10 components coveredField manual · Water Heater
Noritz EZ series tank-replacement tankless (EZ98, EZ111, EZTR kits): quick sheet
Covers: Noritz EZ98 and EZ111 condensing tankless heaters and the EZTR40/50/75 tank-replacement bundles built around them. Water side, condensate, electrical and diagnostics; gas, burner and venting are referral items.
The EZ series is Noritz's 'swap the tank' platform: water connections on top (like a tank, so the old flex connectors can often be reused), a gas connection underneath, and Noritz's claim that it works on many existing 1/2 in gas lines. It is a condensing unit with dual stainless heat exchangers, so unlike non-condensing units it has a condensate drain and neutralizer to look after. EZ98 replaces roughly a 50-gal tank and EZ111 a 75-gal tank.
Safety first
- GAS: no work on the gas valve, burner, gas line sizing or venting; refer to a licensed plumber or gas technician
- Unplug before opening the cabinet
- Condensate is acidic: wear gloves and eye protection
- Scald risk at outlet and flush ports right after operation
How it works
Flow through the cold inlet and filter turns the flow sensor; at about 0.5 gpm the board starts the fan, ignites and modulates input from about 18,000 BTU/h up to 180,000 (EZ98) or 199,900 BTU/h (EZ111). Max flow is listed as 9.8 gpm (EZ98) and 11.1 gpm (EZ111) at a low temperature rise; real-world flow at a 70°F rise is closer to 5-6 gpm.
Hot flue gas passes a primary and then a secondary stainless heat exchanger. The secondary exchanger cools the gas below its dew point, which is where the high efficiency (UEF about 0.95-0.98 depending on version) comes from, and also why acidic condensate is produced. Condensate drains through a trap and neutralizer to a floor drain; a blocked or frozen drain triggers code 29.
Temperature is set at the built-in operation panel (bundles list a 100-140°F range). Inlet, outlet and heat exchanger thermistors (codes 31, 32, 33) and a main flow-control servo (code 65) let the board hold outlet temperature; an outlet temperature spike (code 16) is usually scale.
Newer EZ units add an app connection (Bluetooth setup / Wi-Fi adapter) for settings and diagnostics. Codes 92 and 93 on Noritz condensing units warn that the neutralizer is near or at end of life.
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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Clothes dryer with its vent duct in a small laundry closet by Introspectivedsgn, Pexels License
