Rheem Smart Tank Alarm Codes (A005, A105, AB): EcoNet & Hybrid Guide

Hybrid heat-pump water heaters and EcoNet-connected smart models do not blink or flash two-digit codes — they raise alarms: letter-and-number reports, A-codes that shut things down and T-codes that warn, readable on the unit's display and in the EcoNet app. This guide decodes the alarm system itself, then takes the three codes owners ask about most — A005 and A105, each of which means two different things on two different Rheem platforms, and AB, which does not exist — before touring the rest of the hybrid alarm family so a scrolling alarm list never looks like alphabet soup again.

The EcoNet alarm system: how hybrids and smart tanks report

A Rheem hybrid heat-pump heater is really two heaters in one cabinet — a refrigeration circuit that moves heat from the room air into the water, and conventional electric elements that back it up — supervised by a control that watches compressor temperatures and pressures, a rack of temperature sensors, the elements and their relays, a condensate drain, and a leak sensor. When something leaves its allowed range, the control posts an alarm you can retrieve on the display: press Next until 'Current Alarm' appears, then use the Down arrow to scroll the active alarms (the T-prefixed twin of many A-codes appears when the same condition is an alert rather than a shutdown). Smart electric tanks on the Performance Platinum platform use the same A-code grammar for their own hardware — thermistors, elements, relays, ECO — and the commercial Triton line uses it too, for burner and airflow proving faults. That shared grammar with platform-specific vocabulary is the trap this whole guide exists to disarm: an alarm code is only half a sentence until you add the platform. A005, A105 and their neighbours each carry two documented Rheem meanings, and acting on the wrong platform's meaning wastes a service visit at best. So the first step with any A-code is always the same: read the model plate, name the platform, then read the code.

Alarm A005: compressor discharge temperature high (hybrid) — or airflow proving (Triton)

On a hybrid heat-pump water heater, A005 means compressor shutdown: discharge temperature high. The compressor's discharge line has run hotter than allowed, the control has shut the compressor down to protect it, and — this is the part owners notice first — the heater quietly falls back to its electric elements, so hot water continues but at electric-resistance cost and recovery. Rheem's manual lists the same condition as alert T005 and gives its working causes: the heat pump is defaulting to elements due to low airflow. Its checks are refreshingly concrete: is the fan operational, is the filter screen clean, are there signs of a refrigerant leak? Work them in that order as an owner: the washable air filter screen on the unit is the single most neglected maintenance item on these heaters, and a clogged screen strangles the evaporator's airflow exactly as the manual implies; then confirm the fan actually runs in heat-pump mode and that the unit has the clearances its manual specifies — a hybrid boxed into a tiny closet breathes its own exhaust air and cooks its discharge temperature. If the screen is clean, the fan runs, and A005 returns, the remaining cause is the sealed refrigerant side — charge level, the compressor itself — which is technician-only territory. Meanwhile, on a commercial Triton tank, A005 means something entirely unrelated: proof-of-airflow switch open during pre-purge, a gas burner airflow fault. Same four characters, two different trades (refrigeration versus combustion) — which is why the platform check comes first.

Alarm A105: evaporator sensor failure (hybrid) — or lower element error (smart electric)

A105 is the other great double-meaning in the Rheem alarm book. On the hybrid heat-pump platform, A105 is evaporator temperature sensor failure: the sensor watching the outdoor (evaporator) coil has failed, and without it the control cannot manage defrost and heat-pump operation intelligently — the sensor family A101-A106 on hybrids maps the refrigeration circuit (suction, ambient, discharge, evaporator) plus the tank's upper and lower heater sensors, and A105 sits squarely in that refrigeration group. On the smart electric tank platform (the Performance Platinum LCD models), A105 means lower element error: the manual's wording is that the lower element or associated wiring or connections are faulty, and its instruction is to call for service. The two faults could hardly differ more — one is a small sensor on a coil, the other is the main lower heating element or its connections — yet they share a code because the platforms share a numbering scheme, not a parts bin. In practice the distinction makes itself: a hybrid showing A105 typically keeps heating (often on elements, with the heat pump sidelined or degraded) and the complaint is efficiency; a smart electric showing A105 typically loses recovery and runs lukewarm, because half its heating power is out. Either way the repair is a service visit — sensors on the refrigeration circuit and tank elements behind covers are not owner parts — but telling the dispatcher your platform and which A105 you have is the difference between the technician arriving with a sensor or an element on the truck.

