Navien Combi Boiler Not Heating the House (Greater Vancouver)

One of the most telling clues with a Navien combi boiler is whether your hot water still works when the house will not warm up. A combi unit does two jobs from one appliance: it makes domestic hot water for your taps and it heats the water that circulates through your radiators or in-floor loops. When the taps run hot but the home stays cold, the problem is almost always on the central-heating side — not the boiler’s ability to fire, but its ability to send heat around the house. That distinction points the diagnosis in the right direction immediately.

For a Greater Vancouver homeowner — whether in a Vancouver character home with cast-iron radiators, a Burnaby townhome with in-floor heat, or a Richmond condo — a Navien that heats water but not the house is worth diagnosing promptly in our damp, cool winters. Navien combi boilers show an error code on their front display when a hard fault occurs, so if you see a code, note it exactly; but a “no heat to the house” complaint often has no code at all, because the boiler thinks it is working fine.

ROMA Heating & Cooling has diagnosed Navien combi boilers across Vancouver, Burnaby, Richmond, Coquitlam and the North Shore since 1999. Here are the common causes, the safe checks, and when to call.

Most likely causes of a Navien combi boiler not heating the house

No call for heat from the thermostat

If the thermostat is not sending a heat call — wrong mode, low setpoint, dead batteries, or a wiring issue — the boiler runs hot water for taps but never starts a central-heating cycle. Safe check: set the thermostat to heat, a few degrees above room temperature, with fresh batteries, and confirm the boiler responds.

Low system pressure

Central heating needs the loop pressurized, typically around the range marked on the gauge. If pressure has dropped too low, the boiler will not circulate heat and may show a low-pressure code. Safe check: read the pressure gauge; if it is very low, the system may need repressurizing, which a technician should do while checking why it dropped.

Air trapped in the system

Air in radiators or loops blocks circulation, so some rooms — or the whole house — stay cold even though the boiler fires. Safe check: bleeding radiators is sometimes homeowner-doable, but persistent air points to a leak or a pump issue for a technician.

Circulator pump not running

The pump moves heated water through the house. If it fails or seizes, hot water still reaches the taps but the heating loop goes cold. Safe check: none internal — a technician tests the pump.

Zone valve or diverter valve stuck

Combi boilers use a diverter valve to switch between domestic hot water and central heating; if it sticks in the hot-water position, taps stay hot while the house gets no heat. A stuck zone valve does the same to a zone. Safe check: none — these are technician items.

Boiler in a fault or lockout

A hard fault shows an error code on the display and can stop the heating side. Safe check: note the exact code, try one reset per the manual, and if it returns, call.

No-heat quick reference

📞 Talk to a licensed ROMA boiler technician — (604) 704-0300

Safe things to try once

Confirm the thermostat is set to heat, a few degrees above room temperature, with fresh batteries, and that it is actually calling for heat. Check the boiler’s pressure gauge against the normal range marked on it — if pressure is very low, note it for the technician rather than repeatedly topping it up, because a dropping pressure usually means a leak or an expansion-vessel issue. If only some radiators are cold and you are comfortable doing so, you can bleed trapped air from them. Note any error code shown on the Navien display exactly as it appears, and try a single reset as described in your manual. If the house still will not heat, the pressure keeps dropping, a code returns, or the pump or diverter is suspected, stop and call a licensed gas technician. Never open the sealed boiler or attempt gas or combustion work.

How ROMA pinpoints a Navien not heating the house

Because the hot water working already tells us the boiler can fire, we focus on the heating circuit. We confirm the thermostat’s heat call is reaching the boiler, read and test system pressure and look for why it dropped, and check for air in the loops. We test the circulator pump and the diverter valve directly, since a stuck diverter that stays in domestic-hot-water mode is a classic reason taps stay hot while the house goes cold on a combi unit. If the display shows a code, we read it against Navien’s documentation rather than guessing, and we verify condensate drainage, because a blocked condensate trap — common in our damp climate — can fault a condensing boiler. When you call (604) 704-0300, tell us whether hot water still works, whether all or only some rooms are cold, what the pressure gauge reads, and any code on the display; those four details usually point us to the cause before we arrive.

