NTI Compass 1 05 — Supply Temperature Exceeded Return Temperature by More Than 99f Three Times in a Row
1 05
Supply temperature exceeded return temperature by more than 99F three times in a row. The supply temperature exceeded the return temperature by more than 99F three times in a row; listed causes are air in the system, a failed internal circulator or internal circulator not powered, a plugged plate heat exchanger (combi only) or indirect hot water tank, improper piping or boiler commissioning, a damaged or malfunctioning temperature sensor, and PCB failure. The table classifies it as Blocking (Manual Reset).
Applies to
This sensor fault code is displayed by the Compass control on Compass models (NC085, NC110, NC150, NC199 and combis NC110C, NC150C, NC199C), as documented in NTI Compass Installation and Operation Manual, doc 420011304100 Rev 04 (20240404), Part 13-B Boiler Error Codes (420011304100 Rev 04). Codes can differ between controller generations, so always check the manual that matches your unit.
- NTI Boilers NTI Compass
- NTI Compass NC085
- NTI Compass NC110
- NTI Compass NC150
- NTI Compass NC199
- NTI Compass NC110C
- NTI Compass NC150C
- NTI Compass NC199C
Controller: Compass control. Source manual: 420011304100 Rev 04 (2024-04-04).
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.
Plate heat exchanger
A plate heat exchanger is a stack of corrugated stainless plates that transfers heat between two water circuits — most often from boiler water to…
What a technician checks →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 →Control board / PCB
The control board — also called the PCB, or printed circuit board — is the boiler's main computer.
What a technician checks →Circulator pump
The circulator is the pump that moves heated water from a boiler out to the radiators, baseboards or in-floor loops and back again.
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…
- Gas Boiler Replacement
ROMA replaces old, failed or inefficient gas boilers in Greater Vancouver, handling removal, venting and gas-supply changes,…
Every boiler part explained — what it does, how it fails and what a technician checks.
Documented for NTI Boilers NTI Compass.
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
- NTI Compass Installation and Operation Manual, doc 420011304100 Rev 04 (20240404), Part 13-B Boiler Error Codes · 420011304100 Rev 04 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.