AB: the alarm code Rheem never made

Search for a Rheem 'AB' alarm and you will find forum questions but no manual entry, because AB does not exist in Rheem's alarm system. Hybrid and EcoNet alarms are a letter plus three digits (A005, A105, A200); smart electric alarms run A100-A111; Triton alarms the same pattern. 'AB' matches none of them. Where does it come from? The traceable sightings point at a different Rheem system entirely: owners of power-vent tank heaters with IntelliVent gas controls describe 'the A and B lights' being on — the IntelliVent control has six LEDs labelled A, B, C, D, E and F that show temperature settings and, in combination, error states. Two lamps lit together (A and B) is a temperature indication or an LED combination on that control, not an alarm named AB, and reading it with an EcoNet alarm table produces nonsense. The second source of phantom ABs is partial displays: a failing LCD segment can butcher a real code into unfamiliar shapes. If you believe your Rheem is showing AB, do three things: photograph the display, read the model number off the rating plate, and identify which control your heater actually has before searching anything. Then decode with the right system's chart — blink counts for a combination gas control, letter combinations for IntelliVent, A-plus-three-digits for EcoNet platforms. Codes are platform property; an unattributed code is a riddle, not a diagnosis.

The rest of the hybrid alarm family, in one pass

Once the grammar clicks, the hybrid alarm list reads like a systems map, and a quick tour makes future alarms self-explanatory. The A00x group watches the compressor: A004 is a discharge-to-suction trip, A005 discharge temperature high, A006 suction temperature too low, A009 compressor wiring. The A10x group is sensors and safety: A101 suction sensor, A102 ambient sensor, A103 and A104 the tank's lower and upper heater sensors (A103 disables the heater), A105 evaporator sensor, A106 discharge sensor — and then two that are not sensors at all: A107, water detected on the floor by the leak rope sensor (with its documented 24-hour override, holding Clear Alarm for 5 seconds, meant only to buy time to fix the leak), and A108, condensate blocked, whose manual instruction is simply to unclog the condensate line — a genuinely owner-level fix. The A12x group covers the electric side and water control: A120-A123 shutoff valve errors, A125/A126 element errors or relays stuck closed, A127 element wire routing, A128/A129 relays failing to close. A130 is the unit refusing to run its compressor in freezing air; A200 is the serious one — high water temperature, ECO tripped, heater disabled until serviced. Around the alarms orbit the T-alerts: T131 clean the filter, T132 the heater is struggling to satisfy demand, T300 leak sensor not installed. Scroll your alarms with Next and Down, write them all down — multiple simultaneous alarms are a pattern, and patterns are diagnoses.

Two alarms at once: reading combinations

Single alarms name a system; pairs of alarms often name a cause, and learning to report pairs is a genuine diagnostic skill. Consider the patterns the alarm map makes plausible. A005 (compressor discharge hot) arriving with T132 (difficulty satisfying demand) on a hybrid tells one story — the heat pump is struggling and falling back on elements — and both point first at airflow: filter screen, clearances, fan. A107 (water on the floor) together with a shutoff valve alarm (A120 family) is the protection system mid-performance: the leak was detected and the valve response is being reported too, so the visit is about the leak, not two faults. A sensor alarm paired with an element alarm — say A103 with A125 on a hybrid — should raise the wiring question before the parts question, because sensors and elements share the control's attention and a shared harness or board fault can manufacture both reports. And any alarm that arrives in the company of A200 (ECO tripped) is subordinate to it: the overheat is the headline, everything else is context. The practical rule is humble: never report or research just the first code on the list. Scroll the whole list (Next, then Down, on the hybrid display), write every code down in order, and hand the full set to whoever you call. Combinations are how controls confess to root causes.

Where alarms live: the control display and the EcoNet connection

An alarm you never see cannot help you, so it is worth knowing where these reports surface. The authoritative copy is on the unit itself: the hybrid's control panel holds the current alarm list behind the Next/Down sequence described earlier, and it keeps showing the alarm until the condition clears or is cleared — walking past the unit weekly and glancing at the display is genuinely good practice, because a hybrid silently running on backup elements after an A005 looks, from the bathroom, like a healthy heater while costing resistance-heat money. On EcoNet-connected models, the same alarms are pushed to the EcoNet app, which is where most owners actually meet them — a phone notification that the water heater needs attention, often before anyone noticed a symptom. Treat app and display as two views of one list: if they ever disagree, believe the unit, and re-check after the condition changes, since connectivity lags and stale app states are a known nuisance on every connected appliance platform. One more display habit pays off: when an alarm appears, photograph the screen. Alarm lists scroll, get cleared by helpful family members, and get lost in power cuts; a dated photo of 'A005 + T132 together on a cold morning' is diagnostic evidence a technician can reason from, and it anchors warranty conversations in fact rather than recollection.

