IBC Technologies · Error codes
IBC VX “Reversed flow” alert
Error – Reversed Flow
The manual lists this alert when the return (inlet) temperature reads higher than the supply (outlet) temperature for ten minutes. The boiler expects hot water to leave the supply connection and cooler water to come back on the return; the opposite reading means flow is backwards or the sensors are crossed.
Applies to
This alert is shown by the V-10 touchscreen controller on VX Series residential boilers (VX 110, VX 150 and VX 199), as documented in IBC Installation & Operating Manual — VX 110 / VX 150 / VX 199, doc 120-347E6, sections 9.2–9.4.
Controller: V-10 touchscreen controller. Source manual: 120-347E6 (2026-08-07).
Why a code is not a diagnosis
The alert can be a genuinely reversed pump or piping connection, or simply supply and return sensors swapped or mis-wired. The manual lists checking pump flow direction and the sensor wiring as the first steps.
Safe things to observe
- Note the alert text and whether the boiler still heats the building.
- If the boiler is running and heating normally, the cause may be a sensor-wiring issue rather than piping.
Do not
- Do not reverse pumps or piping yourself.
- Do not swap sensor connections without confirming which sensor is which.
How professional service helps
- A technician verifies the pump's flow direction and the piping arrangement around the boiler.
- Supply and return sensor wiring and readings are checked and corrected if crossed.
Where ROMA provides on-site service
On-site service is currently offered in Greater Vancouver, BC, including Vancouver, Burnaby, Richmond, Surrey, Coquitlam, North Vancouver, West Vancouver, New Westminster, Port Coquitlam, Port Moody, Delta, Langley, Maple Ridge, Abbotsford, Chilliwack, White Rock, Pitt Meadows, Tsawwassen, Anmore, Lions Bay, Belcarra, Bowen Island, Mission. Everything else on this site is reference information you can use anywhere in Canada.
Parts and service
Parts commonly involved
These parts appear in the documented text for this alert. A code reports a condition, not a failed part — a technician confirms the cause by testing before anything is replaced.
Boiler sensors (thermistors)
Boiler sensors are small temperature probes, usually thermistors, that tell the control how hot the water and flue gases are so it can fire safely…
What a technician checks →
Service for this alert
- Gas Boiler Repair
Licensed gas technicians from ROMA Heating & Cooling diagnose and repair residential and light-commercial gas boilers across…
Every boiler part explained — what it does, how it fails and what a technician checks.
Documented for IBC Technologies VX Series.
Frequently asked questions
Can reversed flow damage the boiler?
Running with flow in the wrong direction can cause incorrect temperature readings and poor heat transfer; the control flags it rather than silently misbehaving. A technician corrects the cause before the boiler is relied on.
Boiler locked out? Call with the alert text ready.
The brand, model and this alert are passed along when you request service online, so the technician arrives prepared.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Sources and verification
- IBC Installation & Operating Manual — VX 110 / VX 150 / VX 199, doc 120-347E6, sections 9.2–9.4 · 120-347E6 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.