Rheem Furnace Limit & Rollout Codes (22, 33): Meaning & Fixes

Two Rheem codes guard the furnace against its own heat, and they are not the same device wearing two numbers: 22 is the main limit control open — the automatic, self-reclosing switch that watches heat-exchanger temperature — while 33 is the Manual Reset Limit Control (MRLC, the roll-out switch) open, reporting flame in the burner compartment, a code Rheem says should rarely if ever be seen and indicates a very serious problem. This guide separates the two switches, times the 150-second rule that turns a 22 into a blower verdict, and is explicit about the safety framing Rheem demands: a tripped roll-out is found and fixed by a technician first, and reset by hand second — never the other way round.

Two switches, two philosophies: the limit circuit explained

Rheem's limit protection is a series circuit of temperature switches wired so that any one of them opening shuts the burners down — but the two switches behind codes 22 and 33 embody opposite philosophies about what happens next. The main limit control (code 22's device; on (-)801S models the chart reads 'main limit or HALC') watches the temperature around the heat exchanger, where the danger is heat being made faster than the circulating air carries it away. It is an automatic device: it opens hot and re-closes as the furnace cools, ready to protect again on the next cycle, because its expected story — a transient airflow shortfall — resolves when the temperature falls. The Manual Reset Limit Control (code 33's device, the roll-out switch) watches the burner compartment instead, where the danger is flame itself escaping the burners and rolling out into a space full of wiring and gas controls. It is a manual device by deliberate design: once it opens it stays open until a human being opens the compartment, looks at what flame did there, and resets it by hand. The design is the diagnosis in miniature. A switch the factory expects to recover on its own reports a condition that cooling can cure; a switch the factory refuses to let recover reports a condition that cooling cannot cure — flame went somewhere it must never go, and the cause (venting, flame stability, a damaged exchanger) will still be there at any temperature. That is why the two codes must never be merged into a generic 'limit fault': a 22 invites airflow work, a 33 demands a combustion investigation, and treating a 33 with a 22's casualness — reset it, run it, see — is the single most dangerous misreading on the Rheem chart. The sections below keep the two devices apart the way Rheem's manuals do, and the one place they genuinely interact — the 150-second rule, where a stubborn 22 becomes evidence about the blower — gets its own section, because it belongs to neither switch alone.

Code 22: main limit open — the overheating report

Rheem's chart definition is terse: the main limit control is open. Unpack what the control is witnessing. The burners made heat; the air crossing the heat exchanger did not carry it away fast enough; the metal and the air around it climbed past the limit's set temperature; the switch opened and the burners stopped. The blower's job in that moment is to keep moving air across the exchanger to pull the stored heat out, and as the temperature falls the switch re-closes by itself — a 22 that clears on cooling has behaved exactly as designed, and the code is a report about airflow, not about the switch. Rheem's own reading of the code proves the point by where it sends you next: a limit open is read as an airflow-and-blower event, and a limit that stays open is escalated into a blower verdict (the next section). The airflow census behind a 22 is the familiar one, and it should be worked in its proper order even though this article's ground truth states it through the 61 connection: air that cannot get to the exchanger (a filter loaded enough to matter, returns blocked, supply registers closed down), and air that cannot be moved (a blower weakened, obstructed or silent). Owners consistently underrate the first half because a filter can look 'not that bad' while passing half its rated air — on a limit code, the filter is replaced, not judged. What 22 is not, on Rheem's evidence, is a switch complaint: the switch is the last suspect, condemned only when temperature measurements prove the furnace was never as hot as the switch claimed. One more behaviour to expect while 22 shows: the furnace is protecting, not broken — burners held off, blower running its cooling work — and a household that hears the blower running with no heat and a 22 on the display is hearing the protection do its job. The repair conversation is about why the heat had nowhere to go, and it starts with air.

The 150-second rule: when a 22 becomes a blower verdict (61 + 22)

Rheem builds a clock into code 22, and the *96V lockout section states it exactly: the control will declare the blower motor inoperable (dead) if the main limit control has been open for more than 150 seconds. The reasoning is thermodynamic and elegant. A healthy blower, running against an open limit, moves enough air to cool the exchanger and re-close the switch well inside that window; a limit still open after 150 seconds therefore means the air is not moving — the blower is dead, obstructed, or never started — and the control says so by changing the display: open over 150 seconds during a heat call, the verified chart entry reads, the display alternates 61 and 22. Gas heating is terminated, but the control is not finished being fair about it: it continues to try to operate heating for up to four attempts in case the blower starts working again, and only a fourth dead-blower declaration in one heat call enters hard lockout. A single dead-blower declaration pairs instead with the one-hour lockout. For the owner, the alternating display is the most information-dense pattern in this article, because it reroutes the whole diagnosis: a plain 22 says 'find the airflow restriction'; a 61 + 22 says 'find why the blower is not moving air at all' — motor, wheel, wiring, choke, model data, the full code-61 list on this site — with the limit switch demoted to witness. It also forbids the tempting shortcut: replacing the limit switch on a 61 + 22 furnace fits a new witness to the same dead blower, and the new switch will file the same 150-second report. If your furnace shows the pair, quote both numbers when you call; a technician who hears '61 alternating with 22' arrives thinking about blowers, while one who hears 'a limit code' arrives thinking about filters, and only one of them has read the furnace correctly.