Elements, relays and shutoff valves: the A112 and A12x family in plain terms

The A12x block of hybrid alarms, plus Triton's A112, covers the hardware that switches power and water — and its logic is simple once translated. A heating element is just a controlled resistor: the control asks a relay (an electrically operated switch) to close, current flows, water heats. A relay that fails to close (A128/A129) produces the mildest symptom in the alarm book — slow recovery, lukewarm water at peak times, no danger, just a heater quietly working at half strength. A relay stuck closed (A125/A126 on hybrids; the same fault appears as A108/A109 on smart electric tanks) is the dangerous mirror image: the element keeps heating after the control says stop, which is why these alarms pair with the ECO high-limit as the last defence and why the correct response is breaker off, not a cleared alarm and a shrug. A127, element wire routing error, almost always follows human hands — it appears after an element or control board replacement when leads land on the wrong terminals, which is why it belongs in the 'what changed recently' conversation. The shutoff valve errors (A120-A123 on hybrids, A112 on Triton) concern the motorised valve that many smart models use to close the water supply when a leak is detected: 'not open' or 'not operating as commanded' means the protection itself needs attention — the heater may disable heating (as Triton does under A112) precisely because its leak defence cannot be trusted. None of these are owner repairs, but all of them are owner-reportable with precision: which code, which platform, and what work was last done near the unit.

Working an alarm list: order of operations for owners

When the EcoNet app or the display shows alarms, run a fixed routine. First, record before you clear: photograph or write every active alarm, because clearing erases the evidence and because combinations (say A005 with a filthy filter, or A107 with a wet floor) diagnose faster than single codes. Second, name the platform from the rating plate before looking anything up — hybrid, smart electric, or Triton — since this guide's headline lesson is that the same code is a different sentence on each. Third, do the owner-level physical checks the manual itself assigns: filter screen washed and dried, airflow clearances real, condensate line traced and unclogged for A108, floor and fittings inspected for A107, tank proven full and air purged for A008 dry-fire. Fourth, clear the alarm the documented way — the display controls, or a clean power recycle where the manual allows — exactly once, and watch whether the alarm returns immediately (a hard fault: failed sensor, dead element, stuck relay) or after hours of running (a conditional fault: airflow, load, temperature). Fifth, escalate with information: platform, code, what you checked, how fast it returned. The alarms that never go to a technician are few (a filter reminder, a condensate line you cleared); the alarms that should never be wrestled with are the safety ones — A200's tripped ECO, relays stuck closed (A108's smart-electric meaning, A125/A126), and any alarm accompanied by water where water should not be.

Key takeaways

• Retrieve alarms the documented way: press Next until 'Current Alarm' shows, then scroll with the Down arrow — and write them down before clearing anything.
• A005 and A105 each have two Rheem meanings. Name your platform (hybrid vs smart electric vs Triton) before you act on either code.
• There is no Rheem alarm called AB. 'A and B lights' stories come from IntelliVent controls on power-vent tanks — a different system with its own chart.
• A107's 24-hour leak override (hold Clear Alarm 5 seconds) buys time to fix a leak; it is not a way to live with one.
• T-codes are alerts (heater still runs); A-codes are alarms (something has shut down). Read the letter before the number.

Resetting the Rheem water heater

Each Rheem platform resets the way its manual documents, and only that way. Tankless models: close the hot faucet, turn the controller off, switch off the electrical supply, wait 5 minutes, restore power, turn the controller on, and open a hot tap; IKONIC displays also clear alarms via ENTER and 'Clear Alarms?' — Yes; hard lockouts (10, 13, 99) have a DIP-switch procedure that ends with the remote flashing CL (fault history cleared) or UL (reset confirmed). Tank gas controls have no reset button: the status LED clears when the underlying fault clears, and Rheem's chart routes 4, 5, 7 and 8 flashes straight to a qualified technician. Hybrids and smart electric tanks: read and note the alarm first (Next / Down arrows on the hybrid display), fix the cause, then clear; a leak alarm such as A107 can be overridden for 24 hours only by holding Clear Alarm for 5 seconds — time bought to arrange the repair, not to skip it. One reset after fixing the cause is the documented pattern on every platform; repeated resets against a live fault are not a strategy.

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Facts on this page were checked against manufacturer documentation: files.myrheem.com · files.myrheem.com · www.manualshelf.com · www.manualshelf.com · www.manualshelf.com · mans.io · manuals.plus · manuals.plus · manuals.plus