Navien · Water Heater error code

E445Bypass mixing valve abnormality

Cross-checked High-voltage / caution

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Related diagnostic guides

Guide · Water Heater

Swapping a tank for a heat pump water heater: room air volume, clearances, condensate, 240 V circuit and pan (fit check)

A heat pump water heater pulls heat from the air around it, so the location matters more than with a plain tank. Check four things before the sale: enough air volume (or a louvered door or ducting where the maker allows it), a space that stays within the operating temperature range, a place for the condensate to drain (floor drain, sloped line or condensate pump), and a dedicated 208/240 V circuit sized for the model. Add the usual tank items: pan where required, T&P discharge, expansion tank on closed systems, and a permit where required. The refrigerant circuit is factory sealed: any sealed-system diagnosis or repair is BLOCKED (EPA 608). Replacing a gas unit also means a licensed gas tech must cap the gas line and deal with the old vent.

6 steps ~45 minmoderate

Guide · Water Heater

Field pattern: tankless water heater goes cold mid-shower with no code (flow, inlet filter and scale first)

A tankless heater only fires above a minimum flow rate and drops out when flow falls near that line. Clogged inlet screens, scaled heat exchangers, low-flow showerheads and aerators, and mixing valves that cut hot flow are the usual causes. The wrong turn is calling it a gas or ignition fault and replacing parts when the real issue is water flow.

7 steps ~60 minmoderate

Guide · Water Heater

Water heater: not enough hot water / runs out fast

On electric tanks a failed lower element or lower thermostat leaves only the top of the tank hot. Other common causes on any tank are a broken dip tube, a crossed hot/cold connection in the house plumbing, reversed connections at the heater, and simple undersizing for the demand.

6 steps ~60 minmoderate

More Navien water heater codes

Navien · Water Heater

E003

Ignition failure

Cross-checked Licensed pro only

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E004

False flame detected

Cross-checked Licensed pro only

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E012

Flame loss during operation

Cross-checked Licensed pro only

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E016

Overheating

Cross-checked High-voltage / caution

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E030

Exhaust overheat

Cross-checked Licensed pro only

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E046

Limit control abnormality

Cross-checked High-voltage / caution