Crown Boiler Co. · Error codes
Crown Aruba b 18 — Mcba Supply Sensor Detected Temperatures in Excess of 200°f
b 18
MCBA supply sensor detected temperatures in excess of 200°F. Heating load far below minimum firing rate, defective primary pump or no flow in primary loop (Piping Method 1), control miswired so boiler operation is permitted when no zones are calling The table classifies it as soft lockout.
Applies to
This sensor fault code is displayed by the Bimini control on Bimini BWC models (BWC150, BWC225 and earlier Sola generation), as documented in Bimini Residential (BWC) Installation Instructions (legacy Crown manual). Codes can differ between controller generations, so always check the manual that matches your unit.
- Crown Boiler Co. Bimini (legacy)
- Crown Bimini BWC070
- Crown Bimini BWC090
- Crown Bimini BWC120
- Crown Bimini BWC151
- Crown Bimini BWC150
- Crown Bimini BWC225
Controller: Bimini control. Source manual: see sources.
Why a code is not a diagnosis
A sensor code usually means the sensor, its wiring or its mounting is faulty; the physical condition the sensor measures (temperature, pressure, flow) may be perfectly normal.
Safe things to observe
- Note the code; there is no homeowner-accessible check for sensor circuits.
- If the appliance still runs, watch whether the code returns and report it when you call.
Do not
- Do not open the appliance to test or replace sensors yourself.
How professional service helps
- A technician measures the sensor and harness against the manual's values and replaces the faulty component.
- Combustion and safety devices are verified with an analyser and the manufacturer's procedure after any repair.
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…
- Emergency Boiler Repair
Priority gas boiler repair for homes and buildings in Greater Vancouver with no heat, no hot water, a locked-out boiler or a leak.
Every boiler part explained — what it does, how it fails and what a technician checks.
Documented for Crown Boiler Co. Bimini (legacy).
Frequently asked questions
Can I clear this code myself?
Clearing a code without fixing its cause usually just brings it back. Note the code, check the safe items on this page, then call a licensed technician. If your appliance manual describes a user reset for this exact code and it stays away, no call may be needed.
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
- Bimini Residential (BWC) Installation Instructions (legacy Crown manual) · accessed September 8, 2026
Facts checked September 8, 2026. Last updated September 8, 2026. Technical reviewer: not yet assigned.