Lochinvar Knight XL Anti-cycling — Call for Heat Received Too Quickly After the Previous Call Ended
Anti-cycling
Call for heat received too quickly after the previous call ended. The main control board has received a call for heat too quickly after the previous call for heat has ended; the control board releases the call for heat after a set time period or if the outlet temperature drops too quickly.
Applies to
This electronics fault code is displayed by the Knight XL control (text faults) on Knight XL models (KBX0400 through KBX1000), as documented in Knight XL (KBX) Service Manual, 100383164 Rev C — Table 3-4 fault codes (100383164 Rev C). Codes can differ between controller generations, so always check the manual that matches your unit.
- Lochinvar Knight XL Commercial (KBX)
- Lochinvar Knight XL KBX0400
- Lochinvar Knight XL KBX0500
- Lochinvar Knight XL KBX0650
- Lochinvar Knight XL KBX0800
- Lochinvar Knight XL KBX1000
Controller: Knight XL control (text faults). Source manual: 100383164 Rev C (2025-10).
Why a code is not a diagnosis
An electronics code points at the control board, memory or firmware. It is often triggered by poor incoming power or voltage backfeed from other wiring rather than by the appliance itself.
Safe things to observe
- Note the code and whether it appeared after electrical work or a power event.
Do not
- Do not open the control module.
- Do not repeatedly power-cycle to clear a recurring board code.
How professional service helps
- A technician checks supply voltage and grounding, follows the manual's reset sequence and replaces the module only if the code returns.
- 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.
Control board / PCB
The control board — also called the PCB, or printed circuit board — is the boiler's main computer.
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 Lochinvar Knight XL Commercial (KBX).
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
- Knight XL (KBX) Service Manual, 100383164 Rev C — Table 3-4 fault codes · 100383164 Rev C · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.