When it is an emergency

A boiler that heats water but not the house is usually not an emergency, though no heat in a cold snap with a vulnerable household warrants priority scheduling — tell us when you call. As always, if you smell gas, leave the home and call the FortisBC emergency line and 911 from outside; do not troubleshoot. If a CO alarm sounds or anyone feels unwell, get everyone out and call 911. If you see water leaking from the boiler or pipework, shut off the heating and call.

Repair or replace?

Most “not heating the house” causes are routine, worthwhile repairs on a sound Navien — a thermostat correction, repressurizing and fixing a small leak, bleeding air, a circulator pump, or a diverter valve. Replacement of the boiler only enters the conversation if it is old and multiple components are failing together, in which case we compare the repair against a new high-efficiency combi with any available rebates, honestly. We quote the repair first, after diagnosis.

Keeping your Navien heating the whole home

An annual boiler service is the best prevention: it checks system pressure and the expansion vessel, tests the pump and diverter valve, verifies the condensate drain is clear, and confirms the heating loop is free of air before winter. In Greater Vancouver’s older homes and stratas, small pressure leaks and trapped air are common causes of gradually worsening heat, and catching them on a service visit avoids a cold-house call in January. If your home has multiple zones, having each zone valve checked keeps one room from going cold while the rest stay warm.

A useful first test costs nothing: run a hot tap and confirm the water still gets hot. If it does, you have already narrowed the problem to the central-heating side, which rules out gas supply, the burner and the heat exchanger as the cause and points instead at the thermostat call, circulation, pressure, or the diverter. That single observation saves diagnostic time and is the first thing worth telling us when you call.

Why ROMA for Navien combi boilers in Vancouver

ROMA Heating & Cooling is a TSBC-licensed gas contractor (Gas licence LGA0202903), bonded, insured and Red Seal-trained, rated 4.8★ from 221 Google reviews. We diagnose the heating side of your Navien combi — thermostat call, pressure, air, pump and diverter — and repair it with upfront flat-rate pricing and no hidden fees. Estimates on installs are free, 0% financing is available OAC, and we work seven days a week. See our boiler repair service or book a free estimate. We serve Vancouver, Burnaby, Richmond, Coquitlam and the North Shore — call (604) 704-0300, reach our team, learn about our boiler services, or ask about maintenance plans.

Frequently Asked Questions

Why is my Navien combi boiler not heating the house but hot water works?

When taps run hot but the home stays cold, the problem is on the central-heating side, not the boiler’s ability to fire. Common causes are no thermostat heat call, low system pressure, trapped air, a failed circulator pump, or a diverter valve stuck in hot-water mode. Check the thermostat and pressure gauge, then call ROMA at (604) 704-0300.

What should the pressure be on my Navien combi boiler?

Read the pressure gauge against the normal range marked on it, and note the actual reading for your technician. If pressure is very low the boiler will not circulate heat. Avoid repeatedly topping it up yourself, because a dropping pressure usually signals a leak or an expansion-vessel issue that needs a technician.

What is a diverter valve and can it cause no heat?

A combi boiler uses a diverter valve to switch between domestic hot water and central heating. If it sticks in the hot-water position, your taps stay hot while the house gets no heat — a classic combi symptom. Testing and replacing the diverter is a technician job.

My Navien shows an error code and no heat. What do I do?

Note the code exactly as it appears on the display and try a single reset as described in your manual. Do not keep resetting if it returns — a repeating code means an unresolved fault. We read Navien codes against the manufacturer’s documentation rather than guessing at their meaning. Call ROMA at (604) 704-0300.

Does ROMA repair Navien combi boilers in Greater Vancouver?

Yes. ROMA Heating & Cooling diagnoses the heating side of Navien combi boilers — thermostat call, pressure, air, pump and diverter — across Vancouver, Burnaby, Richmond, Coquitlam and the North Shore. We are TSBC-licensed, bonded and insured. Call (604) 704-0300 seven days a week.

Reviewed by the ROMA Heating & Cooling team — TSBC-licensed gas contractor (Gas LGA0202903), serving Greater Vancouver since 1999. Updated July 2026.

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