Adaptability: The newer I-Series Plus models feature self-calibrating adaptive gas valves, meaning no mechanical conversion kits are needed if you ever switch between Natural Gas and Propane.

    2. Pumping & Piping Setup

    Since you currently have 3 pumps (Boiler Loop/Primary, Baseboards, and Sidearm):

    • Primary/Secondary Loop: Keep a primary/secondary piping setup. The Rinnai requires a specific minimum flow rate through its internal heat exchanger, so keeping a dedicated boiler loop pump (or using Rinnai’s recommended primary loop setup) protects the new unit from flow-restriction issues.
    • DHW Priority Wiring: Route the aquastat from your sidearm tank directly into the Rinnai’s dedicated DHW terminal inputs. The boiler will automatically control the sidearm circulator pump and prioritize domestic hot water calls over space heating.

    3. What About the 18-Year-Old Squire Tank?

    At 18 years old, replace the Squire tank at the same time if it fits your budget.

    • Why replace now? Indirect stainless steel tanks are durable, but 18 years is pushing the upper end of their reliable lifespan. The internal coil or tank shell can develop pinhole leaks over time.
    • Labor Savings: Since the installer is already draining the system, cutting pipe, and rewiring the boiler controls, replacing the tank now will cost significantly less in labor than having them come back in 1–2 years when the old tank finally fails.
    • Alternative: If you want to keep the Squire tank for now, at least replace its internal aquastat switch and inspect the temperature & pressure (T&P) relief valve during the boiler swap.

    Key Checklist for the Install

    1. System Flush: Before firing up the new Rinnai, have the installer thoroughly flush the old baseboard zones to remove iron magnetite and debris from the 18-year-old Lochinvar breakdown.
    2. Magnetic Dirt Separator: Have them install a magnetic dirt separator (like a Caleffi Dirtmag or Spirovent MB) on the return line to protect the new stainless steel heat exchanger from sludge.
    3. Condensate Neutralizer: Since this is a high-efficiency condensing unit, ensure a condensate neutralizer kit is installed on the drain line so acidic condensate doesn't ruin your home's piping or drain system.

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