Code 33: MRLC open — roll-out, the code Rheem says you should rarely see

Code 33's full Rheem name carries its meaning: the Manual Reset Limit Control — aka the roll-out switch — has opened, because flame rolled out into the burner compartment. Rheem's framing of this code is the strongest on its chart, and this article will not soften it: Rheem says 33 should rarely if ever be seen and indicates a very serious problem. Flame belongs inside the burners and the heat exchanger's fire tubes; a roll-out event means combustion gases and flame front escaped backward into the compartment that houses the gas valve, the control wiring and the inducer connections — a space engineered on the assumption that fire never visits it. Rheem's cause list for 33 is correspondingly combustion-side, not airflow-side: insufficient venting (inlet or exhaust), loose or faulty wiring, or an unstable flame pattern. Read them as one story told three ways: exhaust that cannot leave (a vent obstructed, mis-sized or over-long for its run) pushes back against the burner opening until flame spills out of it; a flame already unstable — lifting, fluttering, poorly anchored — needs little push to spill; and the wiring branch covers the switch's own circuit reporting falsely, which must be proved, never assumed, because assuming it is how a real roll-out gets reset into a second one. The switch's manual-reset nature is the final element of Rheem's framing: the code cannot clear on cooling, cannot clear on a timer, and cannot clear by cycling power, because none of those things inspects a burner compartment. The next two sections set out what Rheem requires before that reset is legitimate — a technician's checklist that ends at the switch, not one that starts there — and why the household's correct response to a first-ever 33 is to leave the furnace off and make the call, with the compartment unopened and the switch unpressed.

Before any reset: Rheem's own checklist for a tripped roll-out

Rheem does not merely advise caution around code 33; its documentation structures the repair as an inspection that must precede the reset, and the verified chart entry lists the inspection's contents. A technician must first check vent obstructions and lengths — the inlet and exhaust paths examined for blockage, damage and runs beyond their allowed length, since insufficient venting is the code's first cause. The pressure switches are checked to be neither welded nor bypassed — a switch defeated or stuck in the proved position removes the furnace's draft evidence and lets a bad vent masquerade as a good one, which is why Rheem names the check explicitly in this code's repair. Inducer speed is verified, because the inducer is the machine that pulls combustion gases through the exchanger and out the vent; a lazy inducer is a vent restriction wearing a motor's clothes. Seals are checked — the burner and compartment sealing that keeps flame and gas on their designed paths — and the heat exchanger is checked for damage, because a cracked or failed exchanger both causes roll-out behaviour and is caused further harm by it, and either direction of that sentence ends the furnace's service until it is addressed. Only at the end of that list, with a cause found and corrected, does Rheem's procedure arrive at its final verb: then reset it manually. The order is the safety system. A roll-out reset performed first converts the switch from a witness into an accomplice — the furnace re-fires into the same obstructed vent or unstable flame, and the second roll-out happens with the household's guard now spent: the switch has already been pressed once, and human beings rarely press a reset button with the same respect twice. If a service visit for a 33 proposes to begin at the reset button, that ordering — not the code — is the problem to raise.

Shared ground and clean splits: airflow faults vs combustion faults

Codes 22 and 33 share a circuit, a verb ('open') and a page — and almost nothing else, and the cleanest way to hold them apart is by what each one's world smells like. Code 22's world is air: filters, returns, registers, duct restriction, blower strength. Its events correlate with the house (a filter overdue, registers closed for the season, furniture over a return) and with run length (the longest, coldest cycles trip it), and its switch forgives — cooling re-closes it, and a corrected airflow ends it. Code 33's world is fire: venting, flame stability, seals, exchanger integrity. Its events correlate with the flue (a vent termination buried or nested, a vent run altered in a renovation) and with ignition moments (roll-out is characteristically a light-off event, when the flame front establishes), and its switch never forgives — a human must inspect and reset it. The genuine interactions between the two worlds are worth naming so they are not mistaken for overlap. A blower failure belongs to 22's world but announces through the 150-second rule as 61 + 22, never as a 33. A severely unstable flame belongs to 33's world (and to code 13's flame-lost story) but does not open the main limit — it spills or vanishes rather than overheating the exchanger. And a restricted vent can warm the burner compartment without ever tripping the main limit, which is why a furnace can show a 33 with a spotless filter and honest airflow: the filter was never in this code's story. Diagnosis follows the split. For a 22: replace the filter, open the air path, prove the blower, and only then discuss the switch. For a 33: stop, leave the switch alone, and hand Rheem's pre-reset checklist to a licensed technician. The one-sentence version, worth memorising: 22 asks where the air went; 33 asks where the flame went; and the second question is always a professional's to answer.

What owners can safely do — and the lines they must not cross

The owner's legitimate work on this page is real but asymmetric: generous on the 22 side, nearly empty on the 33 side, and Rheem's framing is the reason for both halves. For a 22, owners can replace the filter (with the correct size, fully seated), open every supply register and return grille, move whatever is blocking a return, and observe one full heat call: does the blower run, does the code return, how long does the furnace heat before it trips? That observation set — especially whether the display escalates to 61 + 22 — is genuine diagnostic value handed to whoever comes next. For a 33, the owner's list ends at reading the code, leaving the furnace off, and calling: the burner compartment stays closed, the roll-out switch stays unpressed, and no power-cycling experiment is run 'to see if it was a fluke', because on this code a fluke and a catastrophe present identically and Rheem has already told you the base rate — rarely if ever seen, very serious. Across both codes, three prohibitions from Rheem's safety framing bind absolutely: never bypass a limit or roll-out switch to get heat (the circuit exists to be the last thing between a fault and a fire); never jumper a pressure switch discovered defeated during a 33 investigation (Rheem's checklist treats a bypassed switch as part of the fault, not a shortcut past it); and never treat repeated manual resets of anything as a maintenance strategy. Add the standing furnace rules — gas smell means the gas utility and a technician, a CO alarm means out of the house and then the call, soot or scorch marks at the burner compartment mean off until inspected — and the owner's role is complete: generous with air and information on the code that wants air and information, and hands-off on the code that wants an inspection.

Patterns over time: what repeating limits are telling you

A limit code's meaning grows with its history, and Rheem's controls are built to notice what households miss: repetition. A single 22 on the coldest night of the year, cured by a filter, is the protection working as designed — file it and move on. A 22 that returns monthly despite a clean filter and open registers is a restriction deepening somewhere the owner cannot see — a blower wheel matted over seasons, an indoor coil furred with bypassed dust, duct liner collapsing inside a run — or a blower losing strength on schedule, and each return trip is another full thermal cycle imposed on a heat exchanger that did not need it. Heat exchangers fail by accumulated stress as much as by age, which is why a furnace 'managed' through winters of limit trips is being consumed by its management. The escalation patterns deserve the same reading: 22s that begin arriving with the 61 pairing have crossed from restriction to blower failure; a 22 pattern that appears only after a duct or renovation change has its cause's address printed on it; and a first 33 at any point in a furnace's life outranks every 22 in its history combined — the roll-out checklist runs once, fully, regardless of how benign the furnace's limit history has been. Rheem gives you the raw material for this reading for free: the controls store fault history (the reset guide on this site details how each generation recalls it — three recent faults flashed on the single-display boards, six in the communicating status menu, the EcoNet fault screens beyond that). Read the history before clearing anything, write down dates and weather alongside the codes, and let the pattern — not the latest single event — decide the urgency. A limit system that speaks rarely and clearly is a healthy furnace; one that has learned to shout weekly is asking, in the only language it has, for a technician rather than another reset.

Key takeaways

• Quote both numbers on the alternating display: 22 alone is an airflow story, but 61 alternating with 22 is Rheem's dead-blower declaration (limit open over 150 seconds) — they send the technician to different parts of the furnace.
• For code 33, the order is Rheem's, not negotiable: venting, pressure switches, inducer, seals and heat exchanger are checked first, and the manual reset comes last. A reset offered first is a red flag about the visit, not a shortcut.
• Never bypass a limit or roll-out switch to get heat, and never reset a tripped roll-out to 'see if it happens again' — Rheem classes 33 as a very serious problem that should rarely if ever be seen.

Resetting the Rheem furnace

Rheem fault codes are shown as two-digit codes on the control's 7-segment display and clear once the fault condition is gone. Lockouts follow Rheem's documented rules: soft lockouts (the one-hour lockout, code 10, and the five-minute lockout when the low pressure switch fails to close after 60 seconds of inducer operation) auto-reset when their timer expires, and any lockout can be cleared immediately — once the original fault is cleared — by cycling power to the unit off and back on, or, for soft lockouts only, by cycling the heat call off for more than 2 seconds but less than 20 seconds. Hard lockouts are the exception: code 93 cannot be reset by cycling the heat call, and a dead-blower hard lockout (code 61, declared four times in one heat call) needs the repair plus a manual reset of power. Clearing a lockout without fixing its cause just restarts the count to the next one.

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Facts on this page were checked against manufacturer documentation: pts.myrheem.com · www.manualslib.com · pts.myrheem.com · pts.myrheem.com · www.manualslib.com · my.ruud.